Switch imgui to docking branch.

6 files changed, 6681 insertions, 313 deletions

diff --git a/imgui/imgui.cpp b/imgui/imgui.cpp
index b57bb195..970fc9cc 100644
--- a/imgui/imgui.cpp
+++ b/imgui/imgui.cpp
@@ -1,4 +1,4 @@
-// dear imgui, v1.76
+// dear imgui, v1.77 WIP
 // (main code and documentation)
 
 // Help:
@@ -75,6 +75,8 @@ CODE
 // [SECTION] DRAG AND DROP
 // [SECTION] LOGGING/CAPTURING
 // [SECTION] SETTINGS
+// [SECTION] VIEWPORTS, PLATFORM WINDOWS
+// [SECTION] DOCKING
 // [SECTION] PLATFORM DEPENDENT HELPERS
 // [SECTION] METRICS/DEBUG WINDOW
 
@@ -372,6 +374,15 @@ CODE
  When you are not sure about a old symbol or function name, try using the Search/Find function of your IDE to look for comments or references in all imgui files.
  You can read releases logs https://github.com/ocornut/imgui/releases for more details.
 
+ (Docking/Viewport Branch)
+ - 2019/XX/XX (1.XX) - when multi-viewports are enabled, all positions will be in your natural OS coordinates space. It means that:
+                        - reference to hard-coded positions such as in SetNextWindowPos(ImVec2(0,0)) are probably not what you want anymore.
+                          you may use GetMainViewport()->Pos to offset hard-coded positions, e.g. SetNextWindowPos(GetMainViewport()->Pos)
+                        - likewise io.MousePos and GetMousePos() will use OS coordinates.
+                          If you query mouse positions to interact with non-imgui coordinates you will need to offset them, e.g. subtract GetWindowViewport()->Pos.
+ - 2019/XX/XX (1.XX) - Moved IME support functions from io.ImeSetInputScreenPosFn, io.ImeWindowHandle to the PlatformIO api.
+
+
  - 2020/01/22 (1.75) - ImDrawList::AddCircle()/AddCircleFilled() functions don't accept negative radius any more.
  - 2019/12/17 (1.75) - [undid this change in 1.76] made Columns() limited to 64 columns by asserting above that limit. While the current code technically supports it, future code may not so we're putting the restriction ahead.
  - 2019/12/13 (1.75) - [imgui_internal.h] changed ImRect() default constructor initializes all fields to 0.0f instead of (FLT_MAX,FLT_MAX,-FLT_MAX,-FLT_MAX). If you used ImRect::Add() to create bounding boxes by adding multiple points into it, you may need to fix your initial value.
@@ -901,11 +912,15 @@ static const float WINDOWS_RESIZE_FROM_EDGES_HALF_THICKNESS = 4.0f;     // Exten
 static const float WINDOWS_RESIZE_FROM_EDGES_FEEDBACK_TIMER = 0.04f;    // Reduce visual noise by only highlighting the border after a certain time.
 static const float WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER    = 2.00f;    // Lock scrolled window (so it doesn't pick child windows that are scrolling through) for a certaint time, unless mouse moved.
 
+// Docking
+static const float DOCKING_TRANSPARENT_PAYLOAD_ALPHA        = 0.50f;    // For use with io.ConfigDockingTransparentPayload. Apply to Viewport _or_ WindowBg in host viewport.
+
 //-------------------------------------------------------------------------
 // [SECTION] FORWARD DECLARATIONS
 //-------------------------------------------------------------------------
 
 static void             SetCurrentWindow(ImGuiWindow* window);
+static void             SetWindowHitTestHole(ImGuiWindow* window, const ImVec2& pos, const ImVec2& size);
 static void             FindHoveredWindow();
 static ImGuiWindow*     CreateNewWindow(const char* name, ImVec2 size, ImGuiWindowFlags flags);
 static ImVec2           CalcNextScrollFromScrollTargetAndClamp(ImGuiWindow* window, bool snap_on_edges);
@@ -913,8 +928,6 @@ static ImVec2           CalcNextScrollFromScrollTargetAndClamp(ImGuiWindow* wind
 static void             AddDrawListToDrawData(ImVector<ImDrawList*>* out_list, ImDrawList* draw_list);
 static void             AddWindowToSortBuffer(ImVector<ImGuiWindow*>* out_sorted_windows, ImGuiWindow* window);
 
-static ImRect           GetViewportRect();
-
 // Settings
 static void*            WindowSettingsHandler_ReadOpen(ImGuiContext*, ImGuiSettingsHandler*, const char* name);
 static void             WindowSettingsHandler_ReadLine(ImGuiContext*, ImGuiSettingsHandler*, void* entry, const char* line);
@@ -923,7 +936,6 @@ static void             WindowSettingsHandler_WriteAll(ImGuiContext*, ImGuiSetti
 // Platform Dependents default implementation for IO functions
 static const char*      GetClipboardTextFn_DefaultImpl(void* user_data);
 static void             SetClipboardTextFn_DefaultImpl(void* user_data, const char* text);
-static void             ImeSetInputScreenPosFn_DefaultImpl(int x, int y);
 
 namespace ImGui
 {
@@ -954,8 +966,23 @@ static void             UpdateTabFocus();
 static void             UpdateDebugToolItemPicker();
 static bool             UpdateWindowManualResize(ImGuiWindow* window, const ImVec2& size_auto_fit, int* border_held, int resize_grip_count, ImU32 resize_grip_col[4]);
 static void             RenderWindowOuterBorders(ImGuiWindow* window);
-static void             RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar_rect, bool title_bar_is_highlight, int resize_grip_count, const ImU32 resize_grip_col[4], float resize_grip_draw_size);
+static void             RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar_rect, bool title_bar_is_highlight, bool handle_borders_and_resize_grips, int resize_grip_count, const ImU32 resize_grip_col[4], float resize_grip_draw_size);
 static void             RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& title_bar_rect, const char* name, bool* p_open);
+static void             EndFrameDrawDimmedBackgrounds();
+
+// Viewports
+const ImGuiID           IMGUI_VIEWPORT_DEFAULT_ID = 0x11111111; // Using an arbitrary constant instead of e.g. ImHashStr("ViewportDefault", 0); so it's easier to spot in the debugger. The exact value doesn't matter.
+static ImGuiViewportP*  AddUpdateViewport(ImGuiWindow* window, ImGuiID id, const ImVec2& platform_pos, const ImVec2& size, ImGuiViewportFlags flags);
+static void             UpdateViewportsNewFrame();
+static void             UpdateViewportsEndFrame();
+static void             UpdateSelectWindowViewport(ImGuiWindow* window);
+static bool             UpdateTryMergeWindowIntoHostViewport(ImGuiWindow* window, ImGuiViewportP* host_viewport);
+static bool             UpdateTryMergeWindowIntoHostViewports(ImGuiWindow* window);
+static void             SetCurrentViewport(ImGuiWindow* window, ImGuiViewportP* viewport);
+static bool             GetWindowAlwaysWantOwnViewport(ImGuiWindow* window);
+static int              FindPlatformMonitorForPos(const ImVec2& pos);
+static int              FindPlatformMonitorForRect(const ImRect& r);
+static void             UpdateViewportPlatformMonitor(ImGuiViewportP* viewport);
 
 }
 
@@ -1096,6 +1123,18 @@ ImGuiIO::ImGuiIO()
     FontAllowUserScaling = false;
     DisplayFramebufferScale = ImVec2(1.0f, 1.0f);
 
+    // Docking options (when ImGuiConfigFlags_DockingEnable is set)
+    ConfigDockingNoSplit = false;
+    ConfigDockingWithShift = false;
+    ConfigDockingAlwaysTabBar = false;
+    ConfigDockingTransparentPayload = false;
+
+    // Viewport options (when ImGuiConfigFlags_ViewportsEnable is set)
+    ConfigViewportsNoAutoMerge = false;
+    ConfigViewportsNoTaskBarIcon = false;
+    ConfigViewportsNoDecoration = true;
+    ConfigViewportsNoDefaultParent = false;
+
     // Miscellaneous options
     MouseDrawCursor = false;
 #ifdef __APPLE__
@@ -1114,8 +1153,6 @@ ImGuiIO::ImGuiIO()
     GetClipboardTextFn = GetClipboardTextFn_DefaultImpl;   // Platform dependent default implementations
     SetClipboardTextFn = SetClipboardTextFn_DefaultImpl;
     ClipboardUserData = NULL;
-    ImeSetInputScreenPosFn = ImeSetInputScreenPosFn_DefaultImpl;
-    ImeWindowHandle = NULL;
 
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
     RenderDrawListsFn = NULL;
@@ -2544,6 +2581,8 @@ const char* ImGui::GetStyleColorName(ImGuiCol idx)
     case ImGuiCol_TabActive: return "TabActive";
     case ImGuiCol_TabUnfocused: return "TabUnfocused";
     case ImGuiCol_TabUnfocusedActive: return "TabUnfocusedActive";
+    case ImGuiCol_DockingPreview: return "DockingPreview";
+    case ImGuiCol_DockingEmptyBg: return "DockingEmptyBg";
     case ImGuiCol_PlotLines: return "PlotLines";
     case ImGuiCol_PlotLinesHovered: return "PlotLinesHovered";
     case ImGuiCol_PlotHistogram: return "PlotHistogram";
@@ -2559,6 +2598,7 @@ const char* ImGui::GetStyleColorName(ImGuiCol idx)
     return "Unknown";
 }
 
+
 //-----------------------------------------------------------------------------
 // [SECTION] RENDER HELPERS
 // Some of those (internal) functions are currently quite a legacy mess - their signature and behavior will change,
@@ -2816,7 +2856,11 @@ ImGuiWindow::ImGuiWindow(ImGuiContext* context, const char* name)
     Name = ImStrdup(name);
     ID = ImHashStr(name);
     IDStack.push_back(ID);
-    Flags = ImGuiWindowFlags_None;
+    Flags = FlagsPreviousFrame = ImGuiWindowFlags_None;
+    Viewport = NULL;
+    ViewportId = 0;
+    ViewportAllowPlatformMonitorExtend = -1;
+    ViewportPos = ImVec2(FLT_MAX, FLT_MAX);
     Pos = ImVec2(0.0f, 0.0f);
     Size = SizeFull = ImVec2(0.0f, 0.0f);
     ContentSize = ContentSizeExplicit = ImVec2(0.0f, 0.0f);
@@ -2831,6 +2875,7 @@ ImGuiWindow::ImGuiWindow(ImGuiContext* context, const char* name)
     ScrollTargetCenterRatio = ImVec2(0.5f, 0.5f);
     ScrollbarSizes = ImVec2(0.0f, 0.0f);
     ScrollbarX = ScrollbarY = false;
+    ViewportOwned = false;
     Active = WasActive = false;
     WriteAccessed = false;
     Collapsed = false;
@@ -2850,21 +2895,23 @@ ImGuiWindow::ImGuiWindow(ImGuiContext* context, const char* name)
     AutoFitOnlyGrows = false;
     AutoPosLastDirection = ImGuiDir_None;
     HiddenFramesCanSkipItems = HiddenFramesCannotSkipItems = 0;
-    SetWindowPosAllowFlags = SetWindowSizeAllowFlags = SetWindowCollapsedAllowFlags = ImGuiCond_Always | ImGuiCond_Once | ImGuiCond_FirstUseEver | ImGuiCond_Appearing;
+    SetWindowPosAllowFlags = SetWindowSizeAllowFlags = SetWindowCollapsedAllowFlags = SetWindowDockAllowFlags = ImGuiCond_Always | ImGuiCond_Once | ImGuiCond_FirstUseEver | ImGuiCond_Appearing;
     SetWindowPosVal = SetWindowPosPivot = ImVec2(FLT_MAX, FLT_MAX);
 
     InnerRect = ImRect(0.0f, 0.0f, 0.0f, 0.0f); // Clear so the InnerRect.GetSize() code in Begin() doesn't lead to overflow even if the result isn't used.
 
     LastFrameActive = -1;
+    LastFrameJustFocused = -1;
     LastTimeActive = -1.0f;
     ItemWidthDefault = 0.0f;
-    FontWindowScale = 1.0f;
+    FontWindowScale = FontDpiScale = 1.0f;
     SettingsOffset = -1;
 
     DrawList = &DrawListInst;
     DrawList->_OwnerName = Name;
     ParentWindow = NULL;
     RootWindow = NULL;
+    RootWindowDockStop = NULL;
     RootWindowForTitleBarHighlight = NULL;
     RootWindowForNav = NULL;
 
@@ -2874,6 +2921,12 @@ ImGuiWindow::ImGuiWindow(ImGuiContext* context, const char* name)
 
     MemoryCompacted = false;
     MemoryDrawListIdxCapacity = MemoryDrawListVtxCapacity = 0;
+
+    DockNode = DockNodeAsHost = NULL;
+    DockId = 0;
+    DockTabItemStatusFlags = ImGuiItemStatusFlags_None;
+    DockOrder = -1;
+    DockIsActive = DockTabIsVisible = DockTabWantClose = false;
 }
 
 ImGuiWindow::~ImGuiWindow()
@@ -2889,6 +2942,10 @@ ImGuiID ImGuiWindow::GetID(const char* str, const char* str_end)
     ImGuiID seed = IDStack.back();
     ImGuiID id = ImHashStr(str, str_end ? (str_end - str) : 0, seed);
     ImGui::KeepAliveID(id);
+#ifdef IMGUI_ENABLE_TEST_ENGINE
+    ImGuiContext& g = *GImGui;
+    IMGUI_TEST_ENGINE_ID_INFO2(id, ImGuiDataType_String, str, str_end);
+#endif
     return id;
 }
 
@@ -2897,6 +2954,10 @@ ImGuiID ImGuiWindow::GetID(const void* ptr)
     ImGuiID seed = IDStack.back();
     ImGuiID id = ImHashData(&ptr, sizeof(void*), seed);
     ImGui::KeepAliveID(id);
+#ifdef IMGUI_ENABLE_TEST_ENGINE
+    ImGuiContext& g = *GImGui;
+    IMGUI_TEST_ENGINE_ID_INFO(id, ImGuiDataType_Pointer, ptr);
+#endif
     return id;
 }
 
@@ -2905,25 +2966,44 @@ ImGuiID ImGuiWindow::GetID(int n)
     ImGuiID seed = IDStack.back();
     ImGuiID id = ImHashData(&n, sizeof(n), seed);
     ImGui::KeepAliveID(id);
+#ifdef IMGUI_ENABLE_TEST_ENGINE
+    ImGuiContext& g = *GImGui;
+    IMGUI_TEST_ENGINE_ID_INFO(id, ImGuiDataType_S32, (intptr_t)n);
+#endif
     return id;
 }
 
 ImGuiID ImGuiWindow::GetIDNoKeepAlive(const char* str, const char* str_end)
 {
     ImGuiID seed = IDStack.back();
-    return ImHashStr(str, str_end ? (str_end - str) : 0, seed);
+    ImGuiID id = ImHashStr(str, str_end ? (str_end - str) : 0, seed);
+#ifdef IMGUI_ENABLE_TEST_ENGINE
+    ImGuiContext& g = *GImGui;
+    IMGUI_TEST_ENGINE_ID_INFO2(id, ImGuiDataType_String, str, str_end);
+#endif
+    return id;
 }
 
 ImGuiID ImGuiWindow::GetIDNoKeepAlive(const void* ptr)
 {
     ImGuiID seed = IDStack.back();
-    return ImHashData(&ptr, sizeof(void*), seed);
+    ImGuiID id = ImHashData(&ptr, sizeof(void*), seed);
+#ifdef IMGUI_ENABLE_TEST_ENGINE
+    ImGuiContext& g = *GImGui;
+    IMGUI_TEST_ENGINE_ID_INFO(id, ImGuiDataType_Pointer, ptr);
+#endif
+    return id;
 }
 
 ImGuiID ImGuiWindow::GetIDNoKeepAlive(int n)
 {
     ImGuiID seed = IDStack.back();
-    return ImHashData(&n, sizeof(n), seed);
+    ImGuiID id = ImHashData(&n, sizeof(n), seed);
+#ifdef IMGUI_ENABLE_TEST_ENGINE
+    ImGuiContext& g = *GImGui;
+    IMGUI_TEST_ENGINE_ID_INFO(id, ImGuiDataType_S32, (intptr_t)n);
+#endif
+    return id;
 }
 
 // This is only used in rare/specific situations to manufacture an ID out of nowhere.
@@ -3064,6 +3144,12 @@ static inline bool IsWindowContentHoverable(ImGuiWindow* window, ImGuiHoveredFla
                 if ((focused_root_window->Flags & ImGuiWindowFlags_Popup) && !(flags & ImGuiHoveredFlags_AllowWhenBlockedByPopup))
                     return false;
             }
+
+    // Filter by viewport
+    if (window->Viewport != g.MouseViewport)
+        if (g.MovingWindow == NULL || window->RootWindow != g.MovingWindow->RootWindow)
+            return false;
+
     return true;
 }
 
@@ -3106,7 +3192,7 @@ bool ImGui::IsItemHovered(ImGuiHoveredFlags flags)
 
     // Special handling for the dummy item after Begin() which represent the title bar or tab.
     // When the window is collapsed (SkipItems==true) that last item will never be overwritten so we need to detect the case.
-    if (window->DC.LastItemId == window->MoveId && window->WriteAccessed)
+    if ((window->DC.LastItemId == window->ID || window->DC.LastItemId == window->MoveId) && window->WriteAccessed)
         return false;
     return true;
 }
@@ -3297,11 +3383,17 @@ ImGuiIO& ImGui::GetIO()
     return GImGui->IO;
 }
 
+ImGuiPlatformIO& ImGui::GetPlatformIO()
+{
+    IM_ASSERT(GImGui != NULL && "No current context. Did you call ImGui::CreateContext() or ImGui::SetCurrentContext()?");
+    return GImGui->PlatformIO;
+}
+
 // Same value as passed to the old io.RenderDrawListsFn function. Valid after Render() and until the next call to NewFrame()
 ImDrawData* ImGui::GetDrawData()
 {
     ImGuiContext& g = *GImGui;
-    return g.DrawData.Valid ? &g.DrawData : NULL;
+    return g.Viewports[0]->DrawDataP.Valid ? &g.Viewports[0]->DrawDataP : NULL;
 }
 
 double ImGui::GetTime()
@@ -3314,14 +3406,50 @@ int ImGui::GetFrameCount()
     return GImGui->FrameCount;
 }
 
+static ImDrawList* GetViewportDrawList(ImGuiViewportP* viewport, size_t drawlist_no, const char* drawlist_name)
+{
+    // Create the draw list on demand, because they are not frequently used for all viewports
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(drawlist_no < IM_ARRAYSIZE(viewport->DrawLists));
+    ImDrawList* draw_list = viewport->DrawLists[drawlist_no];
+    if (draw_list == NULL)
+    {
+        draw_list = IM_NEW(ImDrawList)(&g.DrawListSharedData);
+        draw_list->_OwnerName = drawlist_name;
+        viewport->DrawLists[drawlist_no] = draw_list;
+    }
+
+    // Our ImDrawList system requires that there is always a command
+    if (viewport->LastFrameDrawLists[drawlist_no] != g.FrameCount)
+    {
+        draw_list->Clear();
+        draw_list->PushTextureID(g.IO.Fonts->TexID);
+        draw_list->PushClipRect(viewport->Pos, viewport->Pos + viewport->Size, false);
+        viewport->LastFrameDrawLists[drawlist_no] = g.FrameCount;
+    }
+    return draw_list;
+}
+
+ImDrawList* ImGui::GetBackgroundDrawList(ImGuiViewport* viewport)
+{
+    return GetViewportDrawList((ImGuiViewportP*)viewport, 0, "##Background");
+}
+
 ImDrawList* ImGui::GetBackgroundDrawList()
 {
-    return &GImGui->BackgroundDrawList;
+    ImGuiWindow* window = GImGui->CurrentWindow;
+    return GetBackgroundDrawList(window->Viewport);
+}
+
+ImDrawList* ImGui::GetForegroundDrawList(ImGuiViewport* viewport)
+{
+    return GetViewportDrawList((ImGuiViewportP*)viewport, 1, "##Foreground");
 }
 
 ImDrawList* ImGui::GetForegroundDrawList()
 {
-    return &GImGui->ForegroundDrawList;
+    ImGuiWindow* window = GImGui->CurrentWindow;
+    return GetForegroundDrawList(window->Viewport);
 }
 
 ImDrawListSharedData* ImGui::GetDrawListSharedData()
@@ -3343,10 +3471,45 @@ void ImGui::StartMouseMovingWindow(ImGuiWindow* window)
     bool can_move_window = true;
     if ((window->Flags & ImGuiWindowFlags_NoMove) || (window->RootWindow->Flags & ImGuiWindowFlags_NoMove))
         can_move_window = false;
+    if (ImGuiDockNode* node = window->DockNodeAsHost)
+        if (node->VisibleWindow && (node->VisibleWindow->Flags & ImGuiWindowFlags_NoMove))
+            can_move_window = false;
     if (can_move_window)
         g.MovingWindow = window;
 }
 
+// We use 'undock_floating_node == false' when dragging from title bar to allow moving groups of floating nodes without undocking them.
+// - undock_floating_node == true: when dragging from a floating node within a hierarchy, always undock the node.
+// - undock_floating_node == false: when dragging from a floating node within a hierarchy, move root window.
+void ImGui::StartMouseMovingWindowOrNode(ImGuiWindow* window, ImGuiDockNode* node, bool undock_floating_node)
+{
+    ImGuiContext& g = *GImGui;
+    bool can_undock_node = false;
+    if (node != NULL && node->VisibleWindow && (node->VisibleWindow->Flags & ImGuiWindowFlags_NoMove) == 0)
+    {
+        // Can undock if:
+        // - part of a floating node hierarchy with more than one visible node (if only one is visible, we'll just move the whole hierarchy)
+        // - part of a dockspace node hierarchy (trivia: undocking from a fixed/central node will create a new node and copy windows)
+        ImGuiDockNode* root_node = DockNodeGetRootNode(node);
+        if (root_node->OnlyNodeWithWindows != node || root_node->CentralNode != NULL)   // -V1051 PVS-Studio thinks node should be root_node and is wrong about that.
+            if (undock_floating_node || root_node->IsDockSpace())
+                can_undock_node = true;
+    }
+
+    const bool clicked = IsMouseClicked(0);
+    const bool dragging = IsMouseDragging(0, g.IO.MouseDragThreshold * 1.70f);
+    if (can_undock_node && dragging)
+    {
+        DockContextQueueUndockNode(&g, node);
+        g.ActiveIdClickOffset = g.IO.MouseClickedPos[0] - node->Pos;
+    }
+    else if (!can_undock_node && (clicked || dragging) && g.MovingWindow != window)
+    {
+        StartMouseMovingWindow(window);
+        g.ActiveIdClickOffset = g.IO.MouseClickedPos[0] - window->RootWindow->Pos;
+    }
+}
+
 // Handle mouse moving window
 // Note: moving window with the navigation keys (Square + d-pad / CTRL+TAB + Arrows) are processed in NavUpdateWindowing()
 // FIXME: We don't have strong guarantee that g.MovingWindow stay synched with g.ActiveId == g.MovingWindow->MoveId.
@@ -3369,11 +3532,25 @@ void ImGui::UpdateMouseMovingWindowNewFrame()
             {
                 MarkIniSettingsDirty(moving_window);
                 SetWindowPos(moving_window, pos, ImGuiCond_Always);
+                if (moving_window->ViewportOwned) // Synchronize viewport immediately because some overlays may relies on clipping rectangle before we Begin() into the window.
+                    moving_window->Viewport->Pos = pos;
             }
             FocusWindow(g.MovingWindow);
         }
         else
         {
+            // Try to merge the window back into the main viewport.
+            // This works because MouseViewport should be != MovingWindow->Viewport on release (as per code in UpdateViewports)
+            if (g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable)
+                UpdateTryMergeWindowIntoHostViewport(moving_window, g.MouseViewport);
+
+            // Restore the mouse viewport so that we don't hover the viewport _under_ the moved window during the frame we released the mouse button.
+            if (!IsDragDropPayloadBeingAccepted())
+                g.MouseViewport = moving_window->Viewport;
+
+            // Clear the NoInput window flag set by the Viewport system
+            moving_window->Viewport->Flags &= ~ImGuiViewportFlags_NoInputs;
+
             ClearActiveID();
             g.MovingWindow = NULL;
         }
@@ -3402,15 +3579,18 @@ void ImGui::UpdateMouseMovingWindowEndFrame()
     if (g.NavWindow && g.NavWindow->Appearing)
         return;
 
-    // Click to focus window and start moving (after we're done with all our widgets)
+    // Click on void to focus window and start moving
+    // (after we're done with all our widgets, so e.g. clicking on docking tab-bar which have set HoveredId already and not get us here!)
     if (g.IO.MouseClicked[0])
     {
-        if (g.HoveredRootWindow != NULL)
+        ImGuiWindow* root_window = g.HoveredWindow ? g.HoveredWindow->RootWindowDockStop : NULL;
+        if (root_window != NULL)
         {
             StartMouseMovingWindow(g.HoveredWindow);
-            if (g.IO.ConfigWindowsMoveFromTitleBarOnly && !(g.HoveredRootWindow->Flags & ImGuiWindowFlags_NoTitleBar))
-                if (!g.HoveredRootWindow->TitleBarRect().Contains(g.IO.MouseClickedPos[0]))
-                    g.MovingWindow = NULL;
+            if (g.IO.ConfigWindowsMoveFromTitleBarOnly)
+                if (!(root_window->Flags & ImGuiWindowFlags_NoTitleBar) || root_window->DockIsActive)
+                    if (!root_window->TitleBarRect().Contains(g.IO.MouseClickedPos[0]))
+                        g.MovingWindow = NULL;
         }
         else if (g.NavWindow != NULL && GetTopMostPopupModal() == NULL)
         {
@@ -3442,6 +3622,28 @@ void ImGui::UpdateMouseMovingWindowEndFrame()
     }
 }
 
+static void TranslateWindow(ImGuiWindow* window, const ImVec2& delta)
+{
+    window->Pos += delta;
+    window->ClipRect.Translate(delta);
+    window->OuterRectClipped.Translate(delta);
+    window->InnerRect.Translate(delta);
+    window->DC.CursorPos += delta;
+    window->DC.CursorStartPos += delta;
+    window->DC.CursorMaxPos += delta;
+    window->DC.LastItemRect.Translate(delta);
+    window->DC.LastItemDisplayRect.Translate(delta);
+}
+
+static void ScaleWindow(ImGuiWindow* window, float scale)
+{
+    ImVec2 origin = window->Viewport->Pos;
+    window->Pos = ImFloor((window->Pos - origin) * scale + origin);
+    window->Size = ImFloor(window->Size * scale);
+    window->SizeFull = ImFloor(window->SizeFull * scale);
+    window->ContentSize = ImFloor(window->ContentSize * scale);
+}
+
 static bool IsWindowActiveAndVisible(ImGuiWindow* window)
 {
     return (window->Active) && (!window->Hidden);
@@ -3636,16 +3838,17 @@ void ImGui::UpdateHoveredWindowAndCaptureFlags()
     // - When moving a window we can skip the search, which also conveniently bypasses the fact that window->WindowRectClipped is lagging as this point of the frame.
     // - We also support the moved window toggling the NoInputs flag after moving has started in order to be able to detect windows below it, which is useful for e.g. docking mechanisms.
     FindHoveredWindow();
+    IM_ASSERT(g.HoveredWindow == NULL || g.HoveredWindow == g.MovingWindow || g.HoveredWindow->Viewport == g.MouseViewport);
 
     // Modal windows prevents cursor from hovering behind them.
     ImGuiWindow* modal_window = GetTopMostPopupModal();
     if (modal_window)
         if (g.HoveredRootWindow && !IsWindowChildOf(g.HoveredRootWindow, modal_window))
-            g.HoveredRootWindow = g.HoveredWindow = NULL;
+            g.HoveredWindow = g.HoveredRootWindow = g.HoveredWindowUnderMovingWindow = NULL;
 
     // Disabled mouse?
     if (g.IO.ConfigFlags & ImGuiConfigFlags_NoMouse)
-        g.HoveredWindow = g.HoveredRootWindow = NULL;
+        g.HoveredWindow = g.HoveredRootWindow = g.HoveredWindowUnderMovingWindow = NULL;
 
     // We track click ownership. When clicked outside of a window the click is owned by the application and won't report hovering nor request capture even while dragging over our windows afterward.
     int mouse_earliest_button_down = -1;
@@ -3665,7 +3868,7 @@ void ImGui::UpdateHoveredWindowAndCaptureFlags()
     // FIXME: For patterns of drag and drop across OS windows, we may need to rework/remove this test (first committed 311c0ca9 on 2015/02)
     const bool mouse_dragging_extern_payload = g.DragDropActive && (g.DragDropSourceFlags & ImGuiDragDropFlags_SourceExtern) != 0;
     if (!mouse_avail_to_imgui && !mouse_dragging_extern_payload)
-        g.HoveredWindow = g.HoveredRootWindow = NULL;
+        g.HoveredWindow = g.HoveredRootWindow = g.HoveredWindowUnderMovingWindow = NULL;
 
     // Update io.WantCaptureMouse for the user application (true = dispatch mouse info to imgui, false = dispatch mouse info to Dear ImGui + app)
     if (g.WantCaptureMouseNextFrame != -1)
@@ -3706,7 +3909,9 @@ void ImGui::NewFrame()
 #endif
 
     // Check and assert for various common IO and Configuration mistakes
+    g.ConfigFlagsLastFrame = g.ConfigFlagsCurrFrame;
     ErrorCheckNewFrameSanityChecks();
+    g.ConfigFlagsCurrFrame = g.IO.ConfigFlags;
 
     // Load settings on first frame, save settings when modified (after a delay)
     UpdateSettings();
@@ -3724,11 +3929,17 @@ void ImGui::NewFrame()
     g.FramerateSecPerFrameIdx = (g.FramerateSecPerFrameIdx + 1) % IM_ARRAYSIZE(g.FramerateSecPerFrame);
     g.IO.Framerate = (g.FramerateSecPerFrameAccum > 0.0f) ? (1.0f / (g.FramerateSecPerFrameAccum / (float)IM_ARRAYSIZE(g.FramerateSecPerFrame))) : FLT_MAX;
 
+    UpdateViewportsNewFrame();
+
     // Setup current font and draw list shared data
+    // FIXME-VIEWPORT: the concept of a single ClipRectFullscreen is not ideal!
     g.IO.Fonts->Locked = true;
     SetCurrentFont(GetDefaultFont());
     IM_ASSERT(g.Font->IsLoaded());
-    g.DrawListSharedData.ClipRectFullscreen = ImVec4(0.0f, 0.0f, g.IO.DisplaySize.x, g.IO.DisplaySize.y);
+    ImRect virtual_space(FLT_MAX, FLT_MAX, -FLT_MAX, -FLT_MAX);
+    for (int n = 0; n < g.Viewports.Size; n++)
+        virtual_space.Add(g.Viewports[n]->GetMainRect());
+    g.DrawListSharedData.ClipRectFullscreen = ImVec4(virtual_space.Min.x, virtual_space.Min.y, virtual_space.Max.x, virtual_space.Max.y);
     g.DrawListSharedData.CurveTessellationTol = g.Style.CurveTessellationTol;
     g.DrawListSharedData.SetCircleSegmentMaxError(g.Style.CircleSegmentMaxError);
     g.DrawListSharedData.InitialFlags = ImDrawListFlags_None;
@@ -3739,16 +3950,13 @@ void ImGui::NewFrame()
     if (g.IO.BackendFlags & ImGuiBackendFlags_RendererHasVtxOffset)
         g.DrawListSharedData.InitialFlags |= ImDrawListFlags_AllowVtxOffset;
 
-    g.BackgroundDrawList.Clear();
-    g.BackgroundDrawList.PushTextureID(g.IO.Fonts->TexID);
-    g.BackgroundDrawList.PushClipRectFullScreen();
-
-    g.ForegroundDrawList.Clear();
-    g.ForegroundDrawList.PushTextureID(g.IO.Fonts->TexID);
-    g.ForegroundDrawList.PushClipRectFullScreen();
-
     // Mark rendering data as invalid to prevent user who may have a handle on it to use it.
-    g.DrawData.Clear();
+    for (int n = 0; n < g.Viewports.Size; n++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[n];
+        viewport->DrawData = NULL;
+        viewport->DrawDataP.Clear();
+    }
 
     // Drag and drop keep the source ID alive so even if the source disappear our state is consistent
     if (g.DragDropActive && g.DragDropPayload.SourceId == g.ActiveId)
@@ -3795,6 +4003,7 @@ void ImGui::NewFrame()
     g.DragDropAcceptIdCurrRectSurface = FLT_MAX;
     g.DragDropWithinSource = false;
     g.DragDropWithinTarget = false;
+    g.DragDropHoldJustPressedId = 0;
 
     // Update keyboard input state
     // Synchronize io.KeyMods with individual modifiers io.KeyXXX bools
@@ -3809,6 +4018,10 @@ void ImGui::NewFrame()
     // Update mouse input state
     UpdateMouseInputs();
 
+    // Undocking
+    // (needs to be before UpdateMouseMovingWindowNewFrame so the window is already offset and following the mouse on the detaching frame)
+    DockContextUpdateUndocking(&g);
+
     // Find hovered window
     // (needs to be before UpdateMouseMovingWindowNewFrame so we fill g.HoveredWindowUnderMovingWindow on the mouse release frame)
     UpdateHoveredWindowAndCaptureFlags();
@@ -3825,6 +4038,7 @@ void ImGui::NewFrame()
     g.MouseCursor = ImGuiMouseCursor_Arrow;
     g.WantCaptureMouseNextFrame = g.WantCaptureKeyboardNextFrame = g.WantTextInputNextFrame = -1;
     g.PlatformImePos = ImVec2(1.0f, 1.0f); // OS Input Method Editor showing on top-left of our window by default
+    g.PlatformImePosViewport = NULL;
 
     // Mouse wheel scrolling, scale
     UpdateMouseWheel();
@@ -3858,6 +4072,9 @@ void ImGui::NewFrame()
     g.BeginPopupStack.resize(0);
     ClosePopupsOverWindow(g.NavWindow, false);
 
+    // Docking
+    DockContextUpdateDocking(&g);
+
     // [DEBUG] Item picker tool - start with DebugStartItemPicker() - useful to visually select an item and break into its call-stack.
     UpdateDebugToolItemPicker();
 
@@ -3929,6 +4146,18 @@ void ImGui::Initialize(ImGuiContext* context)
 #endif // #ifdef IMGUI_HAS_TABLE
 
 #ifdef IMGUI_HAS_DOCK
+    // Create default viewport
+    ImGuiViewportP* viewport = IM_NEW(ImGuiViewportP)();
+    viewport->ID = IMGUI_VIEWPORT_DEFAULT_ID;
+    viewport->Idx = 0;
+    viewport->PlatformWindowCreated = true;
+    g.Viewports.push_back(viewport);
+    g.PlatformIO.MainViewport = g.Viewports[0]; // Make it accessible in public-facing GetPlatformIO() immediately (before the first call to EndFrame)
+    g.PlatformIO.Viewports.push_back(g.Viewports[0]);
+
+    // Extensions
+    IM_ASSERT(g.DockContext == NULL);
+    DockContextInitialize(&g);
 #endif // #ifdef IMGUI_HAS_DOCK
 
     g.Initialized = true;
@@ -3959,6 +4188,16 @@ void ImGui::Shutdown(ImGuiContext* context)
         SetCurrentContext(backup_context);
     }
 
+    // Destroy platform windows
+    ImGuiContext* backup_context = ImGui::GetCurrentContext();
+    SetCurrentContext(context);
+    DestroyPlatformWindows();
+    SetCurrentContext(backup_context);
+
+    // Shutdown extensions
+    IM_ASSERT(g.DockContext != NULL);
+    DockContextShutdown(&g);
+
     // Clear everything else
     for (int i = 0; i < g.Windows.Size; i++)
         IM_DELETE(g.Windows[i]);
@@ -3969,7 +4208,7 @@ void ImGui::Shutdown(ImGuiContext* context)
     g.CurrentWindowStack.clear();
     g.WindowsById.Clear();
     g.NavWindow = NULL;
-    g.HoveredWindow = g.HoveredRootWindow = NULL;
+    g.HoveredWindow = g.HoveredRootWindow = g.HoveredWindowUnderMovingWindow = NULL;
     g.ActiveIdWindow = g.ActiveIdPreviousFrameWindow = NULL;
     g.MovingWindow = NULL;
     g.ColorModifiers.clear();
@@ -3977,9 +4216,11 @@ void ImGui::Shutdown(ImGuiContext* context)
     g.FontStack.clear();
     g.OpenPopupStack.clear();
     g.BeginPopupStack.clear();
-    g.DrawDataBuilder.ClearFreeMemory();
-    g.BackgroundDrawList.ClearFreeMemory();
-    g.ForegroundDrawList.ClearFreeMemory();
+
+    g.CurrentViewport = g.MouseViewport = g.MouseLastHoveredViewport = NULL;
+    for (int i = 0; i < g.Viewports.Size; i++)
+        IM_DELETE(g.Viewports[i]);
+    g.Viewports.clear();
 
     g.TabBars.Clear();
     g.CurrentTabBarStack.clear();
@@ -4076,25 +4317,24 @@ static void AddDrawListToDrawData(ImVector<ImDrawList*>* out_list, ImDrawList* d
     out_list->push_back(draw_list);
 }
 
-static void AddWindowToDrawData(ImVector<ImDrawList*>* out_render_list, ImGuiWindow* window)
+static void AddWindowToDrawData(ImGuiWindow* window, int layer)
 {
     ImGuiContext& g = *GImGui;
     g.IO.MetricsRenderWindows++;
-    AddDrawListToDrawData(out_render_list, window->DrawList);
+    AddDrawListToDrawData(&window->Viewport->DrawDataBuilder.Layers[layer], window->DrawList);
     for (int i = 0; i < window->DC.ChildWindows.Size; i++)
     {
         ImGuiWindow* child = window->DC.ChildWindows[i];
-        if (IsWindowActiveAndVisible(child)) // clipped children may have been marked not active
-            AddWindowToDrawData(out_render_list, child);
+        if (IsWindowActiveAndVisible(child)) // Clipped children may have been marked not active
+            AddWindowToDrawData(child, layer);
     }
 }
 
 // Layer is locked for the root window, however child windows may use a different viewport (e.g. extruding menu)
 static void AddRootWindowToDrawData(ImGuiWindow* window)
 {
-    ImGuiContext& g = *GImGui;
     int layer = (window->Flags & ImGuiWindowFlags_Tooltip) ? 1 : 0;
-    AddWindowToDrawData(&g.DrawDataBuilder.Layers[layer], window);
+    AddWindowToDrawData(window, layer);
 }
 
 void ImDrawDataBuilder::FlattenIntoSingleLayer()
@@ -4115,16 +4355,18 @@ void ImDrawDataBuilder::FlattenIntoSingleLayer()
     }
 }
 
-static void SetupDrawData(ImVector<ImDrawList*>* draw_lists, ImDrawData* draw_data)
+static void SetupViewportDrawData(ImGuiViewportP* viewport, ImVector<ImDrawList*>* draw_lists)
 {
-    ImGuiIO& io = ImGui::GetIO();
+    ImDrawData* draw_data = &viewport->DrawDataP;
+    viewport->DrawData = draw_data; // Make publicly accessible
     draw_data->Valid = true;
     draw_data->CmdLists = (draw_lists->Size > 0) ? draw_lists->Data : NULL;
     draw_data->CmdListsCount = draw_lists->Size;
     draw_data->TotalVtxCount = draw_data->TotalIdxCount = 0;
-    draw_data->DisplayPos = ImVec2(0.0f, 0.0f);
-    draw_data->DisplaySize = io.DisplaySize;
-    draw_data->FramebufferScale = io.DisplayFramebufferScale;
+    draw_data->DisplayPos = viewport->Pos;
+    draw_data->DisplaySize = viewport->Size;
+    draw_data->FramebufferScale = ImGui::GetIO().DisplayFramebufferScale; // FIXME-VIEWPORT: This may vary on a per-monitor/viewport basis?
+    draw_data->OwnerViewport = viewport;
     for (int n = 0; n < draw_lists->Size; n++)
     {
         draw_data->TotalVtxCount += draw_lists->Data[n]->VtxBuffer.Size;
@@ -4147,6 +4389,64 @@ void ImGui::PopClipRect()
     window->ClipRect = window->DrawList->_ClipRectStack.back();
 }
 
+static ImGuiWindow* FindFrontMostVisibleChildWindow(ImGuiWindow* window)
+{
+    for (int n = window->DC.ChildWindows.Size - 1; n >= 0; n--)
+        if (IsWindowActiveAndVisible(window->DC.ChildWindows[n]))
+            return FindFrontMostVisibleChildWindow(window->DC.ChildWindows[n]);
+    return window;
+}
+
+static void ImGui::EndFrameDrawDimmedBackgrounds()
+{
+    ImGuiContext& g = *GImGui;
+
+    // Draw modal whitening background on _other_ viewports than the one the modal is one
+    ImGuiWindow* modal_window = GetTopMostPopupModal();
+    const bool dim_bg_for_modal = (modal_window != NULL);
+    const bool dim_bg_for_window_list = (g.NavWindowingTargetAnim != NULL);
+    if (dim_bg_for_modal || dim_bg_for_window_list)
+        for (int viewport_n = 0; viewport_n < g.Viewports.Size; viewport_n++)
+        {
+            ImGuiViewportP* viewport = g.Viewports[viewport_n];
+            if (modal_window && viewport == modal_window->Viewport)
+                continue;
+            if (g.NavWindowingList && viewport == g.NavWindowingList->Viewport)
+                continue;
+            if (g.NavWindowingTargetAnim && viewport == g.NavWindowingTargetAnim->Viewport)
+                continue;
+            ImDrawList* draw_list = GetForegroundDrawList(viewport);
+            const ImU32 dim_bg_col = GetColorU32(dim_bg_for_modal ? ImGuiCol_ModalWindowDimBg : ImGuiCol_NavWindowingDimBg, g.DimBgRatio);
+            draw_list->AddRectFilled(viewport->Pos, viewport->Pos + viewport->Size, dim_bg_col);
+        }
+
+    // Draw modal whitening background between CTRL-TAB list
+    if (dim_bg_for_window_list)
+    {
+        // Choose a draw list that will be front-most across all our children
+        ImGuiWindow* window = g.NavWindowingTargetAnim;
+        ImDrawList* draw_list = FindFrontMostVisibleChildWindow(window->RootWindow)->DrawList;
+        draw_list->PushClipRectFullScreen();
+
+        // Docking: draw modal whitening background on other nodes of a same dock tree
+        if (window->RootWindowDockStop->DockIsActive)
+            if (window->RootWindow != window->RootWindowDockStop)
+                RenderRectFilledWithHole(draw_list, window->RootWindow->Rect(), window->RootWindowDockStop->Rect(), GetColorU32(ImGuiCol_NavWindowingDimBg, g.DimBgRatio), g.Style.WindowRounding);
+
+        // Draw navigation selection/windowing rectangle border
+        float rounding = ImMax(window->WindowRounding, g.Style.WindowRounding);
+        ImRect bb = window->Rect();
+        bb.Expand(g.FontSize);
+        if (bb.Contains(window->Viewport->GetMainRect())) // If a window fits the entire viewport, adjust its highlight inward
+        {
+            bb.Expand(-g.FontSize - 1.0f);
+            rounding = window->WindowRounding;
+        }
+        draw_list->AddRect(bb.Min, bb.Max, GetColorU32(ImGuiCol_NavWindowingHighlight, g.NavWindowingHighlightAlpha), rounding, ~0, 3.0f);
+        draw_list->PopClipRect();
+    }
+}
+
 // This is normally called by Render(). You may want to call it directly if you want to avoid calling Render() but the gain will be very minimal.
 void ImGui::EndFrame()
 {
@@ -4161,11 +4461,13 @@ void ImGui::EndFrame()
     ErrorCheckEndFrameSanityChecks();
 
     // Notify OS when our Input Method Editor cursor has moved (e.g. CJK inputs using Microsoft IME)
-    if (g.IO.ImeSetInputScreenPosFn && (g.PlatformImeLastPos.x == FLT_MAX || ImLengthSqr(g.PlatformImeLastPos - g.PlatformImePos) > 0.0001f))
-    {
-        g.IO.ImeSetInputScreenPosFn((int)g.PlatformImePos.x, (int)g.PlatformImePos.y);
-        g.PlatformImeLastPos = g.PlatformImePos;
-    }
+    if (g.PlatformIO.Platform_SetImeInputPos && (g.PlatformImeLastPos.x == FLT_MAX || ImLengthSqr(g.PlatformImePos - g.PlatformImeLastPos) > 0.0001f))
+        if (g.PlatformImePosViewport && g.PlatformImePosViewport->PlatformWindowCreated)
+        {
+            g.PlatformIO.Platform_SetImeInputPos(g.PlatformImePosViewport, g.PlatformImePos);
+            g.PlatformImeLastPos = g.PlatformImePos;
+            g.PlatformImePosViewport = NULL;
+        }
 
     // Hide implicit/fallback "Debug" window if it hasn't been used
     g.WithinFrameScopeWithImplicitWindow = false;
@@ -4173,10 +4475,15 @@ void ImGui::EndFrame()
         g.CurrentWindow->Active = false;
     End();
 
+    // Draw modal whitening background on _other_ viewports than the one the modal is one
+    EndFrameDrawDimmedBackgrounds();
+
     // Show CTRL+TAB list window
     if (g.NavWindowingTarget != NULL)
         NavUpdateWindowingOverlay();
 
+    SetCurrentViewport(NULL, NULL);
+
     // Drag and Drop: Elapse payload (if delivered, or if source stops being submitted)
     if (g.DragDropActive)
     {
@@ -4201,6 +4508,9 @@ void ImGui::EndFrame()
     // Initiate moving window + handle left-click and right-click focus
     UpdateMouseMovingWindowEndFrame();
 
+    // Update user-facing viewport list (g.Viewports -> g.PlatformIO.Viewports after filtering out some)
+    UpdateViewportsEndFrame();
+
     // Sort the window list so that all child windows are after their parent
     // We cannot do that on FocusWindow() because childs may not exist yet
     g.WindowsTempSortBuffer.resize(0);
@@ -4236,11 +4546,15 @@ void ImGui::Render()
         EndFrame();
     g.FrameCountRendered = g.FrameCount;
     g.IO.MetricsRenderWindows = 0;
-    g.DrawDataBuilder.Clear();
 
-    // Add background ImDrawList
-    if (!g.BackgroundDrawList.VtxBuffer.empty())
-        AddDrawListToDrawData(&g.DrawDataBuilder.Layers[0], &g.BackgroundDrawList);
+    // Add background ImDrawList (for each active viewport)
+    for (int n = 0; n != g.Viewports.Size; n++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[n];
+        viewport->DrawDataBuilder.Clear();
+        if (viewport->DrawLists[0] != NULL)
+            AddDrawListToDrawData(&viewport->DrawDataBuilder.Layers[0], GetBackgroundDrawList(viewport));
+    }
 
     // Add ImDrawList to render
     ImGuiWindow* windows_to_render_top_most[2];
@@ -4255,25 +4569,40 @@ void ImGui::Render()
     for (int n = 0; n < IM_ARRAYSIZE(windows_to_render_top_most); n++)
         if (windows_to_render_top_most[n] && IsWindowActiveAndVisible(windows_to_render_top_most[n])) // NavWindowingTarget is always temporarily displayed as the top-most window
             AddRootWindowToDrawData(windows_to_render_top_most[n]);
-    g.DrawDataBuilder.FlattenIntoSingleLayer();
 
-    // Draw software mouse cursor if requested
-    if (g.IO.MouseDrawCursor)
-        RenderMouseCursor(&g.ForegroundDrawList, g.IO.MousePos, g.Style.MouseCursorScale, g.MouseCursor, IM_COL32_WHITE, IM_COL32_BLACK, IM_COL32(0, 0, 0, 48));
+    ImVec2 mouse_cursor_offset, mouse_cursor_size, mouse_cursor_uv[4];
+    if (g.IO.MouseDrawCursor && g.MouseCursor != ImGuiMouseCursor_None)
+        g.IO.Fonts->GetMouseCursorTexData(g.MouseCursor, &mouse_cursor_offset, &mouse_cursor_size, &mouse_cursor_uv[0], &mouse_cursor_uv[2]);
 
-    // Add foreground ImDrawList
-    if (!g.ForegroundDrawList.VtxBuffer.empty())
-        AddDrawListToDrawData(&g.DrawDataBuilder.Layers[0], &g.ForegroundDrawList);
+    // Setup ImDrawData structures for end-user
+    g.IO.MetricsRenderVertices = g.IO.MetricsRenderIndices = 0;
+    for (int n = 0; n < g.Viewports.Size; n++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[n];
+        viewport->DrawDataBuilder.FlattenIntoSingleLayer();
 
-    // Setup ImDrawData structure for end-user
-    SetupDrawData(&g.DrawDataBuilder.Layers[0], &g.DrawData);
-    g.IO.MetricsRenderVertices = g.DrawData.TotalVtxCount;
-    g.IO.MetricsRenderIndices = g.DrawData.TotalIdxCount;
+        // Draw software mouse cursor if requested by io.MouseDrawCursor flag
+        // (note we scale cursor by current viewport/monitor, however Windows 10 for its own hardware cursor seems to be using a different scale factor)
+        if (mouse_cursor_size.x > 0.0f && mouse_cursor_size.y > 0.0f)
+        {
+            float scale = g.Style.MouseCursorScale * viewport->DpiScale;
+            if (viewport->GetMainRect().Overlaps(ImRect(g.IO.MousePos, g.IO.MousePos + ImVec2(mouse_cursor_size.x + 2, mouse_cursor_size.y + 2) * scale)))
+                RenderMouseCursor(GetForegroundDrawList(viewport), g.IO.MousePos, scale, g.MouseCursor, IM_COL32_WHITE, IM_COL32_BLACK, IM_COL32(0, 0, 0, 48));
+        }
+
+        // Add foreground ImDrawList (for each active viewport)
+        if (viewport->DrawLists[1] != NULL)
+            AddDrawListToDrawData(&viewport->DrawDataBuilder.Layers[0], GetForegroundDrawList(viewport));
+
+        SetupViewportDrawData(viewport, &viewport->DrawDataBuilder.Layers[0]);
+        g.IO.MetricsRenderVertices += viewport->DrawData->TotalVtxCount;
+        g.IO.MetricsRenderIndices += viewport->DrawData->TotalIdxCount;
+    }
 
     // (Legacy) Call the Render callback function. The current prefer way is to let the user retrieve GetDrawData() and call the render function themselves.
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
-    if (g.DrawData.CmdListsCount > 0 && g.IO.RenderDrawListsFn != NULL)
-        g.IO.RenderDrawListsFn(&g.DrawData);
+    if (g.Viewports[0]->DrawData->CmdListsCount > 0 && g.IO.RenderDrawListsFn != NULL)
+        g.IO.RenderDrawListsFn(g.Viewports[0]->DrawData);
 #endif
 }
 
@@ -4309,7 +4638,13 @@ static void FindHoveredWindow()
 {
     ImGuiContext& g = *GImGui;
 
+    // Special handling for the window being moved: Ignore the mouse viewport check (because it may reset/lose its viewport during the undocking frame)
+    ImGuiViewportP* moving_window_viewport = g.MovingWindow ? g.MovingWindow->Viewport : NULL;
+    if (g.MovingWindow)
+        g.MovingWindow->Viewport = g.MouseViewport;
+
     ImGuiWindow* hovered_window = NULL;
+    ImGuiWindow* hovered_window_ignoring_moving_window = NULL;
     if (g.MovingWindow && !(g.MovingWindow->Flags & ImGuiWindowFlags_NoMouseInputs))
         hovered_window = g.MovingWindow;
 
@@ -4322,6 +4657,9 @@ static void FindHoveredWindow()
             continue;
         if (window->Flags & ImGuiWindowFlags_NoMouseInputs)
             continue;
+        IM_ASSERT(window->Viewport);
+        if (window->Viewport != g.MouseViewport)
+            continue;
 
         // Using the clipped AABB, a child window will typically be clipped by its parent (not always)
         ImRect bb(window->OuterRectClipped);
@@ -4332,16 +4670,29 @@ static void FindHoveredWindow()
         if (!bb.Contains(g.IO.MousePos))
             continue;
 
-        // Those seemingly unnecessary extra tests are because the code here is a little different in viewport/docking branches.
+        if (window->HitTestHoleSize.x != 0)
+        {
+            // FIXME: Consider generalizing hit-testing override (with more generic data, callback, etc.) (#1512)
+            ImRect hole_bb((float)(window->HitTestHoleOffset.x), (float)(window->HitTestHoleOffset.y),
+                (float)(window->HitTestHoleOffset.x + window->HitTestHoleSize.x), (float)(window->HitTestHoleOffset.y + window->HitTestHoleSize.y));
+            if (hole_bb.Contains(g.IO.MousePos - window->Pos))
+                continue;
+        }
+
         if (hovered_window == NULL)
             hovered_window = window;
-        if (hovered_window)
+        if (hovered_window_ignoring_moving_window == NULL && (!g.MovingWindow || window->RootWindow != g.MovingWindow->RootWindow))
+            hovered_window_ignoring_moving_window = window;
+        if (hovered_window && hovered_window_ignoring_moving_window)
             break;
     }
 
     g.HoveredWindow = hovered_window;
     g.HoveredRootWindow = g.HoveredWindow ? g.HoveredWindow->RootWindow : NULL;
+    g.HoveredWindowUnderMovingWindow = hovered_window_ignoring_moving_window;
 
+    if (g.MovingWindow)
+        g.MovingWindow->Viewport = moving_window_viewport;
 }
 
 // Test if mouse cursor is hovering given rectangle
@@ -4360,6 +4711,8 @@ bool ImGui::IsMouseHoveringRect(const ImVec2& r_min, const ImVec2& r_max, bool c
     const ImRect rect_for_touch(rect_clipped.Min - g.Style.TouchExtraPadding, rect_clipped.Max + g.Style.TouchExtraPadding);
     if (!rect_for_touch.Contains(g.IO.MousePos))
         return false;
+    if (!g.MouseViewport->GetMainRect().Overlaps(rect_clipped))
+        return false;
     return true;
 }
 
@@ -4613,6 +4966,12 @@ bool ImGui::IsItemFocused()
 
     if (g.NavId == 0 || g.NavDisableHighlight || g.NavId != window->DC.LastItemId)
         return false;
+
+    // Special handling for the dummy item after Begin() which represent the title bar or tab.
+    // When the window is collapsed (SkipItems==true) that last item will never be overwritten so we need to detect the case.
+    if (window->DC.LastItemId == window->ID && window->WriteAccessed)
+        return false;
+
     return true;
 }
 
@@ -4691,18 +5050,12 @@ ImVec2 ImGui::GetItemRectSize()
     return window->DC.LastItemRect.GetSize();
 }
 
-static ImRect GetViewportRect()
-{
-    ImGuiContext& g = *GImGui;
-    return ImRect(0.0f, 0.0f, g.IO.DisplaySize.x, g.IO.DisplaySize.y);
-}
-
 bool ImGui::BeginChildEx(const char* name, ImGuiID id, const ImVec2& size_arg, bool border, ImGuiWindowFlags flags)
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindow* parent_window = g.CurrentWindow;
 
-    flags |= ImGuiWindowFlags_NoTitleBar|ImGuiWindowFlags_NoResize|ImGuiWindowFlags_NoSavedSettings|ImGuiWindowFlags_ChildWindow;
+    flags |= ImGuiWindowFlags_NoTitleBar|ImGuiWindowFlags_NoResize|ImGuiWindowFlags_NoSavedSettings|ImGuiWindowFlags_ChildWindow|ImGuiWindowFlags_NoDocking;
     flags |= (parent_window->Flags & ImGuiWindowFlags_NoMove);  // Inherit the NoMove flag
 
     // Size
@@ -4828,6 +5181,7 @@ static void SetWindowConditionAllowFlags(ImGuiWindow* window, ImGuiCond flags, b
     window->SetWindowPosAllowFlags       = enabled ? (window->SetWindowPosAllowFlags       | flags) : (window->SetWindowPosAllowFlags       & ~flags);
     window->SetWindowSizeAllowFlags      = enabled ? (window->SetWindowSizeAllowFlags      | flags) : (window->SetWindowSizeAllowFlags      & ~flags);
     window->SetWindowCollapsedAllowFlags = enabled ? (window->SetWindowCollapsedAllowFlags | flags) : (window->SetWindowCollapsedAllowFlags & ~flags);
+    window->SetWindowDockAllowFlags      = enabled ? (window->SetWindowDockAllowFlags      | flags) : (window->SetWindowDockAllowFlags      & ~flags);
 }
 
 ImGuiWindow* ImGui::FindWindowByID(ImGuiID id)
@@ -4853,7 +5207,8 @@ static ImGuiWindow* CreateNewWindow(const char* name, ImVec2 size, ImGuiWindowFl
     g.WindowsById.SetVoidPtr(window->ID, window);
 
     // Default/arbitrary window position. Use SetNextWindowPos() with the appropriate condition flag to change the initial position of a window.
-    window->Pos = ImVec2(60, 60);
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    window->Pos = main_viewport->Pos + ImVec2(60, 60);
 
     // User can disable loading and saving of settings. Tooltip and child windows also don't store settings.
     if (!(flags & ImGuiWindowFlags_NoSavedSettings))
@@ -4862,10 +5217,21 @@ static ImGuiWindow* CreateNewWindow(const char* name, ImVec2 size, ImGuiWindowFl
             // Retrieve settings from .ini file
             window->SettingsOffset = g.SettingsWindows.offset_from_ptr(settings);
             SetWindowConditionAllowFlags(window, ImGuiCond_FirstUseEver, false);
-            window->Pos = ImVec2(settings->Pos.x, settings->Pos.y);
+            if (settings->ViewportId)
+            {
+                window->ViewportId = settings->ViewportId;
+                window->ViewportPos = ImVec2(settings->ViewportPos.x, settings->ViewportPos.y);
+            }
+            else
+            {
+                window->ViewportPos = main_viewport->Pos;
+            }
+            window->Pos = ImVec2(settings->Pos.x + window->ViewportPos.x, settings->Pos.y + window->ViewportPos.y);
             window->Collapsed = settings->Collapsed;
             if (settings->Size.x > 0 && settings->Size.y > 0)
                 size = ImVec2(settings->Size.x, settings->Size.y);
+            window->DockId = settings->DockId;
+            window->DockOrder = settings->DockOrder;
         }
     window->Size = window->SizeFull = ImFloor(size);
     window->DC.CursorStartPos = window->DC.CursorMaxPos = window->Pos; // So first call to CalcContentSize() doesn't return crazy values
@@ -4892,6 +5258,16 @@ static ImGuiWindow* CreateNewWindow(const char* name, ImVec2 size, ImGuiWindowFl
     return window;
 }
 
+static ImGuiWindow* GetWindowForTitleDisplay(ImGuiWindow* window)
+{
+    return window->DockNodeAsHost ? window->DockNodeAsHost->VisibleWindow : window;
+}
+
+static ImGuiWindow* GetWindowForTitleAndMenuHeight(ImGuiWindow* window)
+{
+    return (window->DockNodeAsHost && window->DockNodeAsHost->VisibleWindow) ? window->DockNodeAsHost->VisibleWindow : window;
+}
+
 static ImVec2 CalcWindowSizeAfterConstraint(ImGuiWindow* window, ImVec2 new_size)
 {
     ImGuiContext& g = *GImGui;
@@ -4918,7 +5294,7 @@ static ImVec2 CalcWindowSizeAfterConstraint(ImGuiWindow* window, ImVec2 new_size
     // Minimum size
     if (!(window->Flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_AlwaysAutoResize)))
     {
-        ImGuiWindow* window_for_height = window;
+        ImGuiWindow* window_for_height = GetWindowForTitleAndMenuHeight(window);
         new_size = ImMax(new_size, g.Style.WindowMinSize);
         new_size.y = ImMax(new_size.y, window_for_height->TitleBarHeight() + window_for_height->MenuBarHeight() + ImMax(0.0f, g.Style.WindowRounding - 1.0f)); // Reduce artifacts with very small windows
     }
@@ -4959,7 +5335,15 @@ static ImVec2 CalcWindowAutoFitSize(ImGuiWindow* window, const ImVec2& size_cont
         ImVec2 size_min = style.WindowMinSize;
         if (is_popup || is_menu) // Popups and menus bypass style.WindowMinSize by default, but we give then a non-zero minimum size to facilitate understanding problematic cases (e.g. empty popups)
             size_min = ImMin(size_min, ImVec2(4.0f, 4.0f));
-        ImVec2 size_auto_fit = ImClamp(size_desired, size_min, ImMax(size_min, g.IO.DisplaySize - style.DisplaySafeAreaPadding * 2.0f));
+
+        // FIXME-VIEWPORT-WORKAREA: May want to use GetWorkSize() instead of Size depending on the type of windows?
+        ImVec2 avail_size = window->Viewport->Size;
+        if (window->ViewportOwned)
+            avail_size = ImVec2(FLT_MAX, FLT_MAX);
+        const int monitor_idx = window->ViewportAllowPlatformMonitorExtend;
+        if (monitor_idx >= 0 && monitor_idx < g.PlatformIO.Monitors.Size)
+            avail_size = g.PlatformIO.Monitors[monitor_idx].WorkSize;
+        ImVec2 size_auto_fit = ImClamp(size_desired, size_min, ImMax(size_min, avail_size - g.Style.DisplaySafeAreaPadding * 2.0f));
 
         // When the window cannot fit all contents (either because of constraints, either because screen is too small),
         // we are growing the size on the other axis to compensate for expected scrollbar. FIXME: Might turn bigger than ViewportSize-WindowPadding.
@@ -5037,7 +5421,7 @@ static ImRect GetResizeBorderRect(ImGuiWindow* window, int border_n, float perp_
 ImGuiID ImGui::GetWindowResizeID(ImGuiWindow* window, int n)
 {
     IM_ASSERT(n >= 0 && n <= 7);
-    ImGuiID id = window->ID;
+    ImGuiID id = window->DockIsActive ? window->DockNode->HostWindow->ID : window->ID;
     id = ImHashStr("#RESIZE", 0, id);
     id = ImHashData(&n, sizeof(int), id);
     return id;
@@ -5064,6 +5448,15 @@ static bool ImGui::UpdateWindowManualResize(ImGuiWindow* window, const ImVec2& s
     ImVec2 pos_target(FLT_MAX, FLT_MAX);
     ImVec2 size_target(FLT_MAX, FLT_MAX);
 
+    // Clip mouse interaction rectangles within the viewport rectangle (in practice the narrowing is going to happen most of the time).
+    // - Not narrowing would mostly benefit the situation where OS windows _without_ decoration have a threshold for hovering when outside their limits.
+    //   This is however not the case with current back-ends under Win32, but a custom borderless window implementation would benefit from it.
+    // - When decoration are enabled we typically benefit from that distance, but then our resize elements would be conflicting with OS resize elements, so we also narrow.
+    // - Note that we are unable to tell if the platform setup allows hovering with a distance threshold (on Win32, decorated window have such threshold).
+    const bool clip_with_viewport_rect = !(g.IO.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport) || (g.IO.MouseHoveredViewport != window->ViewportId) || !(window->Viewport->Flags & ImGuiViewportFlags_NoDecoration);
+    if (clip_with_viewport_rect)
+        PushClipRect(window->Viewport->Pos, window->Viewport->Pos + window->Viewport->Size, true); // Won't incur a draw command as we are not drawing here.
+
     // Resize grips and borders are on layer 1
     window->DC.NavLayerCurrent = ImGuiNavLayer_Menu;
     window->DC.NavLayerCurrentMask = (1 << ImGuiNavLayer_Menu);
@@ -5126,6 +5519,8 @@ static bool ImGui::UpdateWindowManualResize(ImGuiWindow* window, const ImVec2& s
         }
     }
     PopID();
+    if (clip_with_viewport_rect)
+        PopClipRect();
 
     // Restore nav layer
     window->DC.NavLayerCurrent = ImGuiNavLayer_Main;
@@ -5204,7 +5599,7 @@ static void ImGui::RenderWindowOuterBorders(ImGuiWindow* window)
         window->DrawList->PathArcTo(ImLerp(border_r.Min, border_r.Max, def.CornerPosN2) + ImVec2(0.5f, 0.5f) + def.InnerDir * rounding, rounding, def.OuterAngle, def.OuterAngle + IM_PI*0.25f);
         window->DrawList->PathStroke(GetColorU32(ImGuiCol_SeparatorActive), false, ImMax(2.0f, border_size)); // Thicker than usual
     }
-    if (g.Style.FrameBorderSize > 0 && !(window->Flags & ImGuiWindowFlags_NoTitleBar))
+    if (g.Style.FrameBorderSize > 0 && !(window->Flags & ImGuiWindowFlags_NoTitleBar) && !window->DockIsActive)
     {
         float y = window->Pos.y + window->TitleBarHeight() - 1;
         window->DrawList->AddLine(ImVec2(window->Pos.x + border_size, y), ImVec2(window->Pos.x + window->Size.x - border_size, y), GetColorU32(ImGuiCol_Border), g.Style.FrameBorderSize);
@@ -5213,7 +5608,7 @@ static void ImGui::RenderWindowOuterBorders(ImGuiWindow* window)
 
 // Draw background and borders
 // Draw and handle scrollbars
-void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar_rect, bool title_bar_is_highlight, int resize_grip_count, const ImU32 resize_grip_col[4], float resize_grip_draw_size)
+void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar_rect, bool title_bar_is_highlight, bool handle_borders_and_resize_grips, int resize_grip_count, const ImU32 resize_grip_col[4], float resize_grip_draw_size)
 {
     ImGuiContext& g = *GImGui;
     ImGuiStyle& style = g.Style;
@@ -5240,21 +5635,44 @@ void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar
         // Window background
         if (!(flags & ImGuiWindowFlags_NoBackground))
         {
+            bool is_docking_transparent_payload = false;
+            if (g.DragDropActive && (g.FrameCount - g.DragDropAcceptFrameCount) <= 1 && g.IO.ConfigDockingTransparentPayload)
+                if (g.DragDropPayload.IsDataType(IMGUI_PAYLOAD_TYPE_WINDOW) && *(ImGuiWindow**)g.DragDropPayload.Data == window)
+                    is_docking_transparent_payload = true;
+
             ImU32 bg_col = GetColorU32(GetWindowBgColorIdxFromFlags(flags));
-            bool override_alpha = false;
-            float alpha = 1.0f;
-            if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasBgAlpha)
+            if (window->ViewportOwned)
             {
-                alpha = g.NextWindowData.BgAlphaVal;
-                override_alpha = true;
+                // No alpha
+                bg_col = (bg_col | IM_COL32_A_MASK);
+                if (is_docking_transparent_payload)
+                    window->Viewport->Alpha *= DOCKING_TRANSPARENT_PAYLOAD_ALPHA;
+            }
+            else
+            {
+                // Adjust alpha. For docking
+                bool override_alpha = false;
+                float alpha = 1.0f;
+                if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasBgAlpha)
+                {
+                    alpha = g.NextWindowData.BgAlphaVal;
+                    override_alpha = true;
+                }
+                if (is_docking_transparent_payload)
+                {
+                    alpha *= DOCKING_TRANSPARENT_PAYLOAD_ALPHA; // FIXME-DOCK: Should that be an override?
+                    override_alpha = true;
+                }
+                if (override_alpha)
+                    bg_col = (bg_col & ~IM_COL32_A_MASK) | (IM_F32_TO_INT8_SAT(alpha) << IM_COL32_A_SHIFT);
             }
-            if (override_alpha)
-                bg_col = (bg_col & ~IM_COL32_A_MASK) | (IM_F32_TO_INT8_SAT(alpha) << IM_COL32_A_SHIFT);
             window->DrawList->AddRectFilled(window->Pos + ImVec2(0, window->TitleBarHeight()), window->Pos + window->Size, bg_col, window_rounding, (flags & ImGuiWindowFlags_NoTitleBar) ? ImDrawCornerFlags_All : ImDrawCornerFlags_Bot);
         }
 
         // Title bar
-        if (!(flags & ImGuiWindowFlags_NoTitleBar))
+        // (when docked, DockNode are drawing their own title bar. Individual windows however do NOT set the _NoTitleBar flag,
+        // in order for their pos/size to be matching their undocking state.)
+        if (!(flags & ImGuiWindowFlags_NoTitleBar) && !window->DockIsActive)
         {
             ImU32 title_bar_col = GetColorU32(title_bar_is_highlight ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg);
             window->DrawList->AddRectFilled(title_bar_rect.Min, title_bar_rect.Max, title_bar_col, window_rounding, ImDrawCornerFlags_Top);
@@ -5270,6 +5688,25 @@ void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar
                 window->DrawList->AddLine(menu_bar_rect.GetBL(), menu_bar_rect.GetBR(), GetColorU32(ImGuiCol_Border), style.FrameBorderSize);
         }
 
+        // Docking: Unhide tab bar (small triangle in the corner), drag from small triangle to quickly undock
+        ImGuiDockNode* node = window->DockNode;
+        if (window->DockIsActive && node->IsHiddenTabBar() && !node->IsNoTabBar())
+        {
+            float unhide_sz_draw = ImFloor(g.FontSize * 0.70f);
+            float unhide_sz_hit = ImFloor(g.FontSize * 0.55f);
+            ImVec2 p = node->Pos;
+            ImRect r(p, p + ImVec2(unhide_sz_hit, unhide_sz_hit));
+            bool hovered, held;
+            if (ButtonBehavior(r, window->GetID("#UNHIDE"), &hovered, &held, ImGuiButtonFlags_FlattenChildren))
+                node->WantHiddenTabBarToggle = true;
+            else if (held && IsMouseDragging(0))
+                StartMouseMovingWindowOrNode(window, node, true);
+
+            // FIXME-DOCK: Ideally we'd use ImGuiCol_TitleBgActive/ImGuiCol_TitleBg here, but neither is guaranteed to be visible enough at this sort of size..
+            ImU32 col = GetColorU32(((held && hovered) || (node->IsFocused && !hovered)) ? ImGuiCol_ButtonActive : hovered ? ImGuiCol_ButtonHovered : ImGuiCol_Button);
+            window->DrawList->AddTriangleFilled(p, p + ImVec2(unhide_sz_draw, 0.0f), p + ImVec2(0.0f, unhide_sz_draw), col);
+        }
+
         // Scrollbars
         if (window->ScrollbarX)
             Scrollbar(ImGuiAxis_X);
@@ -5277,7 +5714,7 @@ void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar
             Scrollbar(ImGuiAxis_Y);
 
         // Render resize grips (after their input handling so we don't have a frame of latency)
-        if (!(flags & ImGuiWindowFlags_NoResize))
+        if (handle_borders_and_resize_grips && !(flags & ImGuiWindowFlags_NoResize))
         {
             for (int resize_grip_n = 0; resize_grip_n < resize_grip_count; resize_grip_n++)
             {
@@ -5290,12 +5727,14 @@ void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar
             }
         }
 
-        // Borders
-        RenderWindowOuterBorders(window);
+        // Borders (for dock node host they will be rendered over after the tab bar)
+        if (handle_borders_and_resize_grips && !window->DockNodeAsHost)
+            RenderWindowOuterBorders(window);
     }
 }
 
 // Render title text, collapse button, close button
+// When inside a dock node, this is handled in DockNodeUpdateTabBar() instead.
 void ImGui::RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& title_bar_rect, const char* name, bool* p_open)
 {
     ImGuiContext& g = *GImGui;
@@ -5336,7 +5775,7 @@ void ImGui::RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& titl
 
     // Collapse button (submitting first so it gets priority when choosing a navigation init fallback)
     if (has_collapse_button)
-        if (CollapseButton(window->GetID("#COLLAPSE"), collapse_button_pos))
+        if (CollapseButton(window->GetID("#COLLAPSE"), collapse_button_pos, NULL))
             window->WantCollapseToggle = true; // Defer actual collapsing to next frame as we are too far in the Begin() function
 
     // Close button
@@ -5383,9 +5822,13 @@ void ImGui::RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& titl
 void ImGui::UpdateWindowParentAndRootLinks(ImGuiWindow* window, ImGuiWindowFlags flags, ImGuiWindow* parent_window)
 {
     window->ParentWindow = parent_window;
-    window->RootWindow = window->RootWindowForTitleBarHighlight = window->RootWindowForNav = window;
+    window->RootWindow = window->RootWindowDockStop = window->RootWindowForTitleBarHighlight = window->RootWindowForNav = window;
     if (parent_window && (flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Tooltip))
+    {
         window->RootWindow = parent_window->RootWindow;
+        if (!window->DockIsActive && !(parent_window->Flags & ImGuiWindowFlags_DockNodeHost))
+            window->RootWindowDockStop = parent_window->RootWindowDockStop;
+    }
     if (parent_window && !(flags & ImGuiWindowFlags_Modal) && (flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Popup)))
         window->RootWindowForTitleBarHighlight = parent_window->RootWindowForTitleBarHighlight;
     while (window->RootWindowForNav->Flags & ImGuiWindowFlags_NavFlattened)
@@ -5446,6 +5889,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     // Update Flags, LastFrameActive, BeginOrderXXX fields
     if (first_begin_of_the_frame)
     {
+        window->FlagsPreviousFrame = window->Flags;
         window->Flags = (ImGuiWindowFlags)flags;
         window->LastFrameActive = current_frame;
         window->LastTimeActive = (float)g.Time;
@@ -5457,8 +5901,29 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         flags = window->Flags;
     }
 
+    // Docking
+    // (NB: during the frame dock nodes are created, it is possible that (window->DockIsActive == false) even though (window->DockNode->Windows.Size > 1)
+    IM_ASSERT(window->DockNode == NULL || window->DockNodeAsHost == NULL); // Cannot be both
+    if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasDock)
+        SetWindowDock(window, g.NextWindowData.DockId, g.NextWindowData.DockCond);
+    if (first_begin_of_the_frame)
+    {
+        bool has_dock_node = (window->DockId != 0 || window->DockNode != NULL);
+        bool new_auto_dock_node = !has_dock_node && GetWindowAlwaysWantOwnTabBar(window);
+        if (has_dock_node || new_auto_dock_node)
+        {
+            BeginDocked(window, p_open);
+            flags = window->Flags;
+            if (window->DockIsActive)
+                IM_ASSERT(window->DockNode != NULL);
+
+            // Docking currently override constraints
+            g.NextWindowData.Flags &= ~ImGuiNextWindowDataFlags_HasSizeConstraint;
+        }
+    }
+
     // Parent window is latched only on the first call to Begin() of the frame, so further append-calls can be done from a different window stack
-    ImGuiWindow* parent_window_in_stack = g.CurrentWindowStack.empty() ? NULL : g.CurrentWindowStack.back();
+    ImGuiWindow* parent_window_in_stack = window->DockIsActive ? window->DockNode->HostWindow : g.CurrentWindowStack.empty() ? NULL : g.CurrentWindowStack.back();
     ImGuiWindow* parent_window = first_begin_of_the_frame ? ((flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Popup)) ? parent_window_in_stack : NULL) : window->ParentWindow;
     IM_ASSERT(parent_window != NULL || !(flags & ImGuiWindowFlags_ChildWindow));
 
@@ -5487,6 +5952,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         UpdateWindowParentAndRootLinks(window, flags, parent_window);
 
     // Process SetNextWindow***() calls
+    // (FIXME: Consider splitting the HasXXX flags into X/Y components
     bool window_pos_set_by_api = false;
     bool window_size_x_set_by_api = false, window_size_y_set_by_api = false;
     if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasPos)
@@ -5511,10 +5977,25 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         window_size_y_set_by_api = (window->SetWindowSizeAllowFlags & g.NextWindowData.SizeCond) != 0 && (g.NextWindowData.SizeVal.y > 0.0f);
         SetWindowSize(window, g.NextWindowData.SizeVal, g.NextWindowData.SizeCond);
     }
+    if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasScroll)
+    {
+        if (g.NextWindowData.ScrollVal.x >= 0.0f)
+        {
+            window->ScrollTarget.x = g.NextWindowData.ScrollVal.x;
+            window->ScrollTargetCenterRatio.x = 0.0f;
+        }
+        if (g.NextWindowData.ScrollVal.y >= 0.0f)
+        {
+            window->ScrollTarget.y = g.NextWindowData.ScrollVal.y;
+            window->ScrollTargetCenterRatio.y = 0.0f;
+        }
+    }
     if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasContentSize)
         window->ContentSizeExplicit = g.NextWindowData.ContentSizeVal;
     else if (first_begin_of_the_frame)
         window->ContentSizeExplicit = ImVec2(0.0f, 0.0f);
+    if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasWindowClass)
+        window->WindowClass = g.NextWindowData.WindowClass;
     if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasCollapsed)
         SetWindowCollapsed(window, g.NextWindowData.CollapsedVal, g.NextWindowData.CollapsedCond);
     if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasFocus)
@@ -5539,7 +6020,9 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         // Update stored window name when it changes (which can _only_ happen with the "###" operator, so the ID would stay unchanged).
         // The title bar always display the 'name' parameter, so we only update the string storage if it needs to be visible to the end-user elsewhere.
         bool window_title_visible_elsewhere = false;
-        if (g.NavWindowingList != NULL && (window->Flags & ImGuiWindowFlags_NoNavFocus) == 0)   // Window titles visible when using CTRL+TAB
+        if ((window->Viewport && window->Viewport->Window == window) || (window->DockIsActive))
+            window_title_visible_elsewhere = true;
+        else if (g.NavWindowingList != NULL && (window->Flags & ImGuiWindowFlags_NoNavFocus) == 0)   // Window titles visible when using CTRL+TAB
             window_title_visible_elsewhere = true;
         if (window_title_visible_elsewhere && !window_just_created && strcmp(name, window->Name) != 0)
         {
@@ -5577,22 +6060,33 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         }
 
         // SELECT VIEWPORT
-        // FIXME-VIEWPORT: In the docking/viewport branch, this is the point where we select the current viewport (which may affect the style)
+        // We need to do this before using any style/font sizes, as viewport with a different DPI may affect font sizes.
+
+        UpdateSelectWindowViewport(window);
+        SetCurrentViewport(window, window->Viewport);
+        window->FontDpiScale = (g.IO.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleFonts) ? window->Viewport->DpiScale : 1.0f;
         SetCurrentWindow(window);
+        flags = window->Flags;
 
         // LOCK BORDER SIZE AND PADDING FOR THE FRAME (so that altering them doesn't cause inconsistencies)
+        // We read Style data after the call to UpdateSelectWindowViewport() which might be swapping the style.
 
         if (flags & ImGuiWindowFlags_ChildWindow)
             window->WindowBorderSize = style.ChildBorderSize;
         else
             window->WindowBorderSize = ((flags & (ImGuiWindowFlags_Popup | ImGuiWindowFlags_Tooltip)) && !(flags & ImGuiWindowFlags_Modal)) ? style.PopupBorderSize : style.WindowBorderSize;
-        window->WindowPadding = style.WindowPadding;
-        if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & (ImGuiWindowFlags_AlwaysUseWindowPadding | ImGuiWindowFlags_Popup)) && window->WindowBorderSize == 0.0f)
+        if (!window->DockIsActive && (flags & ImGuiWindowFlags_ChildWindow) && !(flags & (ImGuiWindowFlags_AlwaysUseWindowPadding | ImGuiWindowFlags_Popup)) && window->WindowBorderSize == 0.0f)
             window->WindowPadding = ImVec2(0.0f, (flags & ImGuiWindowFlags_MenuBar) ? style.WindowPadding.y : 0.0f);
+        else
+            window->WindowPadding = style.WindowPadding;
+
+        // Lock menu offset so size calculation can use it as menu-bar windows need a minimum size.
+        window->DC.MenuBarOffset.x = ImMax(ImMax(window->WindowPadding.x, style.ItemSpacing.x), g.NextWindowData.MenuBarOffsetMinVal.x);
+        window->DC.MenuBarOffset.y = g.NextWindowData.MenuBarOffsetMinVal.y;
 
         // Collapse window by double-clicking on title bar
         // At this point we don't have a clipping rectangle setup yet, so we can use the title bar area for hit detection and drawing
-        if (!(flags & ImGuiWindowFlags_NoTitleBar) && !(flags & ImGuiWindowFlags_NoCollapse))
+        if (!(flags & ImGuiWindowFlags_NoTitleBar) && !(flags & ImGuiWindowFlags_NoCollapse) && !window->DockIsActive)
         {
             // We don't use a regular button+id to test for double-click on title bar (mostly due to legacy reason, could be fixed), so verify that we don't have items over the title bar.
             ImRect title_bar_rect = window->TitleBarRect();
@@ -5686,21 +6180,120 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         else if ((flags & ImGuiWindowFlags_Tooltip) != 0 && !window_pos_set_by_api && !window_is_child_tooltip)
             window->Pos = FindBestWindowPosForPopup(window);
 
+        // Late create viewport if we don't fit within our current host viewport.
+        if (window->ViewportAllowPlatformMonitorExtend >= 0 && !window->ViewportOwned && !(window->Viewport->Flags & ImGuiViewportFlags_Minimized))
+            if (!window->Viewport->GetMainRect().Contains(window->Rect()))
+            {
+                // This is based on the assumption that the DPI will be known ahead (same as the DPI of the selection done in UpdateSelectWindowViewport)
+                //ImGuiViewport* old_viewport = window->Viewport;
+                window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_NoFocusOnAppearing);
+
+                // FIXME-DPI
+                //IM_ASSERT(old_viewport->DpiScale == window->Viewport->DpiScale); // FIXME-DPI: Something went wrong
+                SetCurrentViewport(window, window->Viewport);
+                window->FontDpiScale = (g.IO.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleFonts) ? window->Viewport->DpiScale : 1.0f;
+                SetCurrentWindow(window);
+            }
+
+        bool viewport_rect_changed = false;
+        if (window->ViewportOwned)
+        {
+            // Synchronize window --> viewport in most situations
+            // Synchronize viewport -> window in case the platform window has been moved or resized from the OS/WM
+            if (window->Viewport->PlatformRequestMove)
+            {
+                window->Pos = window->Viewport->Pos;
+                MarkIniSettingsDirty(window);
+            }
+            else if (memcmp(&window->Viewport->Pos, &window->Pos, sizeof(window->Pos)) != 0)
+            {
+                viewport_rect_changed = true;
+                window->Viewport->Pos = window->Pos;
+            }
+
+            if (window->Viewport->PlatformRequestResize)
+            {
+                window->Size = window->SizeFull = window->Viewport->Size;
+                MarkIniSettingsDirty(window);
+            }
+            else if (memcmp(&window->Viewport->Size, &window->Size, sizeof(window->Size)) != 0)
+            {
+                viewport_rect_changed = true;
+                window->Viewport->Size = window->Size;
+            }
+
+            // The viewport may have changed monitor since the global update in UpdateViewportsNewFrame()
+            // Either a SetNextWindowPos() call in the current frame or a SetWindowPos() call in the previous frame may have this effect.
+            if (viewport_rect_changed)
+                UpdateViewportPlatformMonitor(window->Viewport);
+
+            // Update common viewport flags
+            ImGuiViewportFlags viewport_flags = (window->Viewport->Flags) & ~(ImGuiViewportFlags_TopMost | ImGuiViewportFlags_NoTaskBarIcon | ImGuiViewportFlags_NoDecoration);
+            const bool is_short_lived_floating_window = (flags & (ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup)) != 0;
+            if (flags & ImGuiWindowFlags_Tooltip)
+                viewport_flags |= ImGuiViewportFlags_TopMost;
+            if (g.IO.ConfigViewportsNoTaskBarIcon || is_short_lived_floating_window)
+                viewport_flags |= ImGuiViewportFlags_NoTaskBarIcon;
+            if (g.IO.ConfigViewportsNoDecoration || is_short_lived_floating_window)
+                viewport_flags |= ImGuiViewportFlags_NoDecoration;
+
+            // For popups and menus that may be protruding out of their parent viewport, we enable _NoFocusOnClick so that clicking on them
+            // won't steal the OS focus away from their parent window (which may be reflected in OS the title bar decoration).
+            // Setting _NoFocusOnClick would technically prevent us from bringing back to front in case they are being covered by an OS window from a different app,
+            // but it shouldn't be much of a problem considering those are already popups that are closed when clicking elsewhere.
+            if (is_short_lived_floating_window && (flags & ImGuiWindowFlags_Modal) == 0)
+                viewport_flags |= ImGuiViewportFlags_NoFocusOnAppearing | ImGuiViewportFlags_NoFocusOnClick;
+
+            // We can overwrite viewport flags using ImGuiWindowClass (advanced users)
+            // We don't default to the main viewport because.
+            if (window->WindowClass.ParentViewportId)
+                window->Viewport->ParentViewportId = window->WindowClass.ParentViewportId;
+            else if ((flags & (ImGuiWindowFlags_Popup | ImGuiWindowFlags_Tooltip)) && parent_window_in_stack)
+                window->Viewport->ParentViewportId = parent_window_in_stack->Viewport->ID;
+            else
+                window->Viewport->ParentViewportId = g.IO.ConfigViewportsNoDefaultParent ? 0 : IMGUI_VIEWPORT_DEFAULT_ID;
+            if (window->WindowClass.ViewportFlagsOverrideSet)
+                viewport_flags |= window->WindowClass.ViewportFlagsOverrideSet;
+            if (window->WindowClass.ViewportFlagsOverrideClear)
+                viewport_flags &= ~window->WindowClass.ViewportFlagsOverrideClear;
+
+            // We also tell the back-end that clearing the platform window won't be necessary, as our window is filling the viewport and we have disabled BgAlpha
+            viewport_flags |= ImGuiViewportFlags_NoRendererClear;
+            window->Viewport->Flags = viewport_flags;
+        }
+
         // Clamp position/size so window stays visible within its viewport or monitor
         // Ignore zero-sized display explicitly to avoid losing positions if a window manager reports zero-sized window when initializing or minimizing.
-        ImRect viewport_rect(GetViewportRect());
+        // FIXME: Similar to code in GetWindowAllowedExtentRect()
+        ImRect viewport_rect = window->Viewport->GetMainRect();
         if (!window_pos_set_by_api && !(flags & ImGuiWindowFlags_ChildWindow) && window->AutoFitFramesX <= 0 && window->AutoFitFramesY <= 0)
         {
             ImVec2 clamp_padding = ImMax(style.DisplayWindowPadding, style.DisplaySafeAreaPadding);
-            if (viewport_rect.GetWidth() > 0 && viewport_rect.GetHeight() > 0.0f)
+            if (!window->ViewportOwned && viewport_rect.GetWidth() > 0 && viewport_rect.GetHeight() > 0.0f)
             {
-                ClampWindowRect(window, viewport_rect, clamp_padding);
+                ClampWindowRect(window, window->Viewport->GetWorkRect(), clamp_padding);
+            }
+            else if (window->ViewportOwned && g.PlatformIO.Monitors.Size > 0)
+            {
+                if (window->Viewport->PlatformMonitor == -1)
+                {
+                    // Fallback for "lost" window (e.g. a monitor disconnected): we move the window back over the main viewport
+                    SetWindowPos(window, g.Viewports[0]->Pos + style.DisplayWindowPadding, ImGuiCond_Always);
+                }
+                else
+                {
+                    ImGuiPlatformMonitor& monitor = g.PlatformIO.Monitors[window->Viewport->PlatformMonitor];
+                    ClampWindowRect(window, ImRect(monitor.WorkPos, monitor.WorkPos + monitor.WorkSize), clamp_padding);
+                }
             }
         }
         window->Pos = ImFloor(window->Pos);
 
         // Lock window rounding for the frame (so that altering them doesn't cause inconsistencies)
-        window->WindowRounding = (flags & ImGuiWindowFlags_ChildWindow) ? style.ChildRounding : ((flags & ImGuiWindowFlags_Popup) && !(flags & ImGuiWindowFlags_Modal)) ? style.PopupRounding : style.WindowRounding;
+        if (window->ViewportOwned || window->DockIsActive)
+            window->WindowRounding = 0.0f;
+        else
+            window->WindowRounding = (flags & ImGuiWindowFlags_ChildWindow) ? style.ChildRounding : ((flags & ImGuiWindowFlags_Popup) && !(flags & ImGuiWindowFlags_Modal)) ? style.PopupRounding : style.WindowRounding;
 
         // Apply window focus (new and reactivated windows are moved to front)
         bool want_focus = false;
@@ -5708,20 +6301,36 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         {
             if (flags & ImGuiWindowFlags_Popup)
                 want_focus = true;
-            else if ((flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Tooltip)) == 0)
+            else if ((window->DockIsActive || (flags & ImGuiWindowFlags_ChildWindow) == 0) && !(flags & ImGuiWindowFlags_Tooltip))
                 want_focus = true;
         }
 
+        // Decide if we are going to handle borders and resize grips
+        const bool handle_borders_and_resize_grips = (window->DockNodeAsHost || !window->DockIsActive);
+
         // Handle manual resize: Resize Grips, Borders, Gamepad
         int border_held = -1;
         ImU32 resize_grip_col[4] = {};
         const int resize_grip_count = g.IO.ConfigWindowsResizeFromEdges ? 2 : 1; // Allow resize from lower-left if we have the mouse cursor feedback for it.
         const float resize_grip_draw_size = IM_FLOOR(ImMax(g.FontSize * 1.35f, window->WindowRounding + 1.0f + g.FontSize * 0.2f));
-        if (!window->Collapsed)
+        if (handle_borders_and_resize_grips && !window->Collapsed)
             if (UpdateWindowManualResize(window, size_auto_fit, &border_held, resize_grip_count, &resize_grip_col[0]))
                 use_current_size_for_scrollbar_x = use_current_size_for_scrollbar_y = true;
         window->ResizeBorderHeld = (signed char)border_held;
 
+        // Synchronize window --> viewport again and one last time (clamping and manual resize may have affected either)
+        if (window->ViewportOwned)
+        {
+            if (!window->Viewport->PlatformRequestMove)
+                window->Viewport->Pos = window->Pos;
+            if (!window->Viewport->PlatformRequestResize)
+                window->Viewport->Size = window->Size;
+            viewport_rect = window->Viewport->GetMainRect();
+        }
+
+        // Save last known viewport position within the window itself (so it can be saved in .ini file and restored)
+        window->ViewportPos = window->Viewport->Pos;
+
         // SCROLLBAR VISIBILITY
 
         // Update scrollbar visibility (based on the Size that was effective during last frame or the auto-resized Size).
@@ -5755,6 +6364,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         const ImRect outer_rect = window->Rect();
         const ImRect title_bar_rect = window->TitleBarRect();
         window->OuterRectClipped = outer_rect;
+        if (window->DockIsActive)
+            window->OuterRectClipped.Min.y += window->TitleBarHeight();
         window->OuterRectClipped.ClipWith(host_rect);
 
         // Inner rectangle
@@ -5807,9 +6418,9 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         window->DrawList->PushTextureID(g.Font->ContainerAtlas->TexID);
         PushClipRect(host_rect.Min, host_rect.Max, false);
 
-        // Draw modal window background (darkens what is behind them, all viewports)
+        // Draw modal or window list full viewport dimming background (for other viewports we'll render them in EndFrame)
         const bool dim_bg_for_modal = (flags & ImGuiWindowFlags_Modal) && window == GetTopMostPopupModal() && window->HiddenFramesCannotSkipItems <= 0;
-        const bool dim_bg_for_window_list = g.NavWindowingTargetAnim && (window == g.NavWindowingTargetAnim->RootWindow);
+        const bool dim_bg_for_window_list = g.NavWindowingTargetAnim && ((window == g.NavWindowingTargetAnim->RootWindow) || (g.NavWindowingList && (window == g.NavWindowingList) && g.NavWindowingList->Viewport != g.NavWindowingTargetAnim->Viewport));
         if (dim_bg_for_modal || dim_bg_for_window_list)
         {
             const ImU32 dim_bg_col = GetColorU32(dim_bg_for_modal ? ImGuiCol_ModalWindowDimBg : ImGuiCol_NavWindowingDimBg, g.DimBgRatio);
@@ -5830,6 +6441,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         // We disable this when the parent window has zero vertices, which is a common pattern leading to laying out multiple overlapping child.
         // We also disabled this when we have dimming overlay behind this specific one child.
         // FIXME: More code may rely on explicit sorting of overlapping child window and would need to disable this somehow. Please get in contact if you are affected.
+        const bool is_undocked_or_docked_visible = !window->DockIsActive || window->DockTabIsVisible;
+        if (is_undocked_or_docked_visible)
         {
             bool render_decorations_in_parent = false;
             if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Popup) && !window_is_child_tooltip)
@@ -5840,8 +6453,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
 
             // Handle title bar, scrollbar, resize grips and resize borders
             const ImGuiWindow* window_to_highlight = g.NavWindowingTarget ? g.NavWindowingTarget : g.NavWindow;
-            const bool title_bar_is_highlight = want_focus || (window_to_highlight && window->RootWindowForTitleBarHighlight == window_to_highlight->RootWindowForTitleBarHighlight);
-            RenderWindowDecorations(window, title_bar_rect, title_bar_is_highlight, resize_grip_count, resize_grip_col, resize_grip_draw_size);
+            const bool title_bar_is_highlight = want_focus || (window_to_highlight && (window->RootWindowForTitleBarHighlight == window_to_highlight->RootWindowForTitleBarHighlight || (window->DockNode && window->DockNode == window_to_highlight->DockNode)));
+            RenderWindowDecorations(window, title_bar_rect, title_bar_is_highlight, handle_borders_and_resize_grips, resize_grip_count, resize_grip_col, resize_grip_draw_size);
 
             if (render_decorations_in_parent)
                 window->DrawList = &window->DrawListInst;
@@ -5907,8 +6520,6 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         window->DC.NavHasScroll = (window->ScrollMax.y > 0.0f);
 
         window->DC.MenuBarAppending = false;
-        window->DC.MenuBarOffset.x = ImMax(ImMax(window->WindowPadding.x, style.ItemSpacing.x), g.NextWindowData.MenuBarOffsetMinVal.x);
-        window->DC.MenuBarOffset.y = g.NextWindowData.MenuBarOffsetMinVal.y;
         window->DC.MenuColumns.Update(3, style.ItemSpacing.x, window_just_activated_by_user);
         window->DC.TreeDepth = 0;
         window->DC.TreeJumpToParentOnPopMask = 0x00;
@@ -5941,10 +6552,25 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             NavInitWindow(window, false);
         }
 
+        // Close requested by platform window
+        if (p_open != NULL && window->Viewport->PlatformRequestClose && window->Viewport != GetMainViewport())
+        {
+            if (!window->DockIsActive || window->DockTabIsVisible)
+            {
+                window->Viewport->PlatformRequestClose = false;
+                g.NavWindowingToggleLayer = false; // Assume user mapped PlatformRequestClose on ALT-F4 so we disable ALT for menu toggle. False positive not an issue.
+                IMGUI_DEBUG_LOG_VIEWPORT("Window '%s' PlatformRequestClose\n", window->Name);
+                *p_open = false;
+            }
+        }
+
         // Title bar
-        if (!(flags & ImGuiWindowFlags_NoTitleBar))
+        if (!(flags & ImGuiWindowFlags_NoTitleBar) && !window->DockIsActive)
             RenderWindowTitleBarContents(window, title_bar_rect, name, p_open);
 
+        // Clear hit test shape every frame
+        window->HitTestHoleSize.x = window->HitTestHoleSize.y = 0;
+
         // Pressing CTRL+C while holding on a window copy its content to the clipboard
         // This works but 1. doesn't handle multiple Begin/End pairs, 2. recursing into another Begin/End pair - so we need to work that out and add better logging scope.
         // Maybe we can support CTRL+C on every element?
@@ -5954,11 +6580,36 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
                 LogToClipboard();
         */
 
+        if (g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable)
+        {
+            // Docking: Dragging a dockable window (or any of its child) turns it into a drag and drop source.
+            // We need to do this _before_ we overwrite window->DC.LastItemId below because BeginDockableDragDropSource() also overwrites it.
+            if ((g.MovingWindow == window) && (g.IO.ConfigDockingWithShift == g.IO.KeyShift))
+                if ((window->RootWindow->Flags & ImGuiWindowFlags_NoDocking) == 0)
+                    BeginDockableDragDropSource(window);
+
+            // Docking: Any dockable window can act as a target. For dock node hosts we call BeginDockableDragDropTarget() in DockNodeUpdate() instead.
+            if (g.DragDropActive && !(flags & ImGuiWindowFlags_NoDocking))
+                if (g.MovingWindow == NULL || g.MovingWindow->RootWindow != window)
+                    if ((window == window->RootWindow) && !(window->Flags & ImGuiWindowFlags_DockNodeHost))
+                        BeginDockableDragDropTarget(window);
+        }
+
         // We fill last item data based on Title Bar/Tab, in order for IsItemHovered() and IsItemActive() to be usable after Begin().
         // This is useful to allow creating context menus on title bar only, etc.
-        window->DC.LastItemId = window->MoveId;
-        window->DC.LastItemStatusFlags = IsMouseHoveringRect(title_bar_rect.Min, title_bar_rect.Max, false) ? ImGuiItemStatusFlags_HoveredRect : 0;
-        window->DC.LastItemRect = title_bar_rect;
+        if (window->DockIsActive)
+        {
+            window->DC.LastItemId = window->ID;
+            window->DC.LastItemStatusFlags = window->DockTabItemStatusFlags;
+            window->DC.LastItemRect = window->DockTabItemRect;
+        }
+        else
+        {
+            window->DC.LastItemId = window->MoveId;
+            window->DC.LastItemStatusFlags = IsMouseHoveringRect(title_bar_rect.Min, title_bar_rect.Max, false) ? ImGuiItemStatusFlags_HoveredRect : 0;
+            window->DC.LastItemRect = title_bar_rect;
+        }
+
 #ifdef IMGUI_ENABLE_TEST_ENGINE
         if (!(window->Flags & ImGuiWindowFlags_NoTitleBar))
             IMGUI_TEST_ENGINE_ITEM_ADD(window->DC.LastItemRect, window->DC.LastItemId);
@@ -5967,10 +6618,12 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     else
     {
         // Append
+        SetCurrentViewport(window, window->Viewport);
         SetCurrentWindow(window);
     }
 
-    PushClipRect(window->InnerClipRect.Min, window->InnerClipRect.Max, true);
+    if (!(flags & ImGuiWindowFlags_DockNodeHost))
+        PushClipRect(window->InnerClipRect.Min, window->InnerClipRect.Max, true);
 
     // Clear 'accessed' flag last thing (After PushClipRect which will set the flag. We want the flag to stay false when the default "Debug" window is unused)
     if (first_begin_of_the_frame)
@@ -5979,11 +6632,23 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     window->BeginCount++;
     g.NextWindowData.ClearFlags();
 
+    // When we are about to select this tab (which will only be visible on the _next frame_), flag it with a non-zero HiddenFramesCannotSkipItems.
+    // This will have the important effect of actually returning true in Begin() and not setting SkipItems, allowing an earlier submission of the window contents.
+    // This is analogous to regular windows being hidden from one frame.
+    // It is especially important as e.g. nested TabBars would otherwise generate flicker in the form of one empty frame, or focus requests won't be processed.
+    if (window->DockIsActive && !window->DockTabIsVisible)
+    {
+        if (window->LastFrameJustFocused == g.FrameCount)
+            window->HiddenFramesCannotSkipItems = 1;
+        else
+            window->HiddenFramesCanSkipItems = 1;
+    }
+
     if (flags & ImGuiWindowFlags_ChildWindow)
     {
         // Child window can be out of sight and have "negative" clip windows.
         // Mark them as collapsed so commands are skipped earlier (we can't manually collapse them because they have no title bar).
-        IM_ASSERT((flags & ImGuiWindowFlags_NoTitleBar) != 0);
+        IM_ASSERT((flags & ImGuiWindowFlags_NoTitleBar) != 0 || (window->DockIsActive));
         if (!(flags & ImGuiWindowFlags_AlwaysAutoResize) && window->AutoFitFramesX <= 0 && window->AutoFitFramesY <= 0)
             if (window->OuterRectClipped.Min.x >= window->OuterRectClipped.Max.x || window->OuterRectClipped.Min.y >= window->OuterRectClipped.Max.y)
                 window->HiddenFramesCanSkipItems = 1;
@@ -6026,24 +6691,32 @@ void ImGui::End()
     IM_ASSERT(g.CurrentWindowStack.Size > 0);
 
     // Error checking: verify that user doesn't directly call End() on a child window.
-    if (window->Flags & ImGuiWindowFlags_ChildWindow)
+    if ((window->Flags & ImGuiWindowFlags_ChildWindow) && !window->DockIsActive)
         IM_ASSERT_USER_ERROR(g.WithinEndChild, "Must call EndChild() and not End()!");
 
     // Close anything that is open
     if (window->DC.CurrentColumns)
         EndColumns();
-    PopClipRect();   // Inner window clip rectangle
+    if (!(window->Flags & ImGuiWindowFlags_DockNodeHost))   // Pop inner window clip rectangle
+        PopClipRect();
 
     // Stop logging
     if (!(window->Flags & ImGuiWindowFlags_ChildWindow))    // FIXME: add more options for scope of logging
         LogFinish();
 
+    // Docking: report contents sizes to parent to allow for auto-resize
+    if (window->DockNode && window->DockTabIsVisible)
+        if (ImGuiWindow* host_window = window->DockNode->HostWindow)         // FIXME-DOCK
+            host_window->DC.CursorMaxPos = window->DC.CursorMaxPos + window->WindowPadding - host_window->WindowPadding;
+
     // Pop from window stack
     g.CurrentWindowStack.pop_back();
     if (window->Flags & ImGuiWindowFlags_Popup)
         g.BeginPopupStack.pop_back();
     ErrorCheckBeginEndCompareStacksSize(window, false);
     SetCurrentWindow(g.CurrentWindowStack.empty() ? NULL : g.CurrentWindowStack.back());
+    if (g.CurrentWindow)
+        SetCurrentViewport(g.CurrentWindow, g.CurrentWindow->Viewport);
 }
 
 void ImGui::BringWindowToFocusFront(ImGuiWindow* window)
@@ -6113,10 +6786,15 @@ void ImGui::FocusWindow(ImGuiWindow* window)
     // Passing NULL allow to disable keyboard focus
     if (!window)
         return;
+    window->LastFrameJustFocused = g.FrameCount;
+
+    // Select in dock node
+    if (window->DockNode && window->DockNode->TabBar)
+        window->DockNode->TabBar->SelectedTabId = window->DockNode->TabBar->NextSelectedTabId = window->ID;
 
     // Move the root window to the top of the pile
     IM_ASSERT(window->RootWindow != NULL);
-    ImGuiWindow* focus_front_window = window->RootWindow; // NB: In docking branch this is window->RootWindowDockStop
+    ImGuiWindow* focus_front_window = window->RootWindowDockStop;
     ImGuiWindow* display_front_window = window->RootWindow;
 
     // Steal focus on active widgets
@@ -6126,7 +6804,7 @@ void ImGui::FocusWindow(ImGuiWindow* window)
 
     // Bring to front
     BringWindowToFocusFront(focus_front_window);
-    if (((window->Flags | display_front_window->Flags) & ImGuiWindowFlags_NoBringToFrontOnFocus) == 0)
+    if (((window->Flags | focus_front_window->Flags | display_front_window->Flags) & ImGuiWindowFlags_NoBringToFrontOnFocus) == 0)
         BringWindowToDisplayFront(display_front_window);
 }
 
@@ -6145,9 +6823,13 @@ void ImGui::FocusTopMostWindowUnderOne(ImGuiWindow* under_this_window, ImGuiWind
     {
         // We may later decide to test for different NoXXXInputs based on the active navigation input (mouse vs nav) but that may feel more confusing to the user.
         ImGuiWindow* window = g.WindowsFocusOrder[i];
-        if (window != ignore_window && window->WasActive && !(window->Flags & ImGuiWindowFlags_ChildWindow))
+        if (window != ignore_window && window->WasActive && window->RootWindowDockStop == window)
             if ((window->Flags & (ImGuiWindowFlags_NoMouseInputs | ImGuiWindowFlags_NoNavInputs)) != (ImGuiWindowFlags_NoMouseInputs | ImGuiWindowFlags_NoNavInputs))
             {
+                // FIXME-DOCK: This is failing (lagging by one frame) for docked windows.
+                // If A and B are docked into window and B disappear, at the NewFrame() call site window->NavLastChildNavWindow will still point to B.
+                // We might leverage the tab order implicitly stored in window->DockNodeAsHost->TabBar (essentially the 'most_recently_selected_tab' code in tab bar will do that but on next update)
+                // to tell which is the "previous" window. Or we may leverage 'LastFrameFocused/LastFrameJustFocused' and have this function handle child window itself?
                 ImGuiWindow* focus_window = NavRestoreLastChildNavWindow(window);
                 FocusWindow(focus_window);
                 return;
@@ -6269,11 +6951,11 @@ bool ImGui::IsWindowHovered(ImGuiHoveredFlags flags)
         switch (flags & (ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_ChildWindows))
         {
         case ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_ChildWindows:
-            if (g.HoveredRootWindow != g.CurrentWindow->RootWindow)
+            if (g.HoveredWindow == NULL || g.HoveredWindow->RootWindowDockStop != g.CurrentWindow->RootWindowDockStop)
                 return false;
             break;
         case ImGuiHoveredFlags_RootWindow:
-            if (g.HoveredWindow != g.CurrentWindow->RootWindow)
+            if (g.HoveredWindow != g.CurrentWindow->RootWindowDockStop)
                 return false;
             break;
         case ImGuiHoveredFlags_ChildWindows:
@@ -6306,9 +6988,9 @@ bool ImGui::IsWindowFocused(ImGuiFocusedFlags flags)
     switch (flags & (ImGuiFocusedFlags_RootWindow | ImGuiFocusedFlags_ChildWindows))
     {
     case ImGuiFocusedFlags_RootWindow | ImGuiFocusedFlags_ChildWindows:
-        return g.NavWindow && g.NavWindow->RootWindow == g.CurrentWindow->RootWindow;
+        return g.NavWindow && g.NavWindow->RootWindowDockStop == g.CurrentWindow->RootWindowDockStop;
     case ImGuiFocusedFlags_RootWindow:
-        return g.NavWindow == g.CurrentWindow->RootWindow;
+        return g.NavWindow == g.CurrentWindow->RootWindowDockStop;
     case ImGuiFocusedFlags_ChildWindows:
         return g.NavWindow && IsWindowChildOf(g.NavWindow, g.CurrentWindow);
     default:
@@ -6316,12 +6998,24 @@ bool ImGui::IsWindowFocused(ImGuiFocusedFlags flags)
     }
 }
 
+ImGuiID ImGui::GetWindowDockID()
+{
+    ImGuiContext& g = *GImGui;
+    return g.CurrentWindow->DockId;
+}
+
+bool ImGui::IsWindowDocked()
+{
+    ImGuiContext& g = *GImGui;
+    return g.CurrentWindow->DockIsActive;
+}
+
 // Can we focus this window with CTRL+TAB (or PadMenu + PadFocusPrev/PadFocusNext)
 // Note that NoNavFocus makes the window not reachable with CTRL+TAB but it can still be focused with mouse or programmaticaly.
 // If you want a window to never be focused, you may use the e.g. NoInputs flag.
 bool ImGui::IsWindowNavFocusable(ImGuiWindow* window)
 {
-    return window->Active && window == window->RootWindow && !(window->Flags & ImGuiWindowFlags_NoNavFocus);
+    return window->Active && window == window->RootWindowDockStop && !(window->Flags & ImGuiWindowFlags_NoNavFocus);
 }
 
 float ImGui::GetWindowWidth()
@@ -6434,6 +7128,13 @@ void ImGui::SetWindowCollapsed(ImGuiWindow* window, bool collapsed, ImGuiCond co
     window->Collapsed = collapsed;
 }
 
+static void SetWindowHitTestHole(ImGuiWindow* window, const ImVec2& pos, const ImVec2& size)
+{
+    IM_ASSERT(window->HitTestHoleSize.x == 0);     // We don't support multiple holes/hit test filters
+    window->HitTestHoleSize = ImVec2ih(size);
+    window->HitTestHoleOffset = ImVec2ih(pos - window->Pos);
+}
+
 void ImGui::SetWindowCollapsed(bool collapsed, ImGuiCond cond)
 {
     SetWindowCollapsed(GImGui->CurrentWindow, collapsed, cond);
@@ -6483,6 +7184,7 @@ void ImGui::SetNextWindowPos(const ImVec2& pos, ImGuiCond cond, const ImVec2& pi
     g.NextWindowData.PosVal = pos;
     g.NextWindowData.PosPivotVal = pivot;
     g.NextWindowData.PosCond = cond ? cond : ImGuiCond_Always;
+    g.NextWindowData.PosUndock = true;
 }
 
 void ImGui::SetNextWindowSize(const ImVec2& size, ImGuiCond cond)
@@ -6512,6 +7214,13 @@ void ImGui::SetNextWindowContentSize(const ImVec2& size)
     g.NextWindowData.ContentSizeVal = size;
 }
 
+void ImGui::SetNextWindowScroll(const ImVec2& scroll)
+{
+    ImGuiContext& g = *GImGui;
+    g.NextWindowData.Flags |= ImGuiNextWindowDataFlags_HasScroll;
+    g.NextWindowData.ScrollVal = scroll;
+}
+
 void ImGui::SetNextWindowCollapsed(bool collapsed, ImGuiCond cond)
 {
     ImGuiContext& g = *GImGui;
@@ -6534,12 +7243,48 @@ void ImGui::SetNextWindowBgAlpha(float alpha)
     g.NextWindowData.BgAlphaVal = alpha;
 }
 
+void ImGui::SetNextWindowViewport(ImGuiID id)
+{
+    ImGuiContext& g = *GImGui;
+    g.NextWindowData.Flags |= ImGuiNextWindowDataFlags_HasViewport;
+    g.NextWindowData.ViewportId = id;
+}
+
+void ImGui::SetNextWindowDockID(ImGuiID id, ImGuiCond cond)
+{
+    ImGuiContext& g = *GImGui;
+    g.NextWindowData.Flags |= ImGuiNextWindowDataFlags_HasDock;
+    g.NextWindowData.DockCond = cond ? cond : ImGuiCond_Always;
+    g.NextWindowData.DockId = id;
+}
+
+void ImGui::SetNextWindowClass(const ImGuiWindowClass* window_class)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT((window_class->ViewportFlagsOverrideSet & window_class->ViewportFlagsOverrideClear) == 0); // Cannot set both set and clear for the same bit
+    g.NextWindowData.Flags |= ImGuiNextWindowDataFlags_HasWindowClass;
+    g.NextWindowData.WindowClass = *window_class;
+}
+
 ImDrawList* ImGui::GetWindowDrawList()
 {
     ImGuiWindow* window = GetCurrentWindow();
     return window->DrawList;
 }
 
+float ImGui::GetWindowDpiScale()
+{
+    ImGuiContext& g = *GImGui;
+    return g.CurrentDpiScale;
+}
+
+ImGuiViewport* ImGui::GetWindowViewport()
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(g.CurrentViewport != NULL && g.CurrentViewport == g.CurrentWindow->Viewport);
+    return g.CurrentViewport;
+}
+
 ImFont* ImGui::GetFont()
 {
     return GImGui->Font;
@@ -6626,32 +7371,41 @@ ImGuiStorage* ImGui::GetStateStorage()
 
 void ImGui::PushID(const char* str_id)
 {
-    ImGuiWindow* window = GImGui->CurrentWindow;
-    window->IDStack.push_back(window->GetIDNoKeepAlive(str_id));
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = g.CurrentWindow;
+    ImGuiID id = window->GetIDNoKeepAlive(str_id);
+    window->IDStack.push_back(id);
 }
 
 void ImGui::PushID(const char* str_id_begin, const char* str_id_end)
 {
-    ImGuiWindow* window = GImGui->CurrentWindow;
-    window->IDStack.push_back(window->GetIDNoKeepAlive(str_id_begin, str_id_end));
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = g.CurrentWindow;
+    ImGuiID id = window->GetIDNoKeepAlive(str_id_begin, str_id_end);
+    window->IDStack.push_back(id);
 }
 
 void ImGui::PushID(const void* ptr_id)
 {
-    ImGuiWindow* window = GImGui->CurrentWindow;
-    window->IDStack.push_back(window->GetIDNoKeepAlive(ptr_id));
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = g.CurrentWindow;
+    ImGuiID id = window->GetIDNoKeepAlive(ptr_id);
+    window->IDStack.push_back(id);
 }
 
 void ImGui::PushID(int int_id)
 {
-    ImGuiWindow* window = GImGui->CurrentWindow;
-    window->IDStack.push_back(window->GetIDNoKeepAlive(int_id));
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = g.CurrentWindow;
+    ImGuiID id = window->GetIDNoKeepAlive(int_id);
+    window->IDStack.push_back(id);
 }
 
 // Push a given id value ignoring the ID stack as a seed.
 void ImGui::PushOverrideID(ImGuiID id)
 {
-    ImGuiWindow* window = GImGui->CurrentWindow;
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = g.CurrentWindow;
     window->IDStack.push_back(id);
 }
 
@@ -6749,6 +7503,49 @@ static void ImGui::ErrorCheckNewFrameSanityChecks()
     // Perform simple check: the beta io.ConfigWindowsResizeFromEdges option requires back-end to honor mouse cursor changes and set the ImGuiBackendFlags_HasMouseCursors flag accordingly.
     if (g.IO.ConfigWindowsResizeFromEdges && !(g.IO.BackendFlags & ImGuiBackendFlags_HasMouseCursors))
         g.IO.ConfigWindowsResizeFromEdges = false;
+
+    // Perform simple check: error if Docking or Viewport are enabled _exactly_ on frame 1 (instead of frame 0 or later), which is a common error leading to loss of .ini data.
+    if (g.FrameCount == 1 && (g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable) && (g.ConfigFlagsLastFrame & ImGuiConfigFlags_DockingEnable) == 0)
+        IM_ASSERT(0 && "Please set DockingEnable before the first call to NewFrame()! Otherwise you will lose your .ini settings!");
+    if (g.FrameCount == 1 && (g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) && (g.ConfigFlagsLastFrame & ImGuiConfigFlags_ViewportsEnable) == 0)
+        IM_ASSERT(0 && "Please set ViewportsEnable before the first call to NewFrame()! Otherwise you will lose your .ini settings!");
+
+    // Perform simple checks: multi-viewport and platform windows support
+    if (g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        if ((g.IO.BackendFlags & ImGuiBackendFlags_PlatformHasViewports) && (g.IO.BackendFlags & ImGuiBackendFlags_RendererHasViewports))
+        {
+            IM_ASSERT((g.FrameCount == 0 || g.FrameCount == g.FrameCountPlatformEnded) && "Forgot to call UpdatePlatformWindows() in main loop after EndFrame()? Check examples/ applications for reference.");
+            IM_ASSERT(g.PlatformIO.Platform_CreateWindow  != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Platform_DestroyWindow != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Platform_GetWindowPos  != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Platform_SetWindowPos  != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Platform_GetWindowSize != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Platform_SetWindowSize != NULL && "Platform init didn't install handlers?");
+            IM_ASSERT(g.PlatformIO.Monitors.Size > 0 && "Platform init didn't setup Monitors list?");
+            IM_ASSERT((g.Viewports[0]->PlatformUserData != NULL || g.Viewports[0]->PlatformHandle != NULL) && "Platform init didn't setup main viewport.");
+            if (g.IO.ConfigDockingTransparentPayload && (g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
+                IM_ASSERT(g.PlatformIO.Platform_SetWindowAlpha != NULL && "Platform_SetWindowAlpha handler is required to use io.ConfigDockingTransparent!");
+#ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
+            IM_ASSERT(g.IO.RenderDrawListsFn == NULL);  // Call ImGui::Render() then pass ImGui::GetDrawData() yourself to your render function!
+#endif
+        }
+        else
+        {
+            // Disable feature, our back-ends do not support it
+            g.IO.ConfigFlags &= ~ImGuiConfigFlags_ViewportsEnable;
+        }
+
+        // Perform simple checks on platform monitor data + compute a total bounding box for quick early outs
+        for (int monitor_n = 0; monitor_n < g.PlatformIO.Monitors.Size; monitor_n++)
+        {
+            ImGuiPlatformMonitor& mon = g.PlatformIO.Monitors[monitor_n];
+            IM_UNUSED(mon);
+            IM_ASSERT(mon.MainSize.x > 0.0f && mon.MainSize.y > 0.0f && "Monitor bounds not setup properly.");
+            IM_ASSERT(mon.WorkSize.x > 0.0f && mon.WorkSize.y > 0.0f && "Monitor bounds not setup properly. If you don't have work area information, just copy Min/Max into them.");
+            IM_ASSERT(mon.DpiScale != 0.0f);
+        }
+    }
 }
 
 static void ImGui::ErrorCheckEndFrameSanityChecks()
@@ -7481,7 +8278,7 @@ void ImGui::BeginTooltipEx(ImGuiWindowFlags extra_flags, ImGuiTooltipFlags toolt
                 window->HiddenFramesCanSkipItems = 1;
                 ImFormatString(window_name, IM_ARRAYSIZE(window_name), "##Tooltip_%02d", ++g.TooltipOverrideCount);
             }
-    ImGuiWindowFlags flags = ImGuiWindowFlags_Tooltip|ImGuiWindowFlags_NoInputs|ImGuiWindowFlags_NoTitleBar|ImGuiWindowFlags_NoMove|ImGuiWindowFlags_NoResize|ImGuiWindowFlags_NoSavedSettings|ImGuiWindowFlags_AlwaysAutoResize;
+    ImGuiWindowFlags flags = ImGuiWindowFlags_Tooltip|ImGuiWindowFlags_NoInputs|ImGuiWindowFlags_NoTitleBar|ImGuiWindowFlags_NoMove|ImGuiWindowFlags_NoResize|ImGuiWindowFlags_NoSavedSettings|ImGuiWindowFlags_AlwaysAutoResize|ImGuiWindowFlags_NoDocking;
     Begin(window_name, NULL, flags | extra_flags);
 }
 
@@ -7556,7 +8353,7 @@ void ImGui::OpenPopupEx(ImGuiID id)
     popup_ref.OpenPopupPos = NavCalcPreferredRefPos();
     popup_ref.OpenMousePos = IsMousePosValid(&g.IO.MousePos) ? g.IO.MousePos : popup_ref.OpenPopupPos;
 
-    //IMGUI_DEBUG_LOG("OpenPopupEx(0x%08X)\n", g.FrameCount, id);
+    IMGUI_DEBUG_LOG_POPUP("OpenPopupEx(0x%08X)\n", id);
     if (g.OpenPopupStack.Size < current_stack_size + 1)
     {
         g.OpenPopupStack.push_back(popup_ref);
@@ -7617,7 +8414,7 @@ void ImGui::ClosePopupsOverWindow(ImGuiWindow* ref_window, bool restore_focus_to
     }
     if (popup_count_to_keep < g.OpenPopupStack.Size) // This test is not required but it allows to set a convenient breakpoint on the statement below
     {
-        //IMGUI_DEBUG_LOG("ClosePopupsOverWindow(%s) -> ClosePopupToLevel(%d)\n", ref_window->Name, popup_count_to_keep);
+        IMGUI_DEBUG_LOG_POPUP("ClosePopupsOverWindow(\"%s\") -> ClosePopupToLevel(%d)\n", ref_window->Name, popup_count_to_keep);
         ClosePopupToLevel(popup_count_to_keep, restore_focus_to_window_under_popup);
     }
 }
@@ -7625,6 +8422,7 @@ void ImGui::ClosePopupsOverWindow(ImGuiWindow* ref_window, bool restore_focus_to
 void ImGui::ClosePopupToLevel(int remaining, bool restore_focus_to_window_under_popup)
 {
     ImGuiContext& g = *GImGui;
+    IMGUI_DEBUG_LOG_POPUP("ClosePopupToLevel(%d), restore_focus_to_window_under_popup=%d\n", remaining, restore_focus_to_window_under_popup);
     IM_ASSERT(remaining >= 0 && remaining < g.OpenPopupStack.Size);
     ImGuiWindow* focus_window = g.OpenPopupStack[remaining].SourceWindow;
     ImGuiWindow* popup_window = g.OpenPopupStack[remaining].Window;
@@ -7667,7 +8465,7 @@ void ImGui::CloseCurrentPopup()
             break;
         popup_idx--;
     }
-    //IMGUI_DEBUG_LOG("CloseCurrentPopup %d -> %d\n", g.BeginPopupStack.Size - 1, popup_idx);
+    IMGUI_DEBUG_LOG_POPUP("CloseCurrentPopup %d -> %d\n", g.BeginPopupStack.Size - 1, popup_idx);
     ClosePopupToLevel(popup_idx, true);
 
     // A common pattern is to close a popup when selecting a menu item/selectable that will open another window.
@@ -7692,7 +8490,7 @@ bool ImGui::BeginPopupEx(ImGuiID id, ImGuiWindowFlags flags)
     else
         ImFormatString(name, IM_ARRAYSIZE(name), "##Popup_%08x", id); // Not recycling, so we can close/open during the same frame
 
-    flags |= ImGuiWindowFlags_Popup;
+    flags |= ImGuiWindowFlags_Popup | ImGuiWindowFlags_NoDocking;
     bool is_open = Begin(name, NULL, flags);
     if (!is_open) // NB: Begin can return false when the popup is completely clipped (e.g. zero size display)
         EndPopup();
@@ -7728,9 +8526,12 @@ bool ImGui::BeginPopupModal(const char* name, bool* p_open, ImGuiWindowFlags fla
     // Center modal windows by default
     // FIXME: Should test for (PosCond & window->SetWindowPosAllowFlags) with the upcoming window.
     if ((g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasPos) == 0)
-        SetNextWindowPos(g.IO.DisplaySize * 0.5f, ImGuiCond_Appearing, ImVec2(0.5f, 0.5f));
+    {
+        ImGuiViewportP* viewport = window->WasActive ? window->Viewport : (ImGuiViewportP*)GetMainViewport(); // FIXME-VIEWPORT: What may be our reference viewport?
+        SetNextWindowPos(viewport->GetMainRect().GetCenter(), ImGuiCond_Appearing, ImVec2(0.5f, 0.5f));
+    }
 
-    flags |= ImGuiWindowFlags_Popup | ImGuiWindowFlags_Modal | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoSavedSettings;
+    flags |= ImGuiWindowFlags_Popup | ImGuiWindowFlags_Modal | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoDocking;
     const bool is_open = Begin(name, p_open, flags);
     if (!is_open || (p_open && !*p_open)) // NB: is_open can be 'false' when the popup is completely clipped (e.g. zero size display)
     {
@@ -7811,6 +8612,9 @@ bool ImGui::BeginPopupContextVoid(const char* str_id, ImGuiMouseButton mouse_but
 
 // r_avoid = the rectangle to avoid (e.g. for tooltip it is a rectangle around the mouse cursor which we want to avoid. for popups it's a small point around the cursor.)
 // r_outer = the visible area rectangle, minus safe area padding. If our popup size won't fit because of safe area padding we ignore it.
+// (r_outer is usually equivalent to the viewport rectangle minus padding, but when multi-viewports are enabled and monitor
+//  information are available, it may represent the entire platform monitor from the frame of reference of the current viewport.
+//  this allows us to have tooltips/popups displayed out of the parent viewport.)
 ImVec2 ImGui::FindBestWindowPosForPopupEx(const ImVec2& ref_pos, const ImVec2& size, ImGuiDir* last_dir, const ImRect& r_outer, const ImRect& r_avoid, ImGuiPopupPositionPolicy policy)
 {
     ImVec2 base_pos_clamped = ImClamp(ref_pos, r_outer.Min, r_outer.Max - size);
@@ -7864,11 +8668,25 @@ ImVec2 ImGui::FindBestWindowPosForPopupEx(const ImVec2& ref_pos, const ImVec2& s
     return pos;
 }
 
+// Note that this is used for popups, which can overlap the non work-area of individual viewports.
 ImRect ImGui::GetWindowAllowedExtentRect(ImGuiWindow* window)
 {
-    IM_UNUSED(window);
-    ImVec2 padding = GImGui->Style.DisplaySafeAreaPadding;
-    ImRect r_screen = GetViewportRect();
+    ImGuiContext& g = *GImGui;
+    ImRect r_screen;
+    if (window->ViewportAllowPlatformMonitorExtend >= 0)
+    {
+        // Extent with be in the frame of reference of the given viewport (so Min is likely to be negative here)
+        const ImGuiPlatformMonitor& monitor = g.PlatformIO.Monitors[window->ViewportAllowPlatformMonitorExtend];
+        r_screen.Min = monitor.WorkPos;
+        r_screen.Max = monitor.WorkPos + monitor.WorkSize;
+    }
+    else
+    {
+        // Use the full viewport area (not work area) for popups
+        r_screen.Min = window->Viewport->Pos;
+        r_screen.Max = window->Viewport->Pos + window->Viewport->Size;
+    }
+    ImVec2 padding = g.Style.DisplaySafeAreaPadding;
     r_screen.Expand(ImVec2((r_screen.GetWidth() > padding.x * 2) ? -padding.x : 0.0f, (r_screen.GetHeight() > padding.y * 2) ? -padding.y : 0.0f));
     return r_screen;
 }
@@ -7876,15 +8694,13 @@ ImRect ImGui::GetWindowAllowedExtentRect(ImGuiWindow* window)
 ImVec2 ImGui::FindBestWindowPosForPopup(ImGuiWindow* window)
 {
     ImGuiContext& g = *GImGui;
-
-    ImRect r_outer = GetWindowAllowedExtentRect(window);
     if (window->Flags & ImGuiWindowFlags_ChildMenu)
     {
         // Child menus typically request _any_ position within the parent menu item, and then we move the new menu outside the parent bounds.
         // This is how we end up with child menus appearing (most-commonly) on the right of the parent menu.
-        IM_ASSERT(g.CurrentWindow == window);
-        ImGuiWindow* parent_window = g.CurrentWindowStack[g.CurrentWindowStack.Size - 2];
+        ImGuiWindow* parent_window = window->ParentWindow;
         float horizontal_overlap = g.Style.ItemInnerSpacing.x; // We want some overlap to convey the relative depth of each menu (currently the amount of overlap is hard-coded to style.ItemSpacing.x).
+        ImRect r_outer = GetWindowAllowedExtentRect(window);
         ImRect r_avoid;
         if (parent_window->DC.MenuBarAppending)
             r_avoid = ImRect(-FLT_MAX, parent_window->ClipRect.Min.y, FLT_MAX, parent_window->ClipRect.Max.y); // Avoid parent menu-bar. If we wanted multi-line menu-bar, we may instead want to have the calling window setup e.g. a NextWindowData.PosConstraintAvoidRect field
@@ -7894,6 +8710,7 @@ ImVec2 ImGui::FindBestWindowPosForPopup(ImGuiWindow* window)
     }
     if (window->Flags & ImGuiWindowFlags_Popup)
     {
+        ImRect r_outer = GetWindowAllowedExtentRect(window);
         ImRect r_avoid = ImRect(window->Pos.x - 1, window->Pos.y - 1, window->Pos.x + 1, window->Pos.y + 1);
         return FindBestWindowPosForPopupEx(window->Pos, window->Size, &window->AutoPosLastDirection, r_outer, r_avoid);
     }
@@ -7902,6 +8719,7 @@ ImVec2 ImGui::FindBestWindowPosForPopup(ImGuiWindow* window)
         // Position tooltip (always follows mouse)
         float sc = g.Style.MouseCursorScale;
         ImVec2 ref_pos = NavCalcPreferredRefPos();
+        ImRect r_outer = GetWindowAllowedExtentRect(window);
         ImRect r_avoid;
         if (!g.NavDisableHighlight && g.NavDisableMouseHover && !(g.IO.ConfigFlags & ImGuiConfigFlags_NavEnableSetMousePos))
             r_avoid = ImRect(ref_pos.x - 16, ref_pos.y - 8, ref_pos.x + 16, ref_pos.y + 8);
@@ -8265,18 +9083,23 @@ void ImGui::NavMoveRequestTryWrapping(ImGuiWindow* window, ImGuiNavMoveFlags mov
 // This way we could find the last focused window among our children. It would be much less confusing this way?
 static void ImGui::NavSaveLastChildNavWindowIntoParent(ImGuiWindow* nav_window)
 {
-    ImGuiWindow* parent_window = nav_window;
-    while (parent_window && (parent_window->Flags & ImGuiWindowFlags_ChildWindow) != 0 && (parent_window->Flags & (ImGuiWindowFlags_Popup | ImGuiWindowFlags_ChildMenu)) == 0)
-        parent_window = parent_window->ParentWindow;
-    if (parent_window && parent_window != nav_window)
-        parent_window->NavLastChildNavWindow = nav_window;
+    ImGuiWindow* parent = nav_window;
+    while (parent && parent->RootWindowDockStop != parent && (parent->Flags & ImGuiWindowFlags_ChildWindow) != 0 && (parent->Flags & (ImGuiWindowFlags_Popup | ImGuiWindowFlags_ChildMenu)) == 0)
+        parent = parent->ParentWindow;
+    if (parent && parent != nav_window)
+        parent->NavLastChildNavWindow = nav_window;
 }
 
 // Restore the last focused child.
 // Call when we are expected to land on the Main Layer (0) after FocusWindow()
 static ImGuiWindow* ImGui::NavRestoreLastChildNavWindow(ImGuiWindow* window)
 {
-    return window->NavLastChildNavWindow ? window->NavLastChildNavWindow : window;
+    if (window->NavLastChildNavWindow && window->NavLastChildNavWindow->WasActive)
+        return window->NavLastChildNavWindow;
+    if (window->DockNodeAsHost && window->DockNodeAsHost->TabBar)
+        if (ImGuiTabItem* tab = TabBarFindMostRecentlySelectedTabForActiveWindow(window->DockNodeAsHost->TabBar))
+            return tab->Window;
+    return window;
 }
 
 static void NavRestoreLayer(ImGuiNavLayer layer)
@@ -8286,8 +9109,8 @@ static void NavRestoreLayer(ImGuiNavLayer layer)
     if (layer == 0)
         g.NavWindow = ImGui::NavRestoreLastChildNavWindow(g.NavWindow);
     ImGuiWindow* window = g.NavWindow;
-    if (layer == 0 && window->NavLastIds[0] != 0)
-        ImGui::SetNavIDWithRectRel(window->NavLastIds[0], layer, 0, window->NavRectRel[0]);
+    if (window->NavLastIds[layer] != 0)
+        ImGui::SetNavIDWithRectRel(window->NavLastIds[layer], layer, 0, g.NavWindow->NavRectRel[layer]);
     else
         ImGui::NavInitWindow(window, true);
 }
@@ -8341,7 +9164,7 @@ static ImVec2 ImGui::NavCalcPreferredRefPos()
         // When navigation is active and mouse is disabled, decide on an arbitrary position around the bottom left of the currently navigated item.
         const ImRect& rect_rel = g.NavWindow->NavRectRel[g.NavLayer];
         ImVec2 pos = g.NavWindow->Pos + ImVec2(rect_rel.Min.x + ImMin(g.Style.FramePadding.x * 4, rect_rel.GetWidth()), rect_rel.Max.y - ImMin(g.Style.FramePadding.y, rect_rel.GetHeight()));
-        ImRect visible_rect = GetViewportRect();
+        ImRect visible_rect = g.NavWindow->Viewport->GetMainRect();
         return ImFloor(ImClamp(pos, visible_rect.Min, visible_rect.Max));   // ImFloor() is important because non-integer mouse position application in back-end might be lossy and result in undesirable non-zero delta.
     }
 }
@@ -8492,7 +9315,7 @@ static void ImGui::NavUpdate()
             if (!IsActiveIdUsingNavInput(ImGuiNavInput_Cancel))
                 ClearActiveID();
         }
-        else if (g.NavWindow && (g.NavWindow->Flags & ImGuiWindowFlags_ChildWindow) && !(g.NavWindow->Flags & ImGuiWindowFlags_Popup) && g.NavWindow->ParentWindow)
+        else if (g.NavWindow && (g.NavWindow->Flags & ImGuiWindowFlags_ChildWindow) && !(g.NavWindow->Flags & ImGuiWindowFlags_Popup) && g.NavWindow->ParentWindow && g.NavWindow != g.NavWindow->RootWindowDockStop)
         {
             // Exit child window
             ImGuiWindow* child_window = g.NavWindow;
@@ -8649,7 +9472,7 @@ static void ImGui::NavUpdate()
 
     // For scoring we use a single segment on the left side our current item bounding box (not touching the edge to avoid box overlap with zero-spaced items)
     ImRect nav_rect_rel = (g.NavWindow && !g.NavWindow->NavRectRel[g.NavLayer].IsInverted()) ? g.NavWindow->NavRectRel[g.NavLayer] : ImRect(0,0,0,0);
-    g.NavScoringRect = g.NavWindow ? ImRect(g.NavWindow->Pos + nav_rect_rel.Min, g.NavWindow->Pos + nav_rect_rel.Max) : GetViewportRect();
+    g.NavScoringRect = g.NavWindow ? ImRect(g.NavWindow->Pos + nav_rect_rel.Min, g.NavWindow->Pos + nav_rect_rel.Max) : ImRect(0,0,0,0);
     g.NavScoringRect.TranslateY(nav_scoring_rect_offset_y);
     g.NavScoringRect.Min.x = ImMin(g.NavScoringRect.Min.x + 1.0f, g.NavScoringRect.Max.x);
     g.NavScoringRect.Max.x = g.NavScoringRect.Min.x;
@@ -8865,7 +9688,7 @@ static void ImGui::NavUpdateWindowing()
     if (start_windowing_with_gamepad || start_windowing_with_keyboard)
         if (ImGuiWindow* window = g.NavWindow ? g.NavWindow : FindWindowNavFocusable(g.WindowsFocusOrder.Size - 1, -INT_MAX, -1))
         {
-            g.NavWindowingTarget = g.NavWindowingTargetAnim = window->RootWindow; // FIXME-DOCK: Will need to use RootWindowDockStop
+            g.NavWindowingTarget = g.NavWindowingTargetAnim = window->RootWindowDockStop;
             g.NavWindowingTimer = g.NavWindowingHighlightAlpha = 0.0f;
             g.NavWindowingToggleLayer = start_windowing_with_keyboard ? false : true;
             g.NavInputSource = start_windowing_with_keyboard ? ImGuiInputSource_NavKeyboard : ImGuiInputSource_NavGamepad;
@@ -8936,8 +9759,9 @@ static void ImGui::NavUpdateWindowing()
     }
 
     // Apply final focus
-    if (apply_focus_window && (g.NavWindow == NULL || apply_focus_window != g.NavWindow->RootWindow))
+    if (apply_focus_window && (g.NavWindow == NULL || apply_focus_window != g.NavWindow->RootWindowDockStop))
     {
+        ImGuiViewport* previous_viewport = g.NavWindow ? g.NavWindow->Viewport : NULL;
         ClearActiveID();
         g.NavDisableHighlight = false;
         g.NavDisableMouseHover = true;
@@ -8950,6 +9774,10 @@ static void ImGui::NavUpdateWindowing()
         // If the window only has a menu layer, select it directly
         if (apply_focus_window->DC.NavLayerActiveMask == (1 << ImGuiNavLayer_Menu))
             g.NavLayer = ImGuiNavLayer_Menu;
+
+        // Request OS level focus
+        if (apply_focus_window->Viewport != previous_viewport && g.PlatformIO.Platform_SetWindowFocus)
+            g.PlatformIO.Platform_SetWindowFocus(apply_focus_window->Viewport);
     }
     if (apply_focus_window)
         g.NavWindowingTarget = NULL;
@@ -8973,8 +9801,11 @@ static void ImGui::NavUpdateWindowing()
         g.NavDisableHighlight = false;
         g.NavDisableMouseHover = true;
 
-        // When entering a regular menu bar with the Alt key, we always reinitialize the navigation ID.
+        // When entering a regular menu bar with the Alt key, we always reinitialize the navigation ID. It however persist on docking tab tabs.
         const ImGuiNavLayer new_nav_layer = (g.NavWindow->DC.NavLayerActiveMask & (1 << ImGuiNavLayer_Menu)) ? (ImGuiNavLayer)((int)g.NavLayer ^ 1) : ImGuiNavLayer_Main;
+        const bool preserve_layer_1_nav_id = (new_nav_window->DockNodeAsHost != NULL);
+        if (new_nav_layer == ImGuiNavLayer_Menu && !preserve_layer_1_nav_id)
+            g.NavWindow->NavLastIds[ImGuiNavLayer_Menu] = 0;
         NavRestoreLayer(new_nav_layer);
     }
 }
@@ -8986,6 +9817,8 @@ static const char* GetFallbackWindowNameForWindowingList(ImGuiWindow* window)
         return "(Popup)";
     if ((window->Flags & ImGuiWindowFlags_MenuBar) && strcmp(window->Name, "##MainMenuBar") == 0)
         return "(Main menu bar)";
+    if (window->DockNodeAsHost)
+        return "(Dock node)";
     return "(Untitled)";
 }
 
@@ -9000,8 +9833,9 @@ void ImGui::NavUpdateWindowingOverlay()
 
     if (g.NavWindowingList == NULL)
         g.NavWindowingList = FindWindowByName("###NavWindowingList");
-    SetNextWindowSizeConstraints(ImVec2(g.IO.DisplaySize.x * 0.20f, g.IO.DisplaySize.y * 0.20f), ImVec2(FLT_MAX, FLT_MAX));
-    SetNextWindowPos(g.IO.DisplaySize * 0.5f, ImGuiCond_Always, ImVec2(0.5f, 0.5f));
+    ImGuiViewportP* viewport = /*g.NavWindow ? g.NavWindow->Viewport :*/ (ImGuiViewportP*)GetMainViewport();
+    SetNextWindowSizeConstraints(ImVec2(viewport->Size.x * 0.20f, viewport->Size.y * 0.20f), ImVec2(FLT_MAX, FLT_MAX));
+    SetNextWindowPos(viewport->Pos + viewport->Size * 0.5f, ImGuiCond_Always, ImVec2(0.5f, 0.5f));
     PushStyleVar(ImGuiStyleVar_WindowPadding, g.Style.WindowPadding * 2.0f);
     Begin("###NavWindowingList", NULL, ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoFocusOnAppearing | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoInputs | ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoSavedSettings);
     for (int n = g.WindowsFocusOrder.Size - 1; n >= 0; n--)
@@ -9207,7 +10041,7 @@ bool ImGui::BeginDragDropTargetCustom(const ImRect& bb, ImGuiID id)
         return false;
 
     ImGuiWindow* window = g.CurrentWindow;
-    if (g.HoveredWindow == NULL || window->RootWindow != g.HoveredWindow->RootWindow)
+    if (g.HoveredWindowUnderMovingWindow == NULL || window->RootWindow != g.HoveredWindowUnderMovingWindow->RootWindow)
         return false;
     IM_ASSERT(id != 0);
     if (!IsMouseHoveringRect(bb.Min, bb.Max) || (id == g.DragDropPayload.SourceId))
@@ -9235,7 +10069,7 @@ bool ImGui::BeginDragDropTarget()
     ImGuiWindow* window = g.CurrentWindow;
     if (!(window->DC.LastItemStatusFlags & ImGuiItemStatusFlags_HoveredRect))
         return false;
-    if (g.HoveredWindow == NULL || window->RootWindow != g.HoveredWindow->RootWindow)
+    if (g.HoveredWindowUnderMovingWindow == NULL || window->RootWindow != g.HoveredWindowUnderMovingWindow->RootWindow)
         return false;
 
     const ImRect& display_rect = (window->DC.LastItemStatusFlags & ImGuiItemStatusFlags_HasDisplayRect) ? window->DC.LastItemDisplayRect : window->DC.LastItemRect;
@@ -9530,6 +10364,7 @@ void ImGui::LogButtons()
         LogToClipboard();
 }
 
+
 //-----------------------------------------------------------------------------
 // [SECTION] SETTINGS
 //-----------------------------------------------------------------------------
@@ -9689,6 +10524,7 @@ void ImGui::LoadIniSettingsFromMemory(const char* ini_data, size_t ini_size)
     }
     IM_FREE(buf);
     g.SettingsLoaded = true;
+    DockContextOnLoadSettings(&g);
 }
 
 void ImGui::SaveIniSettingsToDisk(const char* ini_filename)
@@ -9737,9 +10573,15 @@ static void WindowSettingsHandler_ReadLine(ImGuiContext*, ImGuiSettingsHandler*,
     ImGuiWindowSettings* settings = (ImGuiWindowSettings*)entry;
     int x, y;
     int i;
-    if (sscanf(line, "Pos=%i,%i", &x, &y) == 2)         settings->Pos = ImVec2ih((short)x, (short)y);
-    else if (sscanf(line, "Size=%i,%i", &x, &y) == 2)   settings->Size = ImVec2ih((short)x, (short)y);
-    else if (sscanf(line, "Collapsed=%d", &i) == 1)     settings->Collapsed = (i != 0);
+    ImU32 u1;
+    if (sscanf(line, "Pos=%i,%i", &x, &y) == 2)                 { settings->Pos = ImVec2ih((short)x, (short)y); }
+    else if (sscanf(line, "Size=%i,%i", &x, &y) == 2)           { settings->Size = ImVec2ih((short)x, (short)y); }
+    else if (sscanf(line, "ViewportId=0x%08X", &u1) == 1)       { settings->ViewportId = u1; }
+    else if (sscanf(line, "ViewportPos=%i,%i", &x, &y) == 2)    { settings->ViewportPos = ImVec2ih((short)x, (short)y); }
+    else if (sscanf(line, "Collapsed=%d", &i) == 1)             { settings->Collapsed = (i != 0); }
+    else if (sscanf(line, "DockId=0x%X,%d", &u1, &i) == 2)      { settings->DockId = u1; settings->DockOrder = (short)i; }
+    else if (sscanf(line, "DockId=0x%X", &u1) == 1)             { settings->DockId = u1; settings->DockOrder = -1; }
+    else if (sscanf(line, "ClassId=0x%X", &u1) == 1)            { settings->ClassId = u1; }
 }
 
 static void WindowSettingsHandler_WriteAll(ImGuiContext* ctx, ImGuiSettingsHandler* handler, ImGuiTextBuffer* buf)
@@ -9760,8 +10602,14 @@ static void WindowSettingsHandler_WriteAll(ImGuiContext* ctx, ImGuiSettingsHandl
             window->SettingsOffset = g.SettingsWindows.offset_from_ptr(settings);
         }
         IM_ASSERT(settings->ID == window->ID);
-        settings->Pos = ImVec2ih((short)window->Pos.x, (short)window->Pos.y);
-        settings->Size = ImVec2ih((short)window->SizeFull.x, (short)window->SizeFull.y);
+        settings->Pos = ImVec2ih(window->Pos - window->ViewportPos);
+        settings->Size = ImVec2ih(window->SizeFull);
+        settings->ViewportId = window->ViewportId;
+        settings->ViewportPos = ImVec2ih(window->ViewportPos);
+        IM_ASSERT(window->DockNode == NULL || window->DockNode->ID == window->DockId);
+        settings->DockId = window->DockId;
+        settings->ClassId = window->WindowClass.ClassId;
+        settings->DockOrder = window->DockOrder;
         settings->Collapsed = window->Collapsed;
     }
 
@@ -9771,9 +10619,26 @@ static void WindowSettingsHandler_WriteAll(ImGuiContext* ctx, ImGuiSettingsHandl
     {
         const char* settings_name = settings->GetName();
         buf->appendf("[%s][%s]\n", handler->TypeName, settings_name);
-        buf->appendf("Pos=%d,%d\n", settings->Pos.x, settings->Pos.y);
-        buf->appendf("Size=%d,%d\n", settings->Size.x, settings->Size.y);
+        if (settings->ViewportId != 0 && settings->ViewportId != ImGui::IMGUI_VIEWPORT_DEFAULT_ID)
+        {
+            buf->appendf("ViewportPos=%d,%d\n", settings->ViewportPos.x, settings->ViewportPos.y);
+            buf->appendf("ViewportId=0x%08X\n", settings->ViewportId);
+        }
+        if (settings->Pos.x != 0 || settings->Pos.y != 0 || settings->ViewportId == ImGui::IMGUI_VIEWPORT_DEFAULT_ID)
+            buf->appendf("Pos=%d,%d\n", settings->Pos.x, settings->Pos.y);
+        if (settings->Size.x != 0 || settings->Size.y != 0)
+            buf->appendf("Size=%d,%d\n", settings->Size.x, settings->Size.y);
         buf->appendf("Collapsed=%d\n", settings->Collapsed);
+        if (settings->DockId != 0)
+        {
+            // Write DockId as 4 digits if possible. Automatic DockId are small numbers, but full explicit DockSpace() are full ImGuiID range.
+            if (settings->DockOrder == -1)
+                buf->appendf("DockId=0x%08X\n", settings->DockId);
+            else
+                buf->appendf("DockId=0x%08X,%d\n", settings->DockId, settings->DockOrder);
+            if (settings->ClassId != 0)
+                buf->appendf("ClassId=0x%08X\n", settings->ClassId);
+        }
         buf->append("\n");
     }
 }
@@ -9782,15 +10647,4314 @@ static void WindowSettingsHandler_WriteAll(ImGuiContext* ctx, ImGuiSettingsHandl
 //-----------------------------------------------------------------------------
 // [SECTION] VIEWPORTS, PLATFORM WINDOWS
 //-----------------------------------------------------------------------------
+// - GetMainViewport()
+// - FindViewportByID()
+// - FindViewportByPlatformHandle()
+// - SetCurrentViewport() [Internal]
+// - SetWindowViewport() [Internal]
+// - GetWindowAlwaysWantOwnViewport() [Internal]
+// - UpdateTryMergeWindowIntoHostViewport() [Internal]
+// - UpdateTryMergeWindowIntoHostViewports() [Internal]
+// - TranslateWindowsInViewport() [Internal]
+// - ScaleWindowsInViewport() [Internal]
+// - FindHoveredViewportFromPlatformWindowStack() [Internal]
+// - UpdateViewportsNewFrame() [Internal]
+// - UpdateViewportsEndFrame() [Internal]
+// - AddUpdateViewport() [Internal]
+// - UpdateSelectWindowViewport() [Internal]
+// - UpdatePlatformWindows()
+// - RenderPlatformWindowsDefault()
+// - FindPlatformMonitorForPos() [Internal]
+// - FindPlatformMonitorForRect() [Internal]
+// - UpdateViewportPlatformMonitor() [Internal]
+// - DestroyPlatformWindow() [Internal]
+// - DestroyPlatformWindows()
+//-----------------------------------------------------------------------------
+
+ImGuiViewport* ImGui::GetMainViewport()
+{
+    ImGuiContext& g = *GImGui;
+    return g.Viewports[0];
+}
+
+ImGuiViewport* ImGui::FindViewportByID(ImGuiID id)
+{
+    ImGuiContext& g = *GImGui;
+    for (int n = 0; n < g.Viewports.Size; n++)
+        if (g.Viewports[n]->ID == id)
+            return g.Viewports[n];
+    return NULL;
+}
+
+ImGuiViewport* ImGui::FindViewportByPlatformHandle(void* platform_handle)
+{
+    ImGuiContext& g = *GImGui;
+    for (int i = 0; i != g.Viewports.Size; i++)
+        if (g.Viewports[i]->PlatformHandle == platform_handle)
+            return g.Viewports[i];
+    return NULL;
+}
+
+void ImGui::SetCurrentViewport(ImGuiWindow* current_window, ImGuiViewportP* viewport)
+{
+    ImGuiContext& g = *GImGui;
+    (void)current_window;
+
+    if (viewport)
+        viewport->LastFrameActive = g.FrameCount;
+    if (g.CurrentViewport == viewport)
+        return;
+    g.CurrentDpiScale = viewport ? viewport->DpiScale : 1.0f;
+    g.CurrentViewport = viewport;
+    //IMGUI_DEBUG_LOG_VIEWPORT("SetCurrentViewport changed '%s' 0x%08X\n", current_window ? current_window->Name : NULL, viewport ? viewport->ID : 0);
+
+    // Notify platform layer of viewport changes
+    // FIXME-DPI: This is only currently used for experimenting with handling of multiple DPI
+    if (g.CurrentViewport && g.PlatformIO.Platform_OnChangedViewport)
+        g.PlatformIO.Platform_OnChangedViewport(g.CurrentViewport);
+}
+
+static void SetWindowViewport(ImGuiWindow* window, ImGuiViewportP* viewport)
+{
+    window->Viewport = viewport;
+    window->ViewportId = viewport->ID;
+    window->ViewportOwned = (viewport->Window == window);
+}
+
+static bool ImGui::GetWindowAlwaysWantOwnViewport(ImGuiWindow* window)
+{
+    // Tooltips and menus are not automatically forced into their own viewport when the NoMerge flag is set, however the multiplication of viewports makes them more likely to protrude and create their own.
+    ImGuiContext& g = *GImGui;
+    if (g.IO.ConfigViewportsNoAutoMerge || (window->WindowClass.ViewportFlagsOverrideSet & ImGuiViewportFlags_NoAutoMerge))
+        if (g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable)
+            if (!window->DockIsActive)
+                if ((window->Flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip)) == 0)
+                    if ((window->Flags & ImGuiWindowFlags_Popup) == 0 || (window->Flags & ImGuiWindowFlags_Modal) != 0)
+                        return true;
+    return false;
+}
+
+static bool ImGui::UpdateTryMergeWindowIntoHostViewport(ImGuiWindow* window, ImGuiViewportP* viewport)
+{
+    ImGuiContext& g = *GImGui;
+    if (window->Viewport == viewport)
+        return false;
+    if ((viewport->Flags & ImGuiViewportFlags_CanHostOtherWindows) == 0)
+        return false;
+    if ((viewport->Flags & ImGuiViewportFlags_Minimized) != 0)
+        return false;
+    if (!viewport->GetMainRect().Contains(window->Rect()))
+        return false;
+    if (GetWindowAlwaysWantOwnViewport(window))
+        return false;
+
+    for (int n = 0; n < g.Windows.Size; n++)
+    {
+        ImGuiWindow* window_behind = g.Windows[n];
+        if (window_behind == window)
+            break;
+        if (window_behind->WasActive && window_behind->ViewportOwned && !(window_behind->Flags & ImGuiWindowFlags_ChildWindow))
+            if (window_behind->Viewport->GetMainRect().Overlaps(window->Rect()))
+                return false;
+    }
+
+    // Move to the existing viewport, Move child/hosted windows as well (FIXME-OPT: iterate child)
+    ImGuiViewportP* old_viewport = window->Viewport;
+    if (window->ViewportOwned)
+        for (int n = 0; n < g.Windows.Size; n++)
+            if (g.Windows[n]->Viewport == old_viewport)
+                SetWindowViewport(g.Windows[n], viewport);
+    SetWindowViewport(window, viewport);
+    BringWindowToDisplayFront(window);
+
+    return true;
+}
+
+static bool ImGui::UpdateTryMergeWindowIntoHostViewports(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    return UpdateTryMergeWindowIntoHostViewport(window, g.Viewports[0]);
+}
+
+// Translate imgui windows when a Host Viewport has been moved
+// (This additionally keeps windows at the same place when ImGuiConfigFlags_ViewportsEnable is toggled!)
+void ImGui::TranslateWindowsInViewport(ImGuiViewportP* viewport, const ImVec2& old_pos, const ImVec2& new_pos)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(viewport->Window == NULL && (viewport->Flags & ImGuiViewportFlags_CanHostOtherWindows));
+
+    // 1) We test if ImGuiConfigFlags_ViewportsEnable was just toggled, which allows us to conveniently
+    // translate imgui windows from OS-window-local to absolute coordinates or vice-versa.
+    // 2) If it's not going to fit into the new size, keep it at same absolute position.
+    // One problem with this is that most Win32 applications doesn't update their render while dragging,
+    // and so the window will appear to teleport when releasing the mouse.
+    const bool translate_all_windows = (g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable) != (g.ConfigFlagsLastFrame & ImGuiConfigFlags_ViewportsEnable);
+    ImRect test_still_fit_rect(old_pos, old_pos + viewport->Size);
+    ImVec2 delta_pos = new_pos - old_pos;
+    for (int window_n = 0; window_n < g.Windows.Size; window_n++) // FIXME-OPT
+        if (translate_all_windows || (g.Windows[window_n]->Viewport == viewport && test_still_fit_rect.Contains(g.Windows[window_n]->Rect())))
+            TranslateWindow(g.Windows[window_n], delta_pos);
+}
+
+// Scale all windows (position, size). Use when e.g. changing DPI. (This is a lossy operation!)
+void ImGui::ScaleWindowsInViewport(ImGuiViewportP* viewport, float scale)
+{
+    ImGuiContext& g = *GImGui;
+    if (viewport->Window)
+    {
+        ScaleWindow(viewport->Window, scale);
+    }
+    else
+    {
+        for (int i = 0; i != g.Windows.Size; i++)
+            if (g.Windows[i]->Viewport == viewport)
+                ScaleWindow(g.Windows[i], scale);
+    }
+}
+
+// If the back-end doesn't set MouseLastHoveredViewport or doesn't honor ImGuiViewportFlags_NoInputs, we do a search ourselves.
+// A) It won't take account of the possibility that non-imgui windows may be in-between our dragged window and our target window.
+// B) It requires Platform_GetWindowFocus to be implemented by back-end.
+static ImGuiViewportP* FindHoveredViewportFromPlatformWindowStack(const ImVec2 mouse_platform_pos)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiViewportP* best_candidate = NULL;
+    for (int n = 0; n < g.Viewports.Size; n++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[n];
+        if (!(viewport->Flags & (ImGuiViewportFlags_NoInputs | ImGuiViewportFlags_Minimized)) && viewport->GetMainRect().Contains(mouse_platform_pos))
+            if (best_candidate == NULL || best_candidate->LastFrontMostStampCount < viewport->LastFrontMostStampCount)
+                best_candidate = viewport;
+    }
+    return best_candidate;
+}
+
+// Update viewports and monitor infos
+// Note that this is running even if 'ImGuiConfigFlags_ViewportsEnable' is not set, in order to clear unused viewports (if any) and update monitor info.
+static void ImGui::UpdateViewportsNewFrame()
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(g.PlatformIO.Viewports.Size <= g.Viewports.Size);
+
+    // Update Minimized status (we need it first in order to decide if we'll apply Pos/Size of the main viewport)
+    const bool viewports_enabled = (g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable) != 0;
+    if (viewports_enabled)
+    {
+        for (int n = 0; n < g.Viewports.Size; n++)
+        {
+            ImGuiViewportP* viewport = g.Viewports[n];
+            const bool platform_funcs_available = viewport->PlatformWindowCreated;
+            if (g.PlatformIO.Platform_GetWindowMinimized && platform_funcs_available)
+            {
+                bool minimized = g.PlatformIO.Platform_GetWindowMinimized(viewport);
+                if (minimized)
+                    viewport->Flags |= ImGuiViewportFlags_Minimized;
+                else
+                    viewport->Flags &= ~ImGuiViewportFlags_Minimized;
+            }
+        }
+    }
+
+    // Create/update main viewport with current platform position.
+    // FIXME-VIEWPORT: Size is driven by back-end/user code for backward-compatibility but we should aim to make this more consistent.
+    ImGuiViewportP* main_viewport = g.Viewports[0];
+    IM_ASSERT(main_viewport->ID == IMGUI_VIEWPORT_DEFAULT_ID);
+    IM_ASSERT(main_viewport->Window == NULL);
+    ImVec2 main_viewport_pos = viewports_enabled ? g.PlatformIO.Platform_GetWindowPos(main_viewport) : ImVec2(0.0f, 0.0f);
+    ImVec2 main_viewport_size = g.IO.DisplaySize;
+    if (viewports_enabled && (main_viewport->Flags & ImGuiViewportFlags_Minimized))
+    {
+        main_viewport_pos = main_viewport->Pos;    // Preserve last pos/size when minimized (FIXME: We don't do the same for Size outside of the viewport path)
+        main_viewport_size = main_viewport->Size;
+    }
+    AddUpdateViewport(NULL, IMGUI_VIEWPORT_DEFAULT_ID, main_viewport_pos, main_viewport_size, ImGuiViewportFlags_CanHostOtherWindows);
+
+    g.CurrentDpiScale = 0.0f;
+    g.CurrentViewport = NULL;
+    g.MouseViewport = NULL;
+    for (int n = 0; n < g.Viewports.Size; n++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[n];
+        viewport->Idx = n;
+
+        // Erase unused viewports
+        if (n > 0 && viewport->LastFrameActive < g.FrameCount - 2)
+        {
+            // Clear references to this viewport in windows (window->ViewportId becomes the master data)
+            for (int window_n = 0; window_n < g.Windows.Size; window_n++)
+                if (g.Windows[window_n]->Viewport == viewport)
+                {
+                    g.Windows[window_n]->Viewport = NULL;
+                    g.Windows[window_n]->ViewportOwned = false;
+                }
+            if (viewport == g.MouseLastHoveredViewport)
+                g.MouseLastHoveredViewport = NULL;
+            g.Viewports.erase(g.Viewports.Data + n);
+
+            // Destroy
+            IMGUI_DEBUG_LOG_VIEWPORT("Delete Viewport %08X (%s)\n", viewport->ID, viewport->Window ? viewport->Window->Name : "n/a");
+            DestroyPlatformWindow(viewport); // In most circumstances the platform window will already be destroyed here.
+            IM_ASSERT(g.PlatformIO.Viewports.contains(viewport) == false);
+            IM_DELETE(viewport);
+            n--;
+            continue;
+        }
+
+        const bool platform_funcs_available = viewport->PlatformWindowCreated;
+        if (viewports_enabled)
+        {
+            // Update Position and Size (from Platform Window to ImGui) if requested.
+            // We do it early in the frame instead of waiting for UpdatePlatformWindows() to avoid a frame of lag when moving/resizing using OS facilities.
+            if (!(viewport->Flags & ImGuiViewportFlags_Minimized) && platform_funcs_available)
+            {
+                if (viewport->PlatformRequestMove)
+                    viewport->Pos = viewport->LastPlatformPos = g.PlatformIO.Platform_GetWindowPos(viewport);
+                if (viewport->PlatformRequestResize)
+                    viewport->Size = viewport->LastPlatformSize = g.PlatformIO.Platform_GetWindowSize(viewport);
+            }
+        }
+
+        // Update/copy monitor info
+        UpdateViewportPlatformMonitor(viewport);
+
+        // Lock down space taken by menu bars and status bars, reset the offset for fucntions like BeginMainMenuBar() to alter them again.
+        viewport->WorkOffsetMin = viewport->CurrWorkOffsetMin;
+        viewport->WorkOffsetMax = viewport->CurrWorkOffsetMax;
+        viewport->CurrWorkOffsetMin = viewport->CurrWorkOffsetMax = ImVec2(0.0f, 0.0f);
+
+        // Reset alpha every frame. Users of transparency (docking) needs to request a lower alpha back.
+        viewport->Alpha = 1.0f;
+
+        // Translate imgui windows when a Host Viewport has been moved
+        // (This additionally keeps windows at the same place when ImGuiConfigFlags_ViewportsEnable is toggled!)
+        const ImVec2 viewport_delta_pos = viewport->Pos - viewport->LastPos;
+        if ((viewport->Flags & ImGuiViewportFlags_CanHostOtherWindows) && (viewport_delta_pos.x != 0.0f || viewport_delta_pos.y != 0.0f))
+            TranslateWindowsInViewport(viewport, viewport->LastPos, viewport->Pos);
+
+        // Update DPI scale
+        float new_dpi_scale;
+        if (g.PlatformIO.Platform_GetWindowDpiScale && platform_funcs_available)
+            new_dpi_scale = g.PlatformIO.Platform_GetWindowDpiScale(viewport);
+        else if (viewport->PlatformMonitor != -1)
+            new_dpi_scale = g.PlatformIO.Monitors[viewport->PlatformMonitor].DpiScale;
+        else
+            new_dpi_scale = (viewport->DpiScale != 0.0f) ? viewport->DpiScale : 1.0f;
+        if (viewport->DpiScale != 0.0f && new_dpi_scale != viewport->DpiScale)
+        {
+            float scale_factor = new_dpi_scale / viewport->DpiScale;
+            if (g.IO.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleViewports)
+                ScaleWindowsInViewport(viewport, scale_factor);
+            //if (viewport == GetMainViewport())
+            //    g.PlatformInterface.SetWindowSize(viewport, viewport->Size * scale_factor);
+
+            // Scale our window moving pivot so that the window will rescale roughly around the mouse position.
+            // FIXME-VIEWPORT: This currently creates a resizing feedback loop when a window is straddling a DPI transition border.
+            // (Minor: since our sizes do not perfectly linearly scale, deferring the click offset scale until we know the actual window scale ratio may get us slightly more precise mouse positioning.)
+            //if (g.MovingWindow != NULL && g.MovingWindow->Viewport == viewport)
+            //    g.ActiveIdClickOffset = ImFloor(g.ActiveIdClickOffset * scale_factor);
+        }
+        viewport->DpiScale = new_dpi_scale;
+    }
+
+    if (!viewports_enabled)
+    {
+        g.MouseViewport = main_viewport;
+        return;
+    }
+
+    // Mouse handling: decide on the actual mouse viewport for this frame between the active/focused viewport and the hovered viewport.
+    // Note that 'viewport_hovered' should skip over any viewport that has the ImGuiViewportFlags_NoInputs flags set.
+    ImGuiViewportP* viewport_hovered = NULL;
+    if (g.IO.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport)
+    {
+        viewport_hovered = g.IO.MouseHoveredViewport ? (ImGuiViewportP*)FindViewportByID(g.IO.MouseHoveredViewport) : NULL;
+        if (viewport_hovered && (viewport_hovered->Flags & ImGuiViewportFlags_NoInputs))
+        {
+            // Back-end failed at honoring its contract if it returned a viewport with the _NoInputs flag.
+            IM_ASSERT(0);
+            viewport_hovered = FindHoveredViewportFromPlatformWindowStack(g.IO.MousePos);
+        }
+    }
+    else
+    {
+        // If the back-end doesn't know how to honor ImGuiViewportFlags_NoInputs, we do a search ourselves. Note that this search:
+        // A) won't take account of the possibility that non-imgui windows may be in-between our dragged window and our target window.
+        // B) uses LastFrameAsRefViewport as a flawed replacement for the last time a window was focused (we could/should fix that by introducing Focus functions in PlatformIO)
+        viewport_hovered = FindHoveredViewportFromPlatformWindowStack(g.IO.MousePos);
+    }
+    if (viewport_hovered != NULL)
+        g.MouseLastHoveredViewport = viewport_hovered;
+    else if (g.MouseLastHoveredViewport == NULL)
+        g.MouseLastHoveredViewport = g.Viewports[0];
+
+    // Update mouse reference viewport
+    // (when moving a window we aim at its viewport, but this will be overwritten below if we go in drag and drop mode)
+    if (g.MovingWindow)
+        g.MouseViewport = g.MovingWindow->Viewport;
+    else
+        g.MouseViewport = g.MouseLastHoveredViewport;
+
+    // When dragging something, always refer to the last hovered viewport.
+    // - when releasing a moving window we will revert to aiming behind (at viewport_hovered)
+    // - when we are between viewports, our dragged preview will tend to show in the last viewport _even_ if we don't have tooltips in their viewports (when lacking monitor info)
+    // - consider the case of holding on a menu item to browse child menus: even thou a mouse button is held, there's no active id because menu items only react on mouse release.
+    const bool is_mouse_dragging_with_an_expected_destination = g.DragDropActive;
+    if (is_mouse_dragging_with_an_expected_destination && viewport_hovered == NULL)
+        viewport_hovered = g.MouseLastHoveredViewport;
+    if (is_mouse_dragging_with_an_expected_destination || g.ActiveId == 0 || !IsAnyMouseDown())
+        if (viewport_hovered != NULL && viewport_hovered != g.MouseViewport && !(viewport_hovered->Flags & ImGuiViewportFlags_NoInputs))
+            g.MouseViewport = viewport_hovered;
+
+    IM_ASSERT(g.MouseViewport != NULL);
+}
+
+// Update user-facing viewport list (g.Viewports -> g.PlatformIO.Viewports after filtering out some)
+static void ImGui::UpdateViewportsEndFrame()
+{
+    ImGuiContext& g = *GImGui;
+    g.PlatformIO.MainViewport = g.Viewports[0];
+    g.PlatformIO.Viewports.resize(0);
+    for (int i = 0; i < g.Viewports.Size; i++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[i];
+        viewport->LastPos = viewport->Pos;
+        if (viewport->LastFrameActive < g.FrameCount || viewport->Size.x <= 0.0f || viewport->Size.y <= 0.0f)
+            if (i > 0) // Always include main viewport in the list
+                continue;
+        if (viewport->Window && !IsWindowActiveAndVisible(viewport->Window))
+            continue;
+        if (i > 0)
+            IM_ASSERT(viewport->Window != NULL);
+        g.PlatformIO.Viewports.push_back(viewport);
+    }
+    g.Viewports[0]->ClearRequestFlags(); // Clear main viewport flags because UpdatePlatformWindows() won't do it and may not even be called
+}
+
+// FIXME: We should ideally refactor the system to call this every frame (we currently don't)
+ImGuiViewportP* ImGui::AddUpdateViewport(ImGuiWindow* window, ImGuiID id, const ImVec2& pos, const ImVec2& size, ImGuiViewportFlags flags)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(id != 0);
+
+    if (window != NULL)
+    {
+        if (g.MovingWindow && g.MovingWindow->RootWindow == window)
+            flags |= ImGuiViewportFlags_NoInputs | ImGuiViewportFlags_NoFocusOnAppearing;
+        if ((window->Flags & ImGuiWindowFlags_NoMouseInputs) && (window->Flags & ImGuiWindowFlags_NoNavInputs))
+            flags |= ImGuiViewportFlags_NoInputs;
+        if (window->Flags & ImGuiWindowFlags_NoFocusOnAppearing)
+            flags |= ImGuiViewportFlags_NoFocusOnAppearing;
+    }
+
+    ImGuiViewportP* viewport = (ImGuiViewportP*)FindViewportByID(id);
+    if (viewport)
+    {
+        if (!viewport->PlatformRequestMove)
+            viewport->Pos = pos;
+        if (!viewport->PlatformRequestResize)
+            viewport->Size = size;
+        viewport->Flags = flags | (viewport->Flags & ImGuiViewportFlags_Minimized); // Preserve existing flags
+    }
+    else
+    {
+        // New viewport
+        viewport = IM_NEW(ImGuiViewportP)();
+        viewport->ID = id;
+        viewport->Idx = g.Viewports.Size;
+        viewport->Pos = viewport->LastPos = pos;
+        viewport->Size = size;
+        viewport->Flags = flags;
+        UpdateViewportPlatformMonitor(viewport);
+        g.Viewports.push_back(viewport);
+        IMGUI_DEBUG_LOG_VIEWPORT("Add Viewport %08X (%s)\n", id, window->Name);
+
+        // We normally setup for all viewports in NewFrame() but here need to handle the mid-frame creation of a new viewport.
+        // We need to extend the fullscreen clip rect so the OverlayDrawList clip is correct for that the first frame
+        g.DrawListSharedData.ClipRectFullscreen.x = ImMin(g.DrawListSharedData.ClipRectFullscreen.x, viewport->Pos.x);
+        g.DrawListSharedData.ClipRectFullscreen.y = ImMin(g.DrawListSharedData.ClipRectFullscreen.y, viewport->Pos.y);
+        g.DrawListSharedData.ClipRectFullscreen.z = ImMax(g.DrawListSharedData.ClipRectFullscreen.z, viewport->Pos.x + viewport->Size.x);
+        g.DrawListSharedData.ClipRectFullscreen.w = ImMax(g.DrawListSharedData.ClipRectFullscreen.w, viewport->Pos.y + viewport->Size.y);
+
+        // Store initial DpiScale before the OS platform window creation, based on expected monitor data.
+        // This is so we can select an appropriate font size on the first frame of our window lifetime
+        if (viewport->PlatformMonitor != -1)
+            viewport->DpiScale = g.PlatformIO.Monitors[viewport->PlatformMonitor].DpiScale;
+    }
+
+    viewport->Window = window;
+    viewport->LastFrameActive = g.FrameCount;
+    IM_ASSERT(window == NULL || viewport->ID == window->ID);
+
+    if (window != NULL)
+        window->ViewportOwned = true;
+
+    return viewport;
+}
+
+// FIXME-VIEWPORT: This is all super messy and ought to be clarified or rewritten.
+static void ImGui::UpdateSelectWindowViewport(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiWindowFlags flags = window->Flags;
+    window->ViewportAllowPlatformMonitorExtend = -1;
+
+    // Restore main viewport if multi-viewport is not supported by the back-end
+    ImGuiViewportP* main_viewport = g.Viewports[0];
+    if (!(g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable))
+    {
+        SetWindowViewport(window, main_viewport);
+        return;
+    }
+    window->ViewportOwned = false;
+
+    // Appearing popups reset their viewport so they can inherit again
+    if ((flags & (ImGuiWindowFlags_Popup | ImGuiWindowFlags_Tooltip)) && window->Appearing)
+    {
+        window->Viewport = NULL;
+        window->ViewportId = 0;
+    }
+
+    if ((g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasViewport) == 0)
+    {
+        // By default inherit from parent window
+        if (window->Viewport == NULL && window->ParentWindow && !window->ParentWindow->IsFallbackWindow)
+            window->Viewport = window->ParentWindow->Viewport;
+
+        // Attempt to restore saved viewport id (= window that hasn't been activated yet), try to restore the viewport based on saved 'window->ViewportPos' restored from .ini file
+        if (window->Viewport == NULL && window->ViewportId != 0)
+        {
+            window->Viewport = (ImGuiViewportP*)FindViewportByID(window->ViewportId);
+            if (window->Viewport == NULL && window->ViewportPos.x != FLT_MAX && window->ViewportPos.y != FLT_MAX)
+                window->Viewport = AddUpdateViewport(window, window->ID, window->ViewportPos, window->Size, ImGuiViewportFlags_None);
+        }
+    }
+
+    bool lock_viewport = false;
+    if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasViewport)
+    {
+        // Code explicitly request a viewport
+        window->Viewport = (ImGuiViewportP*)FindViewportByID(g.NextWindowData.ViewportId);
+        window->ViewportId = g.NextWindowData.ViewportId; // Store ID even if Viewport isn't resolved yet.
+        lock_viewport = true;
+    }
+    else if ((flags & ImGuiWindowFlags_ChildWindow) || (flags & ImGuiWindowFlags_ChildMenu))
+    {
+        // Always inherit viewport from parent window
+        window->Viewport = window->ParentWindow->Viewport;
+    }
+    else if (flags & ImGuiWindowFlags_Tooltip)
+    {
+        window->Viewport = g.MouseViewport;
+    }
+    else if (GetWindowAlwaysWantOwnViewport(window))
+    {
+        window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_None);
+    }
+    else if (g.MovingWindow && g.MovingWindow->RootWindow == window && IsMousePosValid())
+    {
+        if (window->Viewport != NULL && window->Viewport->Window == window)
+            window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_None);
+    }
+    else
+    {
+        // Merge into host viewport?
+        // We cannot test window->ViewportOwned as it set lower in the function.
+        bool try_to_merge_into_host_viewport = (window->Viewport && window == window->Viewport->Window && g.ActiveId == 0);
+        if (try_to_merge_into_host_viewport)
+            UpdateTryMergeWindowIntoHostViewports(window);
+    }
+
+    // Fallback to default viewport
+    if (window->Viewport == NULL)
+        window->Viewport = main_viewport;
+
+    // Mark window as allowed to protrude outside of its viewport and into the current monitor
+    if (!lock_viewport)
+    {
+        if (flags & (ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup))
+        {
+            // We need to take account of the possibility that mouse may become invalid.
+            // Popups/Tooltip always set ViewportAllowPlatformMonitorExtend so GetWindowAllowedExtentRect() will return full monitor bounds.
+            ImVec2 mouse_ref = (flags & ImGuiWindowFlags_Tooltip) ? g.IO.MousePos : g.BeginPopupStack.back().OpenMousePos;
+            bool use_mouse_ref = (g.NavDisableHighlight || !g.NavDisableMouseHover || !g.NavWindow);
+            bool mouse_valid = IsMousePosValid(&mouse_ref);
+            if ((window->Appearing || (flags & (ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_ChildMenu))) && (!use_mouse_ref || mouse_valid))
+                window->ViewportAllowPlatformMonitorExtend = FindPlatformMonitorForPos((use_mouse_ref && mouse_valid) ? mouse_ref : NavCalcPreferredRefPos());
+            else
+                window->ViewportAllowPlatformMonitorExtend = window->Viewport->PlatformMonitor;
+        }
+        else if (window->Viewport && window != window->Viewport->Window && window->Viewport->Window && !(flags & ImGuiWindowFlags_ChildWindow))
+        {
+            // When called from Begin() we don't have access to a proper version of the Hidden flag yet, so we replicate this code.
+            const bool will_be_visible = (window->DockIsActive && !window->DockTabIsVisible) ? false : true;
+            if ((window->Flags & ImGuiWindowFlags_DockNodeHost) && window->Viewport->LastFrameActive < g.FrameCount && will_be_visible)
+            {
+                // Steal/transfer ownership
+                IMGUI_DEBUG_LOG_VIEWPORT("Window '%s' steal Viewport %08X from Window '%s'\n", window->Name, window->Viewport->ID, window->Viewport->Window->Name);
+                window->Viewport->Window = window;
+                window->Viewport->ID = window->ID;
+                window->Viewport->LastNameHash = 0;
+            }
+            else if (!UpdateTryMergeWindowIntoHostViewports(window)) // Merge?
+            {
+                // New viewport
+                window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_NoFocusOnAppearing);
+            }
+        }
+        else if (window->ViewportAllowPlatformMonitorExtend < 0 && (flags & ImGuiWindowFlags_ChildWindow) == 0)
+        {
+            // Regular (non-child, non-popup) windows by default are also allowed to protrude
+            // Child windows are kept contained within their parent.
+            window->ViewportAllowPlatformMonitorExtend = window->Viewport->PlatformMonitor;
+        }
+    }
+
+    // Update flags
+    window->ViewportOwned = (window == window->Viewport->Window);
+    window->ViewportId = window->Viewport->ID;
+
+    // If the OS window has a title bar, hide our imgui title bar
+    //if (window->ViewportOwned && !(window->Viewport->Flags & ImGuiViewportFlags_NoDecoration))
+    //    window->Flags |= ImGuiWindowFlags_NoTitleBar;
+}
+
+// Called by user at the end of the main loop, after EndFrame()
+// This will handle the creation/update of all OS windows via function defined in the ImGuiPlatformIO api.
+void ImGui::UpdatePlatformWindows()
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(g.FrameCountEnded == g.FrameCount && "Forgot to call Render() or EndFrame() before UpdatePlatformWindows()?");
+    IM_ASSERT(g.FrameCountPlatformEnded < g.FrameCount);
+    g.FrameCountPlatformEnded = g.FrameCount;
+    if (!(g.ConfigFlagsCurrFrame & ImGuiConfigFlags_ViewportsEnable))
+        return;
+
+    // Create/resize/destroy platform windows to match each active viewport.
+    // Skip the main viewport (index 0), which is always fully handled by the application!
+    for (int i = 1; i < g.Viewports.Size; i++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[i];
+
+        // Destroy platform window if the viewport hasn't been submitted or if it is hosting a hidden window
+        // (the implicit/fallback Debug##Default window will be registering its viewport then be disabled, causing a dummy DestroyPlatformWindow to be made each frame)
+        bool destroy_platform_window = false;
+        destroy_platform_window |= (viewport->LastFrameActive < g.FrameCount - 1);
+        destroy_platform_window |= (viewport->Window && !IsWindowActiveAndVisible(viewport->Window));
+        if (destroy_platform_window)
+        {
+            DestroyPlatformWindow(viewport);
+            continue;
+        }
+
+        // New windows that appears directly in a new viewport won't always have a size on their first frame
+        if (viewport->LastFrameActive < g.FrameCount || viewport->Size.x <= 0 || viewport->Size.y <= 0)
+            continue;
+
+        // Create window
+        bool is_new_platform_window = (viewport->PlatformWindowCreated == false);
+        if (is_new_platform_window)
+        {
+            IMGUI_DEBUG_LOG_VIEWPORT("Create Platform Window %08X (%s)\n", viewport->ID, viewport->Window ? viewport->Window->Name : "n/a");
+            g.PlatformIO.Platform_CreateWindow(viewport);
+            if (g.PlatformIO.Renderer_CreateWindow != NULL)
+                g.PlatformIO.Renderer_CreateWindow(viewport);
+            viewport->LastNameHash = 0;
+            viewport->LastPlatformPos = viewport->LastPlatformSize = ImVec2(FLT_MAX, FLT_MAX); // By clearing those we'll enforce a call to Platform_SetWindowPos/Size below, before Platform_ShowWindow (FIXME: Is that necessary?)
+            viewport->LastRendererSize = viewport->Size;                                       // We don't need to call Renderer_SetWindowSize() as it is expected Renderer_CreateWindow() already did it.
+            viewport->PlatformWindowCreated = true;
+        }
+
+        // Apply Position and Size (from ImGui to Platform/Renderer back-ends)
+        if ((viewport->LastPlatformPos.x != viewport->Pos.x || viewport->LastPlatformPos.y != viewport->Pos.y) && !viewport->PlatformRequestMove)
+            g.PlatformIO.Platform_SetWindowPos(viewport, viewport->Pos);
+        if ((viewport->LastPlatformSize.x != viewport->Size.x || viewport->LastPlatformSize.y != viewport->Size.y) && !viewport->PlatformRequestResize)
+            g.PlatformIO.Platform_SetWindowSize(viewport, viewport->Size);
+        if ((viewport->LastRendererSize.x != viewport->Size.x || viewport->LastRendererSize.y != viewport->Size.y) && g.PlatformIO.Renderer_SetWindowSize)
+            g.PlatformIO.Renderer_SetWindowSize(viewport, viewport->Size);
+        viewport->LastPlatformPos = viewport->Pos;
+        viewport->LastPlatformSize = viewport->LastRendererSize = viewport->Size;
+
+        // Update title bar (if it changed)
+        if (ImGuiWindow* window_for_title = GetWindowForTitleDisplay(viewport->Window))
+        {
+            const char* title_begin = window_for_title->Name;
+            char* title_end = (char*)(intptr_t)FindRenderedTextEnd(title_begin);
+            const ImGuiID title_hash = ImHashStr(title_begin, title_end - title_begin);
+            if (viewport->LastNameHash != title_hash)
+            {
+                char title_end_backup_c = *title_end;
+                *title_end = 0; // Cut existing buffer short instead of doing an alloc/free, no small gain.
+                g.PlatformIO.Platform_SetWindowTitle(viewport, title_begin);
+                *title_end = title_end_backup_c;
+                viewport->LastNameHash = title_hash;
+            }
+        }
+
+        // Update alpha (if it changed)
+        if (viewport->LastAlpha != viewport->Alpha && g.PlatformIO.Platform_SetWindowAlpha)
+            g.PlatformIO.Platform_SetWindowAlpha(viewport, viewport->Alpha);
+        viewport->LastAlpha = viewport->Alpha;
+
+        // Optional, general purpose call to allow the back-end to perform general book-keeping even if things haven't changed.
+        if (g.PlatformIO.Platform_UpdateWindow)
+            g.PlatformIO.Platform_UpdateWindow(viewport);
+
+        if (is_new_platform_window)
+        {
+            // On startup ensure new platform window don't steal focus (give it a few frames, as nested contents may lead to viewport being created a few frames late)
+            if (g.FrameCount < 3)
+                viewport->Flags |= ImGuiViewportFlags_NoFocusOnAppearing;
+
+            // Show window
+            g.PlatformIO.Platform_ShowWindow(viewport);
+
+            // Even without focus, we assume the window becomes front-most.
+            // This is useful for our platform z-order heuristic when io.MouseHoveredViewport is not available.
+            if (viewport->LastFrontMostStampCount != g.ViewportFrontMostStampCount)
+                viewport->LastFrontMostStampCount = ++g.ViewportFrontMostStampCount;
+        }
+
+        // Clear request flags
+        viewport->ClearRequestFlags();
+    }
+
+    // Update our implicit z-order knowledge of platform windows, which is used when the back-end cannot provide io.MouseHoveredViewport.
+    // When setting Platform_GetWindowFocus, it is expected that the platform back-end can handle calls without crashing if it doesn't have data stored.
+    if (g.PlatformIO.Platform_GetWindowFocus != NULL)
+    {
+        ImGuiViewportP* focused_viewport = NULL;
+        for (int n = 0; n < g.Viewports.Size && focused_viewport == NULL; n++)
+        {
+            ImGuiViewportP* viewport = g.Viewports[n];
+            if (viewport->PlatformWindowCreated)
+                if (g.PlatformIO.Platform_GetWindowFocus(viewport))
+                    focused_viewport = viewport;
+        }
+        if (focused_viewport && g.PlatformLastFocusedViewport != focused_viewport->ID)
+        {
+            if (focused_viewport->LastFrontMostStampCount != g.ViewportFrontMostStampCount)
+                focused_viewport->LastFrontMostStampCount = ++g.ViewportFrontMostStampCount;
+            g.PlatformLastFocusedViewport = focused_viewport->ID;
+        }
+    }
+}
 
-// (this section is filled in the 'docking' branch)
+// This is a default/basic function for performing the rendering/swap of multiple Platform Windows.
+// Custom renderers may prefer to not call this function at all, and instead iterate the publicly exposed platform data and handle rendering/sync themselves.
+// The Render/Swap functions stored in ImGuiPlatformIO are merely here to allow for this helper to exist, but you can do it yourself:
+//
+//    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+//    for (int i = 1; i < platform_io.Viewports.Size; i++)
+//        if ((platform_io.Viewports[i]->Flags & ImGuiViewportFlags_Minimized) == 0)
+//            MyRenderFunction(platform_io.Viewports[i], my_args);
+//    for (int i = 1; i < platform_io.Viewports.Size; i++)
+//        if ((platform_io.Viewports[i]->Flags & ImGuiViewportFlags_Minimized) == 0)
+//            MySwapBufferFunction(platform_io.Viewports[i], my_args);
+//
+void ImGui::RenderPlatformWindowsDefault(void* platform_render_arg, void* renderer_render_arg)
+{
+    // Skip the main viewport (index 0), which is always fully handled by the application!
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    for (int i = 1; i < platform_io.Viewports.Size; i++)
+    {
+        ImGuiViewport* viewport = platform_io.Viewports[i];
+        if (viewport->Flags & ImGuiViewportFlags_Minimized)
+            continue;
+        if (platform_io.Platform_RenderWindow) platform_io.Platform_RenderWindow(viewport, platform_render_arg);
+        if (platform_io.Renderer_RenderWindow) platform_io.Renderer_RenderWindow(viewport, renderer_render_arg);
+    }
+    for (int i = 1; i < platform_io.Viewports.Size; i++)
+    {
+        ImGuiViewport* viewport = platform_io.Viewports[i];
+        if (viewport->Flags & ImGuiViewportFlags_Minimized)
+            continue;
+        if (platform_io.Platform_SwapBuffers) platform_io.Platform_SwapBuffers(viewport, platform_render_arg);
+        if (platform_io.Renderer_SwapBuffers) platform_io.Renderer_SwapBuffers(viewport, renderer_render_arg);
+    }
+}
+
+static int ImGui::FindPlatformMonitorForPos(const ImVec2& pos)
+{
+    ImGuiContext& g = *GImGui;
+    for (int monitor_n = 0; monitor_n < g.PlatformIO.Monitors.Size; monitor_n++)
+    {
+        const ImGuiPlatformMonitor& monitor = g.PlatformIO.Monitors[monitor_n];
+        if (ImRect(monitor.MainPos, monitor.MainPos + monitor.MainSize).Contains(pos))
+            return monitor_n;
+    }
+    return -1;
+}
+
+// Search for the monitor with the largest intersection area with the given rectangle
+// We generally try to avoid searching loops but the monitor count should be very small here
+// FIXME-OPT: We could test the last monitor used for that viewport first, and early
+static int ImGui::FindPlatformMonitorForRect(const ImRect& rect)
+{
+    ImGuiContext& g = *GImGui;
+
+    const int monitor_count = g.PlatformIO.Monitors.Size;
+    if (monitor_count <= 1)
+        return monitor_count - 1;
+
+    // Use a minimum threshold of 1.0f so a zero-sized rect won't false positive, and will still find the correct monitor given its position.
+    // This is necessary for tooltips which always resize down to zero at first.
+    const float surface_threshold = ImMax(rect.GetWidth() * rect.GetHeight() * 0.5f, 1.0f);
+    int best_monitor_n = -1;
+    float best_monitor_surface = 0.001f;
+
+    for (int monitor_n = 0; monitor_n < g.PlatformIO.Monitors.Size && best_monitor_surface < surface_threshold; monitor_n++)
+    {
+        const ImGuiPlatformMonitor& monitor = g.PlatformIO.Monitors[monitor_n];
+        const ImRect monitor_rect = ImRect(monitor.MainPos, monitor.MainPos + monitor.MainSize);
+        if (monitor_rect.Contains(rect))
+            return monitor_n;
+        ImRect overlapping_rect = rect;
+        overlapping_rect.ClipWithFull(monitor_rect);
+        float overlapping_surface = overlapping_rect.GetWidth() * overlapping_rect.GetHeight();
+        if (overlapping_surface < best_monitor_surface)
+            continue;
+        best_monitor_surface = overlapping_surface;
+        best_monitor_n = monitor_n;
+    }
+    return best_monitor_n;
+}
+
+// Update monitor from viewport rectangle (we'll use this info to clamp windows and save windows lost in a removed monitor)
+static void ImGui::UpdateViewportPlatformMonitor(ImGuiViewportP* viewport)
+{
+    viewport->PlatformMonitor = (short)FindPlatformMonitorForRect(viewport->GetMainRect());
+}
+
+void ImGui::DestroyPlatformWindow(ImGuiViewportP* viewport)
+{
+    ImGuiContext& g = *GImGui;
+    if (viewport->PlatformWindowCreated)
+    {
+        if (g.PlatformIO.Renderer_DestroyWindow)
+            g.PlatformIO.Renderer_DestroyWindow(viewport);
+        if (g.PlatformIO.Platform_DestroyWindow)
+            g.PlatformIO.Platform_DestroyWindow(viewport);
+        IM_ASSERT(viewport->RendererUserData == NULL && viewport->PlatformUserData == NULL);
+
+        // Don't clear PlatformWindowCreated for the main viewport, as we initially set that up to true in Initialize()
+        // The right-er way may be to leave it to the back-end to set this flag all-together, and made the flag public.
+        if (viewport->ID != IMGUI_VIEWPORT_DEFAULT_ID)
+            viewport->PlatformWindowCreated = false;
+    }
+    else
+    {
+        IM_ASSERT(viewport->RendererUserData == NULL && viewport->PlatformUserData == NULL && viewport->PlatformHandle == NULL);
+    }
+    viewport->RendererUserData = viewport->PlatformUserData = viewport->PlatformHandle = NULL;
+    viewport->ClearRequestFlags();
+}
+
+void ImGui::DestroyPlatformWindows()
+{
+    // We call the destroy window on every viewport (including the main viewport, index 0) to give a chance to the back-end
+    // to clear any data they may have stored in e.g. PlatformUserData, RendererUserData.
+    // It is convenient for the platform back-end code to store something in the main viewport, in order for e.g. the mouse handling
+    // code to operator a consistent manner.
+    // It is expected that the back-end can handle calls to Renderer_DestroyWindow/Platform_DestroyWindow without
+    // crashing if it doesn't have data stored.
+    ImGuiContext& g = *GImGui;
+    for (int i = 0; i < g.Viewports.Size; i++)
+        DestroyPlatformWindow(g.Viewports[i]);
+}
 
 
 //-----------------------------------------------------------------------------
 // [SECTION] DOCKING
 //-----------------------------------------------------------------------------
+// Docking: Internal Types
+// Docking: Forward Declarations
+// Docking: ImGuiDockContext
+// Docking: ImGuiDockContext Docking/Undocking functions
+// Docking: ImGuiDockNode
+// Docking: ImGuiDockNode Tree manipulation functions
+// Docking: Public Functions (SetWindowDock, DockSpace, DockSpaceOverViewport)
+// Docking: Builder Functions
+// Docking: Begin/End Support Functions (called from Begin/End)
+// Docking: Settings
+//-----------------------------------------------------------------------------
+
+//-----------------------------------------------------------------------------
+// Docking: Internal Types
+//-----------------------------------------------------------------------------
+// - ImGuiDockRequestType
+// - ImGuiDockRequest
+// - ImGuiDockPreviewData
+// - ImGuiDockNodeSettings
+// - ImGuiDockContext
+//-----------------------------------------------------------------------------
+
+static float IMGUI_DOCK_SPLITTER_SIZE = 2.0f;
+
+enum ImGuiDockRequestType
+{
+    ImGuiDockRequestType_None = 0,
+    ImGuiDockRequestType_Dock,
+    ImGuiDockRequestType_Undock,
+    ImGuiDockRequestType_Split                  // Split is the same as Dock but without a DockPayload
+};
+
+struct ImGuiDockRequest
+{
+    ImGuiDockRequestType    Type;
+    ImGuiWindow*            DockTargetWindow;   // Destination/Target Window to dock into (may be a loose window or a DockNode, might be NULL in which case DockTargetNode cannot be NULL)
+    ImGuiDockNode*          DockTargetNode;     // Destination/Target Node to dock into
+    ImGuiWindow*            DockPayload;        // Source/Payload window to dock (may be a loose window or a DockNode), [Optional]
+    ImGuiDir                DockSplitDir;
+    float                   DockSplitRatio;
+    bool                    DockSplitOuter;
+    ImGuiWindow*            UndockTargetWindow;
+    ImGuiDockNode*          UndockTargetNode;
+
+    ImGuiDockRequest()
+    {
+        Type = ImGuiDockRequestType_None;
+        DockTargetWindow = DockPayload = UndockTargetWindow = NULL;
+        DockTargetNode = UndockTargetNode = NULL;
+        DockSplitDir = ImGuiDir_None;
+        DockSplitRatio = 0.5f;
+        DockSplitOuter = false;
+    }
+};
+
+struct ImGuiDockPreviewData
+{
+    ImGuiDockNode   FutureNode;
+    bool            IsDropAllowed;
+    bool            IsCenterAvailable;
+    bool            IsSidesAvailable;           // Hold your breath, grammar freaks..
+    bool            IsSplitDirExplicit;         // Set when hovered the drop rect (vs. implicit SplitDir==None when hovered the window)
+    ImGuiDockNode*  SplitNode;
+    ImGuiDir        SplitDir;
+    float           SplitRatio;
+    ImRect          DropRectsDraw[ImGuiDir_COUNT + 1];  // May be slightly different from hit-testing drop rects used in DockNodeCalcDropRects()
+
+    ImGuiDockPreviewData() : FutureNode(0) { IsDropAllowed = IsCenterAvailable = IsSidesAvailable = IsSplitDirExplicit = false; SplitNode = NULL; SplitDir = ImGuiDir_None; SplitRatio = 0.f; }
+};
+
+// Persistent Settings data, stored contiguously in SettingsNodes (sizeof() ~32 bytes)
+struct ImGuiDockNodeSettings
+{
+    ImGuiID             ID;
+    ImGuiID             ParentNodeId;
+    ImGuiID             ParentWindowId;
+    ImGuiID             SelectedWindowId;
+    signed char         SplitAxis;
+    char                Depth;
+    ImGuiDockNodeFlags  Flags;                  // NB: We save individual flags one by one in ascii format (ImGuiDockNodeFlags_SavedFlagsMask_)
+    ImVec2ih            Pos;
+    ImVec2ih            Size;
+    ImVec2ih            SizeRef;
+    ImGuiDockNodeSettings() { ID = ParentNodeId = ParentWindowId = SelectedWindowId = 0; SplitAxis = ImGuiAxis_None; Depth = 0; Flags = ImGuiDockNodeFlags_None; }
+};
+
+struct ImGuiDockContext
+{
+    ImGuiStorage                    Nodes;                      // Map ID -> ImGuiDockNode*: Active nodes
+    ImVector<ImGuiDockRequest>      Requests;
+    ImVector<ImGuiDockNodeSettings> SettingsNodes;
+    bool                            WantFullRebuild;
+    ImGuiDockContext()              { WantFullRebuild = false; }
+};
+
+//-----------------------------------------------------------------------------
+// Docking: Forward Declarations
+//-----------------------------------------------------------------------------
+
+namespace ImGui
+{
+    // ImGuiDockContext
+    static ImGuiDockNode*   DockContextAddNode(ImGuiContext* ctx, ImGuiID id);
+    static void             DockContextRemoveNode(ImGuiContext* ctx, ImGuiDockNode* node, bool merge_sibling_into_parent_node);
+    static void             DockContextQueueNotifyRemovedNode(ImGuiContext* ctx, ImGuiDockNode* node);
+    static void             DockContextProcessDock(ImGuiContext* ctx, ImGuiDockRequest* req);
+    static void             DockContextProcessUndockWindow(ImGuiContext* ctx, ImGuiWindow* window, bool clear_persistent_docking_ref = true);
+    static void             DockContextProcessUndockNode(ImGuiContext* ctx, ImGuiDockNode* node);
+    static void             DockContextPruneUnusedSettingsNodes(ImGuiContext* ctx);
+    static ImGuiDockNode*   DockContextFindNodeByID(ImGuiContext* ctx, ImGuiID id);
+    static ImGuiDockNode*   DockContextBindNodeToWindow(ImGuiContext* ctx, ImGuiWindow* window);
+    static void             DockContextClearNodes(ImGuiContext* ctx, ImGuiID root_id, bool clear_persistent_docking_refs);    // Use root_id==0 to clear all
+    static void             DockContextBuildNodesFromSettings(ImGuiContext* ctx, ImGuiDockNodeSettings* node_settings_array, int node_settings_count);
+    static void             DockContextBuildAddWindowsToNodes(ImGuiContext* ctx, ImGuiID root_id);                            // Use root_id==0 to add all
+
+    // ImGuiDockNode
+    static void             DockNodeAddWindow(ImGuiDockNode* node, ImGuiWindow* window, bool add_to_tab_bar);
+    static void             DockNodeMoveWindows(ImGuiDockNode* dst_node, ImGuiDockNode* src_node);
+    static void             DockNodeMoveChildNodes(ImGuiDockNode* dst_node, ImGuiDockNode* src_node);
+    static ImGuiWindow*     DockNodeFindWindowByID(ImGuiDockNode* node, ImGuiID id);
+    static void             DockNodeApplyPosSizeToWindows(ImGuiDockNode* node);
+    static void             DockNodeRemoveWindow(ImGuiDockNode* node, ImGuiWindow* window, ImGuiID save_dock_id);
+    static void             DockNodeHideHostWindow(ImGuiDockNode* node);
+    static void             DockNodeUpdate(ImGuiDockNode* node);
+    static void             DockNodeUpdateForRootNode(ImGuiDockNode* node);
+    static void             DockNodeUpdateVisibleFlagAndInactiveChilds(ImGuiDockNode* node);
+    static void             DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_window);
+    static void             DockNodeAddTabBar(ImGuiDockNode* node);
+    static void             DockNodeRemoveTabBar(ImGuiDockNode* node);
+    static ImGuiID          DockNodeUpdateWindowMenu(ImGuiDockNode* node, ImGuiTabBar* tab_bar);
+    static void             DockNodeUpdateVisibleFlag(ImGuiDockNode* node);
+    static void             DockNodeStartMouseMovingWindow(ImGuiDockNode* node, ImGuiWindow* window);
+    static bool             DockNodeIsDropAllowed(ImGuiWindow* host_window, ImGuiWindow* payload_window);
+    static void             DockNodePreviewDockSetup(ImGuiWindow* host_window, ImGuiDockNode* host_node, ImGuiWindow* payload_window, ImGuiDockPreviewData* preview_data, bool is_explicit_target, bool is_outer_docking);
+    static void             DockNodePreviewDockRender(ImGuiWindow* host_window, ImGuiDockNode* host_node, ImGuiWindow* payload_window, const ImGuiDockPreviewData* preview_data);
+    static void             DockNodeCalcTabBarLayout(const ImGuiDockNode* node, ImRect* out_title_rect, ImRect* out_tab_bar_rect, ImVec2* out_window_menu_button_pos);
+    static void             DockNodeCalcSplitRects(ImVec2& pos_old, ImVec2& size_old, ImVec2& pos_new, ImVec2& size_new, ImGuiDir dir, ImVec2 size_new_desired);
+    static bool             DockNodeCalcDropRectsAndTestMousePos(const ImRect& parent, ImGuiDir dir, ImRect& out_draw, bool outer_docking, ImVec2* test_mouse_pos);
+    static const char*      DockNodeGetHostWindowTitle(ImGuiDockNode* node, char* buf, int buf_size) { ImFormatString(buf, buf_size, "##DockNode_%02X", node->ID); return buf; }
+    static int              DockNodeGetDepth(const ImGuiDockNode* node) { int depth = 0; while (node->ParentNode) { node = node->ParentNode; depth++; } return depth; }
+    static int              DockNodeGetTabOrder(ImGuiWindow* window);
+
+    // ImGuiDockNode tree manipulations
+    static void             DockNodeTreeSplit(ImGuiContext* ctx, ImGuiDockNode* parent_node, ImGuiAxis split_axis, int split_first_child, float split_ratio, ImGuiDockNode* new_node);
+    static void             DockNodeTreeMerge(ImGuiContext* ctx, ImGuiDockNode* parent_node, ImGuiDockNode* merge_lead_child);
+    static void             DockNodeTreeUpdatePosSize(ImGuiDockNode* node, ImVec2 pos, ImVec2 size, bool only_write_to_marked_nodes = false);
+    static void             DockNodeTreeUpdateSplitter(ImGuiDockNode* node);
+    static ImGuiDockNode*   DockNodeTreeFindNodeByPos(ImGuiDockNode* node, ImVec2 pos);
+    static ImGuiDockNode*   DockNodeTreeFindFallbackLeafNode(ImGuiDockNode* node);
+
+    // Settings
+    static void             DockSettingsRenameNodeReferences(ImGuiID old_node_id, ImGuiID new_node_id);
+    static void             DockSettingsRemoveNodeReferences(ImGuiID* node_ids, int node_ids_count);
+    static ImGuiDockNodeSettings*   DockSettingsFindNodeSettings(ImGuiContext* ctx, ImGuiID node_id);
+    static void*            DockSettingsHandler_ReadOpen(ImGuiContext*, ImGuiSettingsHandler*, const char* name);
+    static void             DockSettingsHandler_ReadLine(ImGuiContext*, ImGuiSettingsHandler*, void* entry, const char* line);
+    static void             DockSettingsHandler_WriteAll(ImGuiContext* imgui_ctx, ImGuiSettingsHandler* handler, ImGuiTextBuffer* buf);
+}
+
+//-----------------------------------------------------------------------------
+// Docking: ImGuiDockContext
+//-----------------------------------------------------------------------------
+// The lifetime model is different from the one of regular windows: we always create a ImGuiDockNode for each ImGuiDockNodeSettings,
+// or we always hold the entire docking node tree. Nodes are frequently hidden, e.g. if the window(s) or child nodes they host are not active.
+// At boot time only, we run a simple GC to remove nodes that have no references.
+// Because dock node settings (which are small, contiguous structures) are always mirrored by their corresponding dock nodes (more complete structures),
+// we can also very easily recreate the nodes from scratch given the settings data (this is what DockContextRebuild() does).
+// This is convenient as docking reconfiguration can be implemented by mostly poking at the simpler settings data.
+//-----------------------------------------------------------------------------
+// - DockContextInitialize()
+// - DockContextShutdown()
+// - DockContextOnLoadSettings()
+// - DockContextClearNodes()
+// - DockContextRebuildNodes()
+// - DockContextUpdateUndocking()
+// - DockContextUpdateDocking()
+// - DockContextFindNodeByID()
+// - DockContextBindNodeToWindow()
+// - DockContextGenNodeID()
+// - DockContextAddNode()
+// - DockContextRemoveNode()
+// - ImGuiDockContextPruneNodeData
+// - DockContextPruneUnusedSettingsNodes()
+// - DockContextBuildNodesFromSettings()
+// - DockContextBuildAddWindowsToNodes()
+//-----------------------------------------------------------------------------
+
+void ImGui::DockContextInitialize(ImGuiContext* ctx)
+{
+    ImGuiContext& g = *ctx;
+    IM_ASSERT(g.DockContext == NULL);
+    g.DockContext = IM_NEW(ImGuiDockContext)();
+
+    // Add .ini handle for persistent docking data
+    ImGuiSettingsHandler ini_handler;
+    ini_handler.TypeName = "Docking";
+    ini_handler.TypeHash = ImHashStr("Docking");
+    ini_handler.ReadOpenFn = DockSettingsHandler_ReadOpen;
+    ini_handler.ReadLineFn = DockSettingsHandler_ReadLine;
+    ini_handler.WriteAllFn = DockSettingsHandler_WriteAll;
+    g.SettingsHandlers.push_back(ini_handler);
+}
+
+void ImGui::DockContextShutdown(ImGuiContext* ctx)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = ctx->DockContext;
+    for (int n = 0; n < dc->Nodes.Data.Size; n++)
+        if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+            IM_DELETE(node);
+    IM_DELETE(g.DockContext);
+    g.DockContext = NULL;
+}
+
+void ImGui::DockContextOnLoadSettings(ImGuiContext* ctx)
+{
+    ImGuiDockContext* dc = ctx->DockContext;
+    DockContextPruneUnusedSettingsNodes(ctx);
+    DockContextBuildNodesFromSettings(ctx, dc->SettingsNodes.Data, dc->SettingsNodes.Size);
+}
+
+void ImGui::DockContextClearNodes(ImGuiContext* ctx, ImGuiID root_id, bool clear_persistent_docking_references)
+{
+    IM_UNUSED(ctx);
+    IM_ASSERT(ctx == GImGui);
+    DockBuilderRemoveNodeDockedWindows(root_id, clear_persistent_docking_references);
+    DockBuilderRemoveNodeChildNodes(root_id);
+}
+
+// This function also acts as a defacto test to make sure we can rebuild from scratch without a glitch
+void ImGui::DockContextRebuildNodes(ImGuiContext* ctx)
+{
+    IMGUI_DEBUG_LOG_DOCKING("DockContextRebuild()\n");
+    ImGuiDockContext* dc = ctx->DockContext;
+    SaveIniSettingsToMemory();
+    ImGuiID root_id = 0; // Rebuild all
+    DockContextClearNodes(ctx, root_id, false);
+    DockContextBuildNodesFromSettings(ctx, dc->SettingsNodes.Data, dc->SettingsNodes.Size);
+    DockContextBuildAddWindowsToNodes(ctx, root_id);
+}
+
+// Docking context update function, called by NewFrame()
+void ImGui::DockContextUpdateUndocking(ImGuiContext* ctx)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = ctx->DockContext;
+    if (!(g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
+    {
+        if (dc->Nodes.Data.Size > 0 || dc->Requests.Size > 0)
+            DockContextClearNodes(ctx, 0, true);
+        return;
+    }
+
+    // Setting NoSplit at runtime merges all nodes
+    if (g.IO.ConfigDockingNoSplit)
+        for (int n = 0; n < dc->Nodes.Data.Size; n++)
+            if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+                if (node->IsRootNode() && node->IsSplitNode())
+                {
+                    DockBuilderRemoveNodeChildNodes(node->ID);
+                    //dc->WantFullRebuild = true;
+                }
+
+    // Process full rebuild
+#if 0
+    if (ImGui::IsKeyPressed(ImGui::GetKeyIndex(ImGuiKey_C)))
+        dc->WantFullRebuild = true;
+#endif
+    if (dc->WantFullRebuild)
+    {
+        DockContextRebuildNodes(ctx);
+        dc->WantFullRebuild = false;
+    }
+
+    // Process Undocking requests (we need to process them _before_ the UpdateMouseMovingWindowNewFrame call in NewFrame)
+    for (int n = 0; n < dc->Requests.Size; n++)
+    {
+        ImGuiDockRequest* req = &dc->Requests[n];
+        if (req->Type == ImGuiDockRequestType_Undock && req->UndockTargetWindow)
+            DockContextProcessUndockWindow(ctx, req->UndockTargetWindow);
+        else if (req->Type == ImGuiDockRequestType_Undock && req->UndockTargetNode)
+            DockContextProcessUndockNode(ctx, req->UndockTargetNode);
+    }
+}
+
+// Docking context update function, called by NewFrame()
+void ImGui::DockContextUpdateDocking(ImGuiContext* ctx)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = ctx->DockContext;
+    if (!(g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
+        return;
+
+    // Process Docking requests
+    for (int n = 0; n < dc->Requests.Size; n++)
+        if (dc->Requests[n].Type == ImGuiDockRequestType_Dock)
+            DockContextProcessDock(ctx, &dc->Requests[n]);
+    dc->Requests.resize(0);
+
+    // Create windows for each automatic docking nodes
+    // We can have NULL pointers when we delete nodes, but because ID are recycled this should amortize nicely (and our node count will never be very high)
+    for (int n = 0; n < dc->Nodes.Data.Size; n++)
+        if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+            if (node->IsFloatingNode())
+                DockNodeUpdate(node);
+}
+
+static ImGuiDockNode* ImGui::DockContextFindNodeByID(ImGuiContext* ctx, ImGuiID id)
+{
+    return (ImGuiDockNode*)ctx->DockContext->Nodes.GetVoidPtr(id);
+}
+
+ImGuiID ImGui::DockContextGenNodeID(ImGuiContext* ctx)
+{
+    // Generate an ID for new node (the exact ID value doesn't matter as long as it is not already used)
+    // FIXME-OPT FIXME-DOCK: This is suboptimal, even if the node count is small enough not to be a worry. We should poke in ctx->Nodes to find a suitable ID faster.
+    ImGuiID id = 0x0001;
+    while (DockContextFindNodeByID(ctx, id) != NULL)
+        id++;
+    return id;
+}
+
+static ImGuiDockNode* ImGui::DockContextAddNode(ImGuiContext* ctx, ImGuiID id)
+{
+    // Generate an ID for the new node (the exact ID value doesn't matter as long as it is not already used) and add the first window.
+    if (id == 0)
+        id = DockContextGenNodeID(ctx);
+    else
+        IM_ASSERT(DockContextFindNodeByID(ctx, id) == NULL);
+
+    // We don't set node->LastFrameAlive on construction. Nodes are always created at all time to reflect .ini settings!
+    IMGUI_DEBUG_LOG_DOCKING("DockContextAddNode 0x%08X\n", id);
+    ImGuiDockNode* node = IM_NEW(ImGuiDockNode)(id);
+    ctx->DockContext->Nodes.SetVoidPtr(node->ID, node);
+    return node;
+}
+
+static void ImGui::DockContextRemoveNode(ImGuiContext* ctx, ImGuiDockNode* node, bool merge_sibling_into_parent_node)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = ctx->DockContext;
+
+    IMGUI_DEBUG_LOG_DOCKING("DockContextRemoveNode 0x%08X\n", node->ID);
+    IM_ASSERT(DockContextFindNodeByID(ctx, node->ID) == node);
+    IM_ASSERT(node->ChildNodes[0] == NULL && node->ChildNodes[1] == NULL);
+    IM_ASSERT(node->Windows.Size == 0);
+
+    if (node->HostWindow)
+        node->HostWindow->DockNodeAsHost = NULL;
+
+    ImGuiDockNode* parent_node = node->ParentNode;
+    const bool merge = (merge_sibling_into_parent_node && parent_node != NULL);
+    if (merge)
+    {
+        IM_ASSERT(parent_node->ChildNodes[0] == node || parent_node->ChildNodes[1] == node);
+        ImGuiDockNode* sibling_node = (parent_node->ChildNodes[0] == node ? parent_node->ChildNodes[1] : parent_node->ChildNodes[0]);
+        DockNodeTreeMerge(&g, parent_node, sibling_node);
+    }
+    else
+    {
+        for (int n = 0; parent_node && n < IM_ARRAYSIZE(parent_node->ChildNodes); n++)
+            if (parent_node->ChildNodes[n] == node)
+                node->ParentNode->ChildNodes[n] = NULL;
+        dc->Nodes.SetVoidPtr(node->ID, NULL);
+        IM_DELETE(node);
+    }
+}
+
+static int IMGUI_CDECL DockNodeComparerDepthMostFirst(const void* lhs, const void* rhs)
+{
+    const ImGuiDockNode* a = *(const ImGuiDockNode* const*)lhs;
+    const ImGuiDockNode* b = *(const ImGuiDockNode* const*)rhs;
+    return ImGui::DockNodeGetDepth(b) - ImGui::DockNodeGetDepth(a);
+}
+
+// Pre C++0x doesn't allow us to use a function-local type (without linkage) as template parameter, so we moved this here.
+struct ImGuiDockContextPruneNodeData
+{
+    int         CountWindows, CountChildWindows, CountChildNodes;
+    ImGuiID     RootId;
+    ImGuiDockContextPruneNodeData() { CountWindows = CountChildWindows = CountChildNodes = 0; RootId = 0; }
+};
+
+// Garbage collect unused nodes (run once at init time)
+static void ImGui::DockContextPruneUnusedSettingsNodes(ImGuiContext* ctx)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = ctx->DockContext;
+    IM_ASSERT(g.Windows.Size == 0);
+
+    ImPool<ImGuiDockContextPruneNodeData> pool;
+    pool.Reserve(dc->SettingsNodes.Size);
+
+    // Count child nodes and compute RootID
+    for (int settings_n = 0; settings_n < dc->SettingsNodes.Size; settings_n++)
+    {
+        ImGuiDockNodeSettings* settings = &dc->SettingsNodes[settings_n];
+        ImGuiDockContextPruneNodeData* parent_data = settings->ParentNodeId ? pool.GetByKey(settings->ParentNodeId) : 0;
+        pool.GetOrAddByKey(settings->ID)->RootId = parent_data ? parent_data->RootId : settings->ID;
+        if (settings->ParentNodeId)
+            pool.GetOrAddByKey(settings->ParentNodeId)->CountChildNodes++;
+    }
+
+    // Count reference to dock ids from dockspaces
+    // We track the 'auto-DockNode <- manual-Window <- manual-DockSpace' in order to avoid 'auto-DockNode' being ditched by DockContextPruneUnusedSettingsNodes()
+    for (int settings_n = 0; settings_n < dc->SettingsNodes.Size; settings_n++)
+    {
+        ImGuiDockNodeSettings* settings = &dc->SettingsNodes[settings_n];
+        if (settings->ParentWindowId != 0)
+            if (ImGuiWindowSettings* window_settings = FindWindowSettings(settings->ParentWindowId))
+                if (window_settings->DockId)
+                    if (ImGuiDockContextPruneNodeData* data = pool.GetByKey(window_settings->DockId))
+                        data->CountChildNodes++;
+    }
+
+    // Count reference to dock ids from window settings
+    // We guard against the possibility of an invalid .ini file (RootID may point to a missing node)
+    for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+        if (ImGuiID dock_id = settings->DockId)
+            if (ImGuiDockContextPruneNodeData* data = pool.GetByKey(dock_id))
+            {
+                data->CountWindows++;
+                if (ImGuiDockContextPruneNodeData* data_root = (data->RootId == dock_id) ? data : pool.GetByKey(data->RootId))
+                    data_root->CountChildWindows++;
+            }
+
+    // Prune
+    for (int settings_n = 0; settings_n < dc->SettingsNodes.Size; settings_n++)
+    {
+        ImGuiDockNodeSettings* settings = &dc->SettingsNodes[settings_n];
+        ImGuiDockContextPruneNodeData* data = pool.GetByKey(settings->ID);
+        if (data->CountWindows > 1)
+            continue;
+        ImGuiDockContextPruneNodeData* data_root = (data->RootId == settings->ID) ? data : pool.GetByKey(data->RootId);
+
+        bool remove = false;
+        remove |= (data->CountWindows == 1 && settings->ParentNodeId == 0 && data->CountChildNodes == 0 && !(settings->Flags & ImGuiDockNodeFlags_CentralNode));  // Floating root node with only 1 window
+        remove |= (data->CountWindows == 0 && settings->ParentNodeId == 0 && data->CountChildNodes == 0); // Leaf nodes with 0 window
+        remove |= (data_root->CountChildWindows == 0);
+        if (remove)
+        {
+            IMGUI_DEBUG_LOG_DOCKING("DockContextPruneUnusedSettingsNodes: Prune 0x%08X\n", settings->ID);
+            DockSettingsRemoveNodeReferences(&settings->ID, 1);
+            settings->ID = 0;
+        }
+    }
+}
+
+static void ImGui::DockContextBuildNodesFromSettings(ImGuiContext* ctx, ImGuiDockNodeSettings* node_settings_array, int node_settings_count)
+{
+    // Build nodes
+    for (int node_n = 0; node_n < node_settings_count; node_n++)
+    {
+        ImGuiDockNodeSettings* settings = &node_settings_array[node_n];
+        if (settings->ID == 0)
+            continue;
+        ImGuiDockNode* node = DockContextAddNode(ctx, settings->ID);
+        node->ParentNode = settings->ParentNodeId ? DockContextFindNodeByID(ctx, settings->ParentNodeId) : NULL;
+        node->Pos = ImVec2(settings->Pos.x, settings->Pos.y);
+        node->Size = ImVec2(settings->Size.x, settings->Size.y);
+        node->SizeRef = ImVec2(settings->SizeRef.x, settings->SizeRef.y);
+        node->AuthorityForPos = node->AuthorityForSize = node->AuthorityForViewport = ImGuiDataAuthority_DockNode;
+        if (node->ParentNode && node->ParentNode->ChildNodes[0] == NULL)
+            node->ParentNode->ChildNodes[0] = node;
+        else if (node->ParentNode && node->ParentNode->ChildNodes[1] == NULL)
+            node->ParentNode->ChildNodes[1] = node;
+        node->SelectedTabId = settings->SelectedWindowId;
+        node->SplitAxis = (ImGuiAxis)settings->SplitAxis;
+        node->LocalFlags |= (settings->Flags & ImGuiDockNodeFlags_SavedFlagsMask_);
+
+        // Bind host window immediately if it already exist (in case of a rebuild)
+        // This is useful as the RootWindowForTitleBarHighlight links necessary to highlight the currently focused node requires node->HostWindow to be set.
+        char host_window_title[20];
+        ImGuiDockNode* root_node = DockNodeGetRootNode(node);
+        node->HostWindow = FindWindowByName(DockNodeGetHostWindowTitle(root_node, host_window_title, IM_ARRAYSIZE(host_window_title)));
+    }
+}
+
+void ImGui::DockContextBuildAddWindowsToNodes(ImGuiContext* ctx, ImGuiID root_id)
+{
+    // Rebind all windows to nodes (they can also lazily rebind but we'll have a visible glitch during the first frame)
+    ImGuiContext& g = *ctx;
+    for (int n = 0; n < g.Windows.Size; n++)
+    {
+        ImGuiWindow* window = g.Windows[n];
+        if (window->DockId == 0 || window->LastFrameActive < g.FrameCount - 1)
+            continue;
+        if (window->DockNode != NULL)
+            continue;
+
+        ImGuiDockNode* node = DockContextFindNodeByID(ctx, window->DockId);
+        IM_ASSERT(node != NULL);   // This should have been called after DockContextBuildNodesFromSettings()
+        if (root_id == 0 || DockNodeGetRootNode(node)->ID == root_id)
+            DockNodeAddWindow(node, window, true);
+    }
+}
+
+//-----------------------------------------------------------------------------
+// Docking: ImGuiDockContext Docking/Undocking functions
+//-----------------------------------------------------------------------------
+// - DockContextQueueDock()
+// - DockContextQueueUndockWindow()
+// - DockContextQueueUndockNode()
+// - DockContextQueueNotifyRemovedNode()
+// - DockContextProcessDock()
+// - DockContextProcessUndockWindow()
+// - DockContextProcessUndockNode()
+// - DockContextCalcDropPosForDocking()
+//-----------------------------------------------------------------------------
+
+void ImGui::DockContextQueueDock(ImGuiContext* ctx, ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload, ImGuiDir split_dir, float split_ratio, bool split_outer)
+{
+    IM_ASSERT(target != payload);
+    ImGuiDockRequest req;
+    req.Type = ImGuiDockRequestType_Dock;
+    req.DockTargetWindow = target;
+    req.DockTargetNode = target_node;
+    req.DockPayload = payload;
+    req.DockSplitDir = split_dir;
+    req.DockSplitRatio = split_ratio;
+    req.DockSplitOuter = split_outer;
+    ctx->DockContext->Requests.push_back(req);
+}
+
+void ImGui::DockContextQueueUndockWindow(ImGuiContext* ctx, ImGuiWindow* window)
+{
+    ImGuiDockRequest req;
+    req.Type = ImGuiDockRequestType_Undock;
+    req.UndockTargetWindow = window;
+    ctx->DockContext->Requests.push_back(req);
+}
+
+void ImGui::DockContextQueueUndockNode(ImGuiContext* ctx, ImGuiDockNode* node)
+{
+    ImGuiDockRequest req;
+    req.Type = ImGuiDockRequestType_Undock;
+    req.UndockTargetNode = node;
+    ctx->DockContext->Requests.push_back(req);
+}
+
+void ImGui::DockContextQueueNotifyRemovedNode(ImGuiContext* ctx, ImGuiDockNode* node)
+{
+    ImGuiDockContext* dc = ctx->DockContext;
+    for (int n = 0; n < dc->Requests.Size; n++)
+        if (dc->Requests[n].DockTargetNode == node)
+            dc->Requests[n].Type = ImGuiDockRequestType_None;
+}
+
+void ImGui::DockContextProcessDock(ImGuiContext* ctx, ImGuiDockRequest* req)
+{
+    IM_ASSERT((req->Type == ImGuiDockRequestType_Dock && req->DockPayload != NULL) || (req->Type == ImGuiDockRequestType_Split && req->DockPayload == NULL));
+    IM_ASSERT(req->DockTargetWindow != NULL || req->DockTargetNode != NULL);
+
+    ImGuiContext& g = *ctx;
+    IM_UNUSED(g);
+
+    ImGuiWindow* payload_window = req->DockPayload;     // Optional
+    ImGuiWindow* target_window = req->DockTargetWindow;
+    ImGuiDockNode* node = req->DockTargetNode;
+    if (payload_window)
+        IMGUI_DEBUG_LOG_DOCKING("DockContextProcessDock node 0x%08X target '%s' dock window '%s', split_dir %d\n", node ? node->ID : 0, target_window ? target_window->Name : "NULL", payload_window ? payload_window->Name : "NULL", req->DockSplitDir);
+    else
+        IMGUI_DEBUG_LOG_DOCKING("DockContextProcessDock node 0x%08X, split_dir %d\n", node ? node->ID : 0, req->DockSplitDir);
+
+    // Decide which Tab will be selected at the end of the operation
+    ImGuiID next_selected_id = 0;
+    ImGuiDockNode* payload_node = NULL;
+    if (payload_window)
+    {
+        payload_node = payload_window->DockNodeAsHost;
+        payload_window->DockNodeAsHost = NULL; // Important to clear this as the node will have its life as a child which might be merged/deleted later.
+        if (payload_node && payload_node->IsLeafNode())
+            next_selected_id = payload_node->TabBar->NextSelectedTabId ? payload_node->TabBar->NextSelectedTabId : payload_node->TabBar->SelectedTabId;
+        if (payload_node == NULL)
+            next_selected_id = payload_window->ID;
+    }
+
+    // FIXME-DOCK: When we are trying to dock an existing single-window node into a loose window, transfer Node ID as well
+    // When processing an interactive split, usually LastFrameAlive will be < g.FrameCount. But DockBuilder operations can make it ==.
+    if (node)
+        IM_ASSERT(node->LastFrameAlive <= g.FrameCount);
+    if (node && target_window && node == target_window->DockNodeAsHost)
+        IM_ASSERT(node->Windows.Size > 0 || node->IsSplitNode() || node->IsCentralNode());
+
+    // Create new node and add existing window to it
+    if (node == NULL)
+    {
+        node = DockContextAddNode(ctx, 0);
+        node->Pos = target_window->Pos;
+        node->Size = target_window->Size;
+        if (target_window->DockNodeAsHost == NULL)
+        {
+            DockNodeAddWindow(node, target_window, true);
+            node->TabBar->Tabs[0].Flags &= ~ImGuiTabItemFlags_Unsorted;
+            target_window->DockIsActive = true;
+        }
+    }
+
+    ImGuiDir split_dir = req->DockSplitDir;
+    if (split_dir != ImGuiDir_None)
+    {
+        // Split into one, one side will be our payload node unless we are dropping a loose window
+        const ImGuiAxis split_axis = (split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Right) ? ImGuiAxis_X : ImGuiAxis_Y;
+        const int split_inheritor_child_idx = (split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Up) ? 1 : 0; // Current contents will be moved to the opposite side
+        const float split_ratio = req->DockSplitRatio;
+        DockNodeTreeSplit(ctx, node, split_axis, split_inheritor_child_idx, split_ratio, payload_node);  // payload_node may be NULL here!
+        ImGuiDockNode* new_node = node->ChildNodes[split_inheritor_child_idx ^ 1];
+        new_node->HostWindow = node->HostWindow;
+        node = new_node;
+    }
+    node->LocalFlags &= ~ImGuiDockNodeFlags_HiddenTabBar;
 
-// (this section is filled in the 'docking' branch)
+    if (node != payload_node)
+    {
+        // Create tab bar before we call DockNodeMoveWindows (which would attempt to move the old tab-bar, which would lead us to payload tabs wrongly appearing before target tabs!)
+        if (node->Windows.Size > 0 && node->TabBar == NULL)
+        {
+            DockNodeAddTabBar(node);
+            for (int n = 0; n < node->Windows.Size; n++)
+                TabBarAddTab(node->TabBar, ImGuiTabItemFlags_None, node->Windows[n]);
+        }
+
+        if (payload_node != NULL)
+        {
+            // Transfer full payload node (with 1+ child windows or child nodes)
+            if (payload_node->IsSplitNode())
+            {
+                if (node->Windows.Size > 0)
+                {
+                    // We can dock a split payload into a node that already has windows _only_ if our payload is a node tree with a single visible node.
+                    // In this situation, we move the windows of the target node into the currently visible node of the payload.
+                    // This allows us to preserve some of the underlying dock tree settings nicely.
+                    IM_ASSERT(payload_node->OnlyNodeWithWindows != NULL); // The docking should have been blocked by DockNodePreviewDockSetup() early on and never submitted.
+                    ImGuiDockNode* visible_node = payload_node->OnlyNodeWithWindows;
+                    if (visible_node->TabBar)
+                        IM_ASSERT(visible_node->TabBar->Tabs.Size > 0);
+                    DockNodeMoveWindows(node, visible_node);
+                    DockNodeMoveWindows(visible_node, node);
+                    DockSettingsRenameNodeReferences(node->ID, visible_node->ID);
+                }
+                if (node->IsCentralNode())
+                {
+                    // Central node property needs to be moved to a leaf node, pick the last focused one.
+                    // FIXME-DOCK: If we had to transfer other flags here, what would the policy be?
+                    ImGuiDockNode* last_focused_node = DockContextFindNodeByID(ctx, payload_node->LastFocusedNodeId);
+                    IM_ASSERT(last_focused_node != NULL);
+                    ImGuiDockNode* last_focused_root_node = DockNodeGetRootNode(last_focused_node);
+                    IM_ASSERT(last_focused_root_node == DockNodeGetRootNode(payload_node));
+                    last_focused_node->LocalFlags |= ImGuiDockNodeFlags_CentralNode;
+                    node->LocalFlags &= ~ImGuiDockNodeFlags_CentralNode;
+                    last_focused_root_node->CentralNode = last_focused_node;
+                }
+
+                IM_ASSERT(node->Windows.Size == 0);
+                DockNodeMoveChildNodes(node, payload_node);
+            }
+            else
+            {
+                const ImGuiID payload_dock_id = payload_node->ID;
+                DockNodeMoveWindows(node, payload_node);
+                DockSettingsRenameNodeReferences(payload_dock_id, node->ID);
+            }
+            DockContextRemoveNode(ctx, payload_node, true);
+        }
+        else if (payload_window)
+        {
+            // Transfer single window
+            const ImGuiID payload_dock_id = payload_window->DockId;
+            node->VisibleWindow = payload_window;
+            DockNodeAddWindow(node, payload_window, true);
+            if (payload_dock_id != 0)
+                DockSettingsRenameNodeReferences(payload_dock_id, node->ID);
+        }
+    }
+    else
+    {
+        // When docking a floating single window node we want to reevaluate auto-hiding of the tab bar
+        node->WantHiddenTabBarUpdate = true;
+    }
+
+    // Update selection immediately
+    if (ImGuiTabBar* tab_bar = node->TabBar)
+        tab_bar->NextSelectedTabId = next_selected_id;
+    MarkIniSettingsDirty();
+}
+
+void ImGui::DockContextProcessUndockWindow(ImGuiContext* ctx, ImGuiWindow* window, bool clear_persistent_docking_ref)
+{
+    IMGUI_DEBUG_LOG_DOCKING("DockContextProcessUndockWindow window '%s', clear_persistent_docking_ref = %d\n", window->Name, clear_persistent_docking_ref);
+    IM_UNUSED(ctx);
+    if (window->DockNode)
+        DockNodeRemoveWindow(window->DockNode, window, clear_persistent_docking_ref ? 0 : window->DockId);
+    else
+        window->DockId = 0;
+    window->Collapsed = false;
+    window->DockIsActive = false;
+    window->DockTabIsVisible = false;
+    MarkIniSettingsDirty();
+}
+
+void ImGui::DockContextProcessUndockNode(ImGuiContext* ctx, ImGuiDockNode* node)
+{
+    IMGUI_DEBUG_LOG_DOCKING("DockContextProcessUndockNode node %08X\n", node->ID);
+    IM_ASSERT(node->IsLeafNode());
+    IM_ASSERT(node->Windows.Size >= 1);
+
+    if (node->IsRootNode() || node->IsCentralNode())
+    {
+        // In the case of a root node or central node, the node will have to stay in place. Create a new node to receive the payload.
+        ImGuiDockNode* new_node = DockContextAddNode(ctx, 0);
+        DockNodeMoveWindows(new_node, node);
+        DockSettingsRenameNodeReferences(node->ID, new_node->ID);
+        for (int n = 0; n < new_node->Windows.Size; n++)
+            UpdateWindowParentAndRootLinks(new_node->Windows[n], new_node->Windows[n]->Flags, NULL);
+        node = new_node;
+    }
+    else
+    {
+        // Otherwise extract our node and merging our sibling back into the parent node.
+        IM_ASSERT(node->ParentNode->ChildNodes[0] == node || node->ParentNode->ChildNodes[1] == node);
+        int index_in_parent = (node->ParentNode->ChildNodes[0] == node) ? 0 : 1;
+        node->ParentNode->ChildNodes[index_in_parent] = NULL;
+        DockNodeTreeMerge(ctx, node->ParentNode, node->ParentNode->ChildNodes[index_in_parent ^ 1]);
+        node->ParentNode->AuthorityForViewport = ImGuiDataAuthority_Window; // The node that stays in place keeps the viewport, so our newly dragged out node will create a new viewport
+        node->ParentNode = NULL;
+    }
+    node->AuthorityForPos = node->AuthorityForSize = ImGuiDataAuthority_Window;
+    node->WantMouseMove = true;
+    MarkIniSettingsDirty();
+}
+
+// This is mostly used for automation.
+bool ImGui::DockContextCalcDropPosForDocking(ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload, ImGuiDir split_dir, bool split_outer, ImVec2* out_pos)
+{
+    if (split_outer)
+    {
+        IM_ASSERT(0);
+    }
+    else
+    {
+        ImGuiDockPreviewData split_data;
+        DockNodePreviewDockSetup(target, target_node, payload, &split_data, false, split_outer);
+        if (split_data.DropRectsDraw[split_dir+1].IsInverted())
+            return false;
+        *out_pos = split_data.DropRectsDraw[split_dir+1].GetCenter();
+        return true;
+    }
+    return false;
+}
+
+//-----------------------------------------------------------------------------
+// Docking: ImGuiDockNode
+//-----------------------------------------------------------------------------
+// - DockNodeGetTabOrder()
+// - DockNodeAddWindow()
+// - DockNodeRemoveWindow()
+// - DockNodeMoveChildNodes()
+// - DockNodeMoveWindows()
+// - DockNodeApplyPosSizeToWindows()
+// - DockNodeHideHostWindow()
+// - ImGuiDockNodeFindInfoResults
+// - DockNodeFindInfo()
+// - DockNodeFindWindowByID()
+// - DockNodeUpdateVisibleFlagAndInactiveChilds()
+// - DockNodeUpdateVisibleFlag()
+// - DockNodeStartMouseMovingWindow()
+// - DockNodeUpdate()
+// - DockNodeUpdateWindowMenu()
+// - DockNodeUpdateTabBar()
+// - DockNodeAddTabBar()
+// - DockNodeRemoveTabBar()
+// - DockNodeIsDropAllowedOne()
+// - DockNodeIsDropAllowed()
+// - DockNodeCalcTabBarLayout()
+// - DockNodeCalcSplitRects()
+// - DockNodeCalcDropRectsAndTestMousePos()
+// - DockNodePreviewDockSetup()
+// - DockNodePreviewDockRender()
+//-----------------------------------------------------------------------------
+
+ImGuiDockNode::ImGuiDockNode(ImGuiID id)
+{
+    ID = id;
+    SharedFlags = LocalFlags = ImGuiDockNodeFlags_None;
+    ParentNode = ChildNodes[0] = ChildNodes[1] = NULL;
+    TabBar = NULL;
+    SplitAxis = ImGuiAxis_None;
+
+    State = ImGuiDockNodeState_Unknown;
+    HostWindow = VisibleWindow = NULL;
+    CentralNode = OnlyNodeWithWindows = NULL;
+    LastFrameAlive = LastFrameActive = LastFrameFocused = -1;
+    LastFocusedNodeId = 0;
+    SelectedTabId = 0;
+    WantCloseTabId = 0;
+    AuthorityForPos = AuthorityForSize = ImGuiDataAuthority_DockNode;
+    AuthorityForViewport = ImGuiDataAuthority_Auto;
+    IsVisible = true;
+    IsFocused = HasCloseButton = HasWindowMenuButton = EnableCloseButton = false;
+    WantCloseAll = WantLockSizeOnce = WantMouseMove = WantHiddenTabBarUpdate = WantHiddenTabBarToggle = false;
+    MarkedForPosSizeWrite = false;
+}
+
+ImGuiDockNode::~ImGuiDockNode()
+{
+    IM_DELETE(TabBar);
+    TabBar = NULL;
+    ChildNodes[0] = ChildNodes[1] = NULL;
+}
+
+int ImGui::DockNodeGetTabOrder(ImGuiWindow* window)
+{
+    ImGuiTabBar* tab_bar = window->DockNode->TabBar;
+    if (tab_bar == NULL)
+        return -1;
+    ImGuiTabItem* tab = TabBarFindTabByID(tab_bar, window->ID);
+    return tab ? tab_bar->GetTabOrder(tab) : -1;
+}
+
+static void ImGui::DockNodeAddWindow(ImGuiDockNode* node, ImGuiWindow* window, bool add_to_tab_bar)
+{
+    ImGuiContext& g = *GImGui; (void)g;
+    if (window->DockNode)
+    {
+        // Can overwrite an existing window->DockNode (e.g. pointing to a disabled DockSpace node)
+        IM_ASSERT(window->DockNode->ID != node->ID);
+        DockNodeRemoveWindow(window->DockNode, window, 0);
+    }
+    IM_ASSERT(window->DockNode == NULL || window->DockNodeAsHost == NULL);
+    IMGUI_DEBUG_LOG_DOCKING("DockNodeAddWindow node 0x%08X window '%s'\n", node->ID, window->Name);
+
+    node->Windows.push_back(window);
+    node->WantHiddenTabBarUpdate = true;
+    window->DockNode = node;
+    window->DockId = node->ID;
+    window->DockIsActive = (node->Windows.Size > 1);
+    window->DockTabWantClose = false;
+
+    // If more than 2 windows appeared on the same frame, we'll create a new hosting DockNode from the point of the second window submission.
+    // Then we need to hide the first window (after its been output) otherwise it would be visible as a standalone window for one frame.
+    if (node->HostWindow == NULL && node->Windows.Size == 2 && node->Windows[0]->WasActive == false)
+    {
+        node->Windows[0]->Hidden = true;
+        node->Windows[0]->HiddenFramesCanSkipItems = 1;
+    }
+
+    // When reactivating a node with one or two loose window, the window pos/size/viewport are authoritative over the node storage.
+    // In particular it is important we init the viewport from the first window so we don't create two viewports and drop one.
+    if (node->HostWindow == NULL && node->IsFloatingNode())
+    {
+        if (node->AuthorityForPos == ImGuiDataAuthority_Auto)
+            node->AuthorityForPos = ImGuiDataAuthority_Window;
+        if (node->AuthorityForSize == ImGuiDataAuthority_Auto)
+            node->AuthorityForSize = ImGuiDataAuthority_Window;
+        if (node->AuthorityForViewport == ImGuiDataAuthority_Auto)
+            node->AuthorityForViewport = ImGuiDataAuthority_Window;
+    }
+
+    // Add to tab bar if requested
+    if (add_to_tab_bar)
+    {
+        if (node->TabBar == NULL)
+        {
+            DockNodeAddTabBar(node);
+            node->TabBar->SelectedTabId = node->TabBar->NextSelectedTabId = node->SelectedTabId;
+
+            // Add existing windows
+            for (int n = 0; n < node->Windows.Size - 1; n++)
+                TabBarAddTab(node->TabBar, ImGuiTabItemFlags_None, node->Windows[n]);
+        }
+        TabBarAddTab(node->TabBar, ImGuiTabItemFlags_Unsorted, window);
+    }
+
+    DockNodeUpdateVisibleFlag(node);
+
+    // Update this without waiting for the next time we Begin() in the window, so our host window will have the proper title bar color on its first frame.
+    if (node->HostWindow)
+        UpdateWindowParentAndRootLinks(window, window->Flags | ImGuiWindowFlags_ChildWindow, node->HostWindow);
+}
+
+static void ImGui::DockNodeRemoveWindow(ImGuiDockNode* node, ImGuiWindow* window, ImGuiID save_dock_id)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(window->DockNode == node);
+    //IM_ASSERT(window->RootWindow == node->HostWindow);
+    //IM_ASSERT(window->LastFrameActive < g.FrameCount);    // We may call this from Begin()
+    IM_ASSERT(save_dock_id == 0 || save_dock_id == node->ID);
+    IMGUI_DEBUG_LOG_DOCKING("DockNodeRemoveWindow node 0x%08X window '%s'\n", node->ID, window->Name);
+
+    window->DockNode = NULL;
+    window->DockIsActive = window->DockTabWantClose = false;
+    window->DockId = save_dock_id;
+    UpdateWindowParentAndRootLinks(window, window->Flags & ~ImGuiWindowFlags_ChildWindow, NULL); // Update immediately
+
+    // Remove window
+    bool erased = false;
+    for (int n = 0; n < node->Windows.Size; n++)
+        if (node->Windows[n] == window)
+        {
+            node->Windows.erase(node->Windows.Data + n);
+            erased = true;
+            break;
+        }
+    IM_ASSERT(erased);
+    if (node->VisibleWindow == window)
+        node->VisibleWindow = NULL;
+
+    // Remove tab and possibly tab bar
+    node->WantHiddenTabBarUpdate = true;
+    if (node->TabBar)
+    {
+        TabBarRemoveTab(node->TabBar, window->ID);
+        const int tab_count_threshold_for_tab_bar = node->IsCentralNode() ? 1 : 2;
+        if (node->Windows.Size < tab_count_threshold_for_tab_bar)
+            DockNodeRemoveTabBar(node);
+    }
+
+    if (node->Windows.Size == 0 && !node->IsCentralNode() && !node->IsDockSpace() && window->DockId != node->ID)
+    {
+        // Automatic dock node delete themselves if they are not holding at least one tab
+        DockContextRemoveNode(&g, node, true);
+        return;
+    }
+
+    if (node->Windows.Size == 1 && !node->IsCentralNode() && node->HostWindow)
+    {
+        ImGuiWindow* remaining_window = node->Windows[0];
+        if (node->HostWindow->ViewportOwned && node->IsRootNode())
+        {
+            // Transfer viewport back to the remaining loose window
+            IM_ASSERT(node->HostWindow->Viewport->Window == node->HostWindow);
+            node->HostWindow->Viewport->Window = remaining_window;
+            node->HostWindow->Viewport->ID = remaining_window->ID;
+        }
+        remaining_window->Collapsed = node->HostWindow->Collapsed;
+    }
+
+    // Update visibility immediately is required so the DockNodeUpdateRemoveInactiveChilds() processing can reflect changes up the tree
+    DockNodeUpdateVisibleFlag(node);
+}
+
+static void ImGui::DockNodeMoveChildNodes(ImGuiDockNode* dst_node, ImGuiDockNode* src_node)
+{
+    IM_ASSERT(dst_node->Windows.Size == 0);
+    dst_node->ChildNodes[0] = src_node->ChildNodes[0];
+    dst_node->ChildNodes[1] = src_node->ChildNodes[1];
+    if (dst_node->ChildNodes[0])
+        dst_node->ChildNodes[0]->ParentNode = dst_node;
+    if (dst_node->ChildNodes[1])
+        dst_node->ChildNodes[1]->ParentNode = dst_node;
+    dst_node->SplitAxis = src_node->SplitAxis;
+    dst_node->SizeRef = src_node->SizeRef;
+    src_node->ChildNodes[0] = src_node->ChildNodes[1] = NULL;
+}
+
+static void ImGui::DockNodeMoveWindows(ImGuiDockNode* dst_node, ImGuiDockNode* src_node)
+{
+    // Insert tabs in the same orders as currently ordered (node->Windows isn't ordered)
+    IM_ASSERT(src_node && dst_node && dst_node != src_node);
+    ImGuiTabBar* src_tab_bar = src_node->TabBar;
+    if (src_tab_bar != NULL)
+        IM_ASSERT(src_node->Windows.Size == src_node->TabBar->Tabs.Size);
+
+    // If the dst_node is empty we can just move the entire tab bar (to preserve selection, scrolling, etc.)
+    bool move_tab_bar = (src_tab_bar != NULL) && (dst_node->TabBar == NULL);
+    if (move_tab_bar)
+    {
+        dst_node->TabBar = src_node->TabBar;
+        src_node->TabBar = NULL;
+    }
+
+    for (int n = 0; n < src_node->Windows.Size; n++)
+    {
+        ImGuiWindow* window = src_tab_bar ? src_tab_bar->Tabs[n].Window : src_node->Windows[n];
+        window->DockNode = NULL;
+        window->DockIsActive = false;
+        DockNodeAddWindow(dst_node, window, move_tab_bar ? false : true);
+    }
+    src_node->Windows.clear();
+
+    if (!move_tab_bar && src_node->TabBar)
+    {
+        if (dst_node->TabBar)
+            dst_node->TabBar->SelectedTabId = src_node->TabBar->SelectedTabId;
+        DockNodeRemoveTabBar(src_node);
+    }
+}
+
+static void ImGui::DockNodeApplyPosSizeToWindows(ImGuiDockNode* node)
+{
+    for (int n = 0; n < node->Windows.Size; n++)
+    {
+        SetWindowPos(node->Windows[n], node->Pos, ImGuiCond_Always); // We don't assign directly to Pos because it can break the calculation of SizeContents on next frame
+        SetWindowSize(node->Windows[n], node->Size, ImGuiCond_Always);
+    }
+}
+
+static void ImGui::DockNodeHideHostWindow(ImGuiDockNode* node)
+{
+    if (node->HostWindow)
+    {
+        if (node->HostWindow->DockNodeAsHost == node)
+            node->HostWindow->DockNodeAsHost = NULL;
+        node->HostWindow = NULL;
+    }
+
+    if (node->Windows.Size == 1)
+    {
+        node->VisibleWindow = node->Windows[0];
+        node->Windows[0]->DockIsActive = false;
+    }
+
+    if (node->TabBar)
+        DockNodeRemoveTabBar(node);
+}
+
+// Search function called once by root node in DockNodeUpdate()
+struct ImGuiDockNodeFindInfoResults
+{
+    ImGuiDockNode*      CentralNode;
+    ImGuiDockNode*      FirstNodeWithWindows;
+    int                 CountNodesWithWindows;
+    //ImGuiWindowClass  WindowClassForMerges;
+
+    ImGuiDockNodeFindInfoResults() { CentralNode = FirstNodeWithWindows = NULL; CountNodesWithWindows = 0; }
+};
+
+static void DockNodeFindInfo(ImGuiDockNode* node, ImGuiDockNodeFindInfoResults* results)
+{
+    if (node->Windows.Size > 0)
+    {
+        if (results->FirstNodeWithWindows == NULL)
+            results->FirstNodeWithWindows = node;
+        results->CountNodesWithWindows++;
+    }
+    if (node->IsCentralNode())
+    {
+        IM_ASSERT(results->CentralNode == NULL); // Should be only one
+        IM_ASSERT(node->IsLeafNode() && "If you get this assert: please submit .ini file + repro of actions leading to this.");
+        results->CentralNode = node;
+    }
+    if (results->CountNodesWithWindows > 1 && results->CentralNode != NULL)
+        return;
+    if (node->ChildNodes[0])
+        DockNodeFindInfo(node->ChildNodes[0], results);
+    if (node->ChildNodes[1])
+        DockNodeFindInfo(node->ChildNodes[1], results);
+}
+
+static ImGuiWindow* ImGui::DockNodeFindWindowByID(ImGuiDockNode* node, ImGuiID id)
+{
+    IM_ASSERT(id != 0);
+    for (int n = 0; n < node->Windows.Size; n++)
+        if (node->Windows[n]->ID == id)
+            return node->Windows[n];
+    return NULL;
+}
+
+// - Remove inactive windows/nodes.
+// - Update visibility flag.
+static void ImGui::DockNodeUpdateVisibleFlagAndInactiveChilds(ImGuiDockNode* node)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(node->ParentNode == NULL || node->ParentNode->ChildNodes[0] == node || node->ParentNode->ChildNodes[1] == node);
+
+    // Inherit most flags
+    if (node->ParentNode)
+        node->SharedFlags = node->ParentNode->SharedFlags & ImGuiDockNodeFlags_SharedFlagsInheritMask_;
+
+    // Recurse into children
+    // There is the possibility that one of our child becoming empty will delete itself and moving its sibling contents into 'node'.
+    // If 'node->ChildNode[0]' delete itself, then 'node->ChildNode[1]->Windows' will be moved into 'node'
+    // If 'node->ChildNode[1]' delete itself, then 'node->ChildNode[0]->Windows' will be moved into 'node' and the "remove inactive windows" loop will have run twice on those windows (harmless)
+    if (node->ChildNodes[0])
+        DockNodeUpdateVisibleFlagAndInactiveChilds(node->ChildNodes[0]);
+    if (node->ChildNodes[1])
+        DockNodeUpdateVisibleFlagAndInactiveChilds(node->ChildNodes[1]);
+
+    // Remove inactive windows
+    // Merge node flags overrides stored in windows
+    for (int window_n = 0; window_n < node->Windows.Size; window_n++)
+    {
+        ImGuiWindow* window = node->Windows[window_n];
+        IM_ASSERT(window->DockNode == node);
+
+        bool node_was_active = (node->LastFrameActive + 1 == g.FrameCount);
+        bool remove = false;
+        remove |= node_was_active && (window->LastFrameActive + 1 < g.FrameCount);
+        remove |= node_was_active && (node->WantCloseAll || node->WantCloseTabId == window->ID) && window->HasCloseButton && !(window->Flags & ImGuiWindowFlags_UnsavedDocument);  // Submit all _expected_ closure from last frame
+        remove |= (window->DockTabWantClose);
+        if (remove)
+        {
+            window->DockTabWantClose = false;
+            if (node->Windows.Size == 1 && !node->IsCentralNode())
+            {
+                DockNodeHideHostWindow(node);
+                node->State = ImGuiDockNodeState_HostWindowHiddenBecauseSingleWindow;
+                DockNodeRemoveWindow(node, window, node->ID); // Will delete the node so it'll be invalid on return
+                return;
+            }
+            DockNodeRemoveWindow(node, window, node->ID);
+            window_n--;
+        }
+        else
+        {
+            node->LocalFlags &= ~window->WindowClass.DockNodeFlagsOverrideClear;
+            node->LocalFlags |= window->WindowClass.DockNodeFlagsOverrideSet;
+        }
+    }
+
+    // Auto-hide tab bar option
+    ImGuiDockNodeFlags node_flags = node->GetMergedFlags();
+    if (node->WantHiddenTabBarUpdate && node->Windows.Size == 1 && (node_flags & ImGuiDockNodeFlags_AutoHideTabBar) && !node->IsHiddenTabBar())
+        node->WantHiddenTabBarToggle = true;
+    node->WantHiddenTabBarUpdate = false;
+
+    // Cancel toggling if we know our tab bar is enforced to be hidden at all times
+    if (node->WantHiddenTabBarToggle && node->VisibleWindow && (node->VisibleWindow->WindowClass.DockNodeFlagsOverrideSet & ImGuiDockNodeFlags_HiddenTabBar))
+        node->WantHiddenTabBarToggle = false;
+
+    // Apply toggles at a single point of the frame (here!)
+    if (node->Windows.Size > 1)
+        node->LocalFlags &= ~ImGuiDockNodeFlags_HiddenTabBar;
+    else if (node->WantHiddenTabBarToggle)
+        node->LocalFlags ^= ImGuiDockNodeFlags_HiddenTabBar;
+    node->WantHiddenTabBarToggle = false;
+
+    DockNodeUpdateVisibleFlag(node);
+}
+
+static void ImGui::DockNodeUpdateVisibleFlag(ImGuiDockNode* node)
+{
+    // Update visibility flag
+    bool is_visible = (node->ParentNode == NULL) ? node->IsDockSpace() : node->IsCentralNode();
+    is_visible |= (node->Windows.Size > 0);
+    is_visible |= (node->ChildNodes[0] && node->ChildNodes[0]->IsVisible);
+    is_visible |= (node->ChildNodes[1] && node->ChildNodes[1]->IsVisible);
+    node->IsVisible = is_visible;
+}
+
+static void ImGui::DockNodeStartMouseMovingWindow(ImGuiDockNode* node, ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(node->WantMouseMove == true);
+    ImVec2 backup_active_click_offset = g.ActiveIdClickOffset;
+    StartMouseMovingWindow(window);
+    g.MovingWindow = window; // If we are docked into a non moveable root window, StartMouseMovingWindow() won't set g.MovingWindow. Override that decision.
+    node->WantMouseMove = false;
+    g.ActiveIdClickOffset = backup_active_click_offset;
+}
+
+// Update CentralNode, OnlyNodeWithWindows, LastFocusedNodeID. Copy window class.
+static void ImGui::DockNodeUpdateForRootNode(ImGuiDockNode* node)
+{
+    DockNodeUpdateVisibleFlagAndInactiveChilds(node);
+
+    // FIXME-DOCK: Merge this scan into the one above.
+    // - Setup central node pointers
+    // - Find if there's only a single visible window in the hierarchy (in which case we need to display a regular title bar -> FIXME-DOCK: that last part is not done yet!)
+    ImGuiDockNodeFindInfoResults results;
+    DockNodeFindInfo(node, &results);
+    node->CentralNode = results.CentralNode;
+    node->OnlyNodeWithWindows = (results.CountNodesWithWindows == 1) ? results.FirstNodeWithWindows : NULL;
+    if (node->LastFocusedNodeId == 0 && results.FirstNodeWithWindows != NULL)
+        node->LastFocusedNodeId = results.FirstNodeWithWindows->ID;
+
+    // Copy the window class from of our first window so it can be used for proper dock filtering.
+    // When node has mixed windows, prioritize the class with the most constraint (DockingAllowUnclassed = false) as the reference to copy.
+    // FIXME-DOCK: We don't recurse properly, this code could be reworked to work from DockNodeUpdateScanRec.
+    if (ImGuiDockNode* first_node_with_windows = results.FirstNodeWithWindows)
+    {
+        node->WindowClass = first_node_with_windows->Windows[0]->WindowClass;
+        for (int n = 1; n < first_node_with_windows->Windows.Size; n++)
+            if (first_node_with_windows->Windows[n]->WindowClass.DockingAllowUnclassed == false)
+            {
+                node->WindowClass = first_node_with_windows->Windows[n]->WindowClass;
+                break;
+            }
+    }
+}
+
+static void ImGui::DockNodeUpdate(ImGuiDockNode* node)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(node->LastFrameActive != g.FrameCount);
+    node->LastFrameAlive = g.FrameCount;
+    node->MarkedForPosSizeWrite = false;
+
+    node->CentralNode = node->OnlyNodeWithWindows = NULL;
+    if (node->IsRootNode())
+        DockNodeUpdateForRootNode(node);
+
+    // Remove tab bar if not needed
+    if (node->TabBar && node->IsNoTabBar())
+        DockNodeRemoveTabBar(node);
+
+    // Early out for hidden root dock nodes (when all DockId references are in inactive windows, or there is only 1 floating window holding on the DockId)
+    bool want_to_hide_host_window = false;
+    if (node->Windows.Size <= 1 && node->IsFloatingNode() && node->IsLeafNode())
+        if (!g.IO.ConfigDockingAlwaysTabBar && (node->Windows.Size == 0 || !node->Windows[0]->WindowClass.DockingAlwaysTabBar))
+            want_to_hide_host_window = true;
+    if (want_to_hide_host_window)
+    {
+        if (node->Windows.Size == 1)
+        {
+            // Floating window pos/size is authoritative
+            ImGuiWindow* single_window = node->Windows[0];
+            node->Pos = single_window->Pos;
+            node->Size = single_window->SizeFull;
+            node->AuthorityForPos = node->AuthorityForSize = node->AuthorityForViewport = ImGuiDataAuthority_Window;
+
+            // Transfer focus immediately so when we revert to a regular window it is immediately selected
+            if (node->HostWindow && g.NavWindow == node->HostWindow)
+                FocusWindow(single_window);
+            if (node->HostWindow)
+            {
+                single_window->Viewport = node->HostWindow->Viewport;
+                single_window->ViewportId = node->HostWindow->ViewportId;
+                if (node->HostWindow->ViewportOwned)
+                {
+                    single_window->Viewport->Window = single_window;
+                    single_window->ViewportOwned = true;
+                }
+            }
+        }
+
+        DockNodeHideHostWindow(node);
+        node->State = ImGuiDockNodeState_HostWindowHiddenBecauseSingleWindow;
+        node->WantCloseAll = false;
+        node->WantCloseTabId = 0;
+        node->HasCloseButton = node->HasWindowMenuButton = node->EnableCloseButton = false;
+        node->LastFrameActive = g.FrameCount;
+
+        if (node->WantMouseMove && node->Windows.Size == 1)
+            DockNodeStartMouseMovingWindow(node, node->Windows[0]);
+        return;
+    }
+
+    // In some circumstance we will defer creating the host window (so everything will be kept hidden),
+    // while the expected visible window is resizing itself.
+    // This is important for first-time (no ini settings restored) single window when io.ConfigDockingAlwaysTabBar is enabled,
+    // otherwise the node ends up using the minimum window size. Effectively those windows will take an extra frame to show up:
+    //   N+0: Begin(): window created (with no known size), node is created
+    //   N+1: DockNodeUpdate(): node skip creating host window / Begin(): window size applied, not visible
+    //   N+2: DockNodeUpdate(): node can create host window / Begin(): window becomes visible
+    // We could remove this frame if we could reliably calculate the expected window size during node update, before the Begin() code.
+    // It would require a generalization of CalcWindowExpectedSize(), probably extracting code away from Begin().
+    // In reality it isn't very important as user quickly ends up with size data in .ini file.
+    if (node->IsVisible && node->HostWindow == NULL && node->IsFloatingNode() && node->IsLeafNode())
+    {
+        IM_ASSERT(node->Windows.Size > 0);
+        ImGuiWindow* ref_window = NULL;
+        if (node->SelectedTabId != 0) // Note that we prune single-window-node settings on .ini loading, so this is generally 0 for them!
+            ref_window = DockNodeFindWindowByID(node, node->SelectedTabId);
+        if (ref_window == NULL)
+            ref_window = node->Windows[0];
+        if (ref_window->AutoFitFramesX > 0 || ref_window->AutoFitFramesY > 0)
+        {
+            node->State = ImGuiDockNodeState_HostWindowHiddenBecauseWindowsAreResizing;
+            return;
+        }
+    }
+
+    const ImGuiDockNodeFlags node_flags = node->GetMergedFlags();
+
+    // Bind or create host window
+    ImGuiWindow* host_window = NULL;
+    bool beginned_into_host_window = false;
+    if (node->IsDockSpace())
+    {
+        // [Explicit root dockspace node]
+        IM_ASSERT(node->HostWindow);
+        node->EnableCloseButton = false;
+        node->HasCloseButton = (node_flags & ImGuiDockNodeFlags_NoCloseButton) == 0;
+        node->HasWindowMenuButton = (node_flags & ImGuiDockNodeFlags_NoWindowMenuButton) == 0;
+        host_window = node->HostWindow;
+    }
+    else
+    {
+        // [Automatic root or child nodes]
+        node->EnableCloseButton = false;
+        node->HasCloseButton = (node->Windows.Size > 0) && (node_flags & ImGuiDockNodeFlags_NoCloseButton) == 0;
+        node->HasWindowMenuButton = (node->Windows.Size > 0) && (node_flags & ImGuiDockNodeFlags_NoWindowMenuButton) == 0;
+        for (int window_n = 0; window_n < node->Windows.Size; window_n++)
+        {
+            // FIXME-DOCK: Setting DockIsActive here means that for single active window in a leaf node, DockIsActive will be cleared until the next Begin() call.
+            ImGuiWindow* window = node->Windows[window_n];
+            window->DockIsActive = (node->Windows.Size > 1);
+            node->EnableCloseButton |= window->HasCloseButton;
+        }
+
+        if (node->IsRootNode() && node->IsVisible)
+        {
+            ImGuiWindow* ref_window = (node->Windows.Size > 0) ? node->Windows[0] : NULL;
+
+            // Sync Pos
+            if (node->AuthorityForPos == ImGuiDataAuthority_Window && ref_window)
+                SetNextWindowPos(ref_window->Pos);
+            else if (node->AuthorityForPos == ImGuiDataAuthority_DockNode)
+                SetNextWindowPos(node->Pos);
+
+            // Sync Size
+            if (node->AuthorityForSize == ImGuiDataAuthority_Window && ref_window)
+                SetNextWindowSize(ref_window->SizeFull);
+            else if (node->AuthorityForSize == ImGuiDataAuthority_DockNode)
+                SetNextWindowSize(node->Size);
+
+            // Sync Collapsed
+            if (node->AuthorityForSize == ImGuiDataAuthority_Window && ref_window)
+                SetNextWindowCollapsed(ref_window->Collapsed);
+
+            // Sync Viewport
+            if (node->AuthorityForViewport == ImGuiDataAuthority_Window && ref_window)
+                SetNextWindowViewport(ref_window->ViewportId);
+
+            SetNextWindowClass(&node->WindowClass);
+
+            // Begin into the host window
+            char window_label[20];
+            DockNodeGetHostWindowTitle(node, window_label, IM_ARRAYSIZE(window_label));
+            ImGuiWindowFlags window_flags = ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse | ImGuiWindowFlags_DockNodeHost;
+            window_flags |= ImGuiWindowFlags_NoFocusOnAppearing;
+            window_flags |= ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoNavFocus | ImGuiWindowFlags_NoCollapse;
+            window_flags |= ImGuiWindowFlags_NoTitleBar;
+
+            PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0, 0));
+            Begin(window_label, NULL, window_flags);
+            PopStyleVar();
+            beginned_into_host_window = true;
+
+            node->HostWindow = host_window = g.CurrentWindow;
+            host_window->DockNodeAsHost = node;
+            host_window->DC.CursorPos = host_window->Pos;
+            node->Pos = host_window->Pos;
+            node->Size = host_window->Size;
+
+            // We set ImGuiWindowFlags_NoFocusOnAppearing because we don't want the host window to take full focus (e.g. steal NavWindow)
+            // But we still it bring it to the front of display. There's no way to choose this precise behavior via window flags.
+            // One simple case to ponder if: window A has a toggle to create windows B/C/D. Dock B/C/D together, clear the toggle and enable it again.
+            // When reappearing B/C/D will request focus and be moved to the top of the display pile, but they are not linked to the dock host window
+            // during the frame they appear. The dock host window would keep its old display order, and the sorting in EndFrame would move B/C/D back
+            // after the dock host window, losing their top-most status.
+            if (node->HostWindow->Appearing)
+                BringWindowToDisplayFront(node->HostWindow);
+
+            node->AuthorityForPos = node->AuthorityForSize = node->AuthorityForViewport = ImGuiDataAuthority_Auto;
+        }
+        else if (node->ParentNode)
+        {
+            node->HostWindow = host_window = node->ParentNode->HostWindow;
+            node->AuthorityForPos = node->AuthorityForSize = node->AuthorityForViewport = ImGuiDataAuthority_Auto;
+        }
+        if (node->WantMouseMove && node->HostWindow)
+            DockNodeStartMouseMovingWindow(node, node->HostWindow);
+    }
+
+    // Update focused node (the one whose title bar is highlight) within a node tree
+    if (node->IsSplitNode())
+        IM_ASSERT(node->TabBar == NULL);
+    if (node->IsRootNode())
+        if (g.NavWindow && g.NavWindow->RootWindowDockStop->DockNode && g.NavWindow->RootWindowDockStop->ParentWindow == host_window)
+            node->LastFocusedNodeId = g.NavWindow->RootWindowDockStop->DockNode->ID;
+
+    // We need to draw a background at the root level if requested by ImGuiDockNodeFlags_PassthruCentralNode, but we will only know the correct pos/size after
+    // processing the resizing splitters. So we are using the DrawList channel splitting facility to submit drawing primitives out of order!
+    const bool render_dockspace_bg = node->IsRootNode() && host_window && (node_flags & ImGuiDockNodeFlags_PassthruCentralNode) != 0;
+    if (render_dockspace_bg)
+    {
+        host_window->DrawList->ChannelsSplit(2);
+        host_window->DrawList->ChannelsSetCurrent(1);
+    }
+
+    // Register a hit-test hole in the window unless we are currently dragging a window that is compatible with our dockspace
+    const ImGuiDockNode* central_node = node->CentralNode;
+    const bool central_node_hole = node->IsRootNode() && host_window && (node_flags & ImGuiDockNodeFlags_PassthruCentralNode) != 0 && central_node != NULL && central_node->IsEmpty();
+    bool central_node_hole_register_hit_test_hole = central_node_hole;
+    if (central_node_hole)
+        if (const ImGuiPayload* payload = ImGui::GetDragDropPayload())
+            if (payload->IsDataType(IMGUI_PAYLOAD_TYPE_WINDOW) && DockNodeIsDropAllowed(host_window, *(ImGuiWindow**)payload->Data))
+                central_node_hole_register_hit_test_hole = false;
+    if (central_node_hole_register_hit_test_hole)
+    {
+        // Add a little padding to match the "resize from edges" behavior and allow grabbing the splitter easily.
+        IM_ASSERT(node->IsDockSpace()); // We cannot pass this flag without the DockSpace() api. Testing this because we also setup the hole in host_window->ParentNode
+        ImRect central_hole(central_node->Pos, central_node->Pos + central_node->Size);
+        central_hole.Expand(ImVec2(-WINDOWS_RESIZE_FROM_EDGES_HALF_THICKNESS, -WINDOWS_RESIZE_FROM_EDGES_HALF_THICKNESS));
+        if (central_node_hole && !central_hole.IsInverted())
+        {
+            SetWindowHitTestHole(host_window, central_hole.Min, central_hole.Max - central_hole.Min);
+            SetWindowHitTestHole(host_window->ParentWindow, central_hole.Min, central_hole.Max - central_hole.Min);
+        }
+    }
+
+    // Update position/size, process and draw resizing splitters
+    if (node->IsRootNode() && host_window)
+    {
+        DockNodeTreeUpdatePosSize(node, host_window->Pos, host_window->Size);
+        DockNodeTreeUpdateSplitter(node);
+    }
+
+    // Draw empty node background (currently can only be the Central Node)
+    if (host_window && node->IsEmpty() && node->IsVisible && !(node_flags & ImGuiDockNodeFlags_PassthruCentralNode))
+        host_window->DrawList->AddRectFilled(node->Pos, node->Pos + node->Size, GetColorU32(ImGuiCol_DockingEmptyBg));
+
+    // Draw whole dockspace background if ImGuiDockNodeFlags_PassthruCentralNode if set.
+    if (render_dockspace_bg && node->IsVisible)
+    {
+        host_window->DrawList->ChannelsSetCurrent(0);
+        if (central_node_hole)
+            RenderRectFilledWithHole(host_window->DrawList, node->Rect(), central_node->Rect(), GetColorU32(ImGuiCol_WindowBg), 0.0f);
+        else
+            host_window->DrawList->AddRectFilled(node->Pos, node->Pos + node->Size, GetColorU32(ImGuiCol_WindowBg), 0.0f);
+        host_window->DrawList->ChannelsMerge();
+    }
+
+    // Draw and populate Tab Bar
+    if (host_window && node->Windows.Size > 0)
+    {
+        DockNodeUpdateTabBar(node, host_window);
+    }
+    else
+    {
+        node->WantCloseAll = false;
+        node->WantCloseTabId = 0;
+        node->IsFocused = false;
+    }
+    if (node->TabBar && node->TabBar->SelectedTabId)
+        node->SelectedTabId = node->TabBar->SelectedTabId;
+    else if (node->Windows.Size > 0)
+        node->SelectedTabId = node->Windows[0]->ID;
+
+    // Draw payload drop target
+    if (host_window && node->IsVisible)
+        if (node->IsRootNode() && (g.MovingWindow == NULL || g.MovingWindow->RootWindow != host_window))
+            BeginDockableDragDropTarget(host_window);
+
+    // We update this after DockNodeUpdateTabBar()
+    node->LastFrameActive = g.FrameCount;
+
+    // Recurse into children
+    // FIXME-DOCK FIXME-OPT: Should not need to recurse into children
+    if (host_window)
+    {
+        if (node->ChildNodes[0])
+            DockNodeUpdate(node->ChildNodes[0]);
+        if (node->ChildNodes[1])
+            DockNodeUpdate(node->ChildNodes[1]);
+
+        // Render outer borders last (after the tab bar)
+        if (node->IsRootNode())
+            RenderWindowOuterBorders(host_window);
+    }
+
+    // End host window
+    if (beginned_into_host_window) //-V1020
+        End();
+}
+
+// Compare TabItem nodes given the last known DockOrder (will persist in .ini file as hint), used to sort tabs when multiple tabs are added on the same frame.
+static int IMGUI_CDECL TabItemComparerByDockOrder(const void* lhs, const void* rhs)
+{
+    ImGuiWindow* a = ((const ImGuiTabItem*)lhs)->Window;
+    ImGuiWindow* b = ((const ImGuiTabItem*)rhs)->Window;
+    if (int d = ((a->DockOrder == -1) ? INT_MAX : a->DockOrder) - ((b->DockOrder == -1) ? INT_MAX : b->DockOrder))
+        return d;
+    return (a->BeginOrderWithinContext - b->BeginOrderWithinContext);
+}
+
+static ImGuiID ImGui::DockNodeUpdateWindowMenu(ImGuiDockNode* node, ImGuiTabBar* tab_bar)
+{
+    // Try to position the menu so it is more likely to stays within the same viewport
+    ImGuiContext& g = *GImGui;
+    ImGuiID ret_tab_id = 0;
+    if (g.Style.WindowMenuButtonPosition == ImGuiDir_Left)
+        SetNextWindowPos(ImVec2(node->Pos.x, node->Pos.y + GetFrameHeight()), ImGuiCond_Always, ImVec2(0.0f, 0.0f));
+    else
+        SetNextWindowPos(ImVec2(node->Pos.x + node->Size.x, node->Pos.y + GetFrameHeight()), ImGuiCond_Always, ImVec2(1.0f, 0.0f));
+    if (BeginPopup("#WindowMenu"))
+    {
+        node->IsFocused = true;
+        if (tab_bar->Tabs.Size == 1)
+        {
+            if (MenuItem("Hide tab bar", NULL, node->IsHiddenTabBar()))
+                node->WantHiddenTabBarToggle = true;
+        }
+        else
+        {
+            for (int tab_n = 0; tab_n < tab_bar->Tabs.Size; tab_n++)
+            {
+                ImGuiTabItem* tab = &tab_bar->Tabs[tab_n];
+                IM_ASSERT(tab->Window != NULL);
+                if (Selectable(tab->Window->Name, tab->ID == tab_bar->SelectedTabId))
+                    ret_tab_id = tab->ID;
+                SameLine();
+                Text("   ");
+            }
+        }
+        EndPopup();
+    }
+    return ret_tab_id;
+}
+
+static void ImGui::DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_window)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiStyle& style = g.Style;
+
+    const bool node_was_active = (node->LastFrameActive + 1 == g.FrameCount);
+    const bool closed_all = node->WantCloseAll && node_was_active;
+    const ImGuiID closed_one = node->WantCloseTabId && node_was_active;
+    node->WantCloseAll = false;
+    node->WantCloseTabId = 0;
+
+    // Decide if we should use a focused title bar color
+    bool is_focused = false;
+    ImGuiDockNode* root_node = DockNodeGetRootNode(node);
+    if (g.NavWindowingTarget)
+        is_focused = (g.NavWindowingTarget->DockNode == node);
+    else if (g.NavWindow && g.NavWindow->RootWindowForTitleBarHighlight == host_window->RootWindow && root_node->LastFocusedNodeId == node->ID)
+        is_focused = true;
+
+    // Hidden tab bar will show a triangle on the upper-left (in Begin)
+    if (node->IsHiddenTabBar() || node->IsNoTabBar())
+    {
+        node->VisibleWindow = (node->Windows.Size > 0) ? node->Windows[0] : NULL;
+        node->IsFocused = is_focused;
+        if (is_focused)
+            node->LastFrameFocused = g.FrameCount;
+        if (node->VisibleWindow)
+        {
+            // Notify root of visible window (used to display title in OS task bar)
+            if (is_focused || root_node->VisibleWindow == NULL)
+                root_node->VisibleWindow = node->VisibleWindow;
+            if (node->TabBar)
+                node->TabBar->VisibleTabId = node->VisibleWindow->ID;
+        }
+        return;
+    }
+
+    // Move ourselves to the Menu layer (so we can be accessed by tapping Alt) + undo SkipItems flag in order to draw over the title bar even if the window is collapsed
+    bool backup_skip_item = host_window->SkipItems;
+    if (!node->IsDockSpace())
+    {
+        host_window->SkipItems = false;
+        host_window->DC.NavLayerCurrent = ImGuiNavLayer_Menu;
+        host_window->DC.NavLayerCurrentMask = (1 << ImGuiNavLayer_Menu);
+    }
+
+    // Use PushOverrideID() instead of PushID() to use the node id _without_ the host window ID.
+    // This is to facilitate computing those ID from the outside, and will affect more or less only the ID of the collapse button, popup and tabs,
+    // as docked windows themselves will override the stack with their own root ID.
+    PushOverrideID(node->ID);
+    ImGuiTabBar* tab_bar = node->TabBar;
+    bool tab_bar_is_recreated = (tab_bar == NULL); // Tab bar are automatically destroyed when a node gets hidden
+    if (tab_bar == NULL)
+    {
+        DockNodeAddTabBar(node);
+        tab_bar = node->TabBar;
+    }
+
+    ImGuiID focus_tab_id = 0;
+    node->IsFocused = is_focused;
+
+    const ImGuiDockNodeFlags node_flags = node->GetMergedFlags();
+    const bool has_window_menu_button = (node_flags & ImGuiDockNodeFlags_NoWindowMenuButton) == 0;
+    const bool has_close_button = (node_flags & ImGuiDockNodeFlags_NoCloseButton) == 0;
+
+    // In a dock node, the Collapse Button turns into the Window Menu button.
+    // FIXME-DOCK FIXME-OPT: Could we recycle popups id across multiple dock nodes?
+    if (has_window_menu_button && IsPopupOpen("#WindowMenu"))
+    {
+        if (ImGuiID tab_id = DockNodeUpdateWindowMenu(node, tab_bar))
+            focus_tab_id = tab_bar->NextSelectedTabId = tab_id;
+        is_focused |= node->IsFocused;
+    }
+
+    // Layout
+    ImRect title_bar_rect, tab_bar_rect;
+    ImVec2 window_menu_button_pos;
+    DockNodeCalcTabBarLayout(node, &title_bar_rect, &tab_bar_rect, &window_menu_button_pos);
+
+    // Title bar
+    if (is_focused)
+        node->LastFrameFocused = g.FrameCount;
+    ImU32 title_bar_col = GetColorU32(host_window->Collapsed ? ImGuiCol_TitleBgCollapsed : is_focused ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg);
+    host_window->DrawList->AddRectFilled(title_bar_rect.Min, title_bar_rect.Max, title_bar_col, host_window->WindowRounding, ImDrawCornerFlags_Top);
+
+    // Docking/Collapse button
+    if (has_window_menu_button)
+    {
+        if (CollapseButton(host_window->GetID("#COLLAPSE"), window_menu_button_pos, node))
+            OpenPopup("#WindowMenu");
+        if (IsItemActive())
+            focus_tab_id = tab_bar->SelectedTabId;
+    }
+
+    // Submit new tabs and apply NavWindow focus back to the tab bar. They will be added as Unsorted and sorted below based on relative DockOrder value.
+    const int tabs_count_old = tab_bar->Tabs.Size;
+    for (int window_n = 0; window_n < node->Windows.Size; window_n++)
+    {
+        ImGuiWindow* window = node->Windows[window_n];
+        if (g.NavWindow && g.NavWindow->RootWindowDockStop == window)
+            tab_bar->SelectedTabId = window->ID;
+        if (TabBarFindTabByID(tab_bar, window->ID) == NULL)
+            TabBarAddTab(tab_bar, ImGuiTabItemFlags_Unsorted, window);
+    }
+
+    // If multiple tabs are appearing on the same frame, sort them based on their persistent DockOrder value
+    int tabs_unsorted_start = tab_bar->Tabs.Size;
+    for (int tab_n = tab_bar->Tabs.Size - 1; tab_n >= 0 && (tab_bar->Tabs[tab_n].Flags & ImGuiTabItemFlags_Unsorted); tab_n--)
+    {
+        // FIXME-DOCK: Consider only clearing the flag after the tab has been alive for a few consecutive frames, allowing late comers to not break sorting?
+        tab_bar->Tabs[tab_n].Flags &= ~ImGuiTabItemFlags_Unsorted;
+        tabs_unsorted_start = tab_n;
+    }
+    if (tab_bar->Tabs.Size > tabs_unsorted_start)
+    {
+        IMGUI_DEBUG_LOG_DOCKING("In node 0x%08X: %d new appearing tabs:%s\n", node->ID, tab_bar->Tabs.Size - tabs_unsorted_start, (tab_bar->Tabs.Size > tabs_unsorted_start + 1) ? " (will sort)" : "");
+        for (int tab_n = tabs_unsorted_start; tab_n < tab_bar->Tabs.Size; tab_n++)
+            IMGUI_DEBUG_LOG_DOCKING(" - Tab '%s' Order %d\n", tab_bar->Tabs[tab_n].Window->Name, tab_bar->Tabs[tab_n].Window->DockOrder);
+    if (tab_bar->Tabs.Size > tabs_unsorted_start + 1)
+        ImQsort(tab_bar->Tabs.Data + tabs_unsorted_start, tab_bar->Tabs.Size - tabs_unsorted_start, sizeof(ImGuiTabItem), TabItemComparerByDockOrder);
+    }
+
+    // Selected newly added tabs, or persistent tab ID if the tab bar was just recreated
+    if (tab_bar_is_recreated && TabBarFindTabByID(tab_bar, node->SelectedTabId) != NULL)
+        tab_bar->SelectedTabId = tab_bar->NextSelectedTabId = node->SelectedTabId;
+    else if (tab_bar->Tabs.Size > tabs_count_old)
+        tab_bar->SelectedTabId = tab_bar->NextSelectedTabId = tab_bar->Tabs.back().Window->ID;
+
+    // Begin tab bar
+    ImGuiTabBarFlags tab_bar_flags = ImGuiTabBarFlags_Reorderable | ImGuiTabBarFlags_AutoSelectNewTabs; // | ImGuiTabBarFlags_NoTabListScrollingButtons);
+    tab_bar_flags |= ImGuiTabBarFlags_SaveSettings | ImGuiTabBarFlags_DockNode;
+    if (!host_window->Collapsed && is_focused)
+        tab_bar_flags |= ImGuiTabBarFlags_IsFocused;
+    BeginTabBarEx(tab_bar, tab_bar_rect, tab_bar_flags, node);
+    //host_window->DrawList->AddRect(tab_bar_rect.Min, tab_bar_rect.Max, IM_COL32(255,0,255,255));
+
+    // Submit actual tabs
+    node->VisibleWindow = NULL;
+    for (int window_n = 0; window_n < node->Windows.Size; window_n++)
+    {
+        ImGuiWindow* window = node->Windows[window_n];
+        if ((closed_all || closed_one == window->ID) && window->HasCloseButton && !(window->Flags & ImGuiWindowFlags_UnsavedDocument))
+            continue;
+        if (window->LastFrameActive + 1 >= g.FrameCount || !node_was_active)
+        {
+            ImGuiTabItemFlags tab_item_flags = 0;
+            if (window->Flags & ImGuiWindowFlags_UnsavedDocument)
+                tab_item_flags |= ImGuiTabItemFlags_UnsavedDocument;
+            if (tab_bar->Flags & ImGuiTabBarFlags_NoCloseWithMiddleMouseButton)
+                tab_item_flags |= ImGuiTabItemFlags_NoCloseWithMiddleMouseButton;
+
+            bool tab_open = true;
+            TabItemEx(tab_bar, window->Name, window->HasCloseButton ? &tab_open : NULL, tab_item_flags, window);
+            if (!tab_open)
+                node->WantCloseTabId = window->ID;
+            if (tab_bar->VisibleTabId == window->ID)
+                node->VisibleWindow = window;
+
+            // Store last item data so it can be queried with IsItemXXX functions after the user Begin() call
+            window->DockTabItemStatusFlags = host_window->DC.LastItemStatusFlags;
+            window->DockTabItemRect = host_window->DC.LastItemRect;
+
+            // Update navigation ID on menu layer
+            if (g.NavWindow && g.NavWindow->RootWindowDockStop == window && (window->DC.NavLayerActiveMask & (1 << 1)) == 0)
+                host_window->NavLastIds[1] = window->ID;
+        }
+    }
+
+    // Notify root of visible window (used to display title in OS task bar)
+    if (node->VisibleWindow)
+        if (is_focused || root_node->VisibleWindow == NULL)
+            root_node->VisibleWindow = node->VisibleWindow;
+
+    // Close button (after VisibleWindow was updated)
+    // Note that VisibleWindow may have been overrided by CTRL+Tabbing, so VisibleWindow->ID may be != from tab_bar->SelectedTabId
+    if (has_close_button && node->VisibleWindow)
+    {
+        if (!node->VisibleWindow->HasCloseButton)
+        {
+            PushItemFlag(ImGuiItemFlags_Disabled, true);
+            PushStyleColor(ImGuiCol_Text, style.Colors[ImGuiCol_Text] * ImVec4(1.0f,1.0f,1.0f,0.5f));
+        }
+        const float button_sz = g.FontSize;
+        if (CloseButton(host_window->GetID("#CLOSE"), title_bar_rect.GetTR() + ImVec2(-style.FramePadding.x * 2.0f - button_sz, 0.0f)))
+            if (ImGuiTabItem* tab = TabBarFindTabByID(tab_bar, tab_bar->VisibleTabId))
+            {
+                node->WantCloseTabId = tab->ID;
+                TabBarCloseTab(tab_bar, tab);
+            }
+        //if (IsItemActive())
+        //    focus_tab_id = tab_bar->SelectedTabId;
+        if (!node->VisibleWindow->HasCloseButton)
+        {
+            PopStyleColor();
+            PopItemFlag();
+        }
+    }
+
+    // When clicking on the title bar outside of tabs, we still focus the selected tab for that node
+    // FIXME: TabItem use AllowItemOverlap so we manually perform a more specific test for now (hovered || held)
+    ImGuiID title_bar_id = host_window->GetID("#TITLEBAR");
+    if (g.HoveredId == 0 || g.HoveredId == title_bar_id || g.ActiveId == title_bar_id)
+    {
+        bool held;
+        ButtonBehavior(title_bar_rect, title_bar_id, NULL, &held);
+        if (held)
+        {
+            if (IsMouseClicked(0))
+                focus_tab_id = tab_bar->SelectedTabId;
+
+            // Forward moving request to selected window
+            if (ImGuiTabItem* tab = TabBarFindTabByID(tab_bar, tab_bar->SelectedTabId))
+                StartMouseMovingWindowOrNode(tab->Window, node, false);
+        }
+    }
+
+    // Forward focus from host node to selected window
+    //if (is_focused && g.NavWindow == host_window && !g.NavWindowingTarget)
+    //    focus_tab_id = tab_bar->SelectedTabId;
+
+    // When clicked on a tab we requested focus to the docked child
+    // This overrides the value set by "forward focus from host node to selected window".
+    if (tab_bar->NextSelectedTabId)
+        focus_tab_id = tab_bar->NextSelectedTabId;
+
+    // Apply navigation focus
+    if (focus_tab_id != 0)
+        if (ImGuiTabItem* tab = TabBarFindTabByID(tab_bar, focus_tab_id))
+        {
+            FocusWindow(tab->Window);
+            NavInitWindow(tab->Window, false);
+        }
+
+    EndTabBar();
+    PopID();
+
+    // Restore SkipItems flag
+    if (!node->IsDockSpace())
+    {
+        host_window->DC.NavLayerCurrent = ImGuiNavLayer_Main;
+        host_window->DC.NavLayerCurrentMask = (1 << ImGuiNavLayer_Main);
+        host_window->SkipItems = backup_skip_item;
+    }
+}
+
+static void ImGui::DockNodeAddTabBar(ImGuiDockNode* node)
+{
+    IM_ASSERT(node->TabBar == NULL);
+    node->TabBar = IM_NEW(ImGuiTabBar);
+}
+
+static void ImGui::DockNodeRemoveTabBar(ImGuiDockNode* node)
+{
+    if (node->TabBar == NULL)
+        return;
+    IM_DELETE(node->TabBar);
+    node->TabBar = NULL;
+}
+
+static bool DockNodeIsDropAllowedOne(ImGuiWindow* payload, ImGuiWindow* host_window)
+{
+    if (host_window->DockNodeAsHost && host_window->DockNodeAsHost->IsDockSpace() && payload->BeginOrderWithinContext < host_window->BeginOrderWithinContext)
+        return false;
+
+    ImGuiWindowClass* host_class = host_window->DockNodeAsHost ? &host_window->DockNodeAsHost->WindowClass : &host_window->WindowClass;
+    ImGuiWindowClass* payload_class = &payload->WindowClass;
+    if (host_class->ClassId != payload_class->ClassId)
+    {
+        if (host_class->ClassId != 0 && host_class->DockingAllowUnclassed && payload_class->ClassId == 0)
+            return true;
+        if (payload_class->ClassId != 0 && payload_class->DockingAllowUnclassed && host_class->ClassId == 0)
+            return true;
+        return false;
+    }
+
+    return true;
+}
+
+static bool ImGui::DockNodeIsDropAllowed(ImGuiWindow* host_window, ImGuiWindow* root_payload)
+{
+    if (root_payload->DockNodeAsHost && root_payload->DockNodeAsHost->IsSplitNode())
+        return true;
+
+    const int payload_count = root_payload->DockNodeAsHost ? root_payload->DockNodeAsHost->Windows.Size : 1;
+    for (int payload_n = 0; payload_n < payload_count; payload_n++)
+    {
+        ImGuiWindow* payload = root_payload->DockNodeAsHost ? root_payload->DockNodeAsHost->Windows[payload_n] : root_payload;
+        if (DockNodeIsDropAllowedOne(payload, host_window))
+            return true;
+    }
+    return false;
+}
+
+// window menu button == collapse button when not in a dock node.
+// FIXME: This is similar to RenderWindowTitleBarContents, may want to share code.
+static void ImGui::DockNodeCalcTabBarLayout(const ImGuiDockNode* node, ImRect* out_title_rect, ImRect* out_tab_bar_rect, ImVec2* out_window_menu_button_pos)
+{
+    ImGuiContext& g = *GImGui;
+    ImRect r = ImRect(node->Pos.x, node->Pos.y, node->Pos.x + node->Size.x, node->Pos.y + g.FontSize + g.Style.FramePadding.y * 2.0f);
+    if (out_title_rect) { *out_title_rect = r; }
+
+    ImVec2 window_menu_button_pos = r.Min;
+    r.Min.x += g.Style.FramePadding.x;
+    r.Max.x -= g.Style.FramePadding.x;
+    if (node->HasCloseButton)
+    {
+        r.Max.x -= g.FontSize;// +1.0f; // In DockNodeUpdateTabBar() we currently display a disabled close button even if there is none.
+    }
+    if (node->HasWindowMenuButton && g.Style.WindowMenuButtonPosition == ImGuiDir_Left)
+    {
+        r.Min.x += g.FontSize; // + g.Style.ItemInnerSpacing.x; // <-- Adding ItemInnerSpacing makes the title text moves slightly when in a docking tab bar. Instead we adjusted RenderArrowDockMenu()
+    }
+    else if (node->HasWindowMenuButton && g.Style.WindowMenuButtonPosition == ImGuiDir_Right)
+    {
+        r.Max.x -= g.FontSize + g.Style.FramePadding.x;
+        window_menu_button_pos = ImVec2(r.Max.x, r.Min.y);
+    }
+    if (out_tab_bar_rect) { *out_tab_bar_rect = r; }
+    if (out_window_menu_button_pos) { *out_window_menu_button_pos = window_menu_button_pos; }
+}
+
+void ImGui::DockNodeCalcSplitRects(ImVec2& pos_old, ImVec2& size_old, ImVec2& pos_new, ImVec2& size_new, ImGuiDir dir, ImVec2 size_new_desired)
+{
+    ImGuiContext& g = *GImGui;
+    const float dock_spacing = g.Style.ItemInnerSpacing.x;
+    const ImGuiAxis axis = (dir == ImGuiDir_Left || dir == ImGuiDir_Right) ? ImGuiAxis_X : ImGuiAxis_Y;
+    pos_new[axis ^ 1] = pos_old[axis ^ 1];
+    size_new[axis ^ 1] = size_old[axis ^ 1];
+
+    // Distribute size on given axis (with a desired size or equally)
+    const float w_avail = size_old[axis] - dock_spacing;
+    if (size_new_desired[axis] > 0.0f && size_new_desired[axis] <= w_avail * 0.5f)
+    {
+        size_new[axis] = size_new_desired[axis];
+        size_old[axis] = IM_FLOOR(w_avail - size_new[axis]);
+    }
+    else
+    {
+        size_new[axis] = IM_FLOOR(w_avail * 0.5f);
+        size_old[axis] = IM_FLOOR(w_avail - size_new[axis]);
+    }
+
+    // Position each node
+    if (dir == ImGuiDir_Right || dir == ImGuiDir_Down)
+    {
+        pos_new[axis] = pos_old[axis] + size_old[axis] + dock_spacing;
+    }
+    else if (dir == ImGuiDir_Left || dir == ImGuiDir_Up)
+    {
+        pos_new[axis] = pos_old[axis];
+        pos_old[axis] = pos_new[axis] + size_new[axis] + dock_spacing;
+    }
+}
+
+// Retrieve the drop rectangles for a given direction or for the center + perform hit testing.
+bool ImGui::DockNodeCalcDropRectsAndTestMousePos(const ImRect& parent, ImGuiDir dir, ImRect& out_r, bool outer_docking, ImVec2* test_mouse_pos)
+{
+    ImGuiContext& g = *GImGui;
+
+    const float parent_smaller_axis = ImMin(parent.GetWidth(), parent.GetHeight());
+    const float hs_for_central_nodes = ImMin(g.FontSize * 1.5f, ImMax(g.FontSize * 0.5f, parent_smaller_axis / 8.0f));
+    float hs_w; // Half-size, longer axis
+    float hs_h; // Half-size, smaller axis
+    ImVec2 off; // Distance from edge or center
+    if (outer_docking)
+    {
+        //hs_w = ImFloor(ImClamp(parent_smaller_axis - hs_for_central_nodes * 4.0f, g.FontSize * 0.5f, g.FontSize * 8.0f));
+        //hs_h = ImFloor(hs_w * 0.15f);
+        //off = ImVec2(ImFloor(parent.GetWidth() * 0.5f - GetFrameHeightWithSpacing() * 1.4f - hs_h), ImFloor(parent.GetHeight() * 0.5f - GetFrameHeightWithSpacing() * 1.4f - hs_h));
+        hs_w = ImFloor(hs_for_central_nodes * 1.50f);
+        hs_h = ImFloor(hs_for_central_nodes * 0.80f);
+        off = ImVec2(ImFloor(parent.GetWidth() * 0.5f - hs_h), ImFloor(parent.GetHeight() * 0.5f - hs_h));
+    }
+    else
+    {
+        hs_w = ImFloor(hs_for_central_nodes);
+        hs_h = ImFloor(hs_for_central_nodes * 0.90f);
+        off = ImVec2(ImFloor(hs_w * 2.40f), ImFloor(hs_w * 2.40f));
+    }
+
+    ImVec2 c = ImFloor(parent.GetCenter());
+    if      (dir == ImGuiDir_None)  { out_r = ImRect(c.x - hs_w, c.y - hs_w,         c.x + hs_w, c.y + hs_w);         }
+    else if (dir == ImGuiDir_Up)    { out_r = ImRect(c.x - hs_w, c.y - off.y - hs_h, c.x + hs_w, c.y - off.y + hs_h); }
+    else if (dir == ImGuiDir_Down)  { out_r = ImRect(c.x - hs_w, c.y + off.y - hs_h, c.x + hs_w, c.y + off.y + hs_h); }
+    else if (dir == ImGuiDir_Left)  { out_r = ImRect(c.x - off.x - hs_h, c.y - hs_w, c.x - off.x + hs_h, c.y + hs_w); }
+    else if (dir == ImGuiDir_Right) { out_r = ImRect(c.x + off.x - hs_h, c.y - hs_w, c.x + off.x + hs_h, c.y + hs_w); }
+
+    if (test_mouse_pos == NULL)
+        return false;
+
+    ImRect hit_r = out_r;
+    if (!outer_docking)
+    {
+        // Custom hit testing for the 5-way selection, designed to reduce flickering when moving diagonally between sides
+        hit_r.Expand(ImFloor(hs_w * 0.30f));
+        ImVec2 mouse_delta = (*test_mouse_pos - c);
+        float mouse_delta_len2 = ImLengthSqr(mouse_delta);
+        float r_threshold_center = hs_w * 1.4f;
+        float r_threshold_sides = hs_w * (1.4f + 1.2f);
+        if (mouse_delta_len2 < r_threshold_center * r_threshold_center)
+            return (dir == ImGuiDir_None);
+        if (mouse_delta_len2 < r_threshold_sides * r_threshold_sides)
+            return (dir == ImGetDirQuadrantFromDelta(mouse_delta.x, mouse_delta.y));
+    }
+    return hit_r.Contains(*test_mouse_pos);
+}
+
+// host_node may be NULL if the window doesn't have a DockNode already.
+// FIXME-DOCK: This is misnamed since it's also doing the filtering.
+static void ImGui::DockNodePreviewDockSetup(ImGuiWindow* host_window, ImGuiDockNode* host_node, ImGuiWindow* root_payload, ImGuiDockPreviewData* data, bool is_explicit_target, bool is_outer_docking)
+{
+    ImGuiContext& g = *GImGui;
+
+    // There is an edge case when docking into a dockspace which only has inactive nodes.
+    // In this case DockNodeTreeFindNodeByPos() will have selected a leaf node which is inactive.
+    // Because the inactive leaf node doesn't have proper pos/size yet, we'll use the root node as reference.
+    ImGuiDockNode* root_payload_as_host = root_payload->DockNodeAsHost;
+    ImGuiDockNode* ref_node_for_rect = (host_node && !host_node->IsVisible) ? DockNodeGetRootNode(host_node) : host_node;
+    if (ref_node_for_rect)
+        IM_ASSERT(ref_node_for_rect->IsVisible);
+
+    // Filter, figure out where we are allowed to dock
+    ImGuiDockNodeFlags host_node_flags = host_node ? host_node->GetMergedFlags() : 0;
+    data->IsCenterAvailable = true;
+    if (is_outer_docking)
+        data->IsCenterAvailable = false;
+    else if (host_node && (host_node_flags & ImGuiDockNodeFlags_NoDocking))
+        data->IsCenterAvailable = false;
+    else if (host_node && (host_node_flags & ImGuiDockNodeFlags_NoDockingInCentralNode) && host_node->IsCentralNode())
+        data->IsCenterAvailable = false;
+    else if ((!host_node || !host_node->IsEmpty()) && root_payload_as_host && root_payload_as_host->IsSplitNode() && (root_payload_as_host->OnlyNodeWithWindows == NULL)) // Is _visibly_ split?
+        data->IsCenterAvailable = false;
+
+    data->IsSidesAvailable = true;
+    if ((host_node && (host_node_flags & ImGuiDockNodeFlags_NoSplit)) || g.IO.ConfigDockingNoSplit)
+        data->IsSidesAvailable = false;
+    else if (!is_outer_docking && host_node && host_node->ParentNode == NULL && host_node->IsCentralNode())
+        data->IsSidesAvailable = false;
+
+    // Build a tentative future node (reuse same structure because it is practical. Shape will be readjusted when previewing a split)
+    data->FutureNode.HasCloseButton = (host_node ? host_node->HasCloseButton : host_window->HasCloseButton) || (root_payload->HasCloseButton);
+    data->FutureNode.HasWindowMenuButton = host_node ? true : ((host_window->Flags & ImGuiWindowFlags_NoCollapse) == 0);
+    data->FutureNode.Pos = ref_node_for_rect ? ref_node_for_rect->Pos : host_window->Pos;
+    data->FutureNode.Size = ref_node_for_rect ? ref_node_for_rect->Size : host_window->Size;
+
+    // Calculate drop shapes geometry for allowed splitting directions
+    IM_ASSERT(ImGuiDir_None == -1);
+    data->SplitNode = host_node;
+    data->SplitDir = ImGuiDir_None;
+    data->IsSplitDirExplicit = false;
+    if (!host_window->Collapsed)
+        for (int dir = ImGuiDir_None; dir < ImGuiDir_COUNT; dir++)
+        {
+            if (dir == ImGuiDir_None && !data->IsCenterAvailable)
+                continue;
+            if (dir != ImGuiDir_None && !data->IsSidesAvailable)
+                continue;
+            if (DockNodeCalcDropRectsAndTestMousePos(data->FutureNode.Rect(), (ImGuiDir)dir, data->DropRectsDraw[dir+1], is_outer_docking, &g.IO.MousePos))
+            {
+                data->SplitDir = (ImGuiDir)dir;
+                data->IsSplitDirExplicit = true;
+            }
+        }
+
+    // When docking without holding Shift, we only allow and preview docking when hovering over a drop rect or over the title bar
+    data->IsDropAllowed = (data->SplitDir != ImGuiDir_None) || (data->IsCenterAvailable);
+    if (!is_explicit_target && !data->IsSplitDirExplicit && !g.IO.ConfigDockingWithShift)
+        data->IsDropAllowed = false;
+
+    // Calculate split area
+    data->SplitRatio = 0.0f;
+    if (data->SplitDir != ImGuiDir_None)
+    {
+        ImGuiDir split_dir = data->SplitDir;
+        ImGuiAxis split_axis = (split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Right) ? ImGuiAxis_X : ImGuiAxis_Y;
+        ImVec2 pos_new, pos_old = data->FutureNode.Pos;
+        ImVec2 size_new, size_old = data->FutureNode.Size;
+        DockNodeCalcSplitRects(pos_old, size_old, pos_new, size_new, split_dir, root_payload->Size);
+
+        // Calculate split ratio so we can pass it down the docking request
+        float split_ratio = ImSaturate(size_new[split_axis] / data->FutureNode.Size[split_axis]);
+        data->FutureNode.Pos = pos_new;
+        data->FutureNode.Size = size_new;
+        data->SplitRatio = (split_dir == ImGuiDir_Right || split_dir == ImGuiDir_Down) ? (1.0f - split_ratio) : (split_ratio);
+    }
+}
+
+static void ImGui::DockNodePreviewDockRender(ImGuiWindow* host_window, ImGuiDockNode* host_node, ImGuiWindow* root_payload, const ImGuiDockPreviewData* data)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(g.CurrentWindow == host_window);   // Because we rely on font size to calculate tab sizes
+
+    // With this option, we only display the preview on the target viewport, and the payload viewport is made transparent.
+    // To compensate for the single layer obstructed by the payload, we'll increase the alpha of the preview nodes.
+    const bool is_transparent_payload = g.IO.ConfigDockingTransparentPayload;
+
+    // In case the two windows involved are on different viewports, we will draw the overlay on each of them.
+    int overlay_draw_lists_count = 0;
+    ImDrawList* overlay_draw_lists[2];
+    overlay_draw_lists[overlay_draw_lists_count++] = GetForegroundDrawList(host_window->Viewport);
+    if (host_window->Viewport != root_payload->Viewport && !is_transparent_payload)
+        overlay_draw_lists[overlay_draw_lists_count++] = GetForegroundDrawList(root_payload->Viewport);
+
+    // Draw main preview rectangle
+    const ImU32 overlay_col_tabs = GetColorU32(ImGuiCol_TabActive);
+    const ImU32 overlay_col_main = GetColorU32(ImGuiCol_DockingPreview, is_transparent_payload ? 0.60f : 0.40f);
+    const ImU32 overlay_col_drop = GetColorU32(ImGuiCol_DockingPreview, is_transparent_payload ? 0.90f : 0.70f);
+    const ImU32 overlay_col_drop_hovered = GetColorU32(ImGuiCol_DockingPreview, is_transparent_payload ? 1.20f : 1.00f);
+    const ImU32 overlay_col_lines = GetColorU32(ImGuiCol_NavWindowingHighlight, is_transparent_payload ? 0.80f : 0.60f);
+
+    // Display area preview
+    const bool can_preview_tabs = (root_payload->DockNodeAsHost == NULL || root_payload->DockNodeAsHost->Windows.Size > 0);
+    if (data->IsDropAllowed)
+    {
+        ImRect overlay_rect = data->FutureNode.Rect();
+        if (data->SplitDir == ImGuiDir_None && can_preview_tabs)
+            overlay_rect.Min.y += GetFrameHeight();
+        if (data->SplitDir != ImGuiDir_None || data->IsCenterAvailable)
+            for (int overlay_n = 0; overlay_n < overlay_draw_lists_count; overlay_n++)
+                overlay_draw_lists[overlay_n]->AddRectFilled(overlay_rect.Min, overlay_rect.Max, overlay_col_main, host_window->WindowRounding);
+    }
+
+    // Display tab shape/label preview unless we are splitting node (it generally makes the situation harder to read)
+    if (data->IsDropAllowed && can_preview_tabs && data->SplitDir == ImGuiDir_None && data->IsCenterAvailable)
+    {
+        // Compute target tab bar geometry so we can locate our preview tabs
+        ImRect tab_bar_rect;
+        DockNodeCalcTabBarLayout(&data->FutureNode, NULL, &tab_bar_rect, NULL);
+        ImVec2 tab_pos = tab_bar_rect.Min;
+        if (host_node && host_node->TabBar)
+        {
+            if (!host_node->IsHiddenTabBar() && !host_node->IsNoTabBar())
+                tab_pos.x += host_node->TabBar->OffsetMax + g.Style.ItemInnerSpacing.x; // We don't use OffsetNewTab because when using non-persistent-order tab bar it is incremented with each Tab submission.
+            else
+                tab_pos.x += g.Style.ItemInnerSpacing.x + TabItemCalcSize(host_node->Windows[0]->Name, host_node->Windows[0]->HasCloseButton).x;
+        }
+        else if (!(host_window->Flags & ImGuiWindowFlags_DockNodeHost))
+        {
+            tab_pos.x += g.Style.ItemInnerSpacing.x + TabItemCalcSize(host_window->Name, host_window->HasCloseButton).x; // Account for slight offset which will be added when changing from title bar to tab bar
+        }
+
+        // Draw tab shape/label preview (payload may be a loose window or a host window carrying multiple tabbed windows)
+        if (root_payload->DockNodeAsHost)
+            IM_ASSERT(root_payload->DockNodeAsHost->Windows.Size == root_payload->DockNodeAsHost->TabBar->Tabs.Size);
+        const int payload_count = root_payload->DockNodeAsHost ? root_payload->DockNodeAsHost->TabBar->Tabs.Size : 1;
+        for (int payload_n = 0; payload_n < payload_count; payload_n++)
+        {
+            // Calculate the tab bounding box for each payload window
+            ImGuiWindow* payload = root_payload->DockNodeAsHost ? root_payload->DockNodeAsHost->TabBar->Tabs[payload_n].Window : root_payload;
+            if (!DockNodeIsDropAllowedOne(payload, host_window))
+                continue;
+
+            ImVec2 tab_size = TabItemCalcSize(payload->Name, payload->HasCloseButton);
+            ImRect tab_bb(tab_pos.x, tab_pos.y, tab_pos.x + tab_size.x, tab_pos.y + tab_size.y);
+            tab_pos.x += tab_size.x + g.Style.ItemInnerSpacing.x;
+            for (int overlay_n = 0; overlay_n < overlay_draw_lists_count; overlay_n++)
+            {
+                ImGuiTabItemFlags tab_flags = ImGuiTabItemFlags_Preview | ((payload->Flags & ImGuiWindowFlags_UnsavedDocument) ? ImGuiTabItemFlags_UnsavedDocument : 0);
+                if (!tab_bar_rect.Contains(tab_bb))
+                    overlay_draw_lists[overlay_n]->PushClipRect(tab_bar_rect.Min, tab_bar_rect.Max);
+                TabItemBackground(overlay_draw_lists[overlay_n], tab_bb, tab_flags, overlay_col_tabs);
+                TabItemLabelAndCloseButton(overlay_draw_lists[overlay_n], tab_bb, tab_flags, g.Style.FramePadding, payload->Name, 0, 0);
+                if (!tab_bar_rect.Contains(tab_bb))
+                    overlay_draw_lists[overlay_n]->PopClipRect();
+            }
+        }
+    }
+
+    // Display drop boxes
+    const float overlay_rounding = ImMax(3.0f, g.Style.FrameRounding);
+    for (int dir = ImGuiDir_None; dir < ImGuiDir_COUNT; dir++)
+    {
+        if (!data->DropRectsDraw[dir + 1].IsInverted())
+        {
+            ImRect draw_r = data->DropRectsDraw[dir + 1];
+            ImRect draw_r_in = draw_r;
+            draw_r_in.Expand(-2.0f);
+            ImU32 overlay_col = (data->SplitDir == (ImGuiDir)dir && data->IsSplitDirExplicit) ? overlay_col_drop_hovered : overlay_col_drop;
+            for (int overlay_n = 0; overlay_n < overlay_draw_lists_count; overlay_n++)
+            {
+                ImVec2 center = ImFloor(draw_r_in.GetCenter());
+                overlay_draw_lists[overlay_n]->AddRectFilled(draw_r.Min, draw_r.Max, overlay_col, overlay_rounding);
+                overlay_draw_lists[overlay_n]->AddRect(draw_r_in.Min, draw_r_in.Max, overlay_col_lines, overlay_rounding);
+                if (dir == ImGuiDir_Left || dir == ImGuiDir_Right)
+                    overlay_draw_lists[overlay_n]->AddLine(ImVec2(center.x, draw_r_in.Min.y), ImVec2(center.x, draw_r_in.Max.y), overlay_col_lines);
+                if (dir == ImGuiDir_Up || dir == ImGuiDir_Down)
+                    overlay_draw_lists[overlay_n]->AddLine(ImVec2(draw_r_in.Min.x, center.y), ImVec2(draw_r_in.Max.x, center.y), overlay_col_lines);
+            }
+        }
+
+        // Stop after ImGuiDir_None
+        if ((host_node && (host_node->GetMergedFlags() & ImGuiDockNodeFlags_NoSplit)) || g.IO.ConfigDockingNoSplit)
+            return;
+    }
+}
+
+//-----------------------------------------------------------------------------
+// Docking: ImGuiDockNode Tree manipulation functions
+//-----------------------------------------------------------------------------
+// - DockNodeTreeSplit()
+// - DockNodeTreeMerge()
+// - DockNodeTreeUpdatePosSize()
+// - DockNodeTreeUpdateSplitterFindTouchingNode()
+// - DockNodeTreeUpdateSplitter()
+// - DockNodeTreeFindFallbackLeafNode()
+// - DockNodeTreeFindNodeByPos()
+//-----------------------------------------------------------------------------
+
+void ImGui::DockNodeTreeSplit(ImGuiContext* ctx, ImGuiDockNode* parent_node, ImGuiAxis split_axis, int split_inheritor_child_idx, float split_ratio, ImGuiDockNode* new_node)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(split_axis != ImGuiAxis_None);
+
+    ImGuiDockNode* child_0 = (new_node && split_inheritor_child_idx != 0) ? new_node : DockContextAddNode(ctx, 0);
+    child_0->ParentNode = parent_node;
+
+    ImGuiDockNode* child_1 = (new_node && split_inheritor_child_idx != 1) ? new_node : DockContextAddNode(ctx, 0);
+    child_1->ParentNode = parent_node;
+
+    ImGuiDockNode* child_inheritor = (split_inheritor_child_idx == 0) ? child_0 : child_1;
+    DockNodeMoveChildNodes(child_inheritor, parent_node);
+    parent_node->ChildNodes[0] = child_0;
+    parent_node->ChildNodes[1] = child_1;
+    parent_node->ChildNodes[split_inheritor_child_idx]->VisibleWindow = parent_node->VisibleWindow;
+    parent_node->SplitAxis = split_axis;
+    parent_node->VisibleWindow = NULL;
+    parent_node->AuthorityForPos = parent_node->AuthorityForSize = ImGuiDataAuthority_DockNode;
+
+    float size_avail = (parent_node->Size[split_axis] - IMGUI_DOCK_SPLITTER_SIZE);
+    size_avail = ImMax(size_avail, g.Style.WindowMinSize[split_axis] * 2.0f);
+    IM_ASSERT(size_avail > 0.0f); // If you created a node manually with DockBuilderAddNode(), you need to also call DockBuilderSetNodeSize() before splitting.
+    child_0->SizeRef = child_1->SizeRef = parent_node->Size;
+    child_0->SizeRef[split_axis] = ImFloor(size_avail * split_ratio);
+    child_1->SizeRef[split_axis] = ImFloor(size_avail - child_0->SizeRef[split_axis]);
+
+    DockNodeMoveWindows(parent_node->ChildNodes[split_inheritor_child_idx], parent_node);
+    DockNodeTreeUpdatePosSize(parent_node, parent_node->Pos, parent_node->Size);
+
+    // Flags transfer (e.g. this is where we transfer the ImGuiDockNodeFlags_CentralNode property)
+    child_0->SharedFlags = parent_node->SharedFlags & ImGuiDockNodeFlags_SharedFlagsInheritMask_;
+    child_1->SharedFlags = parent_node->SharedFlags & ImGuiDockNodeFlags_SharedFlagsInheritMask_;
+    child_inheritor->LocalFlags = parent_node->LocalFlags & ImGuiDockNodeFlags_LocalFlagsTransferMask_;
+    parent_node->LocalFlags &= ~ImGuiDockNodeFlags_LocalFlagsTransferMask_;
+    if (child_inheritor->IsCentralNode())
+        DockNodeGetRootNode(parent_node)->CentralNode = child_inheritor;
+}
+
+void ImGui::DockNodeTreeMerge(ImGuiContext* ctx, ImGuiDockNode* parent_node, ImGuiDockNode* merge_lead_child)
+{
+    // When called from DockContextProcessUndockNode() it is possible that one of the child is NULL.
+    ImGuiDockNode* child_0 = parent_node->ChildNodes[0];
+    ImGuiDockNode* child_1 = parent_node->ChildNodes[1];
+    IM_ASSERT(child_0 || child_1);
+    IM_ASSERT(merge_lead_child == child_0 || merge_lead_child == child_1);
+    if ((child_0 && child_0->Windows.Size > 0) || (child_1 && child_1->Windows.Size > 0))
+    {
+        IM_ASSERT(parent_node->TabBar == NULL);
+        IM_ASSERT(parent_node->Windows.Size == 0);
+    }
+    IMGUI_DEBUG_LOG_DOCKING("DockNodeTreeMerge 0x%08X & 0x%08X back into parent 0x%08X\n", child_0 ? child_0->ID : 0, child_1 ? child_1->ID : 0, parent_node->ID);
+
+    ImVec2 backup_last_explicit_size = parent_node->SizeRef;
+    DockNodeMoveChildNodes(parent_node, merge_lead_child);
+    if (child_0)
+    {
+        DockNodeMoveWindows(parent_node, child_0); // Generally only 1 of the 2 child node will have windows
+        DockSettingsRenameNodeReferences(child_0->ID, parent_node->ID);
+    }
+    if (child_1)
+    {
+        DockNodeMoveWindows(parent_node, child_1);
+        DockSettingsRenameNodeReferences(child_1->ID, parent_node->ID);
+    }
+    DockNodeApplyPosSizeToWindows(parent_node);
+    parent_node->AuthorityForPos = parent_node->AuthorityForSize = parent_node->AuthorityForViewport = ImGuiDataAuthority_Auto;
+    parent_node->VisibleWindow = merge_lead_child->VisibleWindow;
+    parent_node->SizeRef = backup_last_explicit_size;
+
+    // Flags transfer
+    parent_node->LocalFlags &= ~ImGuiDockNodeFlags_LocalFlagsTransferMask_; // Preserve Dockspace flag
+    parent_node->LocalFlags |= (child_0 ? child_0->LocalFlags : 0) & ImGuiDockNodeFlags_LocalFlagsTransferMask_;
+    parent_node->LocalFlags |= (child_1 ? child_1->LocalFlags : 0) & ImGuiDockNodeFlags_LocalFlagsTransferMask_;
+
+    if (child_0)
+    {
+        ctx->DockContext->Nodes.SetVoidPtr(child_0->ID, NULL);
+        IM_DELETE(child_0);
+    }
+    if (child_1)
+    {
+        ctx->DockContext->Nodes.SetVoidPtr(child_1->ID, NULL);
+        IM_DELETE(child_1);
+    }
+}
+
+// Update Pos/Size for a node hierarchy (don't affect child Windows yet)
+void ImGui::DockNodeTreeUpdatePosSize(ImGuiDockNode* node, ImVec2 pos, ImVec2 size, bool only_write_to_marked_nodes)
+{
+    // During the regular dock node update we write to all nodes.
+    // 'only_write_to_marked_nodes' is only set when turning a node visible mid-frame and we need its size right-away.
+    const bool write_to_node = (only_write_to_marked_nodes == false) || (node->MarkedForPosSizeWrite);
+    if (write_to_node)
+    {
+        node->Pos = pos;
+        node->Size = size;
+    }
+
+    if (node->IsLeafNode())
+        return;
+
+    ImGuiDockNode* child_0 = node->ChildNodes[0];
+    ImGuiDockNode* child_1 = node->ChildNodes[1];
+    ImVec2 child_0_pos = pos, child_1_pos = pos;
+    ImVec2 child_0_size = size, child_1_size = size;
+    if (child_0->IsVisible && child_1->IsVisible)
+    {
+        const float spacing = IMGUI_DOCK_SPLITTER_SIZE;
+        const ImGuiAxis axis = (ImGuiAxis)node->SplitAxis;
+        const float size_avail = ImMax(size[axis] - spacing, 0.0f);
+
+        // Size allocation policy
+        // 1) The first 0..WindowMinSize[axis]*2 are allocated evenly to both windows.
+        ImGuiContext& g = *GImGui;
+        const float size_min_each = ImFloor(ImMin(size_avail, g.Style.WindowMinSize[axis] * 2.0f) * 0.5f);
+
+        // 2) Process locked absolute size (during a splitter resize we preserve the child of nodes not touching the splitter edge)
+        IM_ASSERT(!(child_0->WantLockSizeOnce && child_1->WantLockSizeOnce));
+        if (child_0->WantLockSizeOnce)
+        {
+            child_0->WantLockSizeOnce = false;
+            child_0_size[axis] = child_0->SizeRef[axis] = child_0->Size[axis];
+            child_1_size[axis] = child_1->SizeRef[axis] = (size_avail - child_0_size[axis]);
+            IM_ASSERT(child_0->SizeRef[axis] > 0.0f && child_1->SizeRef[axis] > 0.0f);
+
+        }
+        else if (child_1->WantLockSizeOnce)
+        {
+            child_1->WantLockSizeOnce = false;
+            child_1_size[axis] = child_1->SizeRef[axis] = child_1->Size[axis];
+            child_0_size[axis] = child_0->SizeRef[axis] = (size_avail - child_1_size[axis]);
+            IM_ASSERT(child_0->SizeRef[axis] > 0.0f && child_1->SizeRef[axis] > 0.0f);
+        }
+
+        // 3) If one window is the central node (~ use remaining space, should be made explicit!), use explicit size from the other, and remainder for the central node
+        else if (child_1->IsCentralNode() && child_0->SizeRef[axis] != 0.0f)
+        {
+            child_0_size[axis] = ImMin(size_avail - size_min_each, child_0->SizeRef[axis]);
+            child_1_size[axis] = (size_avail - child_0_size[axis]);
+        }
+        else if (child_0->IsCentralNode() && child_1->SizeRef[axis] != 0.0f)
+        {
+            child_1_size[axis] = ImMin(size_avail - size_min_each, child_1->SizeRef[axis]);
+            child_0_size[axis] = (size_avail - child_1_size[axis]);
+        }
+        else
+        {
+            // 4) Otherwise distribute according to the relative ratio of each SizeRef value
+            float split_ratio = child_0->SizeRef[axis] / (child_0->SizeRef[axis] + child_1->SizeRef[axis]);
+            child_0_size[axis] = ImMax(size_min_each, ImFloor(size_avail * split_ratio + 0.5F));
+            child_1_size[axis] = (size_avail - child_0_size[axis]);
+        }
+        child_1_pos[axis] += spacing + child_0_size[axis];
+    }
+    if (child_0->IsVisible)
+        DockNodeTreeUpdatePosSize(child_0, child_0_pos, child_0_size);
+    if (child_1->IsVisible)
+        DockNodeTreeUpdatePosSize(child_1, child_1_pos, child_1_size);
+}
+
+static void DockNodeTreeUpdateSplitterFindTouchingNode(ImGuiDockNode* node, ImGuiAxis axis, int side, ImVector<ImGuiDockNode*>* touching_nodes)
+{
+    if (node->IsLeafNode())
+    {
+        touching_nodes->push_back(node);
+        return;
+    }
+    if (node->ChildNodes[0]->IsVisible)
+        if (node->SplitAxis != axis || side == 0 || !node->ChildNodes[1]->IsVisible)
+            DockNodeTreeUpdateSplitterFindTouchingNode(node->ChildNodes[0], axis, side, touching_nodes);
+    if (node->ChildNodes[1]->IsVisible)
+        if (node->SplitAxis != axis || side == 1 || !node->ChildNodes[0]->IsVisible)
+            DockNodeTreeUpdateSplitterFindTouchingNode(node->ChildNodes[1], axis, side, touching_nodes);
+}
+
+void ImGui::DockNodeTreeUpdateSplitter(ImGuiDockNode* node)
+{
+    if (node->IsLeafNode())
+        return;
+
+    ImGuiContext& g = *GImGui;
+
+    ImGuiDockNode* child_0 = node->ChildNodes[0];
+    ImGuiDockNode* child_1 = node->ChildNodes[1];
+    if (child_0->IsVisible && child_1->IsVisible)
+    {
+        // Bounding box of the splitter cover the space between both nodes (w = Spacing, h = Size[xy^1] for when splitting horizontally)
+        const ImGuiAxis axis = (ImGuiAxis)node->SplitAxis;
+        IM_ASSERT(axis != ImGuiAxis_None);
+        ImRect bb;
+        bb.Min = child_0->Pos;
+        bb.Max = child_1->Pos;
+        bb.Min[axis] += child_0->Size[axis];
+        bb.Max[axis ^ 1] += child_1->Size[axis ^ 1];
+        //if (g.IO.KeyCtrl) GetForegroundDrawList(g.CurrentWindow->Viewport)->AddRect(bb.Min, bb.Max, IM_COL32(255,0,255,255));
+
+        if ((child_0->GetMergedFlags() | child_1->GetMergedFlags()) & ImGuiDockNodeFlags_NoResize)
+        {
+            ImGuiWindow* window = g.CurrentWindow;
+            window->DrawList->AddRectFilled(bb.Min, bb.Max, GetColorU32(ImGuiCol_Separator), g.Style.FrameRounding);
+        }
+        else
+        {
+            //bb.Min[axis] += 1; // Display a little inward so highlight doesn't connect with nearby tabs on the neighbor node.
+            //bb.Max[axis] -= 1;
+            PushID(node->ID);
+
+            // Gather list of nodes that are touching the splitter line. Find resizing limits based on those nodes.
+            ImVector<ImGuiDockNode*> touching_nodes[2];
+            float min_size = g.Style.WindowMinSize[axis];
+            float resize_limits[2];
+            resize_limits[0] = node->ChildNodes[0]->Pos[axis] + min_size;
+            resize_limits[1] = node->ChildNodes[1]->Pos[axis] + node->ChildNodes[1]->Size[axis] - min_size;
+
+            ImGuiID splitter_id = GetID("##Splitter");
+            if (g.ActiveId == splitter_id)
+            {
+                // Only process when splitter is active
+                DockNodeTreeUpdateSplitterFindTouchingNode(child_0, axis, 1, &touching_nodes[0]);
+                DockNodeTreeUpdateSplitterFindTouchingNode(child_1, axis, 0, &touching_nodes[1]);
+                for (int touching_node_n = 0; touching_node_n < touching_nodes[0].Size; touching_node_n++)
+                    resize_limits[0] = ImMax(resize_limits[0], touching_nodes[0][touching_node_n]->Rect().Min[axis] + min_size);
+                for (int touching_node_n = 0; touching_node_n < touching_nodes[1].Size; touching_node_n++)
+                    resize_limits[1] = ImMin(resize_limits[1], touching_nodes[1][touching_node_n]->Rect().Max[axis] - min_size);
+
+                /*
+                // [DEBUG] Render limits
+                ImDrawList* draw_list = node->HostWindow ? GetForegroundDrawList(node->HostWindow) : GetForegroundDrawList((ImGuiViewportP*)GetMainViewport());
+                for (int n = 0; n < 2; n++)
+                    if (axis == ImGuiAxis_X)
+                        draw_list->AddLine(ImVec2(resize_limits[n], node->ChildNodes[n]->Pos.y), ImVec2(resize_limits[n], node->ChildNodes[n]->Pos.y + node->ChildNodes[n]->Size.y), IM_COL32(255, 0, 255, 255), 3.0f);
+                    else
+                        draw_list->AddLine(ImVec2(node->ChildNodes[n]->Pos.x, resize_limits[n]), ImVec2(node->ChildNodes[n]->Pos.x + node->ChildNodes[n]->Size.x, resize_limits[n]), IM_COL32(255, 0, 255, 255), 3.0f);
+                */
+            }
+
+            // Use a short delay before highlighting the splitter (and changing the mouse cursor) in order for regular mouse movement to not highlight many splitters
+            float cur_size_0 = child_0->Size[axis];
+            float cur_size_1 = child_1->Size[axis];
+            float min_size_0 = resize_limits[0] - child_0->Pos[axis];
+            float min_size_1 = child_1->Pos[axis] + child_1->Size[axis] - resize_limits[1];
+            if (SplitterBehavior(bb, GetID("##Splitter"), axis, &cur_size_0, &cur_size_1, min_size_0, min_size_1, WINDOWS_RESIZE_FROM_EDGES_HALF_THICKNESS, WINDOWS_RESIZE_FROM_EDGES_FEEDBACK_TIMER))
+            {
+                if (touching_nodes[0].Size > 0 && touching_nodes[1].Size > 0)
+                {
+                    child_0->Size[axis] = child_0->SizeRef[axis] = cur_size_0;
+                    child_1->Pos[axis] -= cur_size_1 - child_1->Size[axis];
+                    child_1->Size[axis] = child_1->SizeRef[axis] = cur_size_1;
+
+                    // Lock the size of every node that is a sibling of the node we are touching
+                    // This might be less desirable if we can merge sibling of a same axis into the same parental level.
+                    for (int side_n = 0; side_n < 2; side_n++)
+                        for (int touching_node_n = 0; touching_node_n < touching_nodes[side_n].Size; touching_node_n++)
+                        {
+                            ImGuiDockNode* touching_node = touching_nodes[side_n][touching_node_n];
+                            //ImDrawList* draw_list = node->HostWindow ? GetForegroundDrawList(node->HostWindow) : GetForegroundDrawList((ImGuiViewportP*)GetMainViewport());
+                            //draw_list->AddRect(touching_node->Pos, touching_node->Pos + touching_node->Size, IM_COL32(255, 128, 0, 255));
+                            while (touching_node->ParentNode != node)
+                            {
+                                if (touching_node->ParentNode->SplitAxis == axis)
+                                {
+                                    // Mark other node so its size will be preserved during the upcoming call to DockNodeTreeUpdatePosSize().
+                                    ImGuiDockNode* node_to_preserve = touching_node->ParentNode->ChildNodes[side_n];
+                                    node_to_preserve->WantLockSizeOnce = true;
+                                    //draw_list->AddRect(touching_node->Pos, touching_node->Rect().Max, IM_COL32(255, 0, 0, 255));
+                                    //draw_list->AddRectFilled(node_to_preserve->Pos, node_to_preserve->Rect().Max, IM_COL32(0, 255, 0, 100));
+                                }
+                                touching_node = touching_node->ParentNode;
+                            }
+                        }
+
+                    DockNodeTreeUpdatePosSize(child_0, child_0->Pos, child_0->Size);
+                    DockNodeTreeUpdatePosSize(child_1, child_1->Pos, child_1->Size);
+                    MarkIniSettingsDirty();
+                }
+            }
+            PopID();
+        }
+    }
+
+    if (child_0->IsVisible)
+        DockNodeTreeUpdateSplitter(child_0);
+    if (child_1->IsVisible)
+        DockNodeTreeUpdateSplitter(child_1);
+}
+
+ImGuiDockNode* ImGui::DockNodeTreeFindFallbackLeafNode(ImGuiDockNode* node)
+{
+    if (node->IsLeafNode())
+        return node;
+    if (ImGuiDockNode* leaf_node = DockNodeTreeFindFallbackLeafNode(node->ChildNodes[0]))
+        return leaf_node;
+    if (ImGuiDockNode* leaf_node = DockNodeTreeFindFallbackLeafNode(node->ChildNodes[1]))
+        return leaf_node;
+    return NULL;
+}
+
+ImGuiDockNode* ImGui::DockNodeTreeFindNodeByPos(ImGuiDockNode* node, ImVec2 pos)
+{
+    if (!node->IsVisible)
+        return NULL;
+
+    ImGuiContext& g = *GImGui;
+    const float dock_spacing = g.Style.ItemInnerSpacing.x;
+    ImRect r(node->Pos, node->Pos + node->Size);
+    r.Expand(dock_spacing * 0.5f);
+    bool inside = r.Contains(pos);
+    if (!inside)
+        return NULL;
+
+    if (node->IsLeafNode())
+        return node;
+    if (ImGuiDockNode* hovered_node = DockNodeTreeFindNodeByPos(node->ChildNodes[0], pos))
+        return hovered_node;
+    if (ImGuiDockNode* hovered_node = DockNodeTreeFindNodeByPos(node->ChildNodes[1], pos))
+        return hovered_node;
+
+    // There is an edge case when docking into a dockspace which only has inactive nodes (because none of the windows are active)
+    // In this case we need to fallback into any leaf mode, possibly the central node.
+    if (node->IsDockSpace() && node->IsRootNode())
+    {
+        if (node->CentralNode && node->IsLeafNode()) // FIXME-20181220: We should not have to test for IsLeafNode() here but we have another bug to fix first.
+            return node->CentralNode;
+        return DockNodeTreeFindFallbackLeafNode(node);
+    }
+
+    return NULL;
+}
+
+//-----------------------------------------------------------------------------
+// Docking: Public Functions (SetWindowDock, DockSpace, DockSpaceOverViewport)
+//-----------------------------------------------------------------------------
+// - SetWindowDock() [Internal]
+// - DockSpace()
+// - DockSpaceOverViewport()
+//-----------------------------------------------------------------------------
+
+// [Internal] Called via SetNextWindowDockID()
+void ImGui::SetWindowDock(ImGuiWindow* window, ImGuiID dock_id, ImGuiCond cond)
+{
+    // Test condition (NB: bit 0 is always true) and clear flags for next time
+    if (cond && (window->SetWindowDockAllowFlags & cond) == 0)
+        return;
+    window->SetWindowDockAllowFlags &= ~(ImGuiCond_Once | ImGuiCond_FirstUseEver | ImGuiCond_Appearing);
+
+    if (window->DockId == dock_id)
+        return;
+
+    // If the user attempt to set a dock id that is a split node, we'll dig within to find a suitable docking spot
+    ImGuiContext* ctx = GImGui;
+    if (ImGuiDockNode* new_node = DockContextFindNodeByID(ctx, dock_id))
+        if (new_node->IsSplitNode())
+        {
+            // Policy: Find central node or latest focused node. We first move back to our root node.
+            new_node = DockNodeGetRootNode(new_node);
+            if (new_node->CentralNode)
+            {
+                IM_ASSERT(new_node->CentralNode->IsCentralNode());
+                dock_id = new_node->CentralNode->ID;
+            }
+            else
+            {
+                dock_id = new_node->LastFocusedNodeId;
+            }
+        }
+
+    if (window->DockId == dock_id)
+        return;
+
+    if (window->DockNode)
+        DockNodeRemoveWindow(window->DockNode, window, 0);
+    window->DockId = dock_id;
+}
+
+// Create an explicit dockspace node within an existing window. Also expose dock node flags and creates a CentralNode by default.
+// The Central Node is always displayed even when empty and shrink/extend according to the requested size of its neighbors.
+// DockSpace() needs to be submitted _before_ any window they can host. If you use a dockspace, submit it early in your app.
+void ImGui::DockSpace(ImGuiID id, const ImVec2& size_arg, ImGuiDockNodeFlags flags, const ImGuiWindowClass* window_class)
+{
+    ImGuiContext* ctx = GImGui;
+    ImGuiContext& g = *ctx;
+    ImGuiWindow* window = GetCurrentWindow();
+    if (!(g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
+        return;
+
+    // Early out if parent window is hidden/collapsed
+    // This is faster but also DockNodeUpdateTabBar() relies on TabBarLayout() running (which won't if SkipItems=true) to set NextSelectedTabId = 0). See #2960.
+    // If for whichever reason this is causing problem we would need to ensure that DockNodeUpdateTabBar() ends up clearing NextSelectedTabId even if SkipItems=true.
+    if (window->SkipItems)
+        flags |= ImGuiDockNodeFlags_KeepAliveOnly;
+
+    IM_ASSERT((flags & ImGuiDockNodeFlags_DockSpace) == 0);
+    ImGuiDockNode* node = DockContextFindNodeByID(ctx, id);
+    if (!node)
+    {
+        IMGUI_DEBUG_LOG_DOCKING("DockSpace: dockspace node 0x%08X created\n", id);
+        node = DockContextAddNode(ctx, id);
+        node->LocalFlags |= ImGuiDockNodeFlags_CentralNode;
+    }
+    if (window_class && window_class->ClassId != node->WindowClass.ClassId)
+        IMGUI_DEBUG_LOG_DOCKING("DockSpace: dockspace node 0x%08X: setup WindowClass 0x%08X -> 0x%08X\n", id, node->WindowClass.ClassId, window_class->ClassId);
+    node->SharedFlags = flags;
+    node->WindowClass = window_class ? *window_class : ImGuiWindowClass();
+
+    // When a DockSpace transitioned form implicit to explicit this may be called a second time
+    // It is possible that the node has already been claimed by a docked window which appeared before the DockSpace() node, so we overwrite IsDockSpace again.
+    if (node->LastFrameActive == g.FrameCount && !(flags & ImGuiDockNodeFlags_KeepAliveOnly))
+    {
+        IM_ASSERT(node->IsDockSpace() == false && "Cannot call DockSpace() twice a frame with the same ID");
+        node->LocalFlags |= ImGuiDockNodeFlags_DockSpace;
+        return;
+    }
+    node->LocalFlags |= ImGuiDockNodeFlags_DockSpace;
+
+    // Keep alive mode, this is allow windows docked into this node so stay docked even if they are not visible
+    if (flags & ImGuiDockNodeFlags_KeepAliveOnly)
+    {
+        node->LastFrameAlive = g.FrameCount;
+        return;
+    }
+
+    const ImVec2 content_avail = GetContentRegionAvail();
+    ImVec2 size = ImFloor(size_arg);
+    if (size.x <= 0.0f)
+        size.x = ImMax(content_avail.x + size.x, 4.0f); // Arbitrary minimum child size (0.0f causing too much issues)
+    if (size.y <= 0.0f)
+        size.y = ImMax(content_avail.y + size.y, 4.0f);
+    IM_ASSERT(size.x > 0.0f && size.y > 0.0f);
+
+    node->Pos = window->DC.CursorPos;
+    node->Size = node->SizeRef = size;
+    SetNextWindowPos(node->Pos);
+    SetNextWindowSize(node->Size);
+    g.NextWindowData.PosUndock = false;
+
+    // FIXME-DOCK Why do we need a child window to host a dockspace, could we host it in the existing window?
+    ImGuiWindowFlags window_flags = ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_DockNodeHost;
+    window_flags |= ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoTitleBar;
+    window_flags |= ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse;
+
+    char title[256];
+    ImFormatString(title, IM_ARRAYSIZE(title), "%s/DockSpace_%08X", window->Name, id);
+
+    if (node->Windows.Size > 0 || node->IsSplitNode())
+        PushStyleColor(ImGuiCol_ChildBg, IM_COL32(0, 0, 0, 0));
+    PushStyleVar(ImGuiStyleVar_ChildBorderSize, 0.0f);
+    Begin(title, NULL, window_flags);
+    PopStyleVar();
+    if (node->Windows.Size > 0 || node->IsSplitNode())
+        PopStyleColor();
+
+    ImGuiWindow* host_window = g.CurrentWindow;
+    host_window->DockNodeAsHost = node;
+    host_window->ChildId = window->GetID(title);
+    node->HostWindow = host_window;
+    node->OnlyNodeWithWindows = NULL;
+
+    IM_ASSERT(node->IsRootNode());
+    DockNodeUpdate(node);
+
+    g.WithinEndChild = true;
+    End();
+    g.WithinEndChild = false;
+}
+
+// Tips: Use with ImGuiDockNodeFlags_PassthruCentralNode!
+// The limitation with this call is that your window won't have a menu bar.
+// Even though we could pass window flags, it would also require the user to be able to call BeginMenuBar() somehow meaning we can't Begin/End in a single function.
+// But you can also use BeginMainMenuBar(). If you really want a menu bar inside the same window as the one hosting the dockspace, you will need to copy this code somewhere and tweak it.
+ImGuiID ImGui::DockSpaceOverViewport(ImGuiViewport* viewport, ImGuiDockNodeFlags dockspace_flags, const ImGuiWindowClass* window_class)
+{
+    if (viewport == NULL)
+        viewport = GetMainViewport();
+
+    SetNextWindowPos(viewport->GetWorkPos());
+    SetNextWindowSize(viewport->GetWorkSize());
+    SetNextWindowViewport(viewport->ID);
+
+    ImGuiWindowFlags host_window_flags = 0;
+    host_window_flags |= ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoDocking;
+    host_window_flags |= ImGuiWindowFlags_NoBringToFrontOnFocus | ImGuiWindowFlags_NoNavFocus;
+    if (dockspace_flags & ImGuiDockNodeFlags_PassthruCentralNode)
+        host_window_flags |= ImGuiWindowFlags_NoBackground;
+
+    char label[32];
+    ImFormatString(label, IM_ARRAYSIZE(label), "DockSpaceViewport_%08X", viewport->ID);
+
+    PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
+    PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
+    PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));
+    Begin(label, NULL, host_window_flags);
+    PopStyleVar(3);
+
+    ImGuiID dockspace_id = GetID("DockSpace");
+    DockSpace(dockspace_id, ImVec2(0.0f, 0.0f), dockspace_flags, window_class);
+    End();
+
+    return dockspace_id;
+}
+
+//-----------------------------------------------------------------------------
+// Docking: Builder Functions
+//-----------------------------------------------------------------------------
+// Very early end-user API to manipulate dock nodes.
+// Only available in imgui_internal.h. Expect this API to change/break!
+// It is expected that those functions are all called _before_ the dockspace node submission.
+//-----------------------------------------------------------------------------
+// - DockBuilderDockWindow()
+// - DockBuilderGetNode()
+// - DockBuilderSetNodePos()
+// - DockBuilderSetNodeSize()
+// - DockBuilderAddNode()
+// - DockBuilderRemoveNode()
+// - DockBuilderRemoveNodeChildNodes()
+// - DockBuilderRemoveNodeDockedWindows()
+// - DockBuilderSplitNode()
+// - DockBuilderCopyNodeRec()
+// - DockBuilderCopyNode()
+// - DockBuilderCopyWindowSettings()
+// - DockBuilderCopyDockSpace()
+// - DockBuilderFinish()
+//-----------------------------------------------------------------------------
+
+void ImGui::DockBuilderDockWindow(const char* window_name, ImGuiID node_id)
+{
+    // We don't preserve relative order of multiple docked windows (by clearing DockOrder back to -1)
+    ImGuiID window_id = ImHashStr(window_name);
+    if (ImGuiWindow* window = FindWindowByID(window_id))
+    {
+        // Apply to created window
+        SetWindowDock(window, node_id, ImGuiCond_Always);
+        window->DockOrder = -1;
+    }
+    else
+    {
+        // Apply to settings
+        ImGuiWindowSettings* settings = FindWindowSettings(window_id);
+        if (settings == NULL)
+            settings = CreateNewWindowSettings(window_name);
+        settings->DockId = node_id;
+        settings->DockOrder = -1;
+    }
+}
+
+ImGuiDockNode* ImGui::DockBuilderGetNode(ImGuiID node_id)
+{
+    ImGuiContext* ctx = GImGui;
+    return DockContextFindNodeByID(ctx, node_id);
+}
+
+void ImGui::DockBuilderSetNodePos(ImGuiID node_id, ImVec2 pos)
+{
+    ImGuiContext* ctx = GImGui;
+    ImGuiDockNode* node = DockContextFindNodeByID(ctx, node_id);
+    if (node == NULL)
+        return;
+    node->Pos = pos;
+    node->AuthorityForPos = ImGuiDataAuthority_DockNode;
+}
+
+void ImGui::DockBuilderSetNodeSize(ImGuiID node_id, ImVec2 size)
+{
+    ImGuiContext* ctx = GImGui;
+    ImGuiDockNode* node = DockContextFindNodeByID(ctx, node_id);
+    if (node == NULL)
+        return;
+    IM_ASSERT(size.x > 0.0f && size.y > 0.0f);
+    node->Size = node->SizeRef = size;
+    node->AuthorityForSize = ImGuiDataAuthority_DockNode;
+}
+
+// Make sure to use the ImGuiDockNodeFlags_DockSpace flag to create a dockspace node! Otherwise this will create a floating node!
+// - Floating node: you can then call DockBuilderSetNodePos()/DockBuilderSetNodeSize() to position and size the floating node.
+// - Dockspace node: calling DockBuilderSetNodePos() is unnecessary.
+// - If you intend to split a node immediately after creation using DockBuilderSplitNode(), make sure to call DockBuilderSetNodeSize() beforehand!
+//   For various reason, the splitting code currently needs a base size otherwise space may not be allocated as precisely as you would expect.
+// - Use (id == 0) to let the system allocate a node identifier.
+ImGuiID ImGui::DockBuilderAddNode(ImGuiID id, ImGuiDockNodeFlags flags)
+{
+    ImGuiContext* ctx = GImGui;
+    ImGuiDockNode* node = NULL;
+    if (flags & ImGuiDockNodeFlags_DockSpace)
+    {
+        DockSpace(id, ImVec2(0, 0), (flags & ~ImGuiDockNodeFlags_DockSpace) | ImGuiDockNodeFlags_KeepAliveOnly);
+        node = DockContextFindNodeByID(ctx, id);
+    }
+    else
+    {
+        if (id != 0)
+            node = DockContextFindNodeByID(ctx, id);
+        if (!node)
+            node = DockContextAddNode(ctx, id);
+        node->LocalFlags = flags;
+    }
+    node->LastFrameAlive = ctx->FrameCount;   // Set this otherwise BeginDocked will undock during the same frame.
+    return node->ID;
+}
+
+void ImGui::DockBuilderRemoveNode(ImGuiID node_id)
+{
+    ImGuiContext* ctx = GImGui;
+    ImGuiDockNode* node = DockContextFindNodeByID(ctx, node_id);
+    if (node == NULL)
+        return;
+    DockBuilderRemoveNodeDockedWindows(node_id, true);
+    DockBuilderRemoveNodeChildNodes(node_id);
+    if (node->IsCentralNode() && node->ParentNode)
+        node->ParentNode->LocalFlags |= ImGuiDockNodeFlags_CentralNode;
+    DockContextRemoveNode(ctx, node, true);
+}
+
+void ImGui::DockBuilderRemoveNodeChildNodes(ImGuiID root_id)
+{
+    ImGuiContext* ctx = GImGui;
+    ImGuiDockContext* dc = ctx->DockContext;
+
+    ImGuiDockNode* root_node = root_id ? DockContextFindNodeByID(ctx, root_id) : NULL;
+    if (root_id && root_node == NULL)
+        return;
+    bool has_central_node = false;
+
+    ImGuiDataAuthority backup_root_node_authority_for_pos = root_node ? root_node->AuthorityForPos : ImGuiDataAuthority_Auto;
+    ImGuiDataAuthority backup_root_node_authority_for_size = root_node ? root_node->AuthorityForSize : ImGuiDataAuthority_Auto;
+
+    // Process active windows
+    ImVector<ImGuiDockNode*> nodes_to_remove;
+    for (int n = 0; n < dc->Nodes.Data.Size; n++)
+        if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+        {
+            bool want_removal = (root_id == 0) || (node->ID != root_id && DockNodeGetRootNode(node)->ID == root_id);
+            if (want_removal)
+            {
+                if (node->IsCentralNode())
+                    has_central_node = true;
+                if (root_id != 0)
+                    DockContextQueueNotifyRemovedNode(ctx, node);
+                if (root_node)
+                    DockNodeMoveWindows(root_node, node);
+                nodes_to_remove.push_back(node);
+            }
+        }
+
+    // DockNodeMoveWindows->DockNodeAddWindow will normally set those when reaching two windows (which is only adequate during interactive merge)
+    // Make sure we don't lose our current pos/size. (FIXME-DOCK: Consider tidying up that code in DockNodeAddWindow instead)
+    if (root_node)
+    {
+        root_node->AuthorityForPos = backup_root_node_authority_for_pos;
+        root_node->AuthorityForSize = backup_root_node_authority_for_size;
+    }
+
+    // Apply to settings
+    for (ImGuiWindowSettings* settings = ctx->SettingsWindows.begin(); settings != NULL; settings = ctx->SettingsWindows.next_chunk(settings))
+        if (ImGuiID window_settings_dock_id = settings->DockId)
+            for (int n = 0; n < nodes_to_remove.Size; n++)
+                if (nodes_to_remove[n]->ID == window_settings_dock_id)
+                {
+                    settings->DockId = root_id;
+                    break;
+                }
+
+    // Not really efficient, but easier to destroy a whole hierarchy considering DockContextRemoveNode is attempting to merge nodes
+    if (nodes_to_remove.Size > 1)
+        ImQsort(nodes_to_remove.Data, nodes_to_remove.Size, sizeof(ImGuiDockNode*), DockNodeComparerDepthMostFirst);
+    for (int n = 0; n < nodes_to_remove.Size; n++)
+        DockContextRemoveNode(ctx, nodes_to_remove[n], false);
+
+    if (root_id == 0)
+    {
+        dc->Nodes.Clear();
+        dc->Requests.clear();
+    }
+    else if (has_central_node)
+    {
+        root_node->LocalFlags |= ImGuiDockNodeFlags_CentralNode;
+        root_node->CentralNode = root_node;
+    }
+}
+
+void ImGui::DockBuilderRemoveNodeDockedWindows(ImGuiID root_id, bool clear_persistent_docking_references)
+{
+    // Clear references in settings
+    ImGuiContext* ctx = GImGui;
+    ImGuiContext& g = *ctx;
+    if (clear_persistent_docking_references)
+    {
+        for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+        {
+            bool want_removal = (root_id == 0) || (settings->DockId == root_id);
+            if (!want_removal && settings->DockId != 0)
+                if (ImGuiDockNode* node = DockContextFindNodeByID(ctx, settings->DockId))
+                    if (DockNodeGetRootNode(node)->ID == root_id)
+                        want_removal = true;
+            if (want_removal)
+                settings->DockId = 0;
+        }
+    }
+
+    // Clear references in windows
+    for (int n = 0; n < g.Windows.Size; n++)
+    {
+        ImGuiWindow* window = g.Windows[n];
+        bool want_removal = (root_id == 0) || (window->DockNode && DockNodeGetRootNode(window->DockNode)->ID == root_id) || (window->DockNodeAsHost && window->DockNodeAsHost->ID == root_id);
+        if (want_removal)
+        {
+            const ImGuiID backup_dock_id = window->DockId;
+            IM_UNUSED(backup_dock_id);
+            DockContextProcessUndockWindow(ctx, window, clear_persistent_docking_references);
+            if (!clear_persistent_docking_references)
+                IM_ASSERT(window->DockId == backup_dock_id);
+        }
+    }
+}
+
+// If 'out_id_at_dir' or 'out_id_at_opposite_dir' are non NULL, the function will write out the ID of the two new nodes created.
+// Return value is ID of the node at the specified direction, so same as (*out_id_at_dir) if that pointer is set.
+// FIXME-DOCK: We are not exposing nor using split_outer.
+ImGuiID ImGui::DockBuilderSplitNode(ImGuiID id, ImGuiDir split_dir, float size_ratio_for_node_at_dir, ImGuiID* out_id_at_dir, ImGuiID* out_id_at_opposite_dir)
+{
+    ImGuiContext* ctx = GImGui;
+    IM_ASSERT(split_dir != ImGuiDir_None);
+    IMGUI_DEBUG_LOG_DOCKING("DockBuilderSplitNode node 0x%08X, split_dir %d\n", id, split_dir);
+
+    ImGuiDockNode* node = DockContextFindNodeByID(ctx, id);
+    if (node == NULL)
+    {
+        IM_ASSERT(node != NULL);
+        return 0;
+    }
+
+    IM_ASSERT(!node->IsSplitNode()); // Assert if already Split
+
+    ImGuiDockRequest req;
+    req.Type = ImGuiDockRequestType_Split;
+    req.DockTargetWindow = NULL;
+    req.DockTargetNode = node;
+    req.DockPayload = NULL;
+    req.DockSplitDir = split_dir;
+    req.DockSplitRatio = ImSaturate((split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Up) ? size_ratio_for_node_at_dir : 1.0f - size_ratio_for_node_at_dir);
+    req.DockSplitOuter = false;
+    DockContextProcessDock(ctx, &req);
+
+    ImGuiID id_at_dir = node->ChildNodes[(split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Up) ? 0 : 1]->ID;
+    ImGuiID id_at_opposite_dir = node->ChildNodes[(split_dir == ImGuiDir_Left || split_dir == ImGuiDir_Up) ? 1 : 0]->ID;
+    if (out_id_at_dir)
+        *out_id_at_dir = id_at_dir;
+    if (out_id_at_opposite_dir)
+        *out_id_at_opposite_dir = id_at_opposite_dir;
+    return id_at_dir;
+}
+
+static ImGuiDockNode* DockBuilderCopyNodeRec(ImGuiDockNode* src_node, ImGuiID dst_node_id_if_known, ImVector<ImGuiID>* out_node_remap_pairs)
+{
+    ImGuiContext* ctx = GImGui;
+    ImGuiDockNode* dst_node = ImGui::DockContextAddNode(ctx, dst_node_id_if_known);
+    dst_node->SharedFlags = src_node->SharedFlags;
+    dst_node->LocalFlags = src_node->LocalFlags;
+    dst_node->Pos = src_node->Pos;
+    dst_node->Size = src_node->Size;
+    dst_node->SizeRef = src_node->SizeRef;
+    dst_node->SplitAxis = src_node->SplitAxis;
+
+    out_node_remap_pairs->push_back(src_node->ID);
+    out_node_remap_pairs->push_back(dst_node->ID);
+
+    for (int child_n = 0; child_n < IM_ARRAYSIZE(src_node->ChildNodes); child_n++)
+        if (src_node->ChildNodes[child_n])
+        {
+            dst_node->ChildNodes[child_n] = DockBuilderCopyNodeRec(src_node->ChildNodes[child_n], 0, out_node_remap_pairs);
+            dst_node->ChildNodes[child_n]->ParentNode = dst_node;
+        }
+
+    IMGUI_DEBUG_LOG_DOCKING("Fork node %08X -> %08X (%d childs)\n", src_node->ID, dst_node->ID, dst_node->IsSplitNode() ? 2 : 0);
+    return dst_node;
+}
+
+void ImGui::DockBuilderCopyNode(ImGuiID src_node_id, ImGuiID dst_node_id, ImVector<ImGuiID>* out_node_remap_pairs)
+{
+    ImGuiContext* ctx = GImGui;
+    IM_ASSERT(src_node_id != 0);
+    IM_ASSERT(dst_node_id != 0);
+    IM_ASSERT(out_node_remap_pairs != NULL);
+
+    ImGuiDockNode* src_node = DockContextFindNodeByID(ctx, src_node_id);
+    IM_ASSERT(src_node != NULL);
+
+    out_node_remap_pairs->clear();
+    DockBuilderRemoveNode(dst_node_id);
+    DockBuilderCopyNodeRec(src_node, dst_node_id, out_node_remap_pairs);
+
+    IM_ASSERT((out_node_remap_pairs->Size % 2) == 0);
+}
+
+void ImGui::DockBuilderCopyWindowSettings(const char* src_name, const char* dst_name)
+{
+    ImGuiWindow* src_window = FindWindowByName(src_name);
+    if (src_window == NULL)
+        return;
+    if (ImGuiWindow* dst_window = FindWindowByName(dst_name))
+    {
+        dst_window->Pos = src_window->Pos;
+        dst_window->Size = src_window->Size;
+        dst_window->SizeFull = src_window->SizeFull;
+        dst_window->Collapsed = src_window->Collapsed;
+    }
+    else if (ImGuiWindowSettings* dst_settings = FindOrCreateWindowSettings(dst_name))
+    {
+        ImVec2ih window_pos_2ih = ImVec2ih(src_window->Pos);
+        if (src_window->ViewportId != 0 && src_window->ViewportId != IMGUI_VIEWPORT_DEFAULT_ID)
+        {
+            dst_settings->ViewportPos = window_pos_2ih;
+            dst_settings->ViewportId = src_window->ViewportId;
+            dst_settings->Pos = ImVec2ih(0, 0);
+        }
+        else
+        {
+            dst_settings->Pos = window_pos_2ih;
+        }
+        dst_settings->Size = ImVec2ih(src_window->SizeFull);
+        dst_settings->Collapsed = src_window->Collapsed;
+    }
+}
+
+// FIXME: Will probably want to change this signature, in particular how the window remapping pairs are passed.
+void ImGui::DockBuilderCopyDockSpace(ImGuiID src_dockspace_id, ImGuiID dst_dockspace_id, ImVector<const char*>* in_window_remap_pairs)
+{
+    IM_ASSERT(src_dockspace_id != 0);
+    IM_ASSERT(dst_dockspace_id != 0);
+    IM_ASSERT(in_window_remap_pairs != NULL);
+    IM_ASSERT((in_window_remap_pairs->Size % 2) == 0);
+
+    // Duplicate entire dock
+    // FIXME: When overwriting dst_dockspace_id, windows that aren't part of our dockspace window class but that are docked in a same node will be split apart,
+    // whereas we could attempt to at least keep them together in a new, same floating node.
+    ImVector<ImGuiID> node_remap_pairs;
+    DockBuilderCopyNode(src_dockspace_id, dst_dockspace_id, &node_remap_pairs);
+
+    // Attempt to transition all the upcoming windows associated to dst_dockspace_id into the newly created hierarchy of dock nodes
+    // (The windows associated to src_dockspace_id are staying in place)
+    ImVector<ImGuiID> src_windows;
+    for (int remap_window_n = 0; remap_window_n < in_window_remap_pairs->Size; remap_window_n += 2)
+    {
+        const char* src_window_name = (*in_window_remap_pairs)[remap_window_n];
+        const char* dst_window_name = (*in_window_remap_pairs)[remap_window_n + 1];
+        ImGuiID src_window_id = ImHashStr(src_window_name);
+        src_windows.push_back(src_window_id);
+
+        // Search in the remapping tables
+        ImGuiID src_dock_id = 0;
+        if (ImGuiWindow* src_window = FindWindowByID(src_window_id))
+            src_dock_id = src_window->DockId;
+        else if (ImGuiWindowSettings* src_window_settings = FindWindowSettings(src_window_id))
+            src_dock_id = src_window_settings->DockId;
+        ImGuiID dst_dock_id = 0;
+        for (int dock_remap_n = 0; dock_remap_n < node_remap_pairs.Size; dock_remap_n += 2)
+            if (node_remap_pairs[dock_remap_n] == src_dock_id)
+            {
+                dst_dock_id = node_remap_pairs[dock_remap_n + 1];
+                //node_remap_pairs[dock_remap_n] = node_remap_pairs[dock_remap_n + 1] = 0; // Clear
+                break;
+            }
+
+        if (dst_dock_id != 0)
+        {
+            // Docked windows gets redocked into the new node hierarchy.
+            IMGUI_DEBUG_LOG_DOCKING("Remap live window '%s' 0x%08X -> '%s' 0x%08X\n", src_window_name, src_dock_id, dst_window_name, dst_dock_id);
+            DockBuilderDockWindow(dst_window_name, dst_dock_id);
+        }
+        else
+        {
+            // Floating windows gets their settings transferred (regardless of whether the new window already exist or not)
+            // When this is leading to a Copy and not a Move, we would get two overlapping floating windows. Could we possibly dock them together?
+            IMGUI_DEBUG_LOG_DOCKING("Remap window settings '%s' -> '%s'\n", src_window_name, dst_window_name);
+            DockBuilderCopyWindowSettings(src_window_name, dst_window_name);
+        }
+    }
+
+    // Anything else in the source nodes of 'node_remap_pairs' are windows that were docked in src_dockspace_id but are not owned by it (unaffiliated windows, e.g. "ImGui Demo")
+    // Find those windows and move to them to the cloned dock node. This may be optional?
+    for (int dock_remap_n = 0; dock_remap_n < node_remap_pairs.Size; dock_remap_n += 2)
+        if (ImGuiID src_dock_id = node_remap_pairs[dock_remap_n])
+        {
+            ImGuiID dst_dock_id = node_remap_pairs[dock_remap_n + 1];
+            ImGuiDockNode* node = DockBuilderGetNode(src_dock_id);
+            for (int window_n = 0; window_n < node->Windows.Size; window_n++)
+            {
+                ImGuiWindow* window = node->Windows[window_n];
+                if (src_windows.contains(window->ID))
+                    continue;
+
+                // Docked windows gets redocked into the new node hierarchy.
+                IMGUI_DEBUG_LOG_DOCKING("Remap window '%s' %08X -> %08X\n", window->Name, src_dock_id, dst_dock_id);
+                DockBuilderDockWindow(window->Name, dst_dock_id);
+            }
+        }
+}
+
+void ImGui::DockBuilderFinish(ImGuiID root_id)
+{
+    ImGuiContext* ctx = GImGui;
+    //DockContextRebuild(ctx);
+    DockContextBuildAddWindowsToNodes(ctx, root_id);
+}
+
+//-----------------------------------------------------------------------------
+// Docking: Begin/End Support Functions (called from Begin/End)
+//-----------------------------------------------------------------------------
+// - GetWindowAlwaysWantOwnTabBar()
+// - DockContextBindNodeToWindow()
+// - BeginDocked()
+// - BeginDockableDragDropSource()
+// - BeginDockableDragDropTarget()
+//-----------------------------------------------------------------------------
+
+bool ImGui::GetWindowAlwaysWantOwnTabBar(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    if (g.IO.ConfigDockingAlwaysTabBar || window->WindowClass.DockingAlwaysTabBar)
+        if ((window->Flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoDocking)) == 0)
+            if (!window->IsFallbackWindow)    // We don't support AlwaysTabBar on the fallback/implicit window to avoid unused dock-node overhead/noise
+                return true;
+    return false;
+}
+
+static ImGuiDockNode* ImGui::DockContextBindNodeToWindow(ImGuiContext* ctx, ImGuiWindow* window)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockNode* node = DockContextFindNodeByID(ctx, window->DockId);
+    IM_ASSERT(window->DockNode == NULL);
+
+    // We should not be docking into a split node (SetWindowDock should avoid this)
+    if (node && node->IsSplitNode())
+    {
+        DockContextProcessUndockWindow(ctx, window);
+        return NULL;
+    }
+
+    // Create node
+    if (node == NULL)
+    {
+        node = DockContextAddNode(ctx, window->DockId);
+        node->AuthorityForPos = node->AuthorityForSize = node->AuthorityForViewport = ImGuiDataAuthority_Window;
+        node->LastFrameAlive = g.FrameCount;
+    }
+
+    // If the node just turned visible and is part of a hierarchy, it doesn't have a Size assigned by DockNodeTreeUpdatePosSize() yet,
+    // so we're forcing a Pos/Size update from the first ancestor that is already visible (often it will be the root node).
+    // If we don't do this, the window will be assigned a zero-size on its first frame, which won't ideally warm up the layout.
+    // This is a little wonky because we don't normally update the Pos/Size of visible node mid-frame.
+    if (!node->IsVisible)
+    {
+        ImGuiDockNode* ancestor_node = node;
+        while (!ancestor_node->IsVisible)
+        {
+            ancestor_node->IsVisible = true;
+            ancestor_node->MarkedForPosSizeWrite = true;
+            if (ancestor_node->ParentNode)
+                ancestor_node = ancestor_node->ParentNode;
+        }
+        IM_ASSERT(ancestor_node->Size.x > 0.0f && ancestor_node->Size.y > 0.0f);
+        DockNodeTreeUpdatePosSize(ancestor_node, ancestor_node->Pos, ancestor_node->Size, true);
+    }
+
+    // Add window to node
+    DockNodeAddWindow(node, window, true);
+    IM_ASSERT(node == window->DockNode);
+    return node;
+}
+
+void ImGui::BeginDocked(ImGuiWindow* window, bool* p_open)
+{
+    ImGuiContext* ctx = GImGui;
+    ImGuiContext& g = *ctx;
+
+    const bool auto_dock_node = GetWindowAlwaysWantOwnTabBar(window);
+    if (auto_dock_node)
+    {
+        if (window->DockId == 0)
+        {
+            IM_ASSERT(window->DockNode == NULL);
+            window->DockId = DockContextGenNodeID(ctx);
+        }
+    }
+    else
+    {
+        // Calling SetNextWindowPos() undock windows by default (by setting PosUndock)
+        bool want_undock = false;
+        want_undock |= (window->Flags & ImGuiWindowFlags_NoDocking) != 0;
+        want_undock |= (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasPos) && (window->SetWindowPosAllowFlags & g.NextWindowData.PosCond) && g.NextWindowData.PosUndock;
+        if (want_undock)
+        {
+            DockContextProcessUndockWindow(ctx, window);
+            return;
+        }
+    }
+
+    // Bind to our dock node
+    ImGuiDockNode* node = window->DockNode;
+    if (node != NULL)
+        IM_ASSERT(window->DockId == node->ID);
+    if (window->DockId != 0 && node == NULL)
+    {
+        node = DockContextBindNodeToWindow(ctx, window);
+        if (node == NULL)
+            return;
+    }
+
+#if 0
+    // Undock if the ImGuiDockNodeFlags_NoDockingInCentralNode got set
+    if (node->IsCentralNode && (node->Flags & ImGuiDockNodeFlags_NoDockingInCentralNode))
+    {
+        DockContextProcessUndockWindow(ctx, window);
+        return;
+    }
+#endif
+
+    // Undock if our dockspace node disappeared
+    // Note how we are testing for LastFrameAlive and NOT LastFrameActive. A DockSpace node can be maintained alive while being inactive with ImGuiDockNodeFlags_KeepAliveOnly.
+    if (node->LastFrameAlive < g.FrameCount)
+    {
+        // If the window has been orphaned, transition the docknode to an implicit node processed in DockContextUpdateDocking()
+        ImGuiDockNode* root_node = DockNodeGetRootNode(node);
+        if (root_node->LastFrameAlive < g.FrameCount)
+        {
+            DockContextProcessUndockWindow(ctx, window);
+        }
+        else
+        {
+            window->DockIsActive = true;
+            window->DockTabIsVisible = false;
+        }
+        return;
+    }
+
+    // Fast path return. It is common for windows to hold on a persistent DockId but be the only visible window,
+    // and never create neither a host window neither a tab bar.
+    // FIXME-DOCK: replace ->HostWindow NULL compare with something more explicit (~was initially intended as a first frame test)
+    if (node->HostWindow == NULL)
+    {
+        window->DockIsActive = (node->State == ImGuiDockNodeState_HostWindowHiddenBecauseWindowsAreResizing);
+        window->DockTabIsVisible = false;
+        return;
+    }
+
+    // We can have zero-sized nodes (e.g. children of a small-size dockspace)
+    IM_ASSERT(node->HostWindow);
+    IM_ASSERT(node->IsLeafNode());
+    IM_ASSERT(node->Size.x >= 0.0f && node->Size.y >= 0.0f);
+    node->State = ImGuiDockNodeState_HostWindowVisible;
+
+    // Undock if we are submitted earlier than the host window
+    if (window->BeginOrderWithinContext < node->HostWindow->BeginOrderWithinContext)
+    {
+        DockContextProcessUndockWindow(ctx, window);
+        return;
+    }
+
+    // Position/Size window
+    SetNextWindowPos(node->Pos);
+    SetNextWindowSize(node->Size);
+    g.NextWindowData.PosUndock = false; // Cancel implicit undocking of SetNextWindowPos()
+    window->DockIsActive = true;
+    window->DockTabIsVisible = false;
+    if (node->SharedFlags & ImGuiDockNodeFlags_KeepAliveOnly)
+        return;
+
+    // When the window is selected we mark it as visible.
+    if (node->VisibleWindow == window)
+        window->DockTabIsVisible = true;
+
+    // Update window flag
+    IM_ASSERT((window->Flags & ImGuiWindowFlags_ChildWindow) == 0);
+    window->Flags |= ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_AlwaysUseWindowPadding | ImGuiWindowFlags_NoResize;
+    if (node->IsHiddenTabBar() || node->IsNoTabBar())
+        window->Flags |= ImGuiWindowFlags_NoTitleBar;
+    else
+        window->Flags &= ~ImGuiWindowFlags_NoTitleBar;      // Clear the NoTitleBar flag in case the user set it: confusingly enough we need a title bar height so we are correctly offset, but it won't be displayed!
+
+    // Save new dock order only if the tab bar has been visible once.
+    // This allows multiple windows to be created in the same frame and have their respective dock orders preserved.
+    if (node->TabBar && node->TabBar->CurrFrameVisible != -1)
+        window->DockOrder = (short)DockNodeGetTabOrder(window);
+
+    if ((node->WantCloseAll || node->WantCloseTabId == window->ID) && p_open != NULL)
+        *p_open = false;
+
+    // Update ChildId to allow returning from Child to Parent with Escape
+    ImGuiWindow* parent_window = window->DockNode->HostWindow;
+    window->ChildId = parent_window->GetID(window->Name);
+}
+
+void ImGui::BeginDockableDragDropSource(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(g.ActiveId == window->MoveId);
+    IM_ASSERT(g.MovingWindow == window);
+
+    window->DC.LastItemId = window->MoveId;
+    window = window->RootWindow;
+    IM_ASSERT((window->Flags & ImGuiWindowFlags_NoDocking) == 0);
+    bool is_drag_docking = (g.IO.ConfigDockingWithShift) || ImRect(0, 0, window->SizeFull.x, GetFrameHeight()).Contains(g.ActiveIdClickOffset);
+    if (is_drag_docking && BeginDragDropSource(ImGuiDragDropFlags_SourceNoPreviewTooltip | ImGuiDragDropFlags_SourceNoHoldToOpenOthers | ImGuiDragDropFlags_SourceAutoExpirePayload))
+    {
+        SetDragDropPayload(IMGUI_PAYLOAD_TYPE_WINDOW, &window, sizeof(window));
+        EndDragDropSource();
+    }
+}
+
+void ImGui::BeginDockableDragDropTarget(ImGuiWindow* window)
+{
+    ImGuiContext* ctx = GImGui;
+    ImGuiContext& g = *ctx;
+
+    //IM_ASSERT(window->RootWindow == window); // May also be a DockSpace
+    IM_ASSERT((window->Flags & ImGuiWindowFlags_NoDocking) == 0);
+    if (!g.DragDropActive)
+        return;
+    if (!BeginDragDropTargetCustom(window->Rect(), window->ID))
+        return;
+
+    // Peek into the payload before calling AcceptDragDropPayload() so we can handle overlapping dock nodes with filtering
+    // (this is a little unusual pattern, normally most code would call AcceptDragDropPayload directly)
+    const ImGuiPayload* payload = &g.DragDropPayload;
+    if (!payload->IsDataType(IMGUI_PAYLOAD_TYPE_WINDOW) || !DockNodeIsDropAllowed(window, *(ImGuiWindow**)payload->Data))
+    {
+        EndDragDropTarget();
+        return;
+    }
+
+    ImGuiWindow* payload_window = *(ImGuiWindow**)payload->Data;
+    if (AcceptDragDropPayload(IMGUI_PAYLOAD_TYPE_WINDOW, ImGuiDragDropFlags_AcceptBeforeDelivery | ImGuiDragDropFlags_AcceptNoDrawDefaultRect))
+    {
+        // Select target node
+        ImGuiDockNode* node = NULL;
+        bool allow_null_target_node = false;
+        if (window->DockNodeAsHost)
+            node = DockNodeTreeFindNodeByPos(window->DockNodeAsHost, g.IO.MousePos);
+        else if (window->DockNode) // && window->DockIsActive)
+            node = window->DockNode;
+        else
+            allow_null_target_node = true; // Dock into a regular window
+
+        const ImRect explicit_target_rect = (node && node->TabBar && !node->IsHiddenTabBar() && !node->IsNoTabBar()) ? node->TabBar->BarRect : ImRect(window->Pos, window->Pos + ImVec2(window->Size.x, GetFrameHeight()));
+        const bool is_explicit_target = g.IO.ConfigDockingWithShift || IsMouseHoveringRect(explicit_target_rect.Min, explicit_target_rect.Max);
+
+        // Preview docking request and find out split direction/ratio
+        //const bool do_preview = true;     // Ignore testing for payload->IsPreview() which removes one frame of delay, but breaks overlapping drop targets within the same window.
+        const bool do_preview = payload->IsPreview() || payload->IsDelivery();
+        if (do_preview && (node != NULL || allow_null_target_node))
+        {
+            ImGuiDockPreviewData split_inner;
+            ImGuiDockPreviewData split_outer;
+            ImGuiDockPreviewData* split_data = &split_inner;
+            if (node && (node->ParentNode || node->IsCentralNode()))
+                if (ImGuiDockNode* root_node = DockNodeGetRootNode(node))
+                {
+                    DockNodePreviewDockSetup(window, root_node, payload_window, &split_outer, is_explicit_target, true);
+                    if (split_outer.IsSplitDirExplicit)
+                        split_data = &split_outer;
+                }
+            DockNodePreviewDockSetup(window, node, payload_window, &split_inner, is_explicit_target, false);
+            if (split_data == &split_outer)
+                split_inner.IsDropAllowed = false;
+
+            // Draw inner then outer, so that previewed tab (in inner data) will be behind the outer drop boxes
+            DockNodePreviewDockRender(window, node, payload_window, &split_inner);
+            DockNodePreviewDockRender(window, node, payload_window, &split_outer);
+
+            // Queue docking request
+            if (split_data->IsDropAllowed && payload->IsDelivery())
+                DockContextQueueDock(ctx, window, split_data->SplitNode, payload_window, split_data->SplitDir, split_data->SplitRatio, split_data == &split_outer);
+        }
+    }
+    EndDragDropTarget();
+}
+
+//-----------------------------------------------------------------------------
+// Docking: Settings
+//-----------------------------------------------------------------------------
+// - DockSettingsRenameNodeReferences()
+// - DockSettingsRemoveNodeReferences()
+// - DockSettingsFindNodeSettings()
+// - DockSettingsHandler_ReadOpen()
+// - DockSettingsHandler_ReadLine()
+// - DockSettingsHandler_DockNodeToSettings()
+// - DockSettingsHandler_WriteAll()
+//-----------------------------------------------------------------------------
+
+static void ImGui::DockSettingsRenameNodeReferences(ImGuiID old_node_id, ImGuiID new_node_id)
+{
+    ImGuiContext& g = *GImGui;
+    IMGUI_DEBUG_LOG_DOCKING("DockSettingsRenameNodeReferences: from 0x%08X -> to 0x%08X\n", old_node_id, new_node_id);
+    for (int window_n = 0; window_n < g.Windows.Size; window_n++)
+    {
+        ImGuiWindow* window = g.Windows[window_n];
+        if (window->DockId == old_node_id && window->DockNode == NULL)
+            window->DockId = new_node_id;
+    }
+    //// FIXME-OPT: We could remove this loop by storing the index in the map
+    for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+        if (settings->DockId == old_node_id)
+            settings->DockId = new_node_id;
+}
+
+// Remove references stored in ImGuiWindowSettings to the given ImGuiDockNodeSettings
+static void ImGui::DockSettingsRemoveNodeReferences(ImGuiID* node_ids, int node_ids_count)
+{
+    ImGuiContext& g = *GImGui;
+    int found = 0;
+    //// FIXME-OPT: We could remove this loop by storing the index in the map
+    for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+        for (int node_n = 0; node_n < node_ids_count; node_n++)
+            if (settings->DockId == node_ids[node_n])
+            {
+                settings->DockId = 0;
+                settings->DockOrder = -1;
+                if (++found < node_ids_count)
+                    break;
+                return;
+            }
+}
+
+static ImGuiDockNodeSettings* ImGui::DockSettingsFindNodeSettings(ImGuiContext* ctx, ImGuiID id)
+{
+    // FIXME-OPT
+    ImGuiDockContext* dc = ctx->DockContext;
+    for (int n = 0; n < dc->SettingsNodes.Size; n++)
+        if (dc->SettingsNodes[n].ID == id)
+            return &dc->SettingsNodes[n];
+    return NULL;
+}
+
+static void* ImGui::DockSettingsHandler_ReadOpen(ImGuiContext*, ImGuiSettingsHandler*, const char* name)
+{
+    if (strcmp(name, "Data") != 0)
+        return NULL;
+    return (void*)1;
+}
+
+static void ImGui::DockSettingsHandler_ReadLine(ImGuiContext* ctx, ImGuiSettingsHandler*, void*, const char* line)
+{
+    char c = 0;
+    int x = 0, y = 0;
+    int r = 0;
+
+    // Parsing, e.g.
+    // " DockNode   ID=0x00000001 Pos=383,193 Size=201,322 Split=Y,0.506 "
+    // "   DockNode ID=0x00000002 Parent=0x00000001 "
+    // Important: this code expect currently fields in a fixed order.
+    ImGuiDockNodeSettings node;
+    line = ImStrSkipBlank(line);
+    if      (strncmp(line, "DockNode", 8) == 0)  { line = ImStrSkipBlank(line + strlen("DockNode")); }
+    else if (strncmp(line, "DockSpace", 9) == 0) { line = ImStrSkipBlank(line + strlen("DockSpace")); node.Flags |= ImGuiDockNodeFlags_DockSpace; }
+    else return;
+    if (sscanf(line, "ID=0x%08X%n",      &node.ID, &r) == 1)            { line += r; } else return;
+    if (sscanf(line, " Parent=0x%08X%n", &node.ParentNodeId, &r) == 1)  { line += r; if (node.ParentNodeId == 0) return; }
+    if (sscanf(line, " Window=0x%08X%n", &node.ParentWindowId, &r) ==1) { line += r; if (node.ParentWindowId == 0) return; }
+    if (node.ParentNodeId == 0)
+    {
+        if (sscanf(line, " Pos=%i,%i%n",  &x, &y, &r) == 2)         { line += r; node.Pos = ImVec2ih((short)x, (short)y); } else return;
+        if (sscanf(line, " Size=%i,%i%n", &x, &y, &r) == 2)         { line += r; node.Size = ImVec2ih((short)x, (short)y); } else return;
+    }
+    else
+    {
+        if (sscanf(line, " SizeRef=%i,%i%n", &x, &y, &r) == 2)      { line += r; node.SizeRef = ImVec2ih((short)x, (short)y); }
+    }
+    if (sscanf(line, " Split=%c%n", &c, &r) == 1)                   { line += r; if (c == 'X') node.SplitAxis = ImGuiAxis_X; else if (c == 'Y') node.SplitAxis = ImGuiAxis_Y; }
+    if (sscanf(line, " NoResize=%d%n", &x, &r) == 1)                { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_NoResize; }
+    if (sscanf(line, " CentralNode=%d%n", &x, &r) == 1)             { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_CentralNode; }
+    if (sscanf(line, " NoTabBar=%d%n", &x, &r) == 1)                { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_NoTabBar; }
+    if (sscanf(line, " HiddenTabBar=%d%n", &x, &r) == 1)            { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_HiddenTabBar; }
+    if (sscanf(line, " NoWindowMenuButton=%d%n", &x, &r) == 1)      { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_NoWindowMenuButton; }
+    if (sscanf(line, " NoCloseButton=%d%n", &x, &r) == 1)           { line += r; if (x != 0) node.Flags |= ImGuiDockNodeFlags_NoCloseButton; }
+    if (sscanf(line, " Selected=0x%08X%n", &node.SelectedWindowId,&r) == 1) { line += r; }
+    ImGuiDockContext* dc = ctx->DockContext;
+    if (node.ParentNodeId != 0)
+        if (ImGuiDockNodeSettings* parent_settings = DockSettingsFindNodeSettings(ctx, node.ParentNodeId))
+            node.Depth = parent_settings->Depth + 1;
+    dc->SettingsNodes.push_back(node);
+}
+
+static void DockSettingsHandler_DockNodeToSettings(ImGuiDockContext* dc, ImGuiDockNode* node, int depth)
+{
+    ImGuiDockNodeSettings node_settings;
+    IM_ASSERT(depth < (1 << (sizeof(node_settings.Depth) << 3)));
+    node_settings.ID = node->ID;
+    node_settings.ParentNodeId = node->ParentNode ? node->ParentNode->ID : 0;
+    node_settings.ParentWindowId = (node->IsDockSpace() && node->HostWindow && node->HostWindow->ParentWindow) ? node->HostWindow->ParentWindow->ID : 0;
+    node_settings.SelectedWindowId = node->SelectedTabId;
+    node_settings.SplitAxis = (signed char)(node->IsSplitNode() ? node->SplitAxis : ImGuiAxis_None);
+    node_settings.Depth = (char)depth;
+    node_settings.Flags = (node->LocalFlags & ImGuiDockNodeFlags_SavedFlagsMask_);
+    node_settings.Pos = ImVec2ih(node->Pos);
+    node_settings.Size = ImVec2ih(node->Size);
+    node_settings.SizeRef = ImVec2ih(node->SizeRef);
+    dc->SettingsNodes.push_back(node_settings);
+    if (node->ChildNodes[0])
+        DockSettingsHandler_DockNodeToSettings(dc, node->ChildNodes[0], depth + 1);
+    if (node->ChildNodes[1])
+        DockSettingsHandler_DockNodeToSettings(dc, node->ChildNodes[1], depth + 1);
+}
+
+static void ImGui::DockSettingsHandler_WriteAll(ImGuiContext* ctx, ImGuiSettingsHandler* handler, ImGuiTextBuffer* buf)
+{
+    ImGuiContext& g = *ctx;
+    ImGuiDockContext* dc = g.DockContext;
+    if (!(g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
+        return;
+
+    // Gather settings data
+    // (unlike our windows settings, because nodes are always built we can do a full rewrite of the SettingsNode buffer)
+    dc->SettingsNodes.resize(0);
+    dc->SettingsNodes.reserve(dc->Nodes.Data.Size);
+    for (int n = 0; n < dc->Nodes.Data.Size; n++)
+        if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+            if (node->IsRootNode())
+                DockSettingsHandler_DockNodeToSettings(dc, node, 0);
+
+    int max_depth = 0;
+    for (int node_n = 0; node_n < dc->SettingsNodes.Size; node_n++)
+        max_depth = ImMax((int)dc->SettingsNodes[node_n].Depth, max_depth);
+
+    // Write to text buffer
+    buf->appendf("[%s][Data]\n", handler->TypeName);
+    for (int node_n = 0; node_n < dc->SettingsNodes.Size; node_n++)
+    {
+        const int line_start_pos = buf->size(); (void)line_start_pos;
+        const ImGuiDockNodeSettings* node_settings = &dc->SettingsNodes[node_n];
+        buf->appendf("%*s%s%*s", node_settings->Depth * 2, "", (node_settings->Flags & ImGuiDockNodeFlags_DockSpace) ? "DockSpace" : "DockNode ", (max_depth - node_settings->Depth) * 2, "");  // Text align nodes to facilitate looking at .ini file
+        buf->appendf(" ID=0x%08X", node_settings->ID);
+        if (node_settings->ParentNodeId)
+        {
+            buf->appendf(" Parent=0x%08X SizeRef=%d,%d", node_settings->ParentNodeId, node_settings->SizeRef.x, node_settings->SizeRef.y);
+        }
+        else
+        {
+            if (node_settings->ParentWindowId)
+                buf->appendf(" Window=0x%08X", node_settings->ParentWindowId);
+            buf->appendf(" Pos=%d,%d Size=%d,%d", node_settings->Pos.x, node_settings->Pos.y, node_settings->Size.x, node_settings->Size.y);
+        }
+        if (node_settings->SplitAxis != ImGuiAxis_None)
+            buf->appendf(" Split=%c", (node_settings->SplitAxis == ImGuiAxis_X) ? 'X' : 'Y');
+        if (node_settings->Flags & ImGuiDockNodeFlags_NoResize)
+            buf->appendf(" NoResize=1");
+        if (node_settings->Flags & ImGuiDockNodeFlags_CentralNode)
+            buf->appendf(" CentralNode=1");
+        if (node_settings->Flags & ImGuiDockNodeFlags_NoTabBar)
+            buf->appendf(" NoTabBar=1");
+        if (node_settings->Flags & ImGuiDockNodeFlags_HiddenTabBar)
+            buf->appendf(" HiddenTabBar=1");
+        if (node_settings->Flags & ImGuiDockNodeFlags_NoWindowMenuButton)
+            buf->appendf(" NoWindowMenuButton=1");
+        if (node_settings->Flags & ImGuiDockNodeFlags_NoCloseButton)
+            buf->appendf(" NoCloseButton=1");
+        if (node_settings->SelectedWindowId)
+            buf->appendf(" Selected=0x%08X", node_settings->SelectedWindowId);
+
+#if IMGUI_DEBUG_INI_SETTINGS
+        // [DEBUG] Include comments in the .ini file to ease debugging
+        if (ImGuiDockNode* node = DockContextFindNodeByID(ctx, node_settings->ID))
+        {
+            buf->appendf("%*s", ImMax(2, (line_start_pos + 92) - buf->size()), "");     // Align everything
+            if (node->IsDockSpace() && node->HostWindow && node->HostWindow->ParentWindow)
+                buf->appendf(" ; in '%s'", node->HostWindow->ParentWindow->Name);
+            // Iterate settings so we can give info about windows that didn't exist during the session.
+            int contains_window = 0;
+            for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+                if (settings->DockId == node_settings->ID)
+                {
+                    if (contains_window++ == 0)
+                        buf->appendf(" ; contains ");
+                    buf->appendf("'%s' ", settings->GetName());
+                }
+        }
+#endif
+        buf->appendf("\n");
+    }
+    buf->appendf("\n");
+}
 
 
 //-----------------------------------------------------------------------------
@@ -9923,41 +15087,72 @@ static void SetClipboardTextFn_DefaultImpl(void*, const char* text)
 
 #endif
 
-// Win32 API IME support (for Asian languages, etc.)
-#if defined(_WIN32) && !defined(__GNUC__) && !defined(IMGUI_DISABLE_WIN32_FUNCTIONS) && !defined(IMGUI_DISABLE_WIN32_DEFAULT_IME_FUNCTIONS)
-
-#include <imm.h>
-#ifdef _MSC_VER
-#pragma comment(lib, "imm32")
-#endif
+//-----------------------------------------------------------------------------
+// [SECTION] METRICS/DEBUG WINDOW
+//-----------------------------------------------------------------------------
 
-static void ImeSetInputScreenPosFn_DefaultImpl(int x, int y)
+static void RenderViewportThumbnail(ImDrawList* draw_list, ImGuiViewportP* viewport, const ImRect& bb)
 {
-    // Notify OS Input Method Editor of text input position
-    ImGuiIO& io = ImGui::GetIO();
-    if (HWND hwnd = (HWND)io.ImeWindowHandle)
-        if (HIMC himc = ::ImmGetContext(hwnd))
-        {
-            COMPOSITIONFORM cf;
-            cf.ptCurrentPos.x = x;
-            cf.ptCurrentPos.y = y;
-            cf.dwStyle = CFS_FORCE_POSITION;
-            ::ImmSetCompositionWindow(himc, &cf);
-            ::ImmReleaseContext(hwnd, himc);
-        }
-}
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = g.CurrentWindow;
 
-#else
+    ImVec2 scale = bb.GetSize() / viewport->Size;
+    ImVec2 off = bb.Min - viewport->Pos * scale;
+    float alpha_mul = (viewport->Flags & ImGuiViewportFlags_Minimized) ? 0.30f : 1.00f;
+    window->DrawList->AddRectFilled(bb.Min, bb.Max, ImGui::GetColorU32(ImGuiCol_Border, alpha_mul * 0.40f));
+    for (int i = 0; i != g.Windows.Size; i++)
+    {
+        ImGuiWindow* thumb_window = g.Windows[i];
+        if (!thumb_window->WasActive || ((thumb_window->Flags & ImGuiWindowFlags_ChildWindow)))
+            continue;
+        if (thumb_window->SkipItems && (thumb_window->Flags & ImGuiWindowFlags_ChildWindow)) // FIXME-DOCK: Skip hidden docked windows. Identify those betters.
+            continue;
+        if (thumb_window->Viewport != viewport)
+            continue;
 
-static void ImeSetInputScreenPosFn_DefaultImpl(int, int) {}
+        ImRect thumb_r = thumb_window->Rect();
+        ImRect title_r = thumb_window->TitleBarRect();
+        ImRect thumb_r_scaled = ImRect(ImFloor(off + thumb_r.Min * scale), ImFloor(off +  thumb_r.Max * scale));
+        ImRect title_r_scaled = ImRect(ImFloor(off + title_r.Min * scale), ImFloor(off +  ImVec2(title_r.Max.x, title_r.Min.y) * scale) + ImVec2(0,5)); // Exaggerate title bar height
+        thumb_r_scaled.ClipWithFull(bb);
+        title_r_scaled.ClipWithFull(bb);
+        const bool window_is_focused = (g.NavWindow && thumb_window->RootWindowForTitleBarHighlight == g.NavWindow->RootWindowForTitleBarHighlight);
+        window->DrawList->AddRectFilled(thumb_r_scaled.Min, thumb_r_scaled.Max, ImGui::GetColorU32(ImGuiCol_WindowBg, alpha_mul));
+        window->DrawList->AddRectFilled(title_r_scaled.Min, title_r_scaled.Max, ImGui::GetColorU32(window_is_focused ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg, alpha_mul));
+        window->DrawList->AddRect(thumb_r_scaled.Min, thumb_r_scaled.Max, ImGui::GetColorU32(ImGuiCol_Border, alpha_mul));
+        if (ImGuiWindow* window_for_title = GetWindowForTitleDisplay(thumb_window))
+            window->DrawList->AddText(g.Font, g.FontSize * 1.0f, title_r_scaled.Min, ImGui::GetColorU32(ImGuiCol_Text, alpha_mul), window_for_title->Name, ImGui::FindRenderedTextEnd(window_for_title->Name));
+    }
+    draw_list->AddRect(bb.Min, bb.Max, ImGui::GetColorU32(ImGuiCol_Border, alpha_mul));
+}
 
-#endif
+void ImGui::ShowViewportThumbnails()
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = g.CurrentWindow;
 
-//-----------------------------------------------------------------------------
-// [SECTION] METRICS/DEBUG WINDOW
-//-----------------------------------------------------------------------------
+    // We don't display full monitor bounds (we could, but it often looks awkward), instead we display just enough to cover all of our viewports.
+    float SCALE = 1.0f / 8.0f;
+    ImRect bb_full;
+    //for (int n = 0; n < g.PlatformIO.Monitors.Size; n++)
+    //    bb_full.Add(GetPlatformMonitorMainRect(g.PlatformIO.Monitors[n]));
+    for (int n = 0; n < g.Viewports.Size; n++)
+        bb_full.Add(g.Viewports[n]->GetMainRect());
+    ImVec2 p = window->DC.CursorPos;
+    ImVec2 off = p - bb_full.Min * SCALE;
+    //for (int n = 0; n < g.PlatformIO.Monitors.Size; n++)
+    //    window->DrawList->AddRect(off + g.PlatformIO.Monitors[n].MainPos * SCALE, off + (g.PlatformIO.Monitors[n].MainPos + g.PlatformIO.Monitors[n].MainSize) * SCALE, ImGui::GetColorU32(ImGuiCol_Border));
+    for (int n = 0; n < g.Viewports.Size; n++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[n];
+        ImRect viewport_draw_bb(off + (viewport->Pos) * SCALE, off + (viewport->Pos + viewport->Size) * SCALE);
+        RenderViewportThumbnail(window->DrawList, viewport, viewport_draw_bb);
+    }
+    ImGui::Dummy(bb_full.GetSize() * SCALE);
+}
 
 #ifndef IMGUI_DISABLE_METRICS_WINDOW
+
 // Avoid naming collision with imgui_demo.cpp's HelpMarker() for unity builds.
 static void MetricsHelpMarker(const char* desc)
 {
@@ -9994,6 +15189,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
     static int  show_tables_rect_type = TRT_WorkRect;
     static bool show_drawcmd_mesh = true;
     static bool show_drawcmd_aabb = true;
+    static bool show_docking_nodes = false;
 
     // Basic info
     ImGuiContext& g = *GImGui;
@@ -10010,6 +15206,8 @@ void ImGui::ShowMetricsWindow(bool* p_open)
     // - NodeColumns()
     // - NodeWindow()
     // - NodeWindows()
+    // - NodeViewport()
+    // - NodeDockNode()
     // - NodeTabBar()
     // - NodeStorage()
     struct Funcs
@@ -10059,7 +15257,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
             fg_draw_list->Flags = backup_flags;
         }
 
-        static void NodeDrawList(ImGuiWindow* window, ImDrawList* draw_list, const char* label)
+        static void NodeDrawList(ImGuiWindow* window, ImGuiViewportP* viewport, ImDrawList* draw_list, const char* label)
         {
             bool node_open = ImGui::TreeNode(draw_list, "%s: '%s' %d vtx, %d indices, %d cmds", label, draw_list->_OwnerName ? draw_list->_OwnerName : "", draw_list->VtxBuffer.Size, draw_list->IdxBuffer.Size, draw_list->CmdBuffer.Size);
             if (draw_list == ImGui::GetWindowDrawList())
@@ -10070,8 +15268,8 @@ void ImGui::ShowMetricsWindow(bool* p_open)
                 return;
             }
 
-            ImDrawList* fg_draw_list = GetForegroundDrawList(window); // Render additional visuals into the top-most draw list
-            if (window && IsItemHovered())
+            ImDrawList* fg_draw_list = viewport ? GetForegroundDrawList(viewport) : NULL; // Render additional visuals into the top-most draw list
+            if (window && fg_draw_list && ImGui::IsItemHovered())
                 fg_draw_list->AddRect(window->Pos, window->Pos + window->Size, IM_COL32(255, 255, 0, 255));
             if (!node_open)
                 return;
@@ -10189,12 +15387,13 @@ void ImGui::ShowMetricsWindow(bool* p_open)
                 ImGui::TextDisabled("Note: some memory buffers have been compacted/freed.");
 
             ImGuiWindowFlags flags = window->Flags;
-            NodeDrawList(window, window->DrawList, "DrawList");
+            NodeDrawList(window, window->Viewport, window->DrawList, "DrawList");
             ImGui::BulletText("Pos: (%.1f,%.1f), Size: (%.1f,%.1f), ContentSize (%.1f,%.1f)", window->Pos.x, window->Pos.y, window->Size.x, window->Size.y, window->ContentSize.x, window->ContentSize.y);
             ImGui::BulletText("Flags: 0x%08X (%s%s%s%s%s%s%s%s%s..)", flags,
                 (flags & ImGuiWindowFlags_ChildWindow)  ? "Child " : "",      (flags & ImGuiWindowFlags_Tooltip)     ? "Tooltip "   : "",  (flags & ImGuiWindowFlags_Popup) ? "Popup " : "",
                 (flags & ImGuiWindowFlags_Modal)        ? "Modal " : "",      (flags & ImGuiWindowFlags_ChildMenu)   ? "ChildMenu " : "",  (flags & ImGuiWindowFlags_NoSavedSettings) ? "NoSavedSettings " : "",
                 (flags & ImGuiWindowFlags_NoMouseInputs)? "NoMouseInputs":"", (flags & ImGuiWindowFlags_NoNavInputs) ? "NoNavInputs" : "", (flags & ImGuiWindowFlags_AlwaysAutoResize) ? "AlwaysAutoResize" : "");
+            ImGui::BulletText("WindowClassId: 0x%08X", window->WindowClass.ClassId);
             ImGui::BulletText("Scroll: (%.2f/%.2f,%.2f/%.2f) Scrollbar:%s%s", window->Scroll.x, window->ScrollMax.x, window->Scroll.y, window->ScrollMax.y, window->ScrollbarX ? "X" : "", window->ScrollbarY ? "Y" : "");
             ImGui::BulletText("Active: %d/%d, WriteAccessed: %d, BeginOrderWithinContext: %d", window->Active, window->WasActive, window->WriteAccessed, (window->Active || window->WasActive) ? window->BeginOrderWithinContext : -1);
             ImGui::BulletText("Appearing: %d, Hidden: %d (CanSkip %d Cannot %d), SkipItems: %d", window->Appearing, window->Hidden, window->HiddenFramesCanSkipItems, window->HiddenFramesCannotSkipItems, window->SkipItems);
@@ -10204,7 +15403,13 @@ void ImGui::ShowMetricsWindow(bool* p_open)
                 ImGui::BulletText("NavRectRel[0]: (%.1f,%.1f)(%.1f,%.1f)", window->NavRectRel[0].Min.x, window->NavRectRel[0].Min.y, window->NavRectRel[0].Max.x, window->NavRectRel[0].Max.y);
             else
                 ImGui::BulletText("NavRectRel[0]: <None>");
+            ImGui::BulletText("Viewport: %d%s, ViewportId: 0x%08X, ViewportPos: (%.1f,%.1f)", window->Viewport ? window->Viewport->Idx : -1, window->ViewportOwned ? " (Owned)" : "", window->ViewportId, window->ViewportPos.x, window->ViewportPos.y);
+            ImGui::BulletText("ViewportMonitor: %d", window->Viewport ? window->Viewport->PlatformMonitor : -1);
+            ImGui::BulletText("DockId: 0x%04X, DockOrder: %d, Act: %d, Vis: %d", window->DockId, window->DockOrder, window->DockIsActive, window->DockTabIsVisible);
+            if (window->DockNode || window->DockNodeAsHost)
+                NodeDockNode(window->DockNodeAsHost ? window->DockNodeAsHost : window->DockNode, window->DockNodeAsHost ? "DockNodeAsHost" : "DockNode");
             if (window->RootWindow != window) NodeWindow(window->RootWindow, "RootWindow");
+            if (window->RootWindowDockStop != window->RootWindow) NodeWindow(window->RootWindowDockStop, "RootWindowDockStop");
             if (window->ParentWindow != NULL) NodeWindow(window->ParentWindow, "ParentWindow");
             if (window->DC.ChildWindows.Size > 0) NodeWindows(window->DC.ChildWindows, "ChildWindows");
             if (window->ColumnsStorage.Size > 0 && ImGui::TreeNode("Columns", "Columns sets (%d)", window->ColumnsStorage.Size))
@@ -10217,6 +15422,70 @@ void ImGui::ShowMetricsWindow(bool* p_open)
             ImGui::TreePop();
         }
 
+        static void NodeViewport(ImGuiViewportP* viewport)
+        {
+            ImGui::SetNextItemOpen(true, ImGuiCond_Once);
+            if (ImGui::TreeNode((void*)(intptr_t)viewport->ID, "Viewport #%d, ID: 0x%08X, Parent: 0x%08X, Window: \"%s\"", viewport->Idx, viewport->ID, viewport->ParentViewportId, viewport->Window ? viewport->Window->Name : "N/A"))
+            {
+                ImGuiWindowFlags flags = viewport->Flags;
+                ImGui::BulletText("Main Pos: (%.0f,%.0f), Size: (%.0f,%.0f)\nWorkArea Offset Left: %.0f Top: %.0f, Right: %.0f, Bottom: %.0f\nMonitor: %d, DpiScale: %.0f%%",
+                    viewport->Pos.x, viewport->Pos.y, viewport->Size.x, viewport->Size.y,
+                    viewport->WorkOffsetMin.x, viewport->WorkOffsetMin.y, viewport->WorkOffsetMax.x, viewport->WorkOffsetMax.y,
+                    viewport->PlatformMonitor, viewport->DpiScale * 100.0f);
+                if (viewport->Idx > 0) { ImGui::SameLine(); if (ImGui::SmallButton("Reset Pos")) { viewport->Pos = ImVec2(200,200); if (viewport->Window) viewport->Window->Pos = ImVec2(200,200); } }
+                ImGui::BulletText("Flags: 0x%04X =%s%s%s%s%s%s%s", viewport->Flags,
+                    (flags & ImGuiViewportFlags_CanHostOtherWindows) ? " CanHostOtherWindows" : "", (flags & ImGuiViewportFlags_NoDecoration) ? " NoDecoration" : "",
+                    (flags & ImGuiViewportFlags_NoFocusOnAppearing)  ? " NoFocusOnAppearing"  : "", (flags & ImGuiViewportFlags_NoInputs)     ? " NoInputs"     : "",
+                    (flags & ImGuiViewportFlags_NoRendererClear)     ? " NoRendererClear"     : "", (flags & ImGuiViewportFlags_Minimized)    ? " Minimized"    : "",
+                    (flags & ImGuiViewportFlags_NoAutoMerge)         ? " NoAutoMerge"         : "");
+                for (int layer_i = 0; layer_i < IM_ARRAYSIZE(viewport->DrawDataBuilder.Layers); layer_i++)
+                    for (int draw_list_i = 0; draw_list_i < viewport->DrawDataBuilder.Layers[layer_i].Size; draw_list_i++)
+                        Funcs::NodeDrawList(NULL, viewport, viewport->DrawDataBuilder.Layers[layer_i][draw_list_i], "DrawList");
+                ImGui::TreePop();
+            }
+        }
+
+        static void NodeDockNode(ImGuiDockNode* node, const char* label)
+        {
+            ImGuiContext& g = *GImGui;
+            bool open;
+            if (node->Windows.Size > 0)
+                open = ImGui::TreeNode((void*)(intptr_t)node->ID, "%s 0x%04X%s: %d windows (vis: '%s')", label, node->ID, node->IsVisible ? "" : " (hidden)", node->Windows.Size, node->VisibleWindow ? node->VisibleWindow->Name : "NULL");
+            else
+                open = ImGui::TreeNode((void*)(intptr_t)node->ID, "%s 0x%04X%s: %s split (vis: '%s')", label, node->ID, node->IsVisible ? "" : " (hidden)", (node->SplitAxis == ImGuiAxis_X) ? "horizontal" : (node->SplitAxis == ImGuiAxis_Y) ? "vertical" : "n/a", node->VisibleWindow ? node->VisibleWindow->Name : "NULL");
+            if (open)
+            {
+                IM_ASSERT(node->ChildNodes[0] == NULL || node->ChildNodes[0]->ParentNode == node);
+                IM_ASSERT(node->ChildNodes[1] == NULL || node->ChildNodes[1]->ParentNode == node);
+                ImGui::BulletText("Pos (%.0f,%.0f), Size (%.0f, %.0f) Ref (%.0f, %.0f)",
+                    node->Pos.x, node->Pos.y, node->Size.x, node->Size.y, node->SizeRef.x, node->SizeRef.y);
+                NodeWindow(node->HostWindow, "HostWindow");
+                NodeWindow(node->VisibleWindow, "VisibleWindow");
+                ImGui::BulletText("SelectedTabID: 0x%08X, LastFocusedNodeID: 0x%08X", node->SelectedTabId, node->LastFocusedNodeId);
+                ImGui::BulletText("Misc:%s%s%s%s", node->IsDockSpace() ? " IsDockSpace" : "", node->IsCentralNode() ? " IsCentralNode" : "", (g.FrameCount - node->LastFrameAlive < 2) ? " IsAlive" : "", (g.FrameCount - node->LastFrameActive < 2) ? " IsActive" : "");
+                if (ImGui::TreeNode("flags", "LocalFlags: 0x%04X SharedFlags: 0x%04X", node->LocalFlags, node->SharedFlags))
+                {
+                    ImGui::CheckboxFlags("LocalFlags: NoDocking", (ImU32*)&node->LocalFlags, ImGuiDockNodeFlags_NoDocking);
+                    ImGui::CheckboxFlags("LocalFlags: NoSplit", (ImU32*)&node->LocalFlags, ImGuiDockNodeFlags_NoSplit);
+                    ImGui::CheckboxFlags("LocalFlags: NoResize", (ImU32*)&node->LocalFlags, ImGuiDockNodeFlags_NoResize);
+                    ImGui::CheckboxFlags("LocalFlags: NoTabBar", (ImU32*)&node->LocalFlags, ImGuiDockNodeFlags_NoTabBar);
+                    ImGui::CheckboxFlags("LocalFlags: HiddenTabBar", (ImU32*)&node->LocalFlags, ImGuiDockNodeFlags_HiddenTabBar);
+                    ImGui::CheckboxFlags("LocalFlags: NoWindowMenuButton", (ImU32*)&node->LocalFlags, ImGuiDockNodeFlags_NoWindowMenuButton);
+                    ImGui::CheckboxFlags("LocalFlags: NoCloseButton", (ImU32*)&node->LocalFlags, ImGuiDockNodeFlags_NoCloseButton);
+                    ImGui::TreePop();
+                }
+                if (node->ParentNode)
+                    NodeDockNode(node->ParentNode, "ParentNode");
+                if (node->ChildNodes[0])
+                    NodeDockNode(node->ChildNodes[0], "Child[0]");
+                if (node->ChildNodes[1])
+                    NodeDockNode(node->ChildNodes[1], "Child[1]");
+                if (node->TabBar)
+                    NodeTabBar(node->TabBar);
+                ImGui::TreePop();
+            }
+        }
+
         static void NodeTabBar(ImGuiTabBar* tab_bar)
         {
             // Standalone tab bars (not associated to docking/windows functionality) currently hold no discernible strings.
@@ -10224,6 +15493,13 @@ void ImGui::ShowMetricsWindow(bool* p_open)
             char* p = buf;
             const char* buf_end = buf + IM_ARRAYSIZE(buf);
             p += ImFormatString(p, buf_end - p, "TabBar (%d tabs)%s", tab_bar->Tabs.Size, (tab_bar->PrevFrameVisible < ImGui::GetFrameCount() - 2) ? " *Inactive*" : "");
+            if (tab_bar->Flags & ImGuiTabBarFlags_DockNode)
+            {
+                p += ImFormatString(p, buf_end - p, "  { ");
+                for (int tab_n = 0; tab_n < ImMin(tab_bar->Tabs.Size, 3); tab_n++)
+                    p += ImFormatString(p, buf_end - p, "%s'%s'", tab_n > 0 ? ", " : "", tab_bar->Tabs[tab_n].Window->Name);
+                p += ImFormatString(p, buf_end - p, (tab_bar->Tabs.Size > 3) ? " ... }" : " } ");
+            }
             if (ImGui::TreeNode(tab_bar, "%s", buf))
             {
                 for (int tab_n = 0; tab_n < tab_bar->Tabs.Size; tab_n++)
@@ -10232,7 +15508,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
                     ImGui::PushID(tab);
                     if (ImGui::SmallButton("<")) { TabBarQueueChangeTabOrder(tab_bar, tab, -1); } ImGui::SameLine(0, 2);
                     if (ImGui::SmallButton(">")) { TabBarQueueChangeTabOrder(tab_bar, tab, +1); } ImGui::SameLine();
-                    ImGui::Text("%02d%c Tab 0x%08X '%s'", tab_n, (tab->ID == tab_bar->SelectedTabId) ? '*' : ' ', tab->ID, (tab->NameOffset != -1) ? tab_bar->GetTabName(tab) : "");
+                    ImGui::Text("%02d%c Tab 0x%08X '%s'", tab_n, (tab->ID == tab_bar->SelectedTabId) ? '*' : ' ', tab->ID, (tab->Window || tab->NameOffset != -1) ? tab_bar->GetTabName(tab) : "");
                     ImGui::PopID();
                 }
                 ImGui::TreePop();
@@ -10286,10 +15562,28 @@ void ImGui::ShowMetricsWindow(bool* p_open)
     // Contents
     Funcs::NodeWindows(g.Windows, "Windows");
     //Funcs::NodeWindows(g.WindowsFocusOrder, "WindowsFocusOrder");
-    if (ImGui::TreeNode("DrawLists", "Active DrawLists (%d)", g.DrawDataBuilder.Layers[0].Size))
+    if (ImGui::TreeNode("Viewport", "Viewports (%d)", g.Viewports.Size))
     {
-        for (int i = 0; i < g.DrawDataBuilder.Layers[0].Size; i++)
-            Funcs::NodeDrawList(NULL, g.DrawDataBuilder.Layers[0][i], "DrawList");
+        ImGui::Indent(ImGui::GetTreeNodeToLabelSpacing());
+        ImGui::ShowViewportThumbnails();
+        ImGui::Unindent(ImGui::GetTreeNodeToLabelSpacing());
+        bool open = ImGui::TreeNode("Monitors", "Monitors (%d)", g.PlatformIO.Monitors.Size);
+        ImGui::SameLine();
+        MetricsHelpMarker("Dear ImGui uses monitor data:\n- to query DPI settings on a per monitor basis\n- to position popup/tooltips so they don't straddle monitors.");
+        if (open)
+        {
+            for (int i = 0; i < g.PlatformIO.Monitors.Size; i++)
+            {
+                const ImGuiPlatformMonitor& mon = g.PlatformIO.Monitors[i];
+                ImGui::BulletText("Monitor #%d: DPI %.0f%%\n MainMin (%.0f,%.0f), MainMax (%.0f,%.0f), MainSize (%.0f,%.0f)\n WorkMin (%.0f,%.0f), WorkMax (%.0f,%.0f), WorkSize (%.0f,%.0f)",
+                    i, mon.DpiScale * 100.0f,
+                    mon.MainPos.x, mon.MainPos.y, mon.MainPos.x + mon.MainSize.x, mon.MainPos.y + mon.MainSize.y, mon.MainSize.x, mon.MainSize.y,
+                    mon.WorkPos.x, mon.WorkPos.y, mon.WorkPos.x + mon.WorkSize.x, mon.WorkPos.y + mon.WorkSize.y, mon.WorkSize.x, mon.WorkSize.y);
+            }
+            ImGui::TreePop();
+        }
+        for (int i = 0; i < g.Viewports.Size; i++)
+            Funcs::NodeViewport(g.Viewports[i]);
         ImGui::TreePop();
     }
 
@@ -10329,6 +15623,50 @@ void ImGui::ShowMetricsWindow(bool* p_open)
 #ifdef IMGUI_HAS_DOCK
     if (ImGui::TreeNode("Docking"))
     {
+        ImGuiDockContext* dc = g.DockContext;
+        ImGui::Checkbox("Ctrl shows window dock info", &show_docking_nodes);
+
+        if (ImGui::TreeNode("Dock nodes"))
+        {
+            if (ImGui::SmallButton("Clear settings")) { DockContextClearNodes(&g, 0, true); }
+            ImGui::SameLine();
+            if (ImGui::SmallButton("Rebuild all")) { dc->WantFullRebuild = true; }
+            for (int n = 0; n < dc->Nodes.Data.Size; n++)
+                if (ImGuiDockNode* node = (ImGuiDockNode*)dc->Nodes.Data[n].val_p)
+                    if (node->IsRootNode())
+                        Funcs::NodeDockNode(node, "Node");
+            ImGui::TreePop();
+        }
+
+        if (ImGui::TreeNode("Settings"))
+        {
+            if (ImGui::SmallButton("Refresh"))
+                SaveIniSettingsToMemory();
+            ImGui::SameLine();
+            if (ImGui::SmallButton("Save to disk"))
+                SaveIniSettingsToDisk(g.IO.IniFilename);
+            ImGui::Separator();
+            ImGui::Text("Docked Windows:");
+            for (ImGuiWindowSettings* settings = g.SettingsWindows.begin(); settings != NULL; settings = g.SettingsWindows.next_chunk(settings))
+                if (settings->DockId != 0)
+                    ImGui::BulletText("Window '%s' -> DockId %08X", settings->GetName(), settings->DockId);
+            ImGui::Separator();
+            ImGui::Text("Dock Nodes:");
+            for (int n = 0; n < dc->SettingsNodes.Size; n++)
+            {
+                ImGuiDockNodeSettings* settings = &dc->SettingsNodes[n];
+                const char* selected_tab_name = NULL;
+                if (settings->SelectedWindowId)
+                {
+                    if (ImGuiWindow* window = FindWindowByID(settings->SelectedWindowId))
+                        selected_tab_name = window->Name;
+                    else if (ImGuiWindowSettings* window_settings = FindWindowSettings(settings->SelectedWindowId))
+                        selected_tab_name = window_settings->GetName();
+                }
+                ImGui::BulletText("Node %08X, Parent %08X, SelectedTab %08X ('%s')", settings->ID, settings->ParentNodeId, settings->SelectedWindowId, selected_tab_name ? selected_tab_name : settings->SelectedWindowId ? "N/A" : "");
+            }
+            ImGui::TreePop();
+        }
         ImGui::TreePop();
     }
 #endif // #define IMGUI_HAS_DOCK
@@ -10339,6 +15677,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
         const char* input_source_names[] = { "None", "Mouse", "Nav", "NavKeyboard", "NavGamepad" }; IM_ASSERT(IM_ARRAYSIZE(input_source_names) == ImGuiInputSource_COUNT);
         ImGui::Text("HoveredWindow: '%s'", g.HoveredWindow ? g.HoveredWindow->Name : "NULL");
         ImGui::Text("HoveredRootWindow: '%s'", g.HoveredRootWindow ? g.HoveredRootWindow->Name : "NULL");
+        ImGui::Text("HoveredWindowUnderMovingWindow: '%s'", g.HoveredWindowUnderMovingWindow ? g.HoveredWindowUnderMovingWindow->Name : "NULL");
         ImGui::Text("HoveredId: 0x%08X/0x%08X (%.2f sec), AllowOverlap: %d", g.HoveredId, g.HoveredIdPreviousFrame, g.HoveredIdTimer, g.HoveredIdAllowOverlap); // Data is "in-flight" so depending on when the Metrics window is called we may see current frame information or not
         ImGui::Text("ActiveId: 0x%08X/0x%08X (%.2f sec), AllowOverlap: %d, Source: %s", g.ActiveId, g.ActiveIdPreviousFrame, g.ActiveIdTimer, g.ActiveIdAllowOverlap, input_source_names[g.ActiveIdSource]);
         ImGui::Text("ActiveIdWindow: '%s'", g.ActiveIdWindow ? g.ActiveIdWindow->Name : "NULL");
@@ -10351,6 +15690,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
         ImGui::Text("NavDisableHighlight: %d, NavDisableMouseHover: %d", g.NavDisableHighlight, g.NavDisableMouseHover);
         ImGui::Text("NavWindowingTarget: '%s'", g.NavWindowingTarget ? g.NavWindowingTarget->Name : "NULL");
         ImGui::Text("DragDrop: %d, SourceId = 0x%08X, Payload \"%s\" (%d bytes)", g.DragDropActive, g.DragDropPayload.SourceId, g.DragDropPayload.DataType, g.DragDropPayload.DataSize);
+        ImGui::Text("MouseViewport: 0x%08X (UserHovered 0x%08X, LastHovered 0x%08X)", g.MouseViewport->ID, g.IO.MouseHoveredViewport, g.MouseLastHoveredViewport ? g.MouseLastHoveredViewport->ID : 0);
         ImGui::TreePop();
     }
 
@@ -10394,6 +15734,26 @@ void ImGui::ShowMetricsWindow(bool* p_open)
     // Overlay: Display Docking info
     if (show_docking_nodes && g.IO.KeyCtrl)
     {
+        for (int n = 0; n < g.DockContext->Nodes.Data.Size; n++)
+            if (ImGuiDockNode* node = (ImGuiDockNode*)g.DockContext->Nodes.Data[n].val_p)
+            {
+                ImGuiDockNode* root_node = DockNodeGetRootNode(node);
+                if (ImGuiDockNode* hovered_node = DockNodeTreeFindNodeByPos(root_node, g.IO.MousePos))
+                    if (hovered_node != node)
+                        continue;
+                char buf[64] = "";
+                char* p = buf;
+                ImDrawList* overlay_draw_list = node->HostWindow ? GetForegroundDrawList(node->HostWindow) : GetForegroundDrawList((ImGuiViewportP*)GetMainViewport());
+                p += ImFormatString(p, buf + IM_ARRAYSIZE(buf) - p, "DockId: %X%s\n", node->ID, node->IsCentralNode() ? " *CentralNode*" : "");
+                p += ImFormatString(p, buf + IM_ARRAYSIZE(buf) - p, "WindowClass: %08X\n", node->WindowClass.ClassId);
+                p += ImFormatString(p, buf + IM_ARRAYSIZE(buf) - p, "Size: (%.0f, %.0f)\n", node->Size.x, node->Size.y);
+                p += ImFormatString(p, buf + IM_ARRAYSIZE(buf) - p, "SizeRef: (%.0f, %.0f)\n", node->SizeRef.x, node->SizeRef.y);
+                int depth = DockNodeGetDepth(node);
+                overlay_draw_list->AddRect(node->Pos + ImVec2(3, 3) * (float)depth, node->Pos + node->Size - ImVec2(3, 3) * (float)depth, IM_COL32(200, 100, 100, 255));
+                ImVec2 pos = node->Pos + ImVec2(3, 3) * (float)depth;
+                overlay_draw_list->AddRectFilled(pos - ImVec2(1, 1), pos + CalcTextSize(buf) + ImVec2(1, 1), IM_COL32(200, 100, 100, 255));
+                overlay_draw_list->AddText(NULL, 0.0f, pos, IM_COL32(255, 255, 255, 255), buf);
+            }
     }
 #endif // #define IMGUI_HAS_DOCK
 
diff --git a/imgui/imgui.h b/imgui/imgui.h
index 92c56740..c939a529 100644
--- a/imgui/imgui.h
+++ b/imgui/imgui.h
@@ -1,4 +1,4 @@
-// dear imgui, v1.76
+// dear imgui, v1.77 WIP
 // (headers)
 
 // Help:
@@ -27,11 +27,12 @@ Index of this file:
 // ImVector<>
 // ImGuiStyle
 // ImGuiIO
-// Misc data structures (ImGuiInputTextCallbackData, ImGuiSizeCallbackData, ImGuiPayload)
+// Misc data structures (ImGuiInputTextCallbackData, ImGuiSizeCallbackData, ImGuiWindowClass, ImGuiPayload)
 // Obsolete functions
 // Helpers (ImGuiOnceUponAFrame, ImGuiTextFilter, ImGuiTextBuffer, ImGuiStorage, ImGuiListClipper, ImColor)
 // Draw List API (ImDrawCallback, ImDrawCmd, ImDrawIdx, ImDrawVert, ImDrawChannel, ImDrawListSplitter, ImDrawListFlags, ImDrawList, ImDrawData)
 // Font API (ImFontConfig, ImFontGlyph, ImFontGlyphRangesBuilder, ImFontAtlasFlags, ImFontAtlas, ImFont)
+// Platform interface for multi-viewport support (ImGuiPlatformIO, ImGuiPlatformMonitor, ImGuiViewportFlags, ImGuiViewport)
 
 */
 
@@ -59,9 +60,11 @@ Index of this file:
 
 // Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals. Work in progress versions typically starts at XYY99 then bounce up to XYY00, XYY01 etc. when release tagging happens)
-#define IMGUI_VERSION               "1.76"
-#define IMGUI_VERSION_NUM           17600
+#define IMGUI_VERSION               "1.77 WIP"
+#define IMGUI_VERSION_NUM           17601
 #define IMGUI_CHECKVERSION()        ImGui::DebugCheckVersionAndDataLayout(IMGUI_VERSION, sizeof(ImGuiIO), sizeof(ImGuiStyle), sizeof(ImVec2), sizeof(ImVec4), sizeof(ImDrawVert), sizeof(ImDrawIdx))
+#define IMGUI_HAS_VIEWPORT          1 // Viewport WIP branch
+#define IMGUI_HAS_DOCK              1 // Docking WIP branch
 
 // Define attributes of all API symbols declarations (e.g. for DLL under Windows)
 // IMGUI_API is used for core imgui functions, IMGUI_IMPL_API is used for the default bindings files (imgui_impl_xxx.h)
@@ -130,11 +133,15 @@ struct ImGuiInputTextCallbackData;  // Shared state of InputText() when using cu
 struct ImGuiListClipper;            // Helper to manually clip large list of items
 struct ImGuiOnceUponAFrame;         // Helper for running a block of code not more than once a frame, used by IMGUI_ONCE_UPON_A_FRAME macro
 struct ImGuiPayload;                // User data payload for drag and drop operations
+struct ImGuiPlatformIO;             // Multi-viewport support: interface for Platform/Renderer back-ends + viewports to render
+struct ImGuiPlatformMonitor;        // Multi-viewport support: user-provided bounds for each connected monitor/display. Used when positioning popups and tooltips to avoid them straddling monitors
 struct ImGuiSizeCallbackData;       // Callback data when using SetNextWindowSizeConstraints() (rare/advanced use)
 struct ImGuiStorage;                // Helper for key->value storage
 struct ImGuiStyle;                  // Runtime data for styling/colors
 struct ImGuiTextBuffer;             // Helper to hold and append into a text buffer (~string builder)
 struct ImGuiTextFilter;             // Helper to parse and apply text filters (e.g. "aaaaa[,bbbbb][,ccccc]")
+struct ImGuiViewport;               // Viewport (generally ~1 per window to output to at the OS level. Need per-platform support to use multiple viewports)
+struct ImGuiWindowClass;            // Window class (rare/advanced uses: provide hints to the platform back-end via altered viewport flags and parent/child info)
 
 // Enums/Flags (declared as int for compatibility with old C++, to allow using as flags and to not pollute the top of this file)
 // - Tip: Use your programming IDE navigation facilities on the names in the _central column_ below to find the actual flags/enum lists!
@@ -156,6 +163,7 @@ typedef int ImGuiBackendFlags;      // -> enum ImGuiBackendFlags_    // Flags: f
 typedef int ImGuiColorEditFlags;    // -> enum ImGuiColorEditFlags_  // Flags: for ColorEdit4(), ColorPicker4() etc.
 typedef int ImGuiConfigFlags;       // -> enum ImGuiConfigFlags_     // Flags: for io.ConfigFlags
 typedef int ImGuiComboFlags;        // -> enum ImGuiComboFlags_      // Flags: for BeginCombo()
+typedef int ImGuiDockNodeFlags;     // -> enum ImGuiDockNodeFlags_   // Flags: for DockSpace()
 typedef int ImGuiDragDropFlags;     // -> enum ImGuiDragDropFlags_   // Flags: for BeginDragDropSource(), AcceptDragDropPayload()
 typedef int ImGuiFocusedFlags;      // -> enum ImGuiFocusedFlags_    // Flags: for IsWindowFocused()
 typedef int ImGuiHoveredFlags;      // -> enum ImGuiHoveredFlags_    // Flags: for IsItemHovered(), IsWindowHovered() etc.
@@ -165,6 +173,7 @@ typedef int ImGuiSelectableFlags;   // -> enum ImGuiSelectableFlags_ // Flags: f
 typedef int ImGuiTabBarFlags;       // -> enum ImGuiTabBarFlags_     // Flags: for BeginTabBar()
 typedef int ImGuiTabItemFlags;      // -> enum ImGuiTabItemFlags_    // Flags: for BeginTabItem()
 typedef int ImGuiTreeNodeFlags;     // -> enum ImGuiTreeNodeFlags_   // Flags: for TreeNode(), TreeNodeEx(), CollapsingHeader()
+typedef int ImGuiViewportFlags;     // -> enum ImGuiViewportFlags_   // Flags: for ImGuiViewport
 typedef int ImGuiWindowFlags;       // -> enum ImGuiWindowFlags_     // Flags: for Begin(), BeginChild()
 
 // Other types
@@ -296,6 +305,8 @@ namespace ImGui
     IMGUI_API bool          IsWindowFocused(ImGuiFocusedFlags flags=0); // is current window focused? or its root/child, depending on flags. see flags for options.
     IMGUI_API bool          IsWindowHovered(ImGuiHoveredFlags flags=0); // is current window hovered (and typically: not blocked by a popup/modal)? see flags for options. NB: If you are trying to check whether your mouse should be dispatched to imgui or to your app, you should use the 'io.WantCaptureMouse' boolean for that! Please read the FAQ!
     IMGUI_API ImDrawList*   GetWindowDrawList();                        // get draw list associated to the current window, to append your own drawing primitives
+    IMGUI_API float         GetWindowDpiScale();                        // get DPI scale currently associated to the current window's viewport.
+    IMGUI_API ImGuiViewport*GetWindowViewport();                        // get viewport currently associated to the current window.
     IMGUI_API ImVec2        GetWindowPos();                             // get current window position in screen space (useful if you want to do your own drawing via the DrawList API)
     IMGUI_API ImVec2        GetWindowSize();                            // get current window size
     IMGUI_API float         GetWindowWidth();                           // get current window width (shortcut for GetWindowSize().x)
@@ -309,6 +320,7 @@ namespace ImGui
     IMGUI_API void          SetNextWindowCollapsed(bool collapsed, ImGuiCond cond = 0);                 // set next window collapsed state. call before Begin()
     IMGUI_API void          SetNextWindowFocus();                                                       // set next window to be focused / top-most. call before Begin()
     IMGUI_API void          SetNextWindowBgAlpha(float alpha);                                          // set next window background color alpha. helper to easily override the Alpha component of ImGuiCol_WindowBg/ChildBg/PopupBg. you may also use ImGuiWindowFlags_NoBackground.
+    IMGUI_API void          SetNextWindowViewport(ImGuiID viewport_id);                                 // set next window viewport
     IMGUI_API void          SetWindowPos(const ImVec2& pos, ImGuiCond cond = 0);                        // (not recommended) set current window position - call within Begin()/End(). prefer using SetNextWindowPos(), as this may incur tearing and side-effects.
     IMGUI_API void          SetWindowSize(const ImVec2& size, ImGuiCond cond = 0);                      // (not recommended) set current window size - call within Begin()/End(). set to ImVec2(0,0) to force an auto-fit. prefer using SetNextWindowSize(), as this may incur tearing and minor side-effects.
     IMGUI_API void          SetWindowCollapsed(bool collapsed, ImGuiCond cond = 0);                     // (not recommended) set current window collapsed state. prefer using SetNextWindowCollapsed().
@@ -391,8 +403,8 @@ namespace ImGui
     IMGUI_API void          SetCursorPosX(float local_x);                                   //    GetWindowPos() + GetCursorPos() == GetCursorScreenPos() etc.)
     IMGUI_API void          SetCursorPosY(float local_y);                                   //
     IMGUI_API ImVec2        GetCursorStartPos();                                            // initial cursor position in window coordinates
-    IMGUI_API ImVec2        GetCursorScreenPos();                                           // cursor position in absolute screen coordinates [0..io.DisplaySize] (useful to work with ImDrawList API)
-    IMGUI_API void          SetCursorScreenPos(const ImVec2& pos);                          // cursor position in absolute screen coordinates [0..io.DisplaySize]
+    IMGUI_API ImVec2        GetCursorScreenPos();                                           // cursor position in absolute screen coordinates (0..io.DisplaySize) or natural OS coordinates when using multiple viewport. Useful to work with ImDrawList API.
+    IMGUI_API void          SetCursorScreenPos(const ImVec2& pos);                          // cursor position in absolute screen coordinates (0..io.DisplaySize) or natural OS coordinates when using multiple viewport.
     IMGUI_API void          AlignTextToFramePadding();                                      // vertically align upcoming text baseline to FramePadding.y so that it will align properly to regularly framed items (call if you have text on a line before a framed item)
     IMGUI_API float         GetTextLineHeight();                                            // ~ FontSize
     IMGUI_API float         GetTextLineHeightWithSpacing();                                 // ~ FontSize + style.ItemSpacing.y (distance in pixels between 2 consecutive lines of text)
@@ -624,12 +636,28 @@ namespace ImGui
     IMGUI_API int           GetColumnsCount();
 
     // Tab Bars, Tabs
+    // Note: Tabs are automatically created by the docking system. Use this to create tab bars/tabs yourself without docking being involved.
     IMGUI_API bool          BeginTabBar(const char* str_id, ImGuiTabBarFlags flags = 0);        // create and append into a TabBar
     IMGUI_API void          EndTabBar();                                                        // only call EndTabBar() if BeginTabBar() returns true!
     IMGUI_API bool          BeginTabItem(const char* label, bool* p_open = NULL, ImGuiTabItemFlags flags = 0);// create a Tab. Returns true if the Tab is selected.
     IMGUI_API void          EndTabItem();                                                       // only call EndTabItem() if BeginTabItem() returns true!
     IMGUI_API void          SetTabItemClosed(const char* tab_or_docked_window_label);           // notify TabBar or Docking system of a closed tab/window ahead (useful to reduce visual flicker on reorderable tab bars). For tab-bar: call after BeginTabBar() and before Tab submissions. Otherwise call with a window name.
 
+    // Docking
+    // [BETA API] Enable with io.ConfigFlags |= ImGuiConfigFlags_DockingEnable.
+    // Note: You can use most Docking facilities without calling any API. You DO NOT need to call DockSpace() to use Docking!
+    // - To dock windows: if io.ConfigDockingWithShift == false (default) drag window from their title bar.
+    // - To dock windows: if io.ConfigDockingWithShift == true: hold SHIFT anywhere while moving windows.
+    // About DockSpace:
+    // - Use DockSpace() to create an explicit dock node _within_ an existing window. See Docking demo for details.
+    // - DockSpace() needs to be submitted _before_ any window they can host. If you use a dockspace, submit it early in your app.
+    IMGUI_API void          DockSpace(ImGuiID id, const ImVec2& size = ImVec2(0, 0), ImGuiDockNodeFlags flags = 0, const ImGuiWindowClass* window_class = NULL);
+    IMGUI_API ImGuiID       DockSpaceOverViewport(ImGuiViewport* viewport = NULL, ImGuiDockNodeFlags flags = 0, const ImGuiWindowClass* window_class = NULL);
+    IMGUI_API void          SetNextWindowDockID(ImGuiID dock_id, ImGuiCond cond = 0);           // set next window dock id (FIXME-DOCK)
+    IMGUI_API void          SetNextWindowClass(const ImGuiWindowClass* window_class);           // set next window class (rare/advanced uses: provide hints to the platform back-end via altered viewport flags and parent/child info)
+    IMGUI_API ImGuiID       GetWindowDockID();
+    IMGUI_API bool          IsWindowDocked();                                                   // is current window docked into another window?
+
     // Logging/Capture
     // - All text output from the interface can be captured into tty/file/clipboard. By default, tree nodes are automatically opened during logging.
     IMGUI_API void          LogToTTY(int auto_open_depth = -1);                                 // start logging to tty (stdout)
@@ -684,8 +712,10 @@ namespace ImGui
     IMGUI_API bool          IsRectVisible(const ImVec2& rect_min, const ImVec2& rect_max);      // test if rectangle (in screen space) is visible / not clipped. to perform coarse clipping on user's side.
     IMGUI_API double        GetTime();                                                          // get global imgui time. incremented by io.DeltaTime every frame.
     IMGUI_API int           GetFrameCount();                                                    // get global imgui frame count. incremented by 1 every frame.
-    IMGUI_API ImDrawList*   GetBackgroundDrawList();                                            // this draw list will be the first rendering one. Useful to quickly draw shapes/text behind dear imgui contents.
-    IMGUI_API ImDrawList*   GetForegroundDrawList();                                            // this draw list will be the last rendered one. Useful to quickly draw shapes/text over dear imgui contents.
+    IMGUI_API ImDrawList*   GetBackgroundDrawList();                                            // get background draw list for the viewport associated to the current window. this draw list will be the first rendering one. Useful to quickly draw shapes/text behind dear imgui contents.
+    IMGUI_API ImDrawList*   GetForegroundDrawList();                                            // get foreground draw list for the viewport associated to the current window. this draw list will be the last rendered one. Useful to quickly draw shapes/text over dear imgui contents.
+    IMGUI_API ImDrawList*   GetBackgroundDrawList(ImGuiViewport* viewport);                     // get background draw list for the given viewport. this draw list will be the first rendering one. Useful to quickly draw shapes/text behind dear imgui contents.
+    IMGUI_API ImDrawList*   GetForegroundDrawList(ImGuiViewport* viewport);                     // get foreground draw list for the given viewport. this draw list will be the last rendered one. Useful to quickly draw shapes/text over dear imgui contents.
     IMGUI_API ImDrawListSharedData* GetDrawListSharedData();                                    // you may use this when creating your own ImDrawList instances.
     IMGUI_API const char*   GetStyleColorName(ImGuiCol idx);                                    // get a string corresponding to the enum value (for display, saving, etc.).
     IMGUI_API void          SetStateStorage(ImGuiStorage* storage);                             // replace current window storage with our own (if you want to manipulate it yourself, typically clear subsection of it)
@@ -704,7 +734,7 @@ namespace ImGui
     IMGUI_API void          ColorConvertHSVtoRGB(float h, float s, float v, float& out_r, float& out_g, float& out_b);
 
     // Inputs Utilities: Keyboard
-    // - For 'int user_key_index' you can use your own indices/enums according to how your backend/engine stored them in io.KeysDown[].
+    // - For 'int user_key_index' you can use your own indices/enums according to how your back-end/engine stored them in io.KeysDown[].
     // - We don't know the meaning of those value. You can use GetKeyIndex() to map a ImGuiKey_ value into the user index.
     IMGUI_API int           GetKeyIndex(ImGuiKey imgui_key);                                    // map ImGuiKey_* values into user's key index. == io.KeyMap[key]
     IMGUI_API bool          IsKeyDown(int user_key_index);                                      // is key being held. == io.KeysDown[user_key_index].
@@ -756,6 +786,17 @@ namespace ImGui
     IMGUI_API void*         MemAlloc(size_t size);
     IMGUI_API void          MemFree(void* ptr);
 
+    // (Optional) Platform/OS interface for multi-viewport support
+    // Read comments around the ImGuiPlatformIO structure for more details.
+    // Note: You may use GetWindowViewport() to get the current viewport of the current window.
+    IMGUI_API ImGuiPlatformIO&  GetPlatformIO();                                                // platform/renderer functions, for back-end to setup + viewports list.
+    IMGUI_API ImGuiViewport*    GetMainViewport();                                              // main viewport. same as GetPlatformIO().MainViewport == GetPlatformIO().Viewports[0].
+    IMGUI_API void              UpdatePlatformWindows();                                        // call in main loop. will call CreateWindow/ResizeWindow/etc. platform functions for each secondary viewport, and DestroyWindow for each inactive viewport.
+    IMGUI_API void              RenderPlatformWindowsDefault(void* platform_render_arg = NULL, void* renderer_render_arg = NULL); // call in main loop. will call RenderWindow/SwapBuffers platform functions for each secondary viewport which doesn't have the ImGuiViewportFlags_Minimized flag set. May be reimplemented by user for custom rendering needs.
+    IMGUI_API void              DestroyPlatformWindows();                                       // call DestroyWindow platform functions for all viewports. call from back-end Shutdown() if you need to close platform windows before imgui shutdown. otherwise will be called by DestroyContext().
+    IMGUI_API ImGuiViewport*    FindViewportByID(ImGuiID id);                                   // this is a helper for back-ends.
+    IMGUI_API ImGuiViewport*    FindViewportByPlatformHandle(void* platform_handle);            // this is a helper for back-ends. the type platform_handle is decided by the back-end (e.g. HWND, MyWindow*, GLFWwindow* etc.)
+
 } // namespace ImGui
 
 //-----------------------------------------------------------------------------
@@ -771,7 +812,7 @@ enum ImGuiWindowFlags_
     ImGuiWindowFlags_NoMove                 = 1 << 2,   // Disable user moving the window
     ImGuiWindowFlags_NoScrollbar            = 1 << 3,   // Disable scrollbars (window can still scroll with mouse or programmatically)
     ImGuiWindowFlags_NoScrollWithMouse      = 1 << 4,   // Disable user vertically scrolling with mouse wheel. On child window, mouse wheel will be forwarded to the parent unless NoScrollbar is also set.
-    ImGuiWindowFlags_NoCollapse             = 1 << 5,   // Disable user collapsing window by double-clicking on it
+    ImGuiWindowFlags_NoCollapse             = 1 << 5,   // Disable user collapsing window by double-clicking on it. Also referred to as "window menu button" within a docking node.
     ImGuiWindowFlags_AlwaysAutoResize       = 1 << 6,   // Resize every window to its content every frame
     ImGuiWindowFlags_NoBackground           = 1 << 7,   // Disable drawing background color (WindowBg, etc.) and outside border. Similar as using SetNextWindowBgAlpha(0.0f).
     ImGuiWindowFlags_NoSavedSettings        = 1 << 8,   // Never load/save settings in .ini file
@@ -786,6 +827,8 @@ enum ImGuiWindowFlags_
     ImGuiWindowFlags_NoNavInputs            = 1 << 18,  // No gamepad/keyboard navigation within the window
     ImGuiWindowFlags_NoNavFocus             = 1 << 19,  // No focusing toward this window with gamepad/keyboard navigation (e.g. skipped by CTRL+TAB)
     ImGuiWindowFlags_UnsavedDocument        = 1 << 20,  // Append '*' to title without affecting the ID, as a convenience to avoid using the ### operator. When used in a tab/docking context, tab is selected on closure and closure is deferred by one frame to allow code to cancel the closure (with a confirmation popup, etc.) without flicker.
+    ImGuiWindowFlags_NoDocking              = 1 << 21,  // Disable docking of this window
+
     ImGuiWindowFlags_NoNav                  = ImGuiWindowFlags_NoNavInputs | ImGuiWindowFlags_NoNavFocus,
     ImGuiWindowFlags_NoDecoration           = ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoCollapse,
     ImGuiWindowFlags_NoInputs               = ImGuiWindowFlags_NoMouseInputs | ImGuiWindowFlags_NoNavInputs | ImGuiWindowFlags_NoNavFocus,
@@ -796,7 +839,8 @@ enum ImGuiWindowFlags_
     ImGuiWindowFlags_Tooltip                = 1 << 25,  // Don't use! For internal use by BeginTooltip()
     ImGuiWindowFlags_Popup                  = 1 << 26,  // Don't use! For internal use by BeginPopup()
     ImGuiWindowFlags_Modal                  = 1 << 27,  // Don't use! For internal use by BeginPopupModal()
-    ImGuiWindowFlags_ChildMenu              = 1 << 28   // Don't use! For internal use by BeginMenu()
+    ImGuiWindowFlags_ChildMenu              = 1 << 28,  // Don't use! For internal use by BeginMenu()
+    ImGuiWindowFlags_DockNodeHost           = 1 << 29   // Don't use! For internal use by Begin()/NewFrame()
 
     // [Obsolete]
     //ImGuiWindowFlags_ShowBorders          = 1 << 7,   // --> Set style.FrameBorderSize=1.0f or style.WindowBorderSize=1.0f to enable borders around items or windows.
@@ -932,6 +976,21 @@ enum ImGuiHoveredFlags_
     ImGuiHoveredFlags_RootAndChildWindows           = ImGuiHoveredFlags_RootWindow | ImGuiHoveredFlags_ChildWindows
 };
 
+// Flags for ImGui::DockSpace(), shared/inherited by child nodes.
+// (Some flags can be applied to individual nodes directly)
+// FIXME-DOCK: Also see ImGuiDockNodeFlagsPrivate_ which may involve using the WIP and internal DockBuilder api.
+enum ImGuiDockNodeFlags_
+{
+    ImGuiDockNodeFlags_None                         = 0,
+    ImGuiDockNodeFlags_KeepAliveOnly                = 1 << 0,   // Shared       // Don't display the dockspace node but keep it alive. Windows docked into this dockspace node won't be undocked.
+    //ImGuiDockNodeFlags_NoCentralNode              = 1 << 1,   // Shared       // Disable Central Node (the node which can stay empty)
+    ImGuiDockNodeFlags_NoDockingInCentralNode       = 1 << 2,   // Shared       // Disable docking inside the Central Node, which will be always kept empty.
+    ImGuiDockNodeFlags_PassthruCentralNode          = 1 << 3,   // Shared       // Enable passthru dockspace: 1) DockSpace() will render a ImGuiCol_WindowBg background covering everything excepted the Central Node when empty. Meaning the host window should probably use SetNextWindowBgAlpha(0.0f) prior to Begin() when using this. 2) When Central Node is empty: let inputs pass-through + won't display a DockingEmptyBg background. See demo for details.
+    ImGuiDockNodeFlags_NoSplit                      = 1 << 4,   // Shared/Local // Disable splitting the node into smaller nodes. Useful e.g. when embedding dockspaces into a main root one (the root one may have splitting disabled to reduce confusion). Note: when turned off, existing splits will be preserved.
+    ImGuiDockNodeFlags_NoResize                     = 1 << 5,   // Shared/Local // Disable resizing node using the splitter/separators. Useful with programatically setup dockspaces.
+    ImGuiDockNodeFlags_AutoHideTabBar               = 1 << 6    // Shared/Local // Tab bar will automatically hide when there is a single window in the dock node.
+};
+
 // Flags for ImGui::BeginDragDropSource(), ImGui::AcceptDragDropPayload()
 enum ImGuiDragDropFlags_
 {
@@ -1065,6 +1124,15 @@ enum ImGuiConfigFlags_
     ImGuiConfigFlags_NoMouse                = 1 << 4,   // Instruct imgui to clear mouse position/buttons in NewFrame(). This allows ignoring the mouse information set by the back-end.
     ImGuiConfigFlags_NoMouseCursorChange    = 1 << 5,   // Instruct back-end to not alter mouse cursor shape and visibility. Use if the back-end cursor changes are interfering with yours and you don't want to use SetMouseCursor() to change mouse cursor. You may want to honor requests from imgui by reading GetMouseCursor() yourself instead.
 
+    // [BETA] Docking
+    ImGuiConfigFlags_DockingEnable          = 1 << 6,   // Docking enable flags.
+
+    // [BETA] Viewports
+    // When using viewports it is recommended that your default value for ImGuiCol_WindowBg is opaque (Alpha=1.0) so transition to a viewport won't be noticeable.
+    ImGuiConfigFlags_ViewportsEnable        = 1 << 10,  // Viewport enable flags (require both ImGuiConfigFlags_PlatformHasViewports + ImGuiConfigFlags_RendererHasViewports set by the respective back-ends)
+    ImGuiConfigFlags_DpiEnableScaleViewports= 1 << 14,  // [BETA: Don't use] FIXME-DPI: Reposition and resize imgui windows when the DpiScale of a viewport changed (mostly useful for the main viewport hosting other window). Note that resizing the main window itself is up to your application.
+    ImGuiConfigFlags_DpiEnableScaleFonts    = 1 << 15,  // [BETA: Don't use] FIXME-DPI: Request bitmap-scaled fonts to match DpiScale. This is a very low-quality workaround. The correct way to handle DPI is _currently_ to replace the atlas and/or fonts in the Platform_OnChangedViewport callback, but this is all early work in progress.
+
     // User storage (to allow your back-end/engine to communicate to code that may be shared between multiple projects. Those flags are not used by core Dear ImGui)
     ImGuiConfigFlags_IsSRGB                 = 1 << 20,  // Application is SRGB-aware.
     ImGuiConfigFlags_IsTouchScreen          = 1 << 21   // Application is using a touch screen instead of a mouse.
@@ -1077,7 +1145,12 @@ enum ImGuiBackendFlags_
     ImGuiBackendFlags_HasGamepad            = 1 << 0,   // Back-end Platform supports gamepad and currently has one connected.
     ImGuiBackendFlags_HasMouseCursors       = 1 << 1,   // Back-end Platform supports honoring GetMouseCursor() value to change the OS cursor shape.
     ImGuiBackendFlags_HasSetMousePos        = 1 << 2,   // Back-end Platform supports io.WantSetMousePos requests to reposition the OS mouse position (only used if ImGuiConfigFlags_NavEnableSetMousePos is set).
-    ImGuiBackendFlags_RendererHasVtxOffset  = 1 << 3    // Back-end Renderer supports ImDrawCmd::VtxOffset. This enables output of large meshes (64K+ vertices) while still using 16-bit indices.
+    ImGuiBackendFlags_RendererHasVtxOffset  = 1 << 3,   // Back-end Renderer supports ImDrawCmd::VtxOffset. This enables output of large meshes (64K+ vertices) while still using 16-bit indices.
+
+    // [BETA] Viewports
+    ImGuiBackendFlags_PlatformHasViewports  = 1 << 10,  // Back-end Platform supports multiple viewports.
+    ImGuiBackendFlags_HasMouseHoveredViewport=1 << 11,  // Back-end Platform supports setting io.MouseHoveredViewport to the viewport directly under the mouse _IGNORING_ viewports with the ImGuiViewportFlags_NoInputs flag and _REGARDLESS_ of whether another viewport is focused and may be capturing the mouse. This information is _NOT EASY_ to provide correctly with most high-level engines! Don't set this without studying how the examples/ back-end handle it!
+    ImGuiBackendFlags_RendererHasViewports  = 1 << 12   // Back-end Renderer supports multiple viewports.
 };
 
 // Enumeration for PushStyleColor() / PopStyleColor()
@@ -1121,6 +1194,8 @@ enum ImGuiCol_
     ImGuiCol_TabActive,
     ImGuiCol_TabUnfocused,
     ImGuiCol_TabUnfocusedActive,
+    ImGuiCol_DockingPreview,        // Preview overlay color when about to docking something
+    ImGuiCol_DockingEmptyBg,        // Background color for empty node (e.g. CentralNode with no window docked into it)
     ImGuiCol_PlotLines,
     ImGuiCol_PlotLinesHovered,
     ImGuiCol_PlotHistogram,
@@ -1392,9 +1467,9 @@ struct ImGuiStyle
     ImGuiDir    ColorButtonPosition;        // Side of the color button in the ColorEdit4 widget (left/right). Defaults to ImGuiDir_Right.
     ImVec2      ButtonTextAlign;            // Alignment of button text when button is larger than text. Defaults to (0.5f, 0.5f) (centered).
     ImVec2      SelectableTextAlign;        // Alignment of selectable text. Defaults to (0.0f, 0.0f) (top-left aligned). It's generally important to keep this left-aligned if you want to lay multiple items on a same line.
-    ImVec2      DisplayWindowPadding;       // Window position are clamped to be visible within the display area by at least this amount. Only applies to regular windows.
+    ImVec2      DisplayWindowPadding;       // Window position are clamped to be visible within the display area or monitors by at least this amount. Only applies to regular windows.
     ImVec2      DisplaySafeAreaPadding;     // If you cannot see the edges of your screen (e.g. on a TV) increase the safe area padding. Apply to popups/tooltips as well regular windows. NB: Prefer configuring your TV sets correctly!
-    float       MouseCursorScale;           // Scale software rendered mouse cursor (when io.MouseDrawCursor is enabled). May be removed later.
+    float       MouseCursorScale;           // Scale software rendered mouse cursor (when io.MouseDrawCursor is enabled). We apply per-monitor DPI scaling over this scale. May be removed later.
     bool        AntiAliasedLines;           // Enable anti-aliasing on lines/borders. Disable if you are really tight on CPU/GPU.
     bool        AntiAliasedFill;            // Enable anti-aliasing on filled shapes (rounded rectangles, circles, etc.)
     float       CurveTessellationTol;       // Tessellation tolerance when using PathBezierCurveTo() without a specific number of segments. Decrease for highly tessellated curves (higher quality, more polygons), increase to reduce quality.
@@ -1419,7 +1494,7 @@ struct ImGuiIO
 
     ImGuiConfigFlags   ConfigFlags;             // = 0              // See ImGuiConfigFlags_ enum. Set by user/application. Gamepad/keyboard navigation options, etc.
     ImGuiBackendFlags  BackendFlags;            // = 0              // See ImGuiBackendFlags_ enum. Set by back-end (imgui_impl_xxx files or custom back-end) to communicate features supported by the back-end.
-    ImVec2      DisplaySize;                    // <unset>          // Main display size, in pixels.
+    ImVec2      DisplaySize;                    // <unset>          // Main display size, in pixels. This is for the default viewport.
     float       DeltaTime;                      // = 1.0f/60.0f     // Time elapsed since last frame, in seconds.
     float       IniSavingRate;                  // = 5.0f           // Minimum time between saving positions/sizes to .ini file, in seconds.
     const char* IniFilename;                    // = "imgui.ini"    // Path to .ini file. Set NULL to disable automatic .ini loading/saving, if e.g. you want to manually load/save from memory.
@@ -1438,6 +1513,18 @@ struct ImGuiIO
     ImFont*     FontDefault;                    // = NULL           // Font to use on NewFrame(). Use NULL to uses Fonts->Fonts[0].
     ImVec2      DisplayFramebufferScale;        // = (1, 1)         // For retina display or other situations where window coordinates are different from framebuffer coordinates. This generally ends up in ImDrawData::FramebufferScale.
 
+    // Docking options (when ImGuiConfigFlags_DockingEnable is set)
+    bool        ConfigDockingNoSplit;           // = false          // Simplified docking mode: disable window splitting, so docking is limited to merging multiple windows together into tab-bars.
+    bool        ConfigDockingWithShift;         // = false          // Enable docking with holding Shift key (reduce visual noise, allows dropping in wider space)
+    bool        ConfigDockingAlwaysTabBar;      // = false          // [BETA] [FIXME: This currently creates regression with auto-sizing and general overhead] Make every single floating window display within a docking node.
+    bool        ConfigDockingTransparentPayload;// = false          // [BETA] Make window or viewport transparent when docking and only display docking boxes on the target viewport. Useful if rendering of multiple viewport cannot be synced. Best used with ConfigViewportsNoAutoMerge.
+
+    // Viewport options (when ImGuiConfigFlags_ViewportsEnable is set)
+    bool        ConfigViewportsNoAutoMerge;     // = false;         // Set to make all floating imgui windows always create their own viewport. Otherwise, they are merged into the main host viewports when overlapping it. May also set ImGuiViewportFlags_NoAutoMerge on individual viewport.
+    bool        ConfigViewportsNoTaskBarIcon;   // = false          // Disable default OS task bar icon flag for secondary viewports. When a viewport doesn't want a task bar icon, ImGuiViewportFlags_NoTaskBarIcon will be set on it.
+    bool        ConfigViewportsNoDecoration;    // = true           // [BETA] Disable default OS window decoration flag for secondary viewports. When a viewport doesn't want window decorations, ImGuiViewportFlags_NoDecoration will be set on it. Enabling decoration can create subsequent issues at OS levels (e.g. minimum window size).
+    bool        ConfigViewportsNoDefaultParent; // = false          // Disable default OS parenting to main viewport for secondary viewports. By default, viewports are marked with ParentViewportId = <main_viewport>, expecting the platform back-end to setup a parent/child relationship between the OS windows (some back-end may ignore this). Set to true if you want the default to be 0, then all viewports will be top-level OS windows.
+
     // Miscellaneous options
     bool        MouseDrawCursor;                // = false          // Request ImGui to draw a mouse cursor for you (if you are on a platform without a mouse cursor). Cannot be easily renamed to 'io.ConfigXXX' because this is frequently used by back-end implementations.
     bool        ConfigMacOSXBehaviors;          // = defined(__APPLE__) // OS X style: Text editing cursor movement using Alt instead of Ctrl, Shortcuts using Cmd/Super instead of Ctrl, Line/Text Start and End using Cmd+Arrows instead of Home/End, Double click selects by word instead of selecting whole text, Multi-selection in lists uses Cmd/Super instead of Ctrl (was called io.OptMacOSXBehaviors prior to 1.63)
@@ -1464,11 +1551,6 @@ struct ImGuiIO
     void        (*SetClipboardTextFn)(void* user_data, const char* text);
     void*       ClipboardUserData;
 
-    // Optional: Notify OS Input Method Editor of the screen position of your cursor for text input position (e.g. when using Japanese/Chinese IME on Windows)
-    // (default to use native imm32 api on Windows)
-    void        (*ImeSetInputScreenPosFn)(int x, int y);
-    void*       ImeWindowHandle;                // = NULL           // (Windows) Set this to your HWND to get automatic IME cursor positioning.
-
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
     // [OBSOLETE since 1.60+] Rendering function, will be automatically called in Render(). Please call your rendering function yourself now!
     // You can obtain the ImDrawData* by calling ImGui::GetDrawData() after Render(). See example applications if you are unsure of how to implement this.
@@ -1486,6 +1568,7 @@ struct ImGuiIO
     bool        MouseDown[5];                   // Mouse buttons: 0=left, 1=right, 2=middle + extras. ImGui itself mostly only uses left button (BeginPopupContext** are using right button). Others buttons allows us to track if the mouse is being used by your application + available to user as a convenience via IsMouse** API.
     float       MouseWheel;                     // Mouse wheel Vertical: 1 unit scrolls about 5 lines text.
     float       MouseWheelH;                    // Mouse wheel Horizontal. Most users don't have a mouse with an horizontal wheel, may not be filled by all back-ends.
+    ImGuiID     MouseHoveredViewport;           // (Optional) When using multiple viewports: viewport the OS mouse cursor is hovering _IGNORING_ viewports with the ImGuiViewportFlags_NoInputs flag, and _REGARDLESS_ of whether another viewport is focused. Set io.BackendFlags |= ImGuiBackendFlags_HasMouseHoveredViewport if you can provide this info. If you don't imgui will infer the value using the rectangles and last focused time of the viewports it knows about (ignoring other OS windows).
     bool        KeyCtrl;                        // Keyboard modifier pressed: Control
     bool        KeyShift;                       // Keyboard modifier pressed: Shift
     bool        KeyAlt;                         // Keyboard modifier pressed: Alt
@@ -1596,6 +1679,27 @@ struct ImGuiSizeCallbackData
     ImVec2  DesiredSize;    // Read-write.  Desired size, based on user's mouse position. Write to this field to restrain resizing.
 };
 
+// [ALPHA] Rarely used / very advanced uses only. Use with SetNextWindowClass() and DockSpace() functions.
+// Important: the content of this class is still highly WIP and likely to change and be refactored
+// before we stabilize Docking features. Please be mindful if using this.
+// Provide hints:
+// - To the platform back-end via altered viewport flags (enable/disable OS decoration, OS task bar icons, etc.) 
+// - To the platform back-end for OS level parent/child relationships of viewport.
+// - To the docking system for various options and filtering.
+struct ImGuiWindowClass
+{
+    ImGuiID             ClassId;                    // User data. 0 = Default class (unclassed). Windows of different classes cannot be docked with each others.
+    ImGuiID             ParentViewportId;           // Hint for the platform back-end. If non-zero, the platform back-end can create a parent<>child relationship between the platform windows. Not conforming back-ends are free to e.g. parent every viewport to the main viewport or not.
+    ImGuiViewportFlags  ViewportFlagsOverrideSet;   // Viewport flags to set when a window of this class owns a viewport. This allows you to enforce OS decoration or task bar icon, override the defaults on a per-window basis.
+    ImGuiViewportFlags  ViewportFlagsOverrideClear; // Viewport flags to clear when a window of this class owns a viewport. This allows you to enforce OS decoration or task bar icon, override the defaults on a per-window basis.
+    ImGuiDockNodeFlags  DockNodeFlagsOverrideSet;   // [EXPERIMENTAL] Dock node flags to set when a window of this class is hosted by a dock node (it doesn't have to be selected!)
+    ImGuiDockNodeFlags  DockNodeFlagsOverrideClear; // [EXPERIMENTAL] 
+    bool                DockingAlwaysTabBar;        // Set to true to enforce single floating windows of this class always having their own docking node (equivalent of setting the global io.ConfigDockingAlwaysTabBar)
+    bool                DockingAllowUnclassed;      // Set to true to allow windows of this class to be docked/merged with an unclassed window.
+
+    ImGuiWindowClass() { ClassId = 0; ParentViewportId = 0; ViewportFlagsOverrideSet = ViewportFlagsOverrideClear = 0x00; DockNodeFlagsOverrideSet = DockNodeFlagsOverrideClear = 0x00; DockingAlwaysTabBar = false; DockingAllowUnclassed = true; }
+};
+
 // Data payload for Drag and Drop operations: AcceptDragDropPayload(), GetDragDropPayload()
 struct ImGuiPayload
 {
@@ -1958,7 +2062,7 @@ enum ImDrawListFlags_
 // Each dear imgui window contains its own ImDrawList. You can use ImGui::GetWindowDrawList() to
 // access the current window draw list and draw custom primitives.
 // You can interleave normal ImGui:: calls and adding primitives to the current draw list.
-// All positions are generally in pixel coordinates (top-left at (0,0), bottom-right at io.DisplaySize), but you are totally free to apply whatever transformation matrix to want to the data (if you apply such transformation you'll want to apply it to ClipRect as well)
+// All positions are generally in pixel coordinates (generally top-left at 0,0, bottom-right at io.DisplaySize, unless multiple viewports are used), but you are totally free to apply whatever transformation matrix to want to the data (if you apply such transformation you'll want to apply it to ClipRect as well)
 // Important: Primitives are always added to the list and not culled (culling is done at higher-level by ImGui:: functions), if you use this API a lot consider coarse culling your drawn objects.
 struct ImDrawList
 {
@@ -2077,11 +2181,12 @@ struct ImDrawData
     ImVec2          DisplayPos;             // Upper-left position of the viewport to render (== upper-left of the orthogonal projection matrix to use)
     ImVec2          DisplaySize;            // Size of the viewport to render (== io.DisplaySize for the main viewport) (DisplayPos + DisplaySize == lower-right of the orthogonal projection matrix to use)
     ImVec2          FramebufferScale;       // Amount of pixels for each unit of DisplaySize. Based on io.DisplayFramebufferScale. Generally (1,1) on normal display, (2,2) on OSX with Retina display.
+    ImGuiViewport*  OwnerViewport;          // Viewport carrying the ImDrawData instance, might be of use to the renderer (generally not).
 
     // Functions
     ImDrawData()    { Valid = false; Clear(); }
     ~ImDrawData()   { Clear(); }
-    void Clear()    { Valid = false; CmdLists = NULL; CmdListsCount = TotalVtxCount = TotalIdxCount = 0; DisplayPos = DisplaySize = FramebufferScale = ImVec2(0.f, 0.f); } // The ImDrawList are owned by ImGuiContext!
+    void Clear()    { Valid = false; CmdLists = NULL; CmdListsCount = TotalVtxCount = TotalIdxCount = 0; DisplayPos = DisplaySize = FramebufferScale = ImVec2(0.f, 0.f); OwnerViewport = NULL; } // The ImDrawList are owned by ImGuiContext!
     IMGUI_API void  DeIndexAllBuffers();                    // Helper to convert all buffers from indexed to non-indexed, in case you cannot render indexed. Note: this is slow and most likely a waste of resources. Always prefer indexed rendering!
     IMGUI_API void  ScaleClipRects(const ImVec2& fb_scale); // Helper to scale the ClipRect field of each ImDrawCmd. Use if your final output buffer is at a different scale than Dear ImGui expects, or if there is a difference between your window resolution and framebuffer resolution.
 };
@@ -2323,6 +2428,180 @@ struct ImFont
     IMGUI_API bool              IsGlyphRangeUnused(unsigned int c_begin, unsigned int c_last);
 };
 
+//-----------------------------------------------------------------------------
+// [BETA] Platform interface for multi-viewport support
+//-----------------------------------------------------------------------------
+// (Optional) This is completely optional, for advanced users!
+// If you are new to Dear ImGui and trying to integrate it into your engine, you can probably ignore this for now.
+//
+// This feature allows you to seamlessly drag Dear ImGui windows outside of your application viewport.
+// This is achieved by creating new Platform/OS windows on the fly, and rendering into them.
+// Dear ImGui manages the viewport structures, and the back-end create and maintain one Platform/OS window for each of those viewports.
+//
+// See Glossary https://github.com/ocornut/imgui/wiki/Glossary for details about some of the terminology.
+// See Thread https://github.com/ocornut/imgui/issues/1542 for gifs, news and questions about this evolving feature.
+//
+// About the coordinates system:
+// - When multi-viewports are enabled, all Dear ImGui coordinates become absolute coordinates (same as OS coordinates!)
+// - So e.g. ImGui::SetNextWindowPos(ImVec2(0,0)) will position a window relative to your primary monitor!
+// - If you want to position windows relative to your main application viewport, use ImGui::GetMainViewport()->Pos as a base position.
+//
+// Steps to use multi-viewports in your application, when using a default back-end from the examples/ folder:
+// - Application:  Enable feature with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+// - Back-end:     The back-end initialization will setup all necessary ImGuiPlatformIO's functions and update monitors info every frame.
+// - Application:  In your main loop, call ImGui::UpdatePlatformWindows(), ImGui::RenderPlatformWindowsDefault() after EndFrame() or Render().
+// - Application:  Fix absolute coordinates used in ImGui::SetWindowPos() or ImGui::SetNextWindowPos() calls.
+//
+// Steps to use multi-viewports in your application, when using a custom back-end:
+// - Important:    THIS IS NOT EASY TO DO and comes with many subtleties not described here!
+//                 It's also an experimental feature, so some of the requirements may evolve.
+//                 Consider using default back-ends if you can. Either way, carefully follow and refer to examples/ back-ends for details.
+// - Application:  Enable feature with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+// - Back-end:     Hook ImGuiPlatformIO's Platform_* and Renderer_* callbacks (see below).
+//                 Set 'io.BackendFlags |= ImGuiBackendFlags_PlatformHasViewports' and 'io.BackendFlags |= ImGuiBackendFlags_PlatformHasViewports'.
+//                 Update ImGuiPlatformIO's Monitors list every frame.
+//                 Update MousePos every frame, in absolute coordinates.
+// - Application:  In your main loop, call ImGui::UpdatePlatformWindows(), ImGui::RenderPlatformWindowsDefault() after EndFrame() or Render().
+//                 You may skip calling RenderPlatformWindowsDefault() if its API is not convenient for your needs. Read comments below.
+// - Application:  Fix absolute coordinates used in ImGui::SetWindowPos() or ImGui::SetNextWindowPos() calls.
+//
+// About ImGui::RenderPlatformWindowsDefault():
+// - This function is a mostly a _helper_ for the common-most cases, and to facilitate using default back-ends.
+// - You can check its simple source code to understand what it does.
+//   It basically iterates secondary viewports and call 4 functions that are setup in ImGuiPlatformIO, if available:
+//     Platform_RenderWindow(), Renderer_RenderWindow(), Platform_SwapBuffers(), Renderer_SwapBuffers()
+//   Those functions pointers exists only for the benefit of RenderPlatformWindowsDefault().
+// - If you have very specific rendering needs (e.g. flipping multiple swap-chain simultaneously, unusual sync/threading issues, etc.),
+//   you may be tempted to ignore RenderPlatformWindowsDefault() and write customized code to perform your renderingg.
+//   You may decide to setup the platform_io's *RenderWindow and *SwapBuffers pointers and call your functions through those pointers,
+//   or you may decide to never setup those pointers and call your code directly. They are a convenience, not an obligatory interface.
+//-----------------------------------------------------------------------------
+
+// (Optional) Access via ImGui::GetPlatformIO()
+struct ImGuiPlatformIO
+{
+    //------------------------------------------------------------------
+    // Input - Back-end interface/functions + Monitor List
+    //------------------------------------------------------------------
+
+    // (Optional) Platform functions (e.g. Win32, GLFW, SDL2)
+    // For reference, the second column shows which function are generally calling the Platform Functions:
+    //   N = ImGui::NewFrame()                        ~ beginning of the dear imgui frame: read info from platform/OS windows (latest size/position)
+    //   F = ImGui::Begin(), ImGui::EndFrame()        ~ during the dear imgui frame
+    //   U = ImGui::UpdatePlatformWindows()           ~ after the dear imgui frame: create and update all platform/OS windows
+    //   R = ImGui::RenderPlatformWindowsDefault()    ~ render
+    //   D = ImGui::DestroyPlatformWindows()          ~ shutdown
+    // The general idea is that NewFrame() we will read the current Platform/OS state, and UpdatePlatformWindows() will write to it.
+    //
+    // The functions are designed so we can mix and match 2 imgui_impl_xxxx files, one for the Platform (~window/input handling), one for Renderer.
+    // Custom engine back-ends will often provide both Platform and Renderer interfaces and so may not need to use all functions.
+    // Platform functions are typically called before their Renderer counterpart, apart from Destroy which are called the other way.
+
+    // Platform function --------------------------------------------------- Called by -----
+    void    (*Platform_CreateWindow)(ImGuiViewport* vp);                    // . . U . .  // Create a new platform window for the given viewport
+    void    (*Platform_DestroyWindow)(ImGuiViewport* vp);                   // N . U . D  //
+    void    (*Platform_ShowWindow)(ImGuiViewport* vp);                      // . . U . .  // Newly created windows are initially hidden so SetWindowPos/Size/Title can be called on them before showing the window
+    void    (*Platform_SetWindowPos)(ImGuiViewport* vp, ImVec2 pos);        // . . U . .  // Set platform window position (given the upper-left corner of client area)
+    ImVec2  (*Platform_GetWindowPos)(ImGuiViewport* vp);                    // N . . . .  //
+    void    (*Platform_SetWindowSize)(ImGuiViewport* vp, ImVec2 size);      // . . U . .  // Set platform window client area size (ignoring OS decorations such as OS title bar etc.)
+    ImVec2  (*Platform_GetWindowSize)(ImGuiViewport* vp);                   // N . . . .  // Get platform window client area size
+    void    (*Platform_SetWindowFocus)(ImGuiViewport* vp);                  // N . . . .  // Move window to front and set input focus
+    bool    (*Platform_GetWindowFocus)(ImGuiViewport* vp);                  // . . U . .  //
+    bool    (*Platform_GetWindowMinimized)(ImGuiViewport* vp);              // N . . . .  // Get platform window minimized state. When minimized, we generally won't attempt to get/set size and contents will be culled more easily
+    void    (*Platform_SetWindowTitle)(ImGuiViewport* vp, const char* str); // . . U . .  // Set platform window title (given an UTF-8 string)
+    void    (*Platform_SetWindowAlpha)(ImGuiViewport* vp, float alpha);     // . . U . .  // (Optional) Setup window transparency
+    void    (*Platform_UpdateWindow)(ImGuiViewport* vp);                    // . . U . .  // (Optional) Called by UpdatePlatformWindows(). Optional hook to allow the platform back-end from doing general book-keeping every frame.
+    void    (*Platform_RenderWindow)(ImGuiViewport* vp, void* render_arg);  // . . . R .  // (Optional) Main rendering (platform side! This is often unused, or just setting a "current" context for OpenGL bindings). 'render_arg' is the value passed to RenderPlatformWindowsDefault().
+    void    (*Platform_SwapBuffers)(ImGuiViewport* vp, void* render_arg);   // . . . R .  // (Optional) Call Present/SwapBuffers (platform side! This is often unused!). 'render_arg' is the value passed to RenderPlatformWindowsDefault().
+    float   (*Platform_GetWindowDpiScale)(ImGuiViewport* vp);               // N . . . .  // (Optional) [BETA] FIXME-DPI: DPI handling: Return DPI scale for this viewport. 1.0f = 96 DPI.
+    void    (*Platform_OnChangedViewport)(ImGuiViewport* vp);               // . F . . .  // (Optional) [BETA] FIXME-DPI: DPI handling: Called during Begin() every time the viewport we are outputting into changes, so back-end has a chance to swap fonts to adjust style.
+    void    (*Platform_SetImeInputPos)(ImGuiViewport* vp, ImVec2 pos);      // . F . . .  // (Optional) Set IME (Input Method Editor, e.g. for Asian languages) input position, so text preview appears over the imgui input box. FIXME: The call timing of this is inconsistent because we want to support without multi-viewports.
+    int     (*Platform_CreateVkSurface)(ImGuiViewport* vp, ImU64 vk_inst, const void* vk_allocators, ImU64* out_vk_surface); // (Optional) For a Vulkan Renderer to call into Platform code (since the surface creation needs to tie them both).
+
+    // (Optional) Renderer functions (e.g. DirectX, OpenGL, Vulkan)
+    void    (*Renderer_CreateWindow)(ImGuiViewport* vp);                    // . . U . .  // Create swap chain, frame buffers etc. (called after Platform_CreateWindow)
+    void    (*Renderer_DestroyWindow)(ImGuiViewport* vp);                   // N . U . D  // Destroy swap chain, frame buffers etc. (called before Platform_DestroyWindow)
+    void    (*Renderer_SetWindowSize)(ImGuiViewport* vp, ImVec2 size);      // . . U . .  // Resize swap chain, frame buffers etc. (called after Platform_SetWindowSize)
+    void    (*Renderer_RenderWindow)(ImGuiViewport* vp, void* render_arg);  // . . . R .  // (Optional) Clear framebuffer, setup render target, then render the viewport->DrawData. 'render_arg' is the value passed to RenderPlatformWindowsDefault().
+    void    (*Renderer_SwapBuffers)(ImGuiViewport* vp, void* render_arg);   // . . . R .  // (Optional) Call Present/SwapBuffers. 'render_arg' is the value passed to RenderPlatformWindowsDefault().
+
+    // (Optional) Monitor list
+    // - Updated by: app/back-end. Update every frame to dynamically support changing monitor or DPI configuration.
+    // - Used by: dear imgui to query DPI info, clamp popups/tooltips within same monitor and not have them straddle monitors.
+    ImVector<ImGuiPlatformMonitor>  Monitors;
+
+    //------------------------------------------------------------------
+    // Output - List of viewports to render into platform windows
+    //------------------------------------------------------------------
+
+    // Viewports list (the list is updated by calling ImGui::EndFrame or ImGui::Render)
+    // (in the future we will attempt to organize this feature to remove the need for a "main viewport")
+    ImGuiViewport*                  MainViewport;                           // Guaranteed to be == Viewports[0]
+    ImVector<ImGuiViewport*>        Viewports;                              // Main viewports, followed by all secondary viewports.
+    ImGuiPlatformIO()               { memset(this, 0, sizeof(*this)); }     // Zero clear
+};
+
+// (Optional) This is required when enabling multi-viewport. Represent the bounds of each connected monitor/display and their DPI.
+// We use this information for multiple DPI support + clamping the position of popups and tooltips so they don't straddle multiple monitors.
+struct ImGuiPlatformMonitor
+{
+    ImVec2  MainPos, MainSize;      // Coordinates of the area displayed on this monitor (Min = upper left, Max = bottom right)
+    ImVec2  WorkPos, WorkSize;      // (Optional) Coordinates without task bars / side bars / menu bars. imgui uses this to avoid positioning popups/tooltips inside this region.
+    float   DpiScale;               // 1.0f = 96 DPI
+    ImGuiPlatformMonitor()          { MainPos = MainSize = WorkPos = WorkSize = ImVec2(0, 0); DpiScale = 1.0f; }
+};
+
+// Flags stored in ImGuiViewport::Flags, giving indications to the platform back-ends.
+enum ImGuiViewportFlags_
+{
+    ImGuiViewportFlags_None                     = 0,
+    ImGuiViewportFlags_NoDecoration             = 1 << 0,   // Platform Window: Disable platform decorations: title bar, borders, etc. (generally set all windows, but if ImGuiConfigFlags_ViewportsDecoration is set we only set this on popups/tooltips)
+    ImGuiViewportFlags_NoTaskBarIcon            = 1 << 1,   // Platform Window: Disable platform task bar icon (generally set on popups/tooltips, or all windows if ImGuiConfigFlags_ViewportsNoTaskBarIcon is set)
+    ImGuiViewportFlags_NoFocusOnAppearing       = 1 << 2,   // Platform Window: Don't take focus when created.
+    ImGuiViewportFlags_NoFocusOnClick           = 1 << 3,   // Platform Window: Don't take focus when clicked on.
+    ImGuiViewportFlags_NoInputs                 = 1 << 4,   // Platform Window: Make mouse pass through so we can drag this window while peaking behind it.
+    ImGuiViewportFlags_NoRendererClear          = 1 << 5,   // Platform Window: Renderer doesn't need to clear the framebuffer ahead (because we will fill it entirely).
+    ImGuiViewportFlags_TopMost                  = 1 << 6,   // Platform Window: Display on top (for tooltips only).
+    ImGuiViewportFlags_Minimized                = 1 << 7,   // Platform Window: Window is minimized, can skip render. When minimized we tend to avoid using the viewport pos/size for clipping window or testing if they are contained in the viewport.
+    ImGuiViewportFlags_NoAutoMerge              = 1 << 8,   // Platform Window: Avoid merging this window into another host window. This can only be set via ImGuiWindowClass viewport flags override (because we need to now ahead if we are going to create a viewport in the first place!).
+    ImGuiViewportFlags_CanHostOtherWindows      = 1 << 9    // Main viewport: can host multiple imgui windows (secondary viewports are associated to a single window).
+};
+
+// The viewports created and managed by Dear ImGui. The role of the platform back-end is to create the platform/OS windows corresponding to each viewport.
+// - Main Area = entire viewport.
+// - Work Area = entire viewport minus sections optionally used by menu bars, status bars. Some positioning code will prefer to use this. Window are also trying to stay within this area.
+struct ImGuiViewport
+{
+    ImGuiID             ID;                     // Unique identifier for the viewport
+    ImGuiViewportFlags  Flags;                  // See ImGuiViewportFlags_
+    ImVec2              Pos;                    // Main Area: Position of the viewport (the imgui coordinates are the same as OS desktop/native coordinates)
+    ImVec2              Size;                   // Main Area: Size of the viewport.
+    ImVec2              WorkOffsetMin;          // Work Area: Offset from Pos to top-left corner of Work Area. Generally (0,0) or (0,+main_menu_bar_height). Work Area is Full Area but without menu-bars/status-bars (so WorkArea always fit inside Pos/Size!)
+    ImVec2              WorkOffsetMax;          // Work Area: Offset from Pos+Size to bottom-right corner of Work Area. Generally (0,0) or (0,-status_bar_height).
+    float               DpiScale;               // 1.0f = 96 DPI = No extra scale.
+    ImDrawData*         DrawData;               // The ImDrawData corresponding to this viewport. Valid after Render() and until the next call to NewFrame().
+    ImGuiID             ParentViewportId;       // (Advanced) 0: no parent. Instruct the platform back-end to setup a parent/child relationship between platform windows.
+
+    // Our design separate the Renderer and Platform back-ends to facilitate combining default back-ends with each others.
+    // When our create your own back-end for a custom engine, it is possible that both Renderer and Platform will be handled
+    // by the same system and you may not need to use all the UserData/Handle fields.
+    // The library never uses those fields, they are merely storage to facilitate back-end implementation.
+    void*               RendererUserData;       // void* to hold custom data structure for the renderer (e.g. swap chain, framebuffers etc.). generally set by your Renderer_CreateWindow function.
+    void*               PlatformUserData;       // void* to hold custom data structure for the OS / platform (e.g. windowing info, render context). generally set by your Platform_CreateWindow function.
+    void*               PlatformHandle;         // void* for FindViewportByPlatformHandle(). (e.g. suggested to use natural platform handle such as HWND, GLFWWindow*, SDL_Window*)
+    void*               PlatformHandleRaw;      // void* to hold lower-level, platform-native window handle (e.g. the HWND) when using an abstraction layer like GLFW or SDL (where PlatformHandle would be a SDL_Window*)
+    bool                PlatformRequestMove;    // Platform window requested move (e.g. window was moved by the OS / host window manager, authoritative position will be OS window position)
+    bool                PlatformRequestResize;  // Platform window requested resize (e.g. window was resized by the OS / host window manager, authoritative size will be OS window size)
+    bool                PlatformRequestClose;   // Platform window requested closure (e.g. window was moved by the OS / host window manager, e.g. pressing ALT-F4)
+
+    ImGuiViewport()     { ID = 0; Flags = 0; DpiScale = 0.0f; DrawData = NULL; ParentViewportId = 0; RendererUserData = PlatformUserData = PlatformHandle = PlatformHandleRaw = NULL; PlatformRequestMove = PlatformRequestResize = PlatformRequestClose = false; }
+    ~ImGuiViewport()    { IM_ASSERT(PlatformUserData == NULL && RendererUserData == NULL); }
+
+    // Access work-area rectangle
+    ImVec2              GetWorkPos()            { return ImVec2(Pos.x + WorkOffsetMin.x, Pos.y + WorkOffsetMin.y); }
+    ImVec2              GetWorkSize()           { return ImVec2(Size.x - WorkOffsetMin.x + WorkOffsetMax.x, Size.y - WorkOffsetMin.y + WorkOffsetMax.y); } // This not clamped
+};
+
 #if defined(__clang__)
 #pragma clang diagnostic pop
 #elif defined(__GNUC__)
diff --git a/imgui/imgui_demo.cpp b/imgui/imgui_demo.cpp
index 1e110ded..ef33ffba 100644
--- a/imgui/imgui_demo.cpp
+++ b/imgui/imgui_demo.cpp
@@ -1,4 +1,4 @@
-// dear imgui, v1.76
+// dear imgui, v1.77 WIP
 // (demo code)
 
 // Help:
@@ -56,6 +56,7 @@ Index of this file:
 // [SECTION] Example App: Simple Overlay / ShowExampleAppSimpleOverlay()
 // [SECTION] Example App: Manipulating Window Titles / ShowExampleAppWindowTitles()
 // [SECTION] Example App: Custom Rendering using ImDrawList API / ShowExampleAppCustomRendering()
+// [SECTION] Example App: Docking, DockSpace / ShowExampleAppDockSpace()
 // [SECTION] Example App: Documents Handling / ShowExampleAppDocuments()
 
 */
@@ -127,6 +128,7 @@ Index of this file:
 #if !defined(IMGUI_DISABLE_DEMO_WINDOWS)
 
 // Forward Declarations
+static void ShowExampleAppDockSpace(bool* p_open);
 static void ShowExampleAppDocuments(bool* p_open);
 static void ShowExampleAppMainMenuBar();
 static void ShowExampleAppConsole(bool* p_open);
@@ -156,6 +158,16 @@ static void HelpMarker(const char* desc)
     }
 }
 
+static void ShowDockingDisabledMessage()
+{
+    ImGuiIO& io = ImGui::GetIO();
+    ImGui::Text("ERROR: Docking is not enabled! See Demo > Configuration.");
+    ImGui::Text("Set io.ConfigFlags |= ImGuiConfigFlags_DockingEnable in your code, or ");
+    ImGui::SameLine(0.0f, 0.0f);
+    if (ImGui::SmallButton("click here"))
+        io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;
+}
+
 // Helper to display basic user controls.
 void ImGui::ShowUserGuide()
 {
@@ -210,8 +222,9 @@ void ImGui::ShowDemoWindow(bool* p_open)
     IM_ASSERT(ImGui::GetCurrentContext() != NULL && "Missing dear imgui context. Refer to examples app!"); // Exceptionally add an extra assert here for people confused with initial dear imgui setup
 
     // Examples Apps (accessible from the "Examples" menu)
-    static bool show_app_documents = false;
     static bool show_app_main_menu_bar = false;
+    static bool show_app_dockspace = false;
+    static bool show_app_documents = false;
     static bool show_app_console = false;
     static bool show_app_log = false;
     static bool show_app_layout = false;
@@ -223,8 +236,9 @@ void ImGui::ShowDemoWindow(bool* p_open)
     static bool show_app_window_titles = false;
     static bool show_app_custom_rendering = false;
 
-    if (show_app_documents)           ShowExampleAppDocuments(&show_app_documents);
     if (show_app_main_menu_bar)       ShowExampleAppMainMenuBar();
+    if (show_app_dockspace)           ShowExampleAppDockSpace(&show_app_dockspace);     // Process the Docking app first, as explicit DockSpace() nodes needs to be submitted early (read comments near the DockSpace function)
+    if (show_app_documents)           ShowExampleAppDocuments(&show_app_documents);     // Process the Document app next, as it may also use a DockSpace()
     if (show_app_console)             ShowExampleAppConsole(&show_app_console);
     if (show_app_log)                 ShowExampleAppLog(&show_app_log);
     if (show_app_layout)              ShowExampleAppLayout(&show_app_layout);
@@ -256,6 +270,7 @@ void ImGui::ShowDemoWindow(bool* p_open)
     static bool no_nav = false;
     static bool no_background = false;
     static bool no_bring_to_front = false;
+    static bool no_docking = false;
 
     ImGuiWindowFlags window_flags = 0;
     if (no_titlebar)        window_flags |= ImGuiWindowFlags_NoTitleBar;
@@ -267,10 +282,12 @@ void ImGui::ShowDemoWindow(bool* p_open)
     if (no_nav)             window_flags |= ImGuiWindowFlags_NoNav;
     if (no_background)      window_flags |= ImGuiWindowFlags_NoBackground;
     if (no_bring_to_front)  window_flags |= ImGuiWindowFlags_NoBringToFrontOnFocus;
+    if (no_docking)         window_flags |= ImGuiWindowFlags_NoDocking;
     if (no_close)           p_open = NULL; // Don't pass our bool* to Begin
 
     // We specify a default position/size in case there's no data in the .ini file. Typically this isn't required! We only do it to make the Demo applications a little more welcoming.
-    ImGui::SetNextWindowPos(ImVec2(650, 20), ImGuiCond_FirstUseEver);
+    ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    ImGui::SetNextWindowPos(ImVec2(main_viewport->GetWorkPos().x + 650, main_viewport->GetWorkPos().y + 20), ImGuiCond_FirstUseEver);
     ImGui::SetNextWindowSize(ImVec2(550, 680), ImGuiCond_FirstUseEver);
 
     // Main body of the Demo window starts here.
@@ -306,6 +323,7 @@ void ImGui::ShowDemoWindow(bool* p_open)
             ImGui::MenuItem("Simple overlay", NULL, &show_app_simple_overlay);
             ImGui::MenuItem("Manipulating window titles", NULL, &show_app_window_titles);
             ImGui::MenuItem("Custom rendering", NULL, &show_app_custom_rendering);
+            ImGui::MenuItem("Dockspace", NULL, &show_app_dockspace);
             ImGui::MenuItem("Documents", NULL, &show_app_documents);
             ImGui::EndMenu();
         }
@@ -368,6 +386,39 @@ void ImGui::ShowDemoWindow(bool* p_open)
             }
             ImGui::CheckboxFlags("io.ConfigFlags: NoMouseCursorChange", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_NoMouseCursorChange);
             ImGui::SameLine(); HelpMarker("Instruct back-end to not alter mouse cursor shape and visibility.");
+
+            ImGui::CheckboxFlags("io.ConfigFlags: DockingEnable", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_DockingEnable);
+            ImGui::SameLine(); HelpMarker(io.ConfigDockingWithShift ? "[beta] Use SHIFT to dock window into each others." : "[beta] Drag from title bar to dock windows into each others.");
+            if (io.ConfigFlags & ImGuiConfigFlags_DockingEnable)
+            {
+                ImGui::Indent();
+                ImGui::Checkbox("io.ConfigDockingNoSplit", &io.ConfigDockingNoSplit);
+                ImGui::SameLine(); HelpMarker("Simplified docking mode: disable window splitting, so docking is limited to merging multiple windows together into tab-bars.");
+                ImGui::Checkbox("io.ConfigDockingWithShift", &io.ConfigDockingWithShift);
+                ImGui::SameLine(); HelpMarker("Enable docking when holding Shift only (allows to drop in wider space, reduce visual noise)");
+                ImGui::Checkbox("io.ConfigDockingAlwaysTabBar", &io.ConfigDockingAlwaysTabBar);
+                ImGui::SameLine(); HelpMarker("Create a docking node and tab-bar on single floating windows.");
+                ImGui::Checkbox("io.ConfigDockingTransparentPayload", &io.ConfigDockingTransparentPayload);
+                ImGui::SameLine(); HelpMarker("Make window or viewport transparent when docking and only display docking boxes on the target viewport. Useful if rendering of multiple viewport cannot be synced. Best used with ConfigViewportsNoAutoMerge.");
+                ImGui::Unindent();
+            }
+
+            ImGui::CheckboxFlags("io.ConfigFlags: ViewportsEnable", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_ViewportsEnable);
+            ImGui::SameLine(); HelpMarker("[beta] Enable beta multi-viewports support. See ImGuiPlatformIO for details.");
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+            {
+                ImGui::Indent();
+                ImGui::Checkbox("io.ConfigViewportsNoAutoMerge", &io.ConfigViewportsNoAutoMerge);
+                ImGui::SameLine(); HelpMarker("Set to make all floating imgui windows always create their own viewport. Otherwise, they are merged into the main host viewports when overlapping it.");
+                ImGui::Checkbox("io.ConfigViewportsNoTaskBarIcon", &io.ConfigViewportsNoTaskBarIcon);
+                ImGui::SameLine(); HelpMarker("Toggling this at runtime is normally unsupported (most platform back-ends won't refresh the task bar icon state right away).");
+                ImGui::Checkbox("io.ConfigViewportsNoDecoration", &io.ConfigViewportsNoDecoration);
+                ImGui::SameLine(); HelpMarker("Toggling this at runtime is normally unsupported (most platform back-ends won't refresh the decoration right away).");
+                ImGui::Checkbox("io.ConfigViewportsNoDefaultParent", &io.ConfigViewportsNoDefaultParent);
+                ImGui::SameLine(); HelpMarker("Toggling this at runtime is normally unsupported (most platform back-ends won't refresh the parenting right away).");
+                ImGui::Unindent();
+            }
+
             ImGui::Checkbox("io.ConfigInputTextCursorBlink", &io.ConfigInputTextCursorBlink);
             ImGui::SameLine(); HelpMarker("Set to false to disable blinking cursor, for users who consider it distracting");
             ImGui::Checkbox("io.ConfigWindowsResizeFromEdges", &io.ConfigWindowsResizeFromEdges);
@@ -386,7 +437,10 @@ void ImGui::ShowDemoWindow(bool* p_open)
             ImGui::CheckboxFlags("io.BackendFlags: HasGamepad", (unsigned int *)&backend_flags, ImGuiBackendFlags_HasGamepad);
             ImGui::CheckboxFlags("io.BackendFlags: HasMouseCursors", (unsigned int *)&backend_flags, ImGuiBackendFlags_HasMouseCursors);
             ImGui::CheckboxFlags("io.BackendFlags: HasSetMousePos", (unsigned int *)&backend_flags, ImGuiBackendFlags_HasSetMousePos);
+            ImGui::CheckboxFlags("io.BackendFlags: PlatformHasViewports", (unsigned int *)&backend_flags, ImGuiBackendFlags_PlatformHasViewports);
+            ImGui::CheckboxFlags("io.BackendFlags: HasMouseHoveredViewport", (unsigned int *)&backend_flags, ImGuiBackendFlags_HasMouseHoveredViewport);
             ImGui::CheckboxFlags("io.BackendFlags: RendererHasVtxOffset", (unsigned int *)&backend_flags, ImGuiBackendFlags_RendererHasVtxOffset);
+            ImGui::CheckboxFlags("io.BackendFlags: RendererHasViewports", (unsigned int *)&backend_flags, ImGuiBackendFlags_RendererHasViewports);
             ImGui::TreePop();
             ImGui::Separator();
         }
@@ -427,6 +481,7 @@ void ImGui::ShowDemoWindow(bool* p_open)
         ImGui::Checkbox("No nav", &no_nav); ImGui::SameLine(300);
         ImGui::Checkbox("No background", &no_background);
         ImGui::Checkbox("No bring to front", &no_bring_to_front);
+        ImGui::Checkbox("No docking", &no_docking);
     }
 
     // All demo contents
@@ -641,11 +696,13 @@ static void ShowDemoWindowWidgets()
             HelpMarker("This is a more typical looking tree with selectable nodes.\nClick to select, CTRL+Click to toggle, click on arrows or double-click to open.");
             static ImGuiTreeNodeFlags base_flags = ImGuiTreeNodeFlags_OpenOnArrow | ImGuiTreeNodeFlags_OpenOnDoubleClick | ImGuiTreeNodeFlags_SpanAvailWidth;
             static bool align_label_with_current_x_position = false;
+            static bool test_drag_and_drop = false;
             ImGui::CheckboxFlags("ImGuiTreeNodeFlags_OpenOnArrow", (unsigned int*)&base_flags, ImGuiTreeNodeFlags_OpenOnArrow);
             ImGui::CheckboxFlags("ImGuiTreeNodeFlags_OpenOnDoubleClick", (unsigned int*)&base_flags, ImGuiTreeNodeFlags_OpenOnDoubleClick);
             ImGui::CheckboxFlags("ImGuiTreeNodeFlags_SpanAvailWidth", (unsigned int*)&base_flags, ImGuiTreeNodeFlags_SpanAvailWidth); ImGui::SameLine(); HelpMarker("Extend hit area to all available width instead of allowing more items to be layed out after the node.");
             ImGui::CheckboxFlags("ImGuiTreeNodeFlags_SpanFullWidth", (unsigned int*)&base_flags, ImGuiTreeNodeFlags_SpanFullWidth);
             ImGui::Checkbox("Align label with current X position", &align_label_with_current_x_position);
+            ImGui::Checkbox("Test tree node as drag source", &test_drag_and_drop);
             ImGui::Text("Hello!");
             if (align_label_with_current_x_position)
                 ImGui::Unindent(ImGui::GetTreeNodeToLabelSpacing());
@@ -665,6 +722,12 @@ static void ShowDemoWindowWidgets()
                     bool node_open = ImGui::TreeNodeEx((void*)(intptr_t)i, node_flags, "Selectable Node %d", i);
                     if (ImGui::IsItemClicked())
                         node_clicked = i;
+                    if (test_drag_and_drop && ImGui::BeginDragDropSource())
+                    {
+                        ImGui::SetDragDropPayload("_TREENODE", NULL, 0);
+                        ImGui::Text("This is a drag and drop source");
+                        ImGui::EndDragDropSource();
+                    }
                     if (node_open)
                     {
                         ImGui::BulletText("Blah blah\nBlah Blah");
@@ -680,6 +743,12 @@ static void ShowDemoWindowWidgets()
                     ImGui::TreeNodeEx((void*)(intptr_t)i, node_flags, "Selectable Leaf %d", i);
                     if (ImGui::IsItemClicked())
                         node_clicked = i;
+                    if (test_drag_and_drop && ImGui::BeginDragDropSource())
+                    {
+                        ImGui::SetDragDropPayload("_TREENODE", NULL, 0);
+                        ImGui::Text("This is a drag and drop source");
+                        ImGui::EndDragDropSource();
+                    }
                 }
             }
             if (node_clicked != -1)
@@ -1751,10 +1820,13 @@ static void ShowDemoWindowWidgets()
 
         // Calling IsItemHovered() after begin returns the hovered status of the title bar.
         // This is useful in particular if you want to create a context menu (with BeginPopupContextItem) associated to the title bar of a window.
+        // This will also work when docked into a Tab (the Tab replace the Title Bar and guarantee the same properties).
         static bool test_window = false;
         ImGui::Checkbox("Hovered/Active tests after Begin() for title bar testing", &test_window);
         if (test_window)
         {
+            // FIXME-DOCK: This window cannot be docked within the ImGui Demo window, this will cause a feedback loop and get them stuck.
+            // Could we fix this through an ImGuiWindowClass feature? Or an API call to tag our parent as "don't skip items"?
             ImGui::Begin("Title bar Hovered/Active tests", &test_window);
             if (ImGui::BeginPopupContextItem()) // <-- This is using IsItemHovered()
             {
@@ -3175,6 +3247,12 @@ void ImGui::ShowAboutWindow(bool* p_open)
 #ifdef __clang_version__
         ImGui::Text("define: __clang_version__=%s", __clang_version__);
 #endif
+#ifdef IMGUI_HAS_VIEWPORT
+        ImGui::Text("define: IMGUI_HAS_VIEWPORT");
+#endif
+#ifdef IMGUI_HAS_DOCK
+        ImGui::Text("define: IMGUI_HAS_DOCK");
+#endif
         ImGui::Separator();
         ImGui::Text("io.BackendPlatformName: %s", io.BackendPlatformName ? io.BackendPlatformName : "NULL");
         ImGui::Text("io.BackendRendererName: %s", io.BackendRendererName ? io.BackendRendererName : "NULL");
@@ -3185,7 +3263,19 @@ void ImGui::ShowAboutWindow(bool* p_open)
         if (io.ConfigFlags & ImGuiConfigFlags_NavNoCaptureKeyboard)     ImGui::Text(" NavNoCaptureKeyboard");
         if (io.ConfigFlags & ImGuiConfigFlags_NoMouse)                  ImGui::Text(" NoMouse");
         if (io.ConfigFlags & ImGuiConfigFlags_NoMouseCursorChange)      ImGui::Text(" NoMouseCursorChange");
+        if (io.ConfigFlags & ImGuiConfigFlags_DockingEnable)            ImGui::Text(" DockingEnable");
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)          ImGui::Text(" ViewportsEnable");
+        if (io.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleViewports)  ImGui::Text(" DpiEnableScaleViewports");
+        if (io.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleFonts)      ImGui::Text(" DpiEnableScaleFonts");
         if (io.MouseDrawCursor)                                         ImGui::Text("io.MouseDrawCursor");
+        if (io.ConfigViewportsNoAutoMerge)                              ImGui::Text("io.ConfigViewportsNoAutoMerge");
+        if (io.ConfigViewportsNoTaskBarIcon)                            ImGui::Text("io.ConfigViewportsNoTaskBarIcon");
+        if (io.ConfigViewportsNoDecoration)                             ImGui::Text("io.ConfigViewportsNoDecoration");
+        if (io.ConfigViewportsNoDefaultParent)                          ImGui::Text("io.ConfigViewportsNoDefaultParent");
+        if (io.ConfigDockingNoSplit)                                    ImGui::Text("io.ConfigDockingNoSplit");
+        if (io.ConfigDockingWithShift)                                  ImGui::Text("io.ConfigDockingWithShift");
+        if (io.ConfigDockingAlwaysTabBar)                               ImGui::Text("io.ConfigDockingAlwaysTabBar");
+        if (io.ConfigDockingTransparentPayload)                         ImGui::Text("io.ConfigDockingTransparentPayload");
         if (io.ConfigMacOSXBehaviors)                                   ImGui::Text("io.ConfigMacOSXBehaviors");
         if (io.ConfigInputTextCursorBlink)                              ImGui::Text("io.ConfigInputTextCursorBlink");
         if (io.ConfigWindowsResizeFromEdges)                            ImGui::Text("io.ConfigWindowsResizeFromEdges");
@@ -3195,7 +3285,10 @@ void ImGui::ShowAboutWindow(bool* p_open)
         if (io.BackendFlags & ImGuiBackendFlags_HasGamepad)             ImGui::Text(" HasGamepad");
         if (io.BackendFlags & ImGuiBackendFlags_HasMouseCursors)        ImGui::Text(" HasMouseCursors");
         if (io.BackendFlags & ImGuiBackendFlags_HasSetMousePos)         ImGui::Text(" HasSetMousePos");
+        if (io.BackendFlags & ImGuiBackendFlags_PlatformHasViewports)   ImGui::Text(" PlatformHasViewports");
+        if (io.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport)ImGui::Text(" HasMouseHoveredViewport");
         if (io.BackendFlags & ImGuiBackendFlags_RendererHasVtxOffset)   ImGui::Text(" RendererHasVtxOffset");
+        if (io.BackendFlags & ImGuiBackendFlags_RendererHasViewports)   ImGui::Text(" RendererHasViewports");
         ImGui::Separator();
         ImGui::Text("io.Fonts: %d fonts, Flags: 0x%08X, TexSize: %d,%d", io.Fonts->Fonts.Size, io.Fonts->Flags, io.Fonts->TexWidth, io.Fonts->TexHeight);
         ImGui::Text("io.DisplaySize: %.2f,%.2f", io.DisplaySize.x, io.DisplaySize.y);
@@ -4369,6 +4462,8 @@ static void ShowExampleAppConstrainedResize(bool* p_open)
             "Custom: Always Square",
             "Custom: Fixed Steps (100)",
         };
+        if (ImGui::IsWindowDocked())
+            ImGui::Text("Warning: Sizing Constraints won't work if the window is docked!");
         if (ImGui::Button("200x200")) { ImGui::SetWindowSize(ImVec2(200, 200)); } ImGui::SameLine();
         if (ImGui::Button("500x500")) { ImGui::SetWindowSize(ImVec2(500, 500)); } ImGui::SameLine();
         if (ImGui::Button("800x200")) { ImGui::SetWindowSize(ImVec2(800, 200)); }
@@ -4390,17 +4485,22 @@ static void ShowExampleAppConstrainedResize(bool* p_open)
 // Demonstrate creating a simple static window with no decoration + a context-menu to choose which corner of the screen to use.
 static void ShowExampleAppSimpleOverlay(bool* p_open)
 {
+    // FIXME-VIEWPORT: Select a default viewport
     const float DISTANCE = 10.0f;
     static int corner = 0;
     ImGuiIO& io = ImGui::GetIO();
     if (corner != -1)
     {
-        ImVec2 window_pos = ImVec2((corner & 1) ? io.DisplaySize.x - DISTANCE : DISTANCE, (corner & 2) ? io.DisplaySize.y - DISTANCE : DISTANCE);
+        ImGuiViewport* viewport = ImGui::GetMainViewport();
+        ImVec2 work_area_pos = viewport->GetWorkPos();   // Instead of using viewport->Pos we use GetWorkPos() to avoid menu bars, if any!
+        ImVec2 work_area_size = viewport->GetWorkSize();
+        ImVec2 window_pos = ImVec2((corner & 1) ? (work_area_pos.x + work_area_size.x - DISTANCE) : (work_area_pos.x + DISTANCE), (corner & 2) ? (work_area_pos.y + work_area_size.y - DISTANCE) : (work_area_pos.y + DISTANCE));
         ImVec2 window_pos_pivot = ImVec2((corner & 1) ? 1.0f : 0.0f, (corner & 2) ? 1.0f : 0.0f);
         ImGui::SetNextWindowPos(window_pos, ImGuiCond_Always, window_pos_pivot);
+        ImGui::SetNextWindowViewport(viewport->ID);
     }
     ImGui::SetNextWindowBgAlpha(0.35f); // Transparent background
-    if (ImGui::Begin("Example: Simple overlay", p_open, (corner != -1 ? ImGuiWindowFlags_NoMove : 0) | ImGuiWindowFlags_NoDecoration | ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoFocusOnAppearing | ImGuiWindowFlags_NoNav))
+    if (ImGui::Begin("Example: Simple overlay", p_open, (corner != -1 ? ImGuiWindowFlags_NoMove : 0) | ImGuiWindowFlags_NoDocking | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoFocusOnAppearing | ImGuiWindowFlags_NoNav))
     {
         ImGui::Text("Simple overlay\n" "in the corner of the screen.\n" "(right-click to change position)");
         ImGui::Separator();
@@ -4632,6 +4732,100 @@ static void ShowExampleAppCustomRendering(bool* p_open)
 }
 
 //-----------------------------------------------------------------------------
+// [SECTION] Example App: Docking, DockSpace / ShowExampleAppDockSpace()
+//-----------------------------------------------------------------------------
+
+// Demonstrate using DockSpace() to create an explicit docking node within an existing window.
+// Note that you already dock windows into each others _without_ a DockSpace() by just moving windows
+// from their title bar (or by holding SHIFT if io.ConfigDockingWithShift is set).
+// DockSpace() is only useful to construct to a central location for your application.
+void ShowExampleAppDockSpace(bool* p_open)
+{
+    static bool opt_fullscreen_persistant = true;
+    bool opt_fullscreen = opt_fullscreen_persistant;
+    static ImGuiDockNodeFlags dockspace_flags = ImGuiDockNodeFlags_None;
+
+    // We are using the ImGuiWindowFlags_NoDocking flag to make the parent window not dockable into,
+    // because it would be confusing to have two docking targets within each others.
+    ImGuiWindowFlags window_flags = ImGuiWindowFlags_MenuBar | ImGuiWindowFlags_NoDocking;
+    if (opt_fullscreen)
+    {
+        ImGuiViewport* viewport = ImGui::GetMainViewport();
+        ImGui::SetNextWindowPos(viewport->GetWorkPos());
+        ImGui::SetNextWindowSize(viewport->GetWorkSize());
+        ImGui::SetNextWindowViewport(viewport->ID);
+        ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
+        ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
+        window_flags |= ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove;
+        window_flags |= ImGuiWindowFlags_NoBringToFrontOnFocus | ImGuiWindowFlags_NoNavFocus;
+    }
+
+    // When using ImGuiDockNodeFlags_PassthruCentralNode, DockSpace() will render our background 
+    // and handle the pass-thru hole, so we ask Begin() to not render a background.
+    if (dockspace_flags & ImGuiDockNodeFlags_PassthruCentralNode)
+        window_flags |= ImGuiWindowFlags_NoBackground;
+
+    // Important: note that we proceed even if Begin() returns false (aka window is collapsed).
+    // This is because we want to keep our DockSpace() active. If a DockSpace() is inactive,
+    // all active windows docked into it will lose their parent and become undocked.
+    // We cannot preserve the docking relationship between an active window and an inactive docking, otherwise
+    // any change of dockspace/settings would lead to windows being stuck in limbo and never being visible.
+    ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));
+    ImGui::Begin("DockSpace Demo", p_open, window_flags);
+    ImGui::PopStyleVar();
+
+    if (opt_fullscreen)
+        ImGui::PopStyleVar(2);
+
+    // DockSpace
+    ImGuiIO& io = ImGui::GetIO();
+    if (io.ConfigFlags & ImGuiConfigFlags_DockingEnable)
+    {
+        ImGuiID dockspace_id = ImGui::GetID("MyDockSpace");
+        ImGui::DockSpace(dockspace_id, ImVec2(0.0f, 0.0f), dockspace_flags);
+    }
+    else
+    {
+        ShowDockingDisabledMessage();
+    }
+
+    if (ImGui::BeginMenuBar())
+    {
+        if (ImGui::BeginMenu("Docking"))
+        {
+            // Disabling fullscreen would allow the window to be moved to the front of other windows,
+            // which we can't undo at the moment without finer window depth/z control.
+            //ImGui::MenuItem("Fullscreen", NULL, &opt_fullscreen_persistant);
+
+            if (ImGui::MenuItem("Flag: NoSplit",                "", (dockspace_flags & ImGuiDockNodeFlags_NoSplit) != 0))                 dockspace_flags ^= ImGuiDockNodeFlags_NoSplit;
+            if (ImGui::MenuItem("Flag: NoResize",               "", (dockspace_flags & ImGuiDockNodeFlags_NoResize) != 0))                dockspace_flags ^= ImGuiDockNodeFlags_NoResize;
+            if (ImGui::MenuItem("Flag: NoDockingInCentralNode", "", (dockspace_flags & ImGuiDockNodeFlags_NoDockingInCentralNode) != 0))  dockspace_flags ^= ImGuiDockNodeFlags_NoDockingInCentralNode;
+            if (ImGui::MenuItem("Flag: PassthruCentralNode",    "", (dockspace_flags & ImGuiDockNodeFlags_PassthruCentralNode) != 0))     dockspace_flags ^= ImGuiDockNodeFlags_PassthruCentralNode;
+            if (ImGui::MenuItem("Flag: AutoHideTabBar",         "", (dockspace_flags & ImGuiDockNodeFlags_AutoHideTabBar) != 0))          dockspace_flags ^= ImGuiDockNodeFlags_AutoHideTabBar;
+            ImGui::Separator();
+            if (ImGui::MenuItem("Close DockSpace", NULL, false, p_open != NULL))
+                *p_open = false;
+            ImGui::EndMenu();
+        }
+        HelpMarker(
+            "When docking is enabled, you can ALWAYS dock MOST window into another! Try it now!" "\n\n"
+            " > if io.ConfigDockingWithShift==false (default):" "\n"
+            "   drag windows from title bar to dock" "\n"
+            " > if io.ConfigDockingWithShift==true:" "\n"
+            "   drag windows from anywhere and hold Shift to dock" "\n\n"
+            "This demo app has nothing to do with it!" "\n\n"
+            "This demo app only demonstrate the use of ImGui::DockSpace() which allows you to manually create a docking node _within_ another window. This is useful so you can decorate your main application window (e.g. with a menu bar)." "\n\n"
+            "ImGui::DockSpace() comes with one hard constraint: it needs to be submitted _before_ any window which may be docked into it. Therefore, if you use a dock spot as the central point of your application, you'll probably want it to be part of the very first window you are submitting to imgui every frame." "\n\n"
+            "(NB: because of this constraint, the implicit \"Debug\" window can not be docked into an explicit DockSpace() node, because that window is submitted as part of the NewFrame() call. An easy workaround is that you can create your own implicit \"Debug##2\" window after calling DockSpace() and leave it in the window stack for anyone to use.)"
+        );
+
+        ImGui::EndMenuBar();
+    }
+
+    ImGui::End();
+}
+
+//-----------------------------------------------------------------------------
 // [SECTION] Example App: Documents Handling / ShowExampleAppDocuments()
 //-----------------------------------------------------------------------------
 
@@ -4729,11 +4923,25 @@ void ShowExampleAppDocuments(bool* p_open)
     static ExampleAppDocuments app;
 
     // Options
+    enum Target
+    {
+        Target_None,
+        Target_Tab,                 // Create documents as local tab into a local tab bar
+        Target_DockSpaceAndWindow   // Create documents as regular windows, and create an embedded dockspace
+    };
+    static Target opt_target = Target_Tab;
     static bool opt_reorderable = true;
     static ImGuiTabBarFlags opt_fitting_flags = ImGuiTabBarFlags_FittingPolicyDefault_;
 
+    // When (opt_target == Target_DockSpaceAndWindow) there is the possibily that one of our child Document window (e.g. "Eggplant")
+    // that we emit gets docked into the same spot as the parent window ("Example: Documents").
+    // This would create a problematic feedback loop because selecting the "Eggplant" tab would make the "Example: Documents" tab
+    // not visible, which in turn would stop submitting the "Eggplant" window.
+    // We avoid this problem by submitting our documents window even if our parent window is not currently visible.
+    // Another solution may be to make the "Example: Documents" window use the ImGuiWindowFlags_NoDocking.
+
     bool window_contents_visible = ImGui::Begin("Example: Documents", p_open, ImGuiWindowFlags_MenuBar);
-    if (!window_contents_visible)
+    if (!window_contents_visible && opt_target != Target_DockSpaceAndWindow)
     {
         ImGui::End();
         return;
@@ -4780,10 +4988,17 @@ void ShowExampleAppDocuments(bool* p_open)
                 doc->DoForceClose();
         ImGui::PopID();
     }
+    ImGui::PushItemWidth(ImGui::GetFontSize() * 12);
+    ImGui::Combo("Output", (int*)&opt_target, "None\0TabBar+Tabs\0DockSpace+Window\0");
+    ImGui::PopItemWidth();
+    bool redock_all = false;
+    if (opt_target == Target_Tab)                { ImGui::SameLine(); ImGui::Checkbox("Reorderable Tabs", &opt_reorderable); }
+    if (opt_target == Target_DockSpaceAndWindow) { ImGui::SameLine(); redock_all = ImGui::Button("Redock all"); }
 
     ImGui::Separator();
 
-    // Submit Tab Bar and Tabs
+    // Tabs
+    if (opt_target == Target_Tab)
     {
         ImGuiTabBarFlags tab_bar_flags = (opt_fitting_flags) | (opt_reorderable ? ImGuiTabBarFlags_Reorderable : 0);
         if (ImGui::BeginTabBar("##tabs", tab_bar_flags))
@@ -4823,6 +5038,53 @@ void ShowExampleAppDocuments(bool* p_open)
             ImGui::EndTabBar();
         }
     }
+    else if (opt_target == Target_DockSpaceAndWindow)
+    {
+        if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_DockingEnable)
+        {
+            NotifyOfDocumentsClosedElsewhere(app);
+
+            // Create a DockSpace node where any window can be docked
+            ImGuiID dockspace_id = ImGui::GetID("MyDockSpace");
+            ImGui::DockSpace(dockspace_id);
+
+            // Create Windows
+            for (int doc_n = 0; doc_n < app.Documents.Size; doc_n++)
+            {
+                MyDocument* doc = &app.Documents[doc_n];
+                if (!doc->Open)
+                    continue;
+
+                ImGui::SetNextWindowDockID(dockspace_id, redock_all ? ImGuiCond_Always : ImGuiCond_FirstUseEver);
+                ImGuiWindowFlags window_flags = (doc->Dirty ? ImGuiWindowFlags_UnsavedDocument : 0);
+                bool visible = ImGui::Begin(doc->Name, &doc->Open, window_flags);
+
+                // Cancel attempt to close when unsaved add to save queue so we can display a popup.
+                if (!doc->Open && doc->Dirty)
+                {
+                    doc->Open = true;
+                    doc->DoQueueClose();
+                }
+
+                MyDocument::DisplayContextMenu(doc);
+                if (visible)
+                    MyDocument::DisplayContents(doc);
+
+                ImGui::End();
+            }
+        }
+        else
+        {
+            ShowDockingDisabledMessage();
+        }
+    }
+
+    // Early out other contents
+    if (!window_contents_visible)
+    {
+        ImGui::End();
+        return;
+    }
 
     // Update closing queue
     static ImVector<MyDocument*> close_queue;
diff --git a/imgui/imgui_draw.cpp b/imgui/imgui_draw.cpp
index 1e08bfd0..20a8a1b2 100644
--- a/imgui/imgui_draw.cpp
+++ b/imgui/imgui_draw.cpp
@@ -1,4 +1,4 @@
-// dear imgui, v1.76
+// dear imgui, v1.77 WIP
 // (drawing and font code)
 
 /*
@@ -218,6 +218,8 @@ void ImGui::StyleColorsDark(ImGuiStyle* dst)
     colors[ImGuiCol_TabActive]              = ImLerp(colors[ImGuiCol_HeaderActive], colors[ImGuiCol_TitleBgActive], 0.60f);
     colors[ImGuiCol_TabUnfocused]           = ImLerp(colors[ImGuiCol_Tab],          colors[ImGuiCol_TitleBg], 0.80f);
     colors[ImGuiCol_TabUnfocusedActive]     = ImLerp(colors[ImGuiCol_TabActive],    colors[ImGuiCol_TitleBg], 0.40f);
+    colors[ImGuiCol_DockingPreview]         = colors[ImGuiCol_HeaderActive] * ImVec4(1.0f, 1.0f, 1.0f, 0.7f);
+    colors[ImGuiCol_DockingEmptyBg]         = ImVec4(0.20f, 0.20f, 0.20f, 1.00f);
     colors[ImGuiCol_PlotLines]              = ImVec4(0.61f, 0.61f, 0.61f, 1.00f);
     colors[ImGuiCol_PlotLinesHovered]       = ImVec4(1.00f, 0.43f, 0.35f, 1.00f);
     colors[ImGuiCol_PlotHistogram]          = ImVec4(0.90f, 0.70f, 0.00f, 1.00f);
@@ -273,6 +275,8 @@ void ImGui::StyleColorsClassic(ImGuiStyle* dst)
     colors[ImGuiCol_TabActive]              = ImLerp(colors[ImGuiCol_HeaderActive], colors[ImGuiCol_TitleBgActive], 0.60f);
     colors[ImGuiCol_TabUnfocused]           = ImLerp(colors[ImGuiCol_Tab],          colors[ImGuiCol_TitleBg], 0.80f);
     colors[ImGuiCol_TabUnfocusedActive]     = ImLerp(colors[ImGuiCol_TabActive],    colors[ImGuiCol_TitleBg], 0.40f);
+    colors[ImGuiCol_DockingPreview]         = colors[ImGuiCol_Header] * ImVec4(1.0f, 1.0f, 1.0f, 0.7f);
+    colors[ImGuiCol_DockingEmptyBg]         = ImVec4(0.20f, 0.20f, 0.20f, 1.00f);
     colors[ImGuiCol_PlotLines]              = ImVec4(1.00f, 1.00f, 1.00f, 1.00f);
     colors[ImGuiCol_PlotLinesHovered]       = ImVec4(0.90f, 0.70f, 0.00f, 1.00f);
     colors[ImGuiCol_PlotHistogram]          = ImVec4(0.90f, 0.70f, 0.00f, 1.00f);
@@ -329,6 +333,8 @@ void ImGui::StyleColorsLight(ImGuiStyle* dst)
     colors[ImGuiCol_TabActive]              = ImLerp(colors[ImGuiCol_HeaderActive], colors[ImGuiCol_TitleBgActive], 0.60f);
     colors[ImGuiCol_TabUnfocused]           = ImLerp(colors[ImGuiCol_Tab],          colors[ImGuiCol_TitleBg], 0.80f);
     colors[ImGuiCol_TabUnfocusedActive]     = ImLerp(colors[ImGuiCol_TabActive],    colors[ImGuiCol_TitleBg], 0.40f);
+    colors[ImGuiCol_DockingPreview]         = colors[ImGuiCol_Header] * ImVec4(1.0f, 1.0f, 1.0f, 0.7f);
+    colors[ImGuiCol_DockingEmptyBg]         = ImVec4(0.20f, 0.20f, 0.20f, 1.00f);
     colors[ImGuiCol_PlotLines]              = ImVec4(0.39f, 0.39f, 0.39f, 1.00f);
     colors[ImGuiCol_PlotLinesHovered]       = ImVec4(1.00f, 0.43f, 0.35f, 1.00f);
     colors[ImGuiCol_PlotHistogram]          = ImVec4(0.90f, 0.70f, 0.00f, 1.00f);
@@ -3168,8 +3174,10 @@ void ImFont::RenderText(ImDrawList* draw_list, float size, ImVec2 pos, ImU32 col
 // - RenderBullet()
 // - RenderCheckMark()
 // - RenderMouseCursor()
+// - RenderArrowDockMenu()
 // - RenderArrowPointingAt()
 // - RenderRectFilledRangeH()
+// - RenderRectFilledWithHole()
 //-----------------------------------------------------------------------------
 // Function in need of a redesign (legacy mess)
 // - RenderColorRectWithAlphaCheckerboard()
@@ -3261,6 +3269,14 @@ void ImGui::RenderArrowPointingAt(ImDrawList* draw_list, ImVec2 pos, ImVec2 half
     }
 }
 
+// This is less wide than RenderArrow() and we use in dock nodes instead of the regular RenderArrow() to denote a change of functionality,
+// and because the saved space means that the left-most tab label can stay at exactly the same position as the label of a loose window.
+void ImGui::RenderArrowDockMenu(ImDrawList* draw_list, ImVec2 p_min, float sz, ImU32 col)
+{
+    draw_list->AddRectFilled(p_min + ImVec2(sz * 0.10f, sz * 0.15f), p_min + ImVec2(sz * 0.70f, sz * 0.30f), col);
+    RenderArrowPointingAt(draw_list, p_min + ImVec2(sz * 0.40f, sz * 0.85f), ImVec2(sz * 0.30f, sz * 0.40f), ImGuiDir_Down, col);
+}
+
 static inline float ImAcos01(float x)
 {
     if (x <= 0.0f) return IM_PI * 0.5f;
@@ -3330,6 +3346,24 @@ void ImGui::RenderRectFilledRangeH(ImDrawList* draw_list, const ImRect& rect, Im
     draw_list->PathFillConvex(col);
 }
 
+// For CTRL+TAB within a docking node we need to render the dimming background in 8 steps
+// (Because the root node renders the background in one shot, in order to avoid flickering when a child dock node is not submitted)
+void ImGui::RenderRectFilledWithHole(ImDrawList* draw_list, ImRect outer, ImRect inner, ImU32 col, float rounding)
+{
+    const bool fill_L = (inner.Min.x > outer.Min.x);
+    const bool fill_R = (inner.Max.x < outer.Max.x);
+    const bool fill_U = (inner.Min.y > outer.Min.y);
+    const bool fill_D = (inner.Max.y < outer.Max.y);
+    if (fill_L) draw_list->AddRectFilled(ImVec2(outer.Min.x, inner.Min.y), ImVec2(inner.Min.x, inner.Max.y), col, rounding, (fill_U ? 0 : ImDrawCornerFlags_TopLeft) | (fill_D ? 0 : ImDrawCornerFlags_BotLeft));
+    if (fill_R) draw_list->AddRectFilled(ImVec2(inner.Max.x, inner.Min.y), ImVec2(outer.Max.x, inner.Max.y), col, rounding, (fill_U ? 0 : ImDrawCornerFlags_TopRight) | (fill_D ? 0 : ImDrawCornerFlags_BotRight));
+    if (fill_U) draw_list->AddRectFilled(ImVec2(inner.Min.x, outer.Min.y), ImVec2(inner.Max.x, inner.Min.y), col, rounding, (fill_L ? 0 : ImDrawCornerFlags_TopLeft) | (fill_R ? 0 : ImDrawCornerFlags_TopRight));
+    if (fill_D) draw_list->AddRectFilled(ImVec2(inner.Min.x, inner.Max.y), ImVec2(inner.Max.x, outer.Max.y), col, rounding, (fill_L ? 0 : ImDrawCornerFlags_BotLeft) | (fill_R ? 0 : ImDrawCornerFlags_BotRight));
+    if (fill_L && fill_U) draw_list->AddRectFilled(ImVec2(outer.Min.x, outer.Min.y), ImVec2(inner.Min.x, inner.Min.y), col, rounding, ImDrawCornerFlags_TopLeft);
+    if (fill_R && fill_U) draw_list->AddRectFilled(ImVec2(inner.Max.x, outer.Min.y), ImVec2(outer.Max.x, inner.Min.y), col, rounding, ImDrawCornerFlags_TopRight);
+    if (fill_L && fill_D) draw_list->AddRectFilled(ImVec2(outer.Min.x, inner.Max.y), ImVec2(inner.Min.x, outer.Max.y), col, rounding, ImDrawCornerFlags_BotLeft);
+    if (fill_R && fill_D) draw_list->AddRectFilled(ImVec2(inner.Max.x, inner.Max.y), ImVec2(outer.Max.x, outer.Max.y), col, rounding, ImDrawCornerFlags_BotRight);
+}
+
 // Helper for ColorPicker4()
 // NB: This is rather brittle and will show artifact when rounding this enabled if rounded corners overlap multiple cells. Caller currently responsible for avoiding that.
 // Spent a non reasonable amount of time trying to getting this right for ColorButton with rounding+anti-aliasing+ImGuiColorEditFlags_HalfAlphaPreview flag + various grid sizes and offsets, and eventually gave up... probably more reasonable to disable rounding alltogether.
diff --git a/imgui/imgui_internal.h b/imgui/imgui_internal.h
index cef0f9a9..13abd67a 100644
--- a/imgui/imgui_internal.h
+++ b/imgui/imgui_internal.h
@@ -1,4 +1,4 @@
-// dear imgui, v1.76
+// dear imgui, v1.77 WIP
 // (internal structures/api)
 
 // You may use this file to debug, understand or extend ImGui features but we don't provide any guarantee of forward compatibility!
@@ -82,6 +82,9 @@ struct ImGuiColumnData;             // Storage data for a single column
 struct ImGuiColumns;                // Storage data for a columns set
 struct ImGuiContext;                // Main Dear ImGui context
 struct ImGuiDataTypeInfo;           // Type information associated to a ImGuiDataType enum
+struct ImGuiDockContext;            // Docking system context
+struct ImGuiDockNode;               // Docking system node (hold a list of Windows OR two child dock nodes)
+struct ImGuiDockNodeSettings;       // Storage for a dock node in .ini file (we preserve those even if the associated dock node isn't active during the session)
 struct ImGuiGroupData;              // Stacked storage data for BeginGroup()/EndGroup()
 struct ImGuiInputTextState;         // Internal state of the currently focused/edited text input box
 struct ImGuiItemHoveredDataBackup;  // Backup and restore IsItemHovered() internal data
@@ -99,6 +102,7 @@ struct ImGuiWindowTempData;         // Temporary storage for one window (that's
 struct ImGuiWindowSettings;         // Storage for a window .ini settings (we keep one of those even if the actual window wasn't instanced during this session)
 
 // Use your programming IDE "Go to definition" facility on the names of the center columns to find the actual flags/enum lists.
+typedef int ImGuiDataAuthority;         // -> enum ImGuiDataAuthority_      // Enum: for storing the source authority (dock node vs window) of a field
 typedef int ImGuiLayoutType;            // -> enum ImGuiLayoutType_         // Enum: Horizontal or vertical
 typedef int ImGuiButtonFlags;           // -> enum ImGuiButtonFlags_        // Flags: for ButtonEx(), ButtonBehavior()
 typedef int ImGuiColumnsFlags;          // -> enum ImGuiColumnsFlags_       // Flags: BeginColumns()
@@ -141,6 +145,9 @@ namespace ImStb
 extern IMGUI_API ImGuiContext* GImGui;  // Current implicit context pointer
 #endif
 
+// Internal Drag and Drop payload types. String starting with '_' are reserved for Dear ImGui.
+#define IMGUI_PAYLOAD_TYPE_WINDOW       "_IMWINDOW"     // Payload == ImGuiWindow*
+
 //-----------------------------------------------------------------------------
 // Macros
 //-----------------------------------------------------------------------------
@@ -150,6 +157,14 @@ extern IMGUI_API ImGuiContext* GImGui;  // Current implicit context pointer
 #define IMGUI_DEBUG_LOG(_FMT,...)       printf("[%05d] " _FMT, GImGui->FrameCount, __VA_ARGS__)
 #endif
 
+// Debug Logging for selected systems. Remove the '((void)0) //' to enable.
+//#define IMGUI_DEBUG_LOG_POPUP         IMGUI_DEBUG_LOG // Enable log
+//#define IMGUI_DEBUG_LOG_VIEWPORT      IMGUI_DEBUG_LOG // Enable log
+//#define IMGUI_DEBUG_LOG_DOCKING       IMGUI_DEBUG_LOG // Enable log
+#define IMGUI_DEBUG_LOG_POPUP(...)      ((void)0)       // Disable log
+#define IMGUI_DEBUG_LOG_VIEWPORT(...)   ((void)0)       // Disable log
+#define IMGUI_DEBUG_LOG_DOCKING(...)    ((void)0)       // Disable log
+
 // Static Asserts
 #if (__cplusplus >= 201100)
 #define IM_STATIC_ASSERT(_COND)         static_assert(_COND, "")
@@ -723,6 +738,14 @@ struct ImGuiDataTypeInfo
     const char* ScanFmt;        // Default scanf format for the type
 };
 
+// Extend ImGuiDataType_
+enum ImGuiDataTypePrivate_
+{
+    ImGuiDataType_String = ImGuiDataType_COUNT + 1,
+    ImGuiDataType_Pointer,
+    ImGuiDataType_ID
+};
+
 // Stacked color modifier, backup of modified data so we can restore it
 struct ImGuiColorMod
 {
@@ -808,11 +831,16 @@ struct IMGUI_API ImGuiInputTextState
 struct ImGuiWindowSettings
 {
     ImGuiID     ID;
-    ImVec2ih    Pos;
+    ImVec2ih    Pos;            // NB: Settings position are stored RELATIVE to the viewport! Whereas runtime ones are absolute positions.
     ImVec2ih    Size;
+    ImVec2ih    ViewportPos;
+    ImGuiID     ViewportId;
+    ImGuiID     DockId;         // ID of last known DockNode (even if the DockNode is invisible because it has only 1 active window), or 0 if none.
+    ImGuiID     ClassId;        // ID of window class if specified
+    short       DockOrder;      // Order of the last time the window was visible within its DockNode. This is used to reorder windows that are reappearing on the same frame. Same value between windows that were active and windows that were none are possible.
     bool        Collapsed;
 
-    ImGuiWindowSettings()       { ID = 0; Pos = Size = ImVec2ih(0, 0); Collapsed = false; }
+    ImGuiWindowSettings()       { ID = 0; Pos = Size = ViewportPos = ImVec2ih(0, 0); ViewportId = DockId = ClassId = 0; DockOrder = -1; Collapsed = false; }
     char* GetName()             { return (char*)(this + 1); }
 };
 
@@ -925,6 +953,37 @@ struct ImDrawDataBuilder
     IMGUI_API void FlattenIntoSingleLayer();
 };
 
+// ImGuiViewport Private/Internals fields (cardinal sin: we are using inheritance!)
+// Note that every instance of ImGuiViewport is in fact a ImGuiViewportP.
+struct ImGuiViewportP : public ImGuiViewport
+{
+    int                 Idx;
+    int                 LastFrameActive;          // Last frame number this viewport was activated by a window
+    int                 LastFrameDrawLists[2];    // Last frame number the background (0) and foreground (1) draw lists were used
+    int                 LastFrontMostStampCount;  // Last stamp number from when a window hosted by this viewport was made front-most (by comparing this value between two viewport we have an implicit viewport z-order
+    ImGuiID             LastNameHash;
+    ImVec2              LastPos;
+    float               Alpha;                    // Window opacity (when dragging dockable windows/viewports we make them transparent)
+    float               LastAlpha;
+    short               PlatformMonitor;
+    bool                PlatformWindowCreated;
+    ImGuiWindow*        Window;                   // Set when the viewport is owned by a window (and ImGuiViewportFlags_CanHostOtherWindows is NOT set)
+    ImDrawList*         DrawLists[2];             // Convenience background (0) and foreground (1) draw lists. We use them to draw software mouser cursor when io.MouseDrawCursor is set and to draw most debug overlays.
+    ImDrawData          DrawDataP;
+    ImDrawDataBuilder   DrawDataBuilder;
+    ImVec2              LastPlatformPos;
+    ImVec2              LastPlatformSize;
+    ImVec2              LastRendererSize;
+    ImVec2              CurrWorkOffsetMin;        // Work area top-left offset being increased during the frame
+    ImVec2              CurrWorkOffsetMax;        // Work area bottom-right offset being decreased during the frame
+
+    ImGuiViewportP()                { Idx = -1; LastFrameActive = LastFrameDrawLists[0] = LastFrameDrawLists[1] = LastFrontMostStampCount = -1; LastNameHash = 0; Alpha = LastAlpha = 1.0f; PlatformMonitor = -1; PlatformWindowCreated = false; Window = NULL; DrawLists[0] = DrawLists[1] = NULL; LastPlatformPos = LastPlatformSize = LastRendererSize = ImVec2(FLT_MAX, FLT_MAX); }
+    ~ImGuiViewportP()               { if (DrawLists[0]) IM_DELETE(DrawLists[0]); if (DrawLists[1]) IM_DELETE(DrawLists[1]); }
+    ImRect  GetMainRect() const     { return ImRect(Pos.x, Pos.y, Pos.x + Size.x, Pos.y + Size.y); }
+    ImRect  GetWorkRect() const     { return ImRect(Pos.x + WorkOffsetMin.x, Pos.y + WorkOffsetMin.y, Pos.x + Size.x + WorkOffsetMax.x, Pos.y + Size.y + WorkOffsetMax.y); }
+    void    ClearRequestFlags()     { PlatformRequestClose = PlatformRequestMove = PlatformRequestResize = false; }
+};
+
 struct ImGuiNavMoveResult
 {
     ImGuiWindow*    Window;             // Best candidate window
@@ -948,7 +1007,11 @@ enum ImGuiNextWindowDataFlags_
     ImGuiNextWindowDataFlags_HasCollapsed       = 1 << 3,
     ImGuiNextWindowDataFlags_HasSizeConstraint  = 1 << 4,
     ImGuiNextWindowDataFlags_HasFocus           = 1 << 5,
-    ImGuiNextWindowDataFlags_HasBgAlpha         = 1 << 6
+    ImGuiNextWindowDataFlags_HasBgAlpha         = 1 << 6,
+    ImGuiNextWindowDataFlags_HasScroll          = 1 << 7,
+    ImGuiNextWindowDataFlags_HasViewport        = 1 << 8,
+    ImGuiNextWindowDataFlags_HasDock            = 1 << 9,
+    ImGuiNextWindowDataFlags_HasWindowClass     = 1 << 10
 };
 
 // Storage for SetNexWindow** functions
@@ -958,16 +1021,22 @@ struct ImGuiNextWindowData
     ImGuiCond                   PosCond;
     ImGuiCond                   SizeCond;
     ImGuiCond                   CollapsedCond;
+    ImGuiCond                   DockCond;
     ImVec2                      PosVal;
     ImVec2                      PosPivotVal;
     ImVec2                      SizeVal;
     ImVec2                      ContentSizeVal;
+    ImVec2                      ScrollVal;
+    bool                        PosUndock;
     bool                        CollapsedVal;
     ImRect                      SizeConstraintRect;
     ImGuiSizeCallback           SizeCallback;
     void*                       SizeCallbackUserData;
     float                       BgAlphaVal;             // Override background alpha
-    ImVec2                      MenuBarOffsetMinVal;    // *Always on* This is not exposed publicly, so we don't clear it.
+    ImGuiID                     ViewportId;
+    ImGuiID                     DockId;
+    ImGuiWindowClass            WindowClass;
+    ImVec2                      MenuBarOffsetMinVal;    // (Always on) This is not exposed publicly, so we don't clear it and it doesn't have a corresponding flag (could we? for consistency?)
 
     ImGuiNextWindowData()       { memset(this, 0, sizeof(*this)); }
     inline void ClearFlags()    { Flags = ImGuiNextWindowDataFlags_None; }
@@ -1012,6 +1081,100 @@ struct ImGuiPtrOrIndex
 };
 
 //-----------------------------------------------------------------------------
+// Docking
+//-----------------------------------------------------------------------------
+
+// Extend ImGuiDockNodeFlags_
+enum ImGuiDockNodeFlagsPrivate_
+{
+    // [Internal]
+    ImGuiDockNodeFlags_DockSpace                = 1 << 10,  // Local, Saved  // A dockspace is a node that occupy space within an existing user window. Otherwise the node is floating and create its own window.
+    ImGuiDockNodeFlags_CentralNode              = 1 << 11,  // Local, Saved  // The central node has 2 main properties: stay visible when empty, only use "remaining" spaces from its neighbor.
+    ImGuiDockNodeFlags_NoTabBar                 = 1 << 12,  // Local, Saved  // Tab bar is completely unavailable. No triangle in the corner to enable it back.
+    ImGuiDockNodeFlags_HiddenTabBar             = 1 << 13,  // Local, Saved  // Tab bar is hidden, with a triangle in the corner to show it again (NB: actual tab-bar instance may be destroyed as this is only used for single-window tab bar)
+    ImGuiDockNodeFlags_NoWindowMenuButton       = 1 << 14,  // Local, Saved  // Disable window/docking menu (that one that appears instead of the collapse button)
+    ImGuiDockNodeFlags_NoCloseButton            = 1 << 15,  // Local, Saved  //
+    ImGuiDockNodeFlags_NoDocking                = 1 << 16,  // Local, Saved  // Disable any form of docking in this dockspace or individual node. (On a whole dockspace, this pretty much defeat the purpose of using a dockspace at all). Note: when turned on, existing docked nodes will be preserved.
+    ImGuiDockNodeFlags_SharedFlagsInheritMask_  = ~0,
+    ImGuiDockNodeFlags_LocalFlagsMask_          = ImGuiDockNodeFlags_NoSplit | ImGuiDockNodeFlags_NoResize | ImGuiDockNodeFlags_AutoHideTabBar | ImGuiDockNodeFlags_DockSpace | ImGuiDockNodeFlags_CentralNode | ImGuiDockNodeFlags_NoTabBar | ImGuiDockNodeFlags_HiddenTabBar | ImGuiDockNodeFlags_NoWindowMenuButton | ImGuiDockNodeFlags_NoCloseButton | ImGuiDockNodeFlags_NoDocking,
+    ImGuiDockNodeFlags_LocalFlagsTransferMask_  = ImGuiDockNodeFlags_LocalFlagsMask_ & ~ImGuiDockNodeFlags_DockSpace,  // When splitting those flags are moved to the inheriting child, never duplicated
+    ImGuiDockNodeFlags_SavedFlagsMask_          = ImGuiDockNodeFlags_NoResize | ImGuiDockNodeFlags_DockSpace | ImGuiDockNodeFlags_CentralNode | ImGuiDockNodeFlags_NoTabBar | ImGuiDockNodeFlags_HiddenTabBar | ImGuiDockNodeFlags_NoWindowMenuButton | ImGuiDockNodeFlags_NoCloseButton | ImGuiDockNodeFlags_NoDocking
+};
+
+// Store the source authority (dock node vs window) of a field
+enum ImGuiDataAuthority_
+{
+    ImGuiDataAuthority_Auto,
+    ImGuiDataAuthority_DockNode,
+    ImGuiDataAuthority_Window
+};
+
+enum ImGuiDockNodeState
+{
+    ImGuiDockNodeState_Unknown,
+    ImGuiDockNodeState_HostWindowHiddenBecauseSingleWindow,
+    ImGuiDockNodeState_HostWindowHiddenBecauseWindowsAreResizing,
+    ImGuiDockNodeState_HostWindowVisible
+};
+
+// sizeof() 116~160
+struct ImGuiDockNode
+{
+    ImGuiID                 ID;
+    ImGuiDockNodeFlags      SharedFlags;                // Flags shared by all nodes of a same dockspace hierarchy (inherited from the root node)
+    ImGuiDockNodeFlags      LocalFlags;                 // Flags specific to this node
+    ImGuiDockNode*          ParentNode;
+    ImGuiDockNode*          ChildNodes[2];              // [Split node only] Child nodes (left/right or top/bottom). Consider switching to an array.
+    ImVector<ImGuiWindow*>  Windows;                    // Note: unordered list! Iterate TabBar->Tabs for user-order.
+    ImGuiTabBar*            TabBar;
+    ImVec2                  Pos;                        // Current position
+    ImVec2                  Size;                       // Current size
+    ImVec2                  SizeRef;                    // [Split node only] Last explicitly written-to size (overridden when using a splitter affecting the node), used to calculate Size.
+    ImGuiAxis               SplitAxis;                  // [Split node only] Split axis (X or Y)
+    ImGuiWindowClass        WindowClass;                // [Root node only]
+
+    ImGuiDockNodeState      State;
+    ImGuiWindow*            HostWindow;
+    ImGuiWindow*            VisibleWindow;              // Generally point to window which is ID is == SelectedTabID, but when CTRL+Tabbing this can be a different window.
+    ImGuiDockNode*          CentralNode;                // [Root node only] Pointer to central node.
+    ImGuiDockNode*          OnlyNodeWithWindows;        // [Root node only] Set when there is a single visible node within the hierarchy.
+    int                     LastFrameAlive;             // Last frame number the node was updated or kept alive explicitly with DockSpace() + ImGuiDockNodeFlags_KeepAliveOnly
+    int                     LastFrameActive;            // Last frame number the node was updated.
+    int                     LastFrameFocused;           // Last frame number the node was focused.
+    ImGuiID                 LastFocusedNodeId;          // [Root node only] Which of our child docking node (any ancestor in the hierarchy) was last focused.
+    ImGuiID                 SelectedTabId;              // [Leaf node only] Which of our tab/window is selected.
+    ImGuiID                 WantCloseTabId;             // [Leaf node only] Set when closing a specific tab/window.
+    ImGuiDataAuthority      AuthorityForPos         :3;
+    ImGuiDataAuthority      AuthorityForSize        :3;
+    ImGuiDataAuthority      AuthorityForViewport    :3;
+    bool                    IsVisible               :1; // Set to false when the node is hidden (usually disabled as it has no active window)
+    bool                    IsFocused               :1;
+    bool                    HasCloseButton          :1;
+    bool                    HasWindowMenuButton     :1;
+    bool                    EnableCloseButton       :1;
+    bool                    WantCloseAll            :1; // Set when closing all tabs at once.
+    bool                    WantLockSizeOnce        :1;
+    bool                    WantMouseMove           :1; // After a node extraction we need to transition toward moving the newly created host window
+    bool                    WantHiddenTabBarUpdate  :1;
+    bool                    WantHiddenTabBarToggle  :1;
+    bool                    MarkedForPosSizeWrite   :1; // Update by DockNodeTreeUpdatePosSize() write-filtering
+
+    ImGuiDockNode(ImGuiID id);
+    ~ImGuiDockNode();
+    bool                    IsRootNode() const      { return ParentNode == NULL; }
+    bool                    IsDockSpace() const     { return (LocalFlags & ImGuiDockNodeFlags_DockSpace) != 0; }
+    bool                    IsFloatingNode() const  { return ParentNode == NULL && (LocalFlags & ImGuiDockNodeFlags_DockSpace) == 0; }
+    bool                    IsCentralNode() const   { return (LocalFlags & ImGuiDockNodeFlags_CentralNode) != 0; }
+    bool                    IsHiddenTabBar() const  { return (LocalFlags & ImGuiDockNodeFlags_HiddenTabBar) != 0; } // Hidden tab bar can be shown back by clicking the small triangle
+    bool                    IsNoTabBar() const      { return (LocalFlags & ImGuiDockNodeFlags_NoTabBar) != 0; }     // Never show a tab bar
+    bool                    IsSplitNode() const     { return ChildNodes[0] != NULL; }
+    bool                    IsLeafNode() const      { return ChildNodes[0] == NULL; }
+    bool                    IsEmpty() const         { return ChildNodes[0] == NULL && Windows.Size == 0; }
+    ImGuiDockNodeFlags      GetMergedFlags() const  { return SharedFlags | LocalFlags; }
+    ImRect                  Rect() const            { return ImRect(Pos.x, Pos.y, Pos.x + Size.x, Pos.y + Size.y); }
+};
+
+//-----------------------------------------------------------------------------
 // Main Dear ImGui context
 //-----------------------------------------------------------------------------
 
@@ -1020,7 +1183,10 @@ struct ImGuiContext
     bool                    Initialized;
     bool                    FontAtlasOwnedByContext;            // IO.Fonts-> is owned by the ImGuiContext and will be destructed along with it.
     ImGuiIO                 IO;
+    ImGuiPlatformIO         PlatformIO;
     ImGuiStyle              Style;
+    ImGuiConfigFlags        ConfigFlagsCurrFrame;               // = g.IO.ConfigFlags at the time of NewFrame()
+    ImGuiConfigFlags        ConfigFlagsLastFrame;
     ImFont*                 Font;                               // (Shortcut) == FontStack.empty() ? IO.Font : FontStack.back()
     float                   FontSize;                           // (Shortcut) == FontBaseSize * g.CurrentWindow->FontWindowScale == window->FontSize(). Text height for current window.
     float                   FontBaseSize;                       // (Shortcut) == IO.FontGlobalScale * Font->Scale * Font->FontSize. Base text height.
@@ -1028,10 +1194,14 @@ struct ImGuiContext
     double                  Time;
     int                     FrameCount;
     int                     FrameCountEnded;
+    int                     FrameCountPlatformEnded;
     int                     FrameCountRendered;
     bool                    WithinFrameScope;                   // Set by NewFrame(), cleared by EndFrame()
     bool                    WithinFrameScopeWithImplicitWindow; // Set by NewFrame(), cleared by EndFrame() when the implicit debug window has been pushed
     bool                    WithinEndChild;                     // Set within EndChild()
+    bool                    TestEngineHookItems;                // Will call test engine hooks: ImGuiTestEngineHook_ItemAdd(), ImGuiTestEngineHook_ItemInfo(), ImGuiTestEngineHook_Log()
+    ImGuiID                 TestEngineHookIdInfo;               // Will call test engine hooks: ImGuiTestEngineHook_IdInfo() from GetID()
+    void*                   TestEngine;                         // Test engine user data
 
     // Windows state
     ImVector<ImGuiWindow*>  Windows;                            // Windows, sorted in display order, back to front
@@ -1043,6 +1213,7 @@ struct ImGuiContext
     ImGuiWindow*            CurrentWindow;                      // Window being drawn into
     ImGuiWindow*            HoveredWindow;                      // Will catch mouse inputs
     ImGuiWindow*            HoveredRootWindow;                  // Will catch mouse inputs (for focus/move only)
+    ImGuiWindow*            HoveredWindowUnderMovingWindow;     // Hovered window ignoring MovingWindow. Only set if MovingWindow is set.
     ImGuiWindow*            MovingWindow;                       // Track the window we clicked on (in order to preserve focus). The actually window that is moved is generally MovingWindow->RootWindow.
     ImGuiWindow*            WheelingWindow;                     // Track the window we started mouse-wheeling on. Until a timer elapse or mouse has moved, generally keep scrolling the same window even if during the course of scrolling the mouse ends up hovering a child window.
     ImVec2                  WheelingWindowRefMousePos;
@@ -1087,6 +1258,15 @@ struct ImGuiContext
     ImVector<ImGuiPopupData>OpenPopupStack;                     // Which popups are open (persistent)
     ImVector<ImGuiPopupData>BeginPopupStack;                    // Which level of BeginPopup() we are in (reset every frame)
 
+    // Viewports
+    ImVector<ImGuiViewportP*> Viewports;                        // Active viewports (always 1+, and generally 1 unless multi-viewports are enabled). Each viewports hold their copy of ImDrawData.
+    float                   CurrentDpiScale;                    // == CurrentViewport->DpiScale
+    ImGuiViewportP*         CurrentViewport;                    // We track changes of viewport (happening in Begin) so we can call Platform_OnChangedViewport()
+    ImGuiViewportP*         MouseViewport;
+    ImGuiViewportP*         MouseLastHoveredViewport;           // Last known viewport that was hovered by mouse (even if we are not hovering any viewport any more) + honoring the _NoInputs flag.
+    ImGuiID                 PlatformLastFocusedViewport;        // Record of last focused platform window/viewport, when this changes we stamp the viewport as front-most
+    int                     ViewportFrontMostStampCount;        // Every time the front-most window changes, we stamp its viewport with an incrementing counter
+
     // Gamepad/keyboard Navigation
     ImGuiWindow*            NavWindow;                          // Focused window for navigation. Could be called 'FocusWindow'
     ImGuiID                 NavId;                              // Focused item for navigation
@@ -1143,11 +1323,7 @@ struct ImGuiContext
     bool                    FocusTabPressed;                    //
 
     // Render
-    ImDrawData              DrawData;                           // Main ImDrawData instance to pass render information to the user
-    ImDrawDataBuilder       DrawDataBuilder;
     float                   DimBgRatio;                         // 0.0..1.0 animation when fading in a dimming background (for modal window and CTRL+TAB list)
-    ImDrawList              BackgroundDrawList;                 // First draw list to be rendered.
-    ImDrawList              ForegroundDrawList;                 // Last draw list to be rendered. This is where we the render software mouse cursor (if io.MouseDrawCursor is set) and most debug overlays.
     ImGuiMouseCursor        MouseCursor;
 
     // Drag and Drop
@@ -1165,6 +1341,7 @@ struct ImGuiContext
     ImGuiID                 DragDropAcceptIdCurr;               // Target item id (set at the time of accepting the payload)
     ImGuiID                 DragDropAcceptIdPrev;               // Target item id from previous frame (we need to store this to allow for overlapping drag and drop targets)
     int                     DragDropAcceptFrameCount;           // Last time a target expressed a desire to accept the source
+    ImGuiID                 DragDropHoldJustPressedId;          // Set when holding a payload just made ButtonBehavior() return a press.
     ImVector<unsigned char> DragDropPayloadBufHeap;             // We don't expose the ImVector<> directly, ImGuiPayload only holds pointer+size
     unsigned char           DragDropPayloadBufLocal[16];        // Local buffer for small payloads
 
@@ -1195,6 +1372,11 @@ struct ImGuiContext
     // Platform support
     ImVec2                  PlatformImePos;                     // Cursor position request & last passed to the OS Input Method Editor
     ImVec2                  PlatformImeLastPos;
+    ImGuiViewportP*         PlatformImePosViewport;
+
+    // Extensions
+    // FIXME: We could provide an API to register one slot in an array held in ImGuiContext?
+    ImGuiDockContext*       DockContext;
 
     // Settings
     bool                    SettingsLoaded;
@@ -1227,22 +1409,27 @@ struct ImGuiContext
     int                     WantTextInputNextFrame;
     char                    TempBuffer[1024*3+1];               // Temporary text buffer
 
-    ImGuiContext(ImFontAtlas* shared_font_atlas) : BackgroundDrawList(&DrawListSharedData), ForegroundDrawList(&DrawListSharedData)
+    ImGuiContext(ImFontAtlas* shared_font_atlas)
     {
         Initialized = false;
+        ConfigFlagsCurrFrame = ConfigFlagsLastFrame = ImGuiConfigFlags_None;
+        FontAtlasOwnedByContext = shared_font_atlas ? false : true;
         Font = NULL;
         FontSize = FontBaseSize = 0.0f;
-        FontAtlasOwnedByContext = shared_font_atlas ? false : true;
         IO.Fonts = shared_font_atlas ? shared_font_atlas : IM_NEW(ImFontAtlas)();
         Time = 0.0f;
         FrameCount = 0;
-        FrameCountEnded = FrameCountRendered = -1;
+        FrameCountEnded = FrameCountPlatformEnded = FrameCountRendered = -1;
         WithinFrameScope = WithinFrameScopeWithImplicitWindow = WithinEndChild = false;
+        TestEngineHookItems = false;
+        TestEngineHookIdInfo = 0;
+        TestEngine = NULL;
 
         WindowsActiveCount = 0;
         CurrentWindow = NULL;
         HoveredWindow = NULL;
         HoveredRootWindow = NULL;
+        HoveredWindowUnderMovingWindow = NULL;
         MovingWindow = NULL;
         WheelingWindow = NULL;
         WheelingWindowTimer = 0.0f;
@@ -1273,6 +1460,12 @@ struct ImGuiContext
         LastActiveId = 0;
         LastActiveIdTimer = 0.0f;
 
+        CurrentDpiScale = 0.0f;
+        CurrentViewport = NULL;
+        MouseViewport = MouseLastHoveredViewport = NULL;
+        PlatformLastFocusedViewport = 0;
+        ViewportFrontMostStampCount = 0;
+
         NavWindow = NULL;
         NavId = NavFocusScopeId = NavActivateId = NavActivateDownId = NavActivatePressedId = NavInputId = 0;
         NavJustTabbedId = NavJustMovedToId = NavJustMovedToFocusScopeId = NavNextActivateId = 0;
@@ -1307,8 +1500,6 @@ struct ImGuiContext
         FocusTabPressed = false;
 
         DimBgRatio = 0.0f;
-        BackgroundDrawList._OwnerName = "##Background"; // Give it a name for debugging
-        ForegroundDrawList._OwnerName = "##Foreground"; // Give it a name for debugging
         MouseCursor = ImGuiMouseCursor_Arrow;
 
         DragDropActive = DragDropWithinSource = DragDropWithinTarget = false;
@@ -1320,6 +1511,7 @@ struct ImGuiContext
         DragDropAcceptIdCurrRectSurface = 0.0f;
         DragDropAcceptIdPrev = DragDropAcceptIdCurr = 0;
         DragDropAcceptFrameCount = -1;
+        DragDropHoldJustPressedId = 0;
         memset(DragDropPayloadBufLocal, 0, sizeof(DragDropPayloadBufLocal));
 
         CurrentTabBar = NULL;
@@ -1336,6 +1528,9 @@ struct ImGuiContext
         TooltipOverrideCount = 0;
 
         PlatformImePos = PlatformImeLastPos = ImVec2(FLT_MAX, FLT_MAX);
+        PlatformImePosViewport = 0;
+
+        DockContext = NULL;
 
         SettingsLoaded = false;
         SettingsDirtyTimer = 0.0f;
@@ -1461,7 +1656,12 @@ struct IMGUI_API ImGuiWindow
 {
     char*                   Name;                               // Window name, owned by the window.
     ImGuiID                 ID;                                 // == ImHashStr(Name)
-    ImGuiWindowFlags        Flags;                              // See enum ImGuiWindowFlags_
+    ImGuiWindowFlags        Flags, FlagsPreviousFrame;          // See enum ImGuiWindowFlags_
+    ImGuiWindowClass        WindowClass;                        // Advanced users only. Set with SetNextWindowClass()
+    ImGuiViewportP*         Viewport;                           // Always set in Begin(), only inactive windows may have a NULL value here
+    ImGuiID                 ViewportId;                         // We backup the viewport id (since the viewport may disappear or never be created if the window is inactive)
+    ImVec2                  ViewportPos;                        // We backup the viewport position (since the viewport may disappear or never be created if the window is inactive)
+    int                     ViewportAllowPlatformMonitorExtend; // Reset to -1 every frame (index is guaranteed to be valid between NewFrame..EndFrame), only used in the Appearing frame of a tooltip/popup to enforce clamping to a given monitor
     ImVec2                  Pos;                                // Position (always rounded-up to nearest pixel)
     ImVec2                  Size;                               // Current size (==SizeFull or collapsed title bar size)
     ImVec2                  SizeFull;                           // Size when non collapsed
@@ -1479,6 +1679,7 @@ struct IMGUI_API ImGuiWindow
     ImVec2                  ScrollTargetCenterRatio;            // 0.0f = scroll so that target position is at top, 0.5f = scroll so that target position is centered
     ImVec2                  ScrollbarSizes;                     // Size taken by each scrollbars on their smaller axis. Pay attention! ScrollbarSizes.x == width of the vertical scrollbar, ScrollbarSizes.y = height of the horizontal scrollbar.
     bool                    ScrollbarX, ScrollbarY;             // Are scrollbars visible?
+    bool                    ViewportOwned;
     bool                    Active;                             // Set to true on Begin(), unless Collapsed
     bool                    WasActive;
     bool                    WriteAccessed;                      // Set to true when any widget access the current window
@@ -1503,6 +1704,7 @@ struct IMGUI_API ImGuiWindow
     ImGuiCond               SetWindowPosAllowFlags;             // store acceptable condition flags for SetNextWindowPos() use.
     ImGuiCond               SetWindowSizeAllowFlags;            // store acceptable condition flags for SetNextWindowSize() use.
     ImGuiCond               SetWindowCollapsedAllowFlags;       // store acceptable condition flags for SetNextWindowCollapsed() use.
+    ImGuiCond               SetWindowDockAllowFlags;            // store acceptable condition flags for SetNextWindowDock() use.
     ImVec2                  SetWindowPosVal;                    // store window position when using a non-zero Pivot (position set needs to be processed when we know the window size)
     ImVec2                  SetWindowPosPivot;                  // store window pivot for positioning. ImVec2(0,0) when positioning from top-left corner; ImVec2(0.5f,0.5f) for centering; ImVec2(1,1) for bottom right.
 
@@ -1517,19 +1719,23 @@ struct IMGUI_API ImGuiWindow
     ImRect                  WorkRect;                           // Cover the whole scrolling region, shrunk by WindowPadding*1.0f on each side. This is meant to replace ContentRegionRect over time (from 1.71+ onward).
     ImRect                  ClipRect;                           // Current clipping/scissoring rectangle, evolve as we are using PushClipRect(), etc. == DrawList->clip_rect_stack.back().
     ImRect                  ContentRegionRect;                  // FIXME: This is currently confusing/misleading. It is essentially WorkRect but not handling of scrolling. We currently rely on it as right/bottom aligned sizing operation need some size to rely on.
+    ImVec2ih                HitTestHoleSize, HitTestHoleOffset;
 
     int                     LastFrameActive;                    // Last frame number the window was Active.
+    int                     LastFrameJustFocused;               // Last frame number the window was made Focused.
     float                   LastTimeActive;                     // Last timestamp the window was Active (using float as we don't need high precision there)
     float                   ItemWidthDefault;
     ImGuiStorage            StateStorage;
     ImVector<ImGuiColumns>  ColumnsStorage;
     float                   FontWindowScale;                    // User scale multiplier per-window, via SetWindowFontScale()
+    float                   FontDpiScale;
     int                     SettingsOffset;                     // Offset into SettingsWindows[] (offsets are always valid as we only grow the array from the back)
 
     ImDrawList*             DrawList;                           // == &DrawListInst (for backward compatibility reason with code using imgui_internal.h we keep this a pointer)
     ImDrawList              DrawListInst;
     ImGuiWindow*            ParentWindow;                       // If we are a child _or_ popup window, this is pointing to our parent. Otherwise NULL.
     ImGuiWindow*            RootWindow;                         // Point to ourself or first ancestor that is not a child window.
+    ImGuiWindow*            RootWindowDockStop;                 // Point to ourself or first ancestor that is not a child window. Doesn't cross through dock nodes. We use this so IsWindowFocused() can behave consistently regardless of docking state.
     ImGuiWindow*            RootWindowForTitleBarHighlight;     // Point to ourself or first ancestor which will display TitleBgActive color when this window is active.
     ImGuiWindow*            RootWindowForNav;                   // Point to ourself or first ancestor which doesn't have the NavFlattened flag.
 
@@ -1541,6 +1747,17 @@ struct IMGUI_API ImGuiWindow
     int                     MemoryDrawListIdxCapacity;
     int                     MemoryDrawListVtxCapacity;
 
+    // Docking
+    ImGuiDockNode*          DockNode;                           // Which node are we docked into. Important: Prefer testing DockIsActive in many cases as this will still be set when the dock node is hidden.
+    ImGuiDockNode*          DockNodeAsHost;                     // Which node are we owning (for parent windows)
+    ImGuiID                 DockId;                             // Backup of last valid DockNode->ID, so single window remember their dock node id even when they are not bound any more
+    ImGuiItemStatusFlags    DockTabItemStatusFlags;
+    ImRect                  DockTabItemRect;
+    short                   DockOrder;                          // Order of the last time the window was visible within its DockNode. This is used to reorder windows that are reappearing on the same frame. Same value between windows that were active and windows that were none are possible.
+    bool                    DockIsActive        :1;             // When docking artifacts are actually visible. When this is set, DockNode is guaranteed to be != NULL. ~~ (DockNode != NULL) && (DockNode->Windows.Size > 1).
+    bool                    DockTabIsVisible    :1;             // Is our window visible this frame? ~~ is the corresponding tab selected?
+    bool                    DockTabWantClose    :1;
+
 public:
     ImGuiWindow(ImGuiContext* context, const char* name);
     ~ImGuiWindow();
@@ -1555,7 +1772,7 @@ public:
 
     // We don't use g.FontSize because the window may be != g.CurrentWidow.
     ImRect      Rect() const                { return ImRect(Pos.x, Pos.y, Pos.x+Size.x, Pos.y+Size.y); }
-    float       CalcFontSize() const        { ImGuiContext& g = *GImGui; float scale = g.FontBaseSize * FontWindowScale; if (ParentWindow) scale *= ParentWindow->FontWindowScale; return scale; }
+    float       CalcFontSize() const        { ImGuiContext& g = *GImGui; float scale = g.FontBaseSize * FontWindowScale * FontDpiScale; if (ParentWindow) scale *= ParentWindow->FontWindowScale; return scale; }
     float       TitleBarHeight() const      { ImGuiContext& g = *GImGui; return (Flags & ImGuiWindowFlags_NoTitleBar) ? 0.0f : CalcFontSize() + g.Style.FramePadding.y * 2.0f; }
     ImRect      TitleBarRect() const        { return ImRect(Pos, ImVec2(Pos.x + SizeFull.x, Pos.y + TitleBarHeight())); }
     float       MenuBarHeight() const       { ImGuiContext& g = *GImGui; return (Flags & ImGuiWindowFlags_MenuBar) ? DC.MenuBarOffset.y + CalcFontSize() + g.Style.FramePadding.y * 2.0f : 0.0f; }
@@ -1590,14 +1807,17 @@ enum ImGuiTabBarFlagsPrivate_
 // Extend ImGuiTabItemFlags_
 enum ImGuiTabItemFlagsPrivate_
 {
-    ImGuiTabItemFlags_NoCloseButton             = 1 << 20   // Track whether p_open was set or not (we'll need this info on the next frame to recompute ContentWidth during layout)
+    ImGuiTabItemFlags_NoCloseButton             = 1 << 20,  // Track whether p_open was set or not (we'll need this info on the next frame to recompute ContentWidth during layout)
+    ImGuiTabItemFlags_Unsorted                  = 1 << 21,  // [Docking] Trailing tabs with the _Unsorted flag will be sorted based on the DockOrder of their Window.
+    ImGuiTabItemFlags_Preview                   = 1 << 22   // [Docking] Display tab shape for docking preview (height is adjusted slightly to compensate for the yet missing tab bar)
 };
 
-// Storage for one active tab item (sizeof() 26~32 bytes)
+// Storage for one active tab item (sizeof() 32~40 bytes)
 struct ImGuiTabItem
 {
     ImGuiID             ID;
     ImGuiTabItemFlags   Flags;
+    ImGuiWindow*        Window;                 // When TabItem is part of a DockNode's TabBar, we hold on to a window.
     int                 LastFrameVisible;
     int                 LastFrameSelected;      // This allows us to infer an ordered list of the last activated tabs with little maintenance
     int                 NameOffset;             // When Window==NULL, offset to name within parent ImGuiTabBar::TabsNames
@@ -1605,7 +1825,7 @@ struct ImGuiTabItem
     float               Width;                  // Width currently displayed
     float               ContentWidth;           // Width of actual contents, stored during BeginTabItem() call
 
-    ImGuiTabItem()      { ID = 0; Flags = ImGuiTabItemFlags_None; LastFrameVisible = LastFrameSelected = -1; NameOffset = -1; Offset = Width = ContentWidth = 0.0f; }
+    ImGuiTabItem()      { ID = 0; Flags = ImGuiTabItemFlags_None; Window = NULL; LastFrameVisible = LastFrameSelected = -1; NameOffset = -1; Offset = Width = ContentWidth = 0.0f; }
 };
 
 // Storage for a tab bar (sizeof() 92~96 bytes)
@@ -1640,6 +1860,8 @@ struct ImGuiTabBar
     int                 GetTabOrder(const ImGuiTabItem* tab) const  { return Tabs.index_from_ptr(tab); }
     const char*         GetTabName(const ImGuiTabItem* tab) const
     {
+        if (tab->Window)
+            return tab->Window->Name;
         IM_ASSERT(tab->NameOffset != -1 && tab->NameOffset < TabsNames.Buf.Size);
         return TabsNames.Buf.Data + tab->NameOffset;
     }
@@ -1680,7 +1902,7 @@ namespace ImGui
     // Fonts, drawing
     IMGUI_API void          SetCurrentFont(ImFont* font);
     inline ImFont*          GetDefaultFont() { ImGuiContext& g = *GImGui; return g.IO.FontDefault ? g.IO.FontDefault : g.IO.Fonts->Fonts[0]; }
-    inline ImDrawList*      GetForegroundDrawList(ImGuiWindow* window) { IM_UNUSED(window); ImGuiContext& g = *GImGui; return &g.ForegroundDrawList; } // This seemingly unnecessary wrapper simplifies compatibility between the 'master' and 'docking' branches.
+    inline ImDrawList*      GetForegroundDrawList(ImGuiWindow* window) { return GetForegroundDrawList(window->Viewport); }
 
     // Init
     IMGUI_API void          Initialize(ImGuiContext* context);
@@ -1689,9 +1911,16 @@ namespace ImGui
     // NewFrame
     IMGUI_API void          UpdateHoveredWindowAndCaptureFlags();
     IMGUI_API void          StartMouseMovingWindow(ImGuiWindow* window);
+    IMGUI_API void          StartMouseMovingWindowOrNode(ImGuiWindow* window, ImGuiDockNode* node, bool undock_floating_node);
     IMGUI_API void          UpdateMouseMovingWindowNewFrame();
     IMGUI_API void          UpdateMouseMovingWindowEndFrame();
 
+    // Viewports
+    IMGUI_API void                  TranslateWindowsInViewport(ImGuiViewportP* viewport, const ImVec2& old_pos, const ImVec2& new_pos);
+    IMGUI_API void                  ScaleWindowsInViewport(ImGuiViewportP* viewport, float scale);
+    IMGUI_API void                  DestroyPlatformWindow(ImGuiViewportP* viewport);
+    IMGUI_API void                  ShowViewportThumbnails();
+
     // Settings
     IMGUI_API void                  MarkIniSettingsDirty();
     IMGUI_API void                  MarkIniSettingsDirty(ImGuiWindow* window);
@@ -1701,6 +1930,7 @@ namespace ImGui
     IMGUI_API ImGuiSettingsHandler* FindSettingsHandler(const char* type_name);
 
     // Scrolling
+    IMGUI_API void          SetNextWindowScroll(const ImVec2& scroll); // Use -1.0f on one axis to leave as-is
     IMGUI_API void          SetScrollX(ImGuiWindow* window, float new_scroll_x);
     IMGUI_API void          SetScrollY(ImGuiWindow* window, float new_scroll_y);
     IMGUI_API void          SetScrollFromPosX(ImGuiWindow* window, float local_x, float center_x_ratio = 0.5f);
@@ -1783,6 +2013,51 @@ namespace ImGui
     inline bool             IsNavInputTest(ImGuiNavInput n, ImGuiInputReadMode rm)      { return (GetNavInputAmount(n, rm) > 0.0f); }
     IMGUI_API ImGuiKeyModFlags GetMergedKeyModFlags();
 
+    // Docking
+    // (some functions are only declared in imgui.cpp, see Docking section)
+    IMGUI_API void          DockContextInitialize(ImGuiContext* ctx);
+    IMGUI_API void          DockContextShutdown(ImGuiContext* ctx);
+    IMGUI_API void          DockContextOnLoadSettings(ImGuiContext* ctx);
+    IMGUI_API void          DockContextRebuildNodes(ImGuiContext* ctx);
+    IMGUI_API void          DockContextUpdateUndocking(ImGuiContext* ctx);
+    IMGUI_API void          DockContextUpdateDocking(ImGuiContext* ctx);
+    IMGUI_API ImGuiID       DockContextGenNodeID(ImGuiContext* ctx);
+    IMGUI_API void          DockContextQueueDock(ImGuiContext* ctx, ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload, ImGuiDir split_dir, float split_ratio, bool split_outer);
+    IMGUI_API void          DockContextQueueUndockWindow(ImGuiContext* ctx, ImGuiWindow* window);
+    IMGUI_API void          DockContextQueueUndockNode(ImGuiContext* ctx, ImGuiDockNode* node);
+    IMGUI_API bool          DockContextCalcDropPosForDocking(ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload, ImGuiDir split_dir, bool split_outer, ImVec2* out_pos);
+    inline ImGuiDockNode*   DockNodeGetRootNode(ImGuiDockNode* node) { while (node->ParentNode) node = node->ParentNode; return node; }
+    inline ImGuiDockNode*   GetWindowDockNode() { ImGuiContext& g = *GImGui; return g.CurrentWindow->DockNode; }
+    IMGUI_API bool          GetWindowAlwaysWantOwnTabBar(ImGuiWindow* window);
+    IMGUI_API void          BeginDocked(ImGuiWindow* window, bool* p_open);
+    IMGUI_API void          BeginDockableDragDropSource(ImGuiWindow* window);
+    IMGUI_API void          BeginDockableDragDropTarget(ImGuiWindow* window);
+    IMGUI_API void          SetWindowDock(ImGuiWindow* window, ImGuiID dock_id, ImGuiCond cond);
+
+    // Docking - Builder function needs to be generally called before the node is used/submitted.
+    // - The DockBuilderXXX functions are designed to _eventually_ become a public API, but it is too early to expose it and guarantee stability.
+    // - Do not hold on ImGuiDockNode* pointers! They may be invalidated by any split/merge/remove operation and every frame.
+    // - To create a DockSpace() node, make sure to set the ImGuiDockNodeFlags_DockSpace flag when calling DockBuilderAddNode().
+    //   You can create dockspace nodes (attached to a window) _or_ floating nodes (carry its own window) with this API.
+    // - DockBuilderSplitNode() create 2 child nodes within 1 node. The initial node becomes a parent node.
+    // - If you intend to split the node immediately after creation using DockBuilderSplitNode(), make sure
+    //   to call DockBuilderSetNodeSize() beforehand. If you don't, the resulting split sizes may not be reliable.
+    // - Call DockBuilderFinish() after you are done.
+    IMGUI_API void          DockBuilderDockWindow(const char* window_name, ImGuiID node_id);
+    IMGUI_API ImGuiDockNode*DockBuilderGetNode(ImGuiID node_id);
+    inline ImGuiDockNode*   DockBuilderGetCentralNode(ImGuiID node_id)              { ImGuiDockNode* node = DockBuilderGetNode(node_id); if (!node) return NULL; return DockNodeGetRootNode(node)->CentralNode; }
+    IMGUI_API ImGuiID       DockBuilderAddNode(ImGuiID node_id = 0, ImGuiDockNodeFlags flags = 0);
+    IMGUI_API void          DockBuilderRemoveNode(ImGuiID node_id);                 // Remove node and all its child, undock all windows
+    IMGUI_API void          DockBuilderRemoveNodeDockedWindows(ImGuiID node_id, bool clear_persistent_docking_references = true);
+    IMGUI_API void          DockBuilderRemoveNodeChildNodes(ImGuiID node_id);       // Remove all split/hierarchy. All remaining docked windows will be re-docked to the root.
+    IMGUI_API void          DockBuilderSetNodePos(ImGuiID node_id, ImVec2 pos);
+    IMGUI_API void          DockBuilderSetNodeSize(ImGuiID node_id, ImVec2 size);
+    IMGUI_API ImGuiID       DockBuilderSplitNode(ImGuiID node_id, ImGuiDir split_dir, float size_ratio_for_node_at_dir, ImGuiID* out_id_at_dir, ImGuiID* out_id_at_opposite_dir); // Create 2 child nodes in this parent node.
+    IMGUI_API void          DockBuilderCopyDockSpace(ImGuiID src_dockspace_id, ImGuiID dst_dockspace_id, ImVector<const char*>* in_window_remap_pairs);
+    IMGUI_API void          DockBuilderCopyNode(ImGuiID src_node_id, ImGuiID dst_node_id, ImVector<ImGuiID>* out_node_remap_pairs);
+    IMGUI_API void          DockBuilderCopyWindowSettings(const char* src_name, const char* dst_name);
+    IMGUI_API void          DockBuilderFinish(ImGuiID node_id);
+
     // Drag and Drop
     IMGUI_API bool          BeginDragDropTargetCustom(const ImRect& bb, ImGuiID id);
     IMGUI_API void          ClearDragDrop();
@@ -1800,12 +2075,14 @@ namespace ImGui
     IMGUI_API float         GetColumnNormFromOffset(const ImGuiColumns* columns, float offset);
 
     // Tab Bars
-    IMGUI_API bool          BeginTabBarEx(ImGuiTabBar* tab_bar, const ImRect& bb, ImGuiTabBarFlags flags);
+    IMGUI_API bool          BeginTabBarEx(ImGuiTabBar* tab_bar, const ImRect& bb, ImGuiTabBarFlags flags, ImGuiDockNode* dock_node);
     IMGUI_API ImGuiTabItem* TabBarFindTabByID(ImGuiTabBar* tab_bar, ImGuiID tab_id);
+    IMGUI_API ImGuiTabItem* TabBarFindMostRecentlySelectedTabForActiveWindow(ImGuiTabBar* tab_bar);
+    IMGUI_API void          TabBarAddTab(ImGuiTabBar* tab_bar, ImGuiTabItemFlags tab_flags, ImGuiWindow* window);
     IMGUI_API void          TabBarRemoveTab(ImGuiTabBar* tab_bar, ImGuiID tab_id);
     IMGUI_API void          TabBarCloseTab(ImGuiTabBar* tab_bar, ImGuiTabItem* tab);
     IMGUI_API void          TabBarQueueChangeTabOrder(ImGuiTabBar* tab_bar, const ImGuiTabItem* tab, int dir);
-    IMGUI_API bool          TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open, ImGuiTabItemFlags flags);
+    IMGUI_API bool          TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open, ImGuiTabItemFlags flags, ImGuiWindow* docked_window);
     IMGUI_API ImVec2        TabItemCalcSize(const char* label, bool has_close_button);
     IMGUI_API void          TabItemBackground(ImDrawList* draw_list, const ImRect& bb, ImGuiTabItemFlags flags, ImU32 col);
     IMGUI_API bool          TabItemLabelAndCloseButton(ImDrawList* draw_list, const ImRect& bb, ImGuiTabItemFlags flags, ImVec2 frame_padding, const char* label, ImGuiID tab_id, ImGuiID close_button_id);
@@ -1831,7 +2108,9 @@ namespace ImGui
     IMGUI_API void          RenderCheckMark(ImDrawList* draw_list, ImVec2 pos, ImU32 col, float sz);
     IMGUI_API void          RenderMouseCursor(ImDrawList* draw_list, ImVec2 pos, float scale, ImGuiMouseCursor mouse_cursor, ImU32 col_fill, ImU32 col_border, ImU32 col_shadow);
     IMGUI_API void          RenderArrowPointingAt(ImDrawList* draw_list, ImVec2 pos, ImVec2 half_sz, ImGuiDir direction, ImU32 col);
+    IMGUI_API void          RenderArrowDockMenu(ImDrawList* draw_list, ImVec2 p_min, float sz, ImU32 col);
     IMGUI_API void          RenderRectFilledRangeH(ImDrawList* draw_list, const ImRect& rect, ImU32 col, float x_start_norm, float x_end_norm, float rounding);
+    IMGUI_API void          RenderRectFilledWithHole(ImDrawList* draw_list, ImRect outer, ImRect inner, ImU32 col, float rounding);
 
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
     // [1.71: 2019/06/07: Updating prototypes of some of the internal functions. Leaving those for reference for a short while]
@@ -1843,7 +2122,7 @@ namespace ImGui
     IMGUI_API void          TextEx(const char* text, const char* text_end = NULL, ImGuiTextFlags flags = 0);
     IMGUI_API bool          ButtonEx(const char* label, const ImVec2& size_arg = ImVec2(0,0), ImGuiButtonFlags flags = 0);
     IMGUI_API bool          CloseButton(ImGuiID id, const ImVec2& pos);
-    IMGUI_API bool          CollapseButton(ImGuiID id, const ImVec2& pos);
+    IMGUI_API bool          CollapseButton(ImGuiID id, const ImVec2& pos, ImGuiDockNode* dock_node);
     IMGUI_API bool          ArrowButtonEx(const char* str_id, ImGuiDir dir, ImVec2 size_arg, ImGuiButtonFlags flags = 0);
     IMGUI_API void          Scrollbar(ImGuiAxis axis);
     IMGUI_API bool          ScrollbarEx(const ImRect& bb, ImGuiID id, ImGuiAxis axis, float* p_scroll_v, float avail_v, float contents_v, ImDrawCornerFlags rounding_corners);
@@ -1932,14 +2211,20 @@ extern void                 ImGuiTestEngineHook_PreNewFrame(ImGuiContext* ctx);
 extern void                 ImGuiTestEngineHook_PostNewFrame(ImGuiContext* ctx);
 extern void                 ImGuiTestEngineHook_ItemAdd(ImGuiContext* ctx, const ImRect& bb, ImGuiID id);
 extern void                 ImGuiTestEngineHook_ItemInfo(ImGuiContext* ctx, ImGuiID id, const char* label, ImGuiItemStatusFlags flags);
+extern void                 ImGuiTestEngineHook_IdInfo(ImGuiContext* ctx, ImGuiDataType data_type, ImGuiID id, const void* data_id);
+extern void                 ImGuiTestEngineHook_IdInfo(ImGuiContext* ctx, ImGuiDataType data_type, ImGuiID id, const void* data_id, const void* data_id_end);
 extern void                 ImGuiTestEngineHook_Log(ImGuiContext* ctx, const char* fmt, ...);
-#define IMGUI_TEST_ENGINE_ITEM_ADD(_BB, _ID)                ImGuiTestEngineHook_ItemAdd(&g, _BB, _ID)               // Register item bounding box
-#define IMGUI_TEST_ENGINE_ITEM_INFO(_ID, _LABEL, _FLAGS)    ImGuiTestEngineHook_ItemInfo(&g, _ID, _LABEL, _FLAGS)   // Register item label and status flags (optional)
-#define IMGUI_TEST_ENGINE_LOG(_FMT, ...)                    ImGuiTestEngineHook_Log(&g, _FMT, __VA_ARGS__)          // Custom log entry from user land into test log
+#define IMGUI_TEST_ENGINE_ITEM_ADD(_BB,_ID)                 if (g.TestEngineHookItems) ImGuiTestEngineHook_ItemAdd(&g, _BB, _ID)               // Register item bounding box
+#define IMGUI_TEST_ENGINE_ITEM_INFO(_ID,_LABEL,_FLAGS)      if (g.TestEngineHookItems) ImGuiTestEngineHook_ItemInfo(&g, _ID, _LABEL, _FLAGS)   // Register item label and status flags (optional)
+#define IMGUI_TEST_ENGINE_LOG(_FMT,...)                     if (g.TestEngineHookItems) ImGuiTestEngineHook_Log(&g, _FMT, __VA_ARGS__)          // Custom log entry from user land into test log
+#define IMGUI_TEST_ENGINE_ID_INFO(_ID,_TYPE,_DATA)          if (g.TestEngineHookIdInfo == id) ImGuiTestEngineHook_IdInfo(&g, _TYPE, _ID, (const void*)(_DATA));
+#define IMGUI_TEST_ENGINE_ID_INFO2(_ID,_TYPE,_DATA,_DATA2)  if (g.TestEngineHookIdInfo == id) ImGuiTestEngineHook_IdInfo(&g, _TYPE, _ID, (const void*)(_DATA), (const void*)(_DATA2));
 #else
-#define IMGUI_TEST_ENGINE_ITEM_ADD(_BB, _ID)                do { } while (0)
-#define IMGUI_TEST_ENGINE_ITEM_INFO(_ID, _LABEL, _FLAGS)    do { } while (0)
-#define IMGUI_TEST_ENGINE_LOG(_FMT, ...)                    do { } while (0)
+#define IMGUI_TEST_ENGINE_ITEM_ADD(_BB,_ID)                 do { } while (0)
+#define IMGUI_TEST_ENGINE_ITEM_INFO(_ID,_LABEL,_FLAGS)      do { } while (0)
+#define IMGUI_TEST_ENGINE_LOG(_FMT,...)                     do { } while (0)
+#define IMGUI_TEST_ENGINE_ID_INFO(_ID,_TYPE,_DATA)          do { } while (0)
+#define IMGUI_TEST_ENGINE_ID_INFO2(_ID,_TYPE,_DATA,_DATA2)  do { } while (0)
 #endif
 
 #if defined(__clang__)
diff --git a/imgui/imgui_widgets.cpp b/imgui/imgui_widgets.cpp
index 27d9e455..4ce46798 100644
--- a/imgui/imgui_widgets.cpp
+++ b/imgui/imgui_widgets.cpp
@@ -1,4 +1,4 @@
-// dear imgui, v1.76
+// dear imgui, v1.77 WIP
 // (widgets code)
 
 /*
@@ -480,13 +480,13 @@ bool ImGui::ButtonBehavior(const ImRect& bb, ImGuiID id, bool* out_hovered, bool
         flags |= ImGuiButtonFlags_PressedOnDefault_;
 
     ImGuiWindow* backup_hovered_window = g.HoveredWindow;
-    const bool flatten_hovered_children = (flags & ImGuiButtonFlags_FlattenChildren) && g.HoveredRootWindow == window;
+    const bool flatten_hovered_children = (flags & ImGuiButtonFlags_FlattenChildren) && g.HoveredRootWindow == window->RootWindow;
     if (flatten_hovered_children)
         g.HoveredWindow = window;
 
 #ifdef IMGUI_ENABLE_TEST_ENGINE
     if (id != 0 && window->DC.LastItemId != id)
-        ImGuiTestEngineHook_ItemAdd(&g, bb, id);
+        IMGUI_TEST_ENGINE_ITEM_ADD(bb, id);
 #endif
 
     bool pressed = false;
@@ -500,11 +500,13 @@ bool ImGui::ButtonBehavior(const ImRect& bb, ImGuiID id, bool* out_hovered, bool
     if (g.DragDropActive && (flags & ImGuiButtonFlags_PressedOnDragDropHold) && !(g.DragDropSourceFlags & ImGuiDragDropFlags_SourceNoHoldToOpenOthers))
         if (IsItemHovered(ImGuiHoveredFlags_AllowWhenBlockedByActiveItem))
         {
+            const float DRAG_DROP_HOLD_TIMER = 0.70f;
             hovered = true;
             SetHoveredID(id);
-            if (CalcTypematicRepeatAmount(g.HoveredIdTimer + 0.0001f - g.IO.DeltaTime, g.HoveredIdTimer + 0.0001f, 0.70f, 0.00f))
+            if (CalcTypematicRepeatAmount(g.HoveredIdTimer + 0.0001f - g.IO.DeltaTime, g.HoveredIdTimer + 0.0001f, DRAG_DROP_HOLD_TIMER, 0.00f))
             {
                 pressed = true;
+                g.DragDropHoldJustPressedId = id;
                 FocusWindow(window);
             }
         }
@@ -784,7 +786,8 @@ bool ImGui::CloseButton(ImGuiID id, const ImVec2& pos)//, float size)
     return pressed;
 }
 
-bool ImGui::CollapseButton(ImGuiID id, const ImVec2& pos)
+// The Collapse button also functions as a Dock Menu button.
+bool ImGui::CollapseButton(ImGuiID id, const ImVec2& pos, ImGuiDockNode* dock_node)
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
@@ -795,16 +798,22 @@ bool ImGui::CollapseButton(ImGuiID id, const ImVec2& pos)
     bool pressed = ButtonBehavior(bb, id, &hovered, &held, ImGuiButtonFlags_None);
 
     // Render
+    //bool is_dock_menu = (window->DockNodeAsHost && !window->Collapsed);
+    ImVec2 off = dock_node ? ImVec2(IM_FLOOR(-g.Style.ItemInnerSpacing.x * 0.5f) + 0.5f, 0.0f) : ImVec2(0.0f, 0.0f);
     ImU32 bg_col = GetColorU32((held && hovered) ? ImGuiCol_ButtonActive : hovered ? ImGuiCol_ButtonHovered : ImGuiCol_Button);
     ImU32 text_col = GetColorU32(ImGuiCol_Text);
     ImVec2 center = bb.GetCenter();
     if (hovered || held)
-        window->DrawList->AddCircleFilled(center/*+ ImVec2(0.0f, -0.5f)*/, g.FontSize * 0.5f + 1.0f, bg_col, 12);
-    RenderArrow(window->DrawList, bb.Min + g.Style.FramePadding, text_col, window->Collapsed ? ImGuiDir_Right : ImGuiDir_Down, 1.0f);
+        window->DrawList->AddCircleFilled(center + off + ImVec2(0,-0.5f), g.FontSize * 0.5f + 1.0f, bg_col, 12);
+
+    if (dock_node)
+        RenderArrowDockMenu(window->DrawList, bb.Min + g.Style.FramePadding, g.FontSize, text_col);
+    else
+        RenderArrow(window->DrawList, bb.Min + g.Style.FramePadding, text_col, window->Collapsed ? ImGuiDir_Right : ImGuiDir_Down, 1.0f);
 
     // Switch to moving the window after mouse is moved beyond the initial drag threshold
     if (IsItemActive() && IsMouseDragging(0))
-        StartMouseMovingWindow(window);
+        StartMouseMovingWindowOrNode(window, dock_node, true);
 
     return pressed;
 }
@@ -1132,6 +1141,7 @@ bool ImGui::RadioButton(const char* label, bool active)
     if (label_size.x > 0.0f)
         RenderText(ImVec2(check_bb.Max.x + style.ItemInnerSpacing.x, check_bb.Min.y + style.FramePadding.y), label);
 
+    IMGUI_TEST_ENGINE_ITEM_INFO(id, label, window->DC.ItemFlags);
     return pressed;
 }
 
@@ -4192,7 +4202,10 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
 
             // Notify OS of text input position for advanced IME (-1 x offset so that Windows IME can cover our cursor. Bit of an extra nicety.)
             if (!is_readonly)
-                g.PlatformImePos = ImVec2(cursor_screen_pos.x - 1.0f, cursor_screen_pos.y - g.FontSize);
+            {
+                g.PlatformImePos = ImVec2(cursor_screen_pos.x - 1, cursor_screen_pos.y - g.FontSize);
+                g.PlatformImePosViewport = window->Viewport;
+            }
         }
     }
     else
@@ -5360,10 +5373,11 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
     // It is rather standard that arrow click react on Down rather than Up and we'd be tempted to make it the default
     // (by removing the _OpenOnArrow test below), however this would have a perhaps surprising effect on CollapsingHeader()?
     // So right now we are making this optional. May evolve later.
+    // We set ImGuiButtonFlags_PressedOnClickRelease on OpenOnDoubleClick because we want the item to be active on the initial MouseDown in order for drag and drop to work.
     if (is_mouse_x_over_arrow && (flags & ImGuiTreeNodeFlags_OpenOnArrow))
         button_flags |= ImGuiButtonFlags_PressedOnClick;
     else if (flags & ImGuiTreeNodeFlags_OpenOnDoubleClick)
-        button_flags |= ImGuiButtonFlags_PressedOnDoubleClick;
+        button_flags |= ImGuiButtonFlags_PressedOnClickRelease | ImGuiButtonFlags_PressedOnDoubleClick;
     else
         button_flags |= ImGuiButtonFlags_PressedOnClickRelease;
 
@@ -5375,7 +5389,7 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
     bool toggled = false;
     if (!is_leaf)
     {
-        if (pressed)
+        if (pressed && g.DragDropHoldJustPressedId != id)
         {
             if ((flags & (ImGuiTreeNodeFlags_OpenOnArrow | ImGuiTreeNodeFlags_OpenOnDoubleClick)) == 0 || (g.NavActivateId == id))
                 toggled = true;
@@ -5383,8 +5397,12 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
                 toggled |= is_mouse_x_over_arrow && !g.NavDisableMouseHover; // Lightweight equivalent of IsMouseHoveringRect() since ButtonBehavior() already did the job
             if ((flags & ImGuiTreeNodeFlags_OpenOnDoubleClick) && g.IO.MouseDoubleClicked[0])
                 toggled = true;
-            if (g.DragDropActive && is_open) // When using Drag and Drop "hold to open" we keep the node highlighted after opening, but never close it again.
-                toggled = false;
+        }
+        else if (pressed && g.DragDropHoldJustPressedId == id)
+        {
+            IM_ASSERT(button_flags & ImGuiButtonFlags_PressedOnDragDropHold);
+            if (!is_open) // When using Drag and Drop "hold to open" we keep the node highlighted after opening, but never close it again.
+                toggled = true;
         }
 
         if (g.NavId == id && g.NavMoveRequest && g.NavMoveDir == ImGuiDir_Left && is_open)
@@ -5485,7 +5503,8 @@ void ImGui::TreePush(const void* ptr_id)
 
 void ImGui::TreePushOverrideID(ImGuiID id)
 {
-    ImGuiWindow* window = GetCurrentWindow();
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = g.CurrentWindow;
     Indent();
     window->DC.TreeDepth++;
     window->IDStack.push_back(id);
@@ -6167,18 +6186,39 @@ void ImGui::EndMenuBar()
     window->DC.MenuBarAppending = false;
 }
 
-// For the main menu bar, which cannot be moved, we honor g.Style.DisplaySafeAreaPadding to ensure text can be visible on a TV set.
 bool ImGui::BeginMainMenuBar()
 {
     ImGuiContext& g = *GImGui;
+    ImGuiViewportP* viewport = g.Viewports[0];
+    ImGuiWindow* menu_bar_window = FindWindowByName("##MainMenuBar");
+
+    // For the main menu bar, which cannot be moved, we honor g.Style.DisplaySafeAreaPadding to ensure text can be visible on a TV set.
     g.NextWindowData.MenuBarOffsetMinVal = ImVec2(g.Style.DisplaySafeAreaPadding.x, ImMax(g.Style.DisplaySafeAreaPadding.y - g.Style.FramePadding.y, 0.0f));
-    SetNextWindowPos(ImVec2(0.0f, 0.0f));
-    SetNextWindowSize(ImVec2(g.IO.DisplaySize.x, g.NextWindowData.MenuBarOffsetMinVal.y + g.FontBaseSize + g.Style.FramePadding.y));
+
+    // Get our rectangle at the top of the work area
+    if (menu_bar_window == NULL || menu_bar_window->BeginCount == 0)
+    {
+        // Set window position
+        // We don't attempt to calculate our height ahead, as it depends on the per-viewport font size. However menu-bar will affect the minimum window size so we'll get the right height.
+        ImVec2 menu_bar_pos = viewport->Pos + viewport->CurrWorkOffsetMin;
+        ImVec2 menu_bar_size = ImVec2(viewport->Size.x - viewport->CurrWorkOffsetMin.x + viewport->CurrWorkOffsetMax.x, 1.0f);
+        SetNextWindowPos(menu_bar_pos);
+        SetNextWindowSize(menu_bar_size);
+    }
+
+    // Create window
+    SetNextWindowViewport(viewport->ID); // Enforce viewport so we don't create our own viewport when ImGuiConfigFlags_ViewportsNoMerge is set.
     PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
-    PushStyleVar(ImGuiStyleVar_WindowMinSize, ImVec2(0, 0));
-    ImGuiWindowFlags window_flags = ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_MenuBar;
+    PushStyleVar(ImGuiStyleVar_WindowMinSize, ImVec2(0, 0));    // Lift normal size constraint, however the presence of a menu-bar will give us the minimum height we want.
+    ImGuiWindowFlags window_flags = ImGuiWindowFlags_NoDocking | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_MenuBar;
     bool is_open = Begin("##MainMenuBar", NULL, window_flags) && BeginMenuBar();
     PopStyleVar(2);
+
+    // Report our size into work area (for next frame) using actual window size
+    menu_bar_window = GetCurrentWindow();
+    if (menu_bar_window->BeginCount == 1)
+        viewport->CurrWorkOffsetMin.y += menu_bar_window->Size.y;
+
     g.NextWindowData.MenuBarOffsetMinVal = ImVec2(0.0f, 0.0f);
     if (!is_open)
     {
@@ -6451,6 +6491,7 @@ bool ImGui::MenuItem(const char* label, const char* shortcut, bool* p_selected,
 // - TabBarCalcTabID() [Internal]
 // - TabBarCalcMaxTabWidth() [Internal]
 // - TabBarFindTabById() [Internal]
+// - TabBarAddTab() [Internal]
 // - TabBarRemoveTab() [Internal]
 // - TabBarCloseTab() [Internal]
 // - TabBarScrollClamp()v
@@ -6518,10 +6559,10 @@ bool    ImGui::BeginTabBar(const char* str_id, ImGuiTabBarFlags flags)
     ImGuiTabBar* tab_bar = g.TabBars.GetOrAddByKey(id);
     ImRect tab_bar_bb = ImRect(window->DC.CursorPos.x, window->DC.CursorPos.y, window->WorkRect.Max.x, window->DC.CursorPos.y + g.FontSize + g.Style.FramePadding.y * 2);
     tab_bar->ID = id;
-    return BeginTabBarEx(tab_bar, tab_bar_bb, flags | ImGuiTabBarFlags_IsFocused);
+    return BeginTabBarEx(tab_bar, tab_bar_bb, flags | ImGuiTabBarFlags_IsFocused, NULL);
 }
 
-bool    ImGui::BeginTabBarEx(ImGuiTabBar* tab_bar, const ImRect& tab_bar_bb, ImGuiTabBarFlags flags)
+bool    ImGui::BeginTabBarEx(ImGuiTabBar* tab_bar, const ImRect& tab_bar_bb, ImGuiTabBarFlags flags, ImGuiDockNode* dock_node)
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
@@ -6538,7 +6579,7 @@ bool    ImGui::BeginTabBarEx(ImGuiTabBar* tab_bar, const ImRect& tab_bar_bb, ImG
     if (tab_bar->CurrFrameVisible == g.FrameCount)
     {
         //IMGUI_DEBUG_LOG("BeginTabBarEx already called this frame\n", g.FrameCount);
-        IM_ASSERT(0);
+        //IM_ASSERT(0);
         return true;
     }
 
@@ -6565,6 +6606,13 @@ bool    ImGui::BeginTabBarEx(ImGuiTabBar* tab_bar, const ImRect& tab_bar_bb, ImG
     // Draw separator
     const ImU32 col = GetColorU32((flags & ImGuiTabBarFlags_IsFocused) ? ImGuiCol_TabActive : ImGuiCol_TabUnfocusedActive);
     const float y = tab_bar->BarRect.Max.y - 1.0f;
+    if (dock_node != NULL)
+    {
+        const float separator_min_x = dock_node->Pos.x + window->WindowBorderSize;
+        const float separator_max_x = dock_node->Pos.x + dock_node->Size.x - window->WindowBorderSize;
+        window->DrawList->AddLine(ImVec2(separator_min_x, y), ImVec2(separator_max_x, y), col, 1.0f);
+    }
+    else
     {
         const float separator_min_x = tab_bar->BarRect.Min.x - IM_FLOOR(window->WindowPadding.x * 0.5f);
         const float separator_max_x = tab_bar->BarRect.Max.x + IM_FLOOR(window->WindowPadding.x * 0.5f);
@@ -6685,7 +6733,7 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
         // Additionally, when using TabBarAddTab() to manipulate tab bar order we occasionally insert new tabs that don't have a width yet,
         // and we cannot wait for the next BeginTabItem() call. We cannot compute this width within TabBarAddTab() because font size depends on the active window.
         const char* tab_name = tab_bar->GetTabName(tab);
-        const bool has_close_button = (tab->Flags & ImGuiTabItemFlags_NoCloseButton) ? false : true;
+        const bool has_close_button = tab->Window ? tab->Window->HasCloseButton : ((tab->Flags & ImGuiTabItemFlags_NoCloseButton) == 0);
         tab->ContentWidth = TabItemCalcSize(tab_name, has_close_button).x;
 
         width_total_contents += (tab_n > 0 ? g.Style.ItemInnerSpacing.x : 0.0f) + tab->ContentWidth;
@@ -6749,6 +6797,10 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
     tab_bar->VisibleTabId = tab_bar->SelectedTabId;
     tab_bar->VisibleTabWasSubmitted = false;
 
+    // CTRL+TAB can override visible tab temporarily
+    if (g.NavWindowingTarget != NULL && g.NavWindowingTarget->DockNode && g.NavWindowingTarget->DockNode->TabBar == tab_bar)
+        tab_bar->VisibleTabId = scroll_track_selected_tab_id = g.NavWindowingTarget->ID;
+
     // Update scrolling
     if (scroll_track_selected_tab_id)
         if (ImGuiTabItem* scroll_track_selected_tab = TabBarFindTabByID(tab_bar, scroll_track_selected_tab_id))
@@ -6805,6 +6857,38 @@ ImGuiTabItem* ImGui::TabBarFindTabByID(ImGuiTabBar* tab_bar, ImGuiID tab_id)
     return NULL;
 }
 
+// FIXME: See references to #2304 in TODO.txt
+ImGuiTabItem* ImGui::TabBarFindMostRecentlySelectedTabForActiveWindow(ImGuiTabBar* tab_bar)
+{
+    ImGuiTabItem* most_recently_selected_tab = NULL;
+    for (int tab_n = 0; tab_n < tab_bar->Tabs.Size; tab_n++)
+    {
+        ImGuiTabItem* tab = &tab_bar->Tabs[tab_n];
+        if (most_recently_selected_tab == NULL || most_recently_selected_tab->LastFrameSelected < tab->LastFrameSelected)
+            if (tab->Window && tab->Window->WasActive)
+                most_recently_selected_tab = tab;
+    }
+    return most_recently_selected_tab;
+}
+
+// The purpose of this call is to register tab in advance so we can control their order at the time they appear.
+// Otherwise calling this is unnecessary as tabs are appending as needed by the BeginTabItem() function.
+void ImGui::TabBarAddTab(ImGuiTabBar* tab_bar, ImGuiTabItemFlags tab_flags, ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(TabBarFindTabByID(tab_bar, window->ID) == NULL);
+    IM_ASSERT(g.CurrentTabBar != tab_bar);  // Can't work while the tab bar is active as our tab doesn't have an X offset yet, in theory we could/should test something like (tab_bar->CurrFrameVisible < g.FrameCount) but we'd need to solve why triggers the commented early-out assert in BeginTabBarEx() (probably dock node going from implicit to explicit in same frame)
+
+    ImGuiTabItem new_tab;
+    new_tab.ID = window->ID;
+    new_tab.Flags = tab_flags;
+    new_tab.LastFrameVisible = tab_bar->CurrFrameVisible;   // Required so BeginTabBar() doesn't ditch the tab
+    if (new_tab.LastFrameVisible == -1)
+        new_tab.LastFrameVisible = g.FrameCount - 1;
+    new_tab.Window = window;                                // Required so tab bar layout can compute the tab width before tab submission
+    tab_bar->Tabs.push_back(new_tab);
+}
+
 // The *TabId fields be already set by the docking system _before_ the actual TabItem was created, so we clear them regardless.
 void ImGui::TabBarRemoveTab(ImGuiTabBar* tab_bar, ImGuiID tab_id)
 {
@@ -6980,7 +7064,7 @@ bool    ImGui::BeginTabItem(const char* label, bool* p_open, ImGuiTabItemFlags f
         IM_ASSERT_USER_ERROR(tab_bar, "BeginTabItem() Needs to be called between BeginTabBar() and EndTabBar()!");
         return false;
     }
-    bool ret = TabItemEx(tab_bar, label, p_open, flags);
+    bool ret = TabItemEx(tab_bar, label, p_open, flags, NULL);
     if (ret && !(flags & ImGuiTabItemFlags_NoPushId))
     {
         ImGuiTabItem* tab = &tab_bar->Tabs[tab_bar->LastTabItemIdx];
@@ -7008,7 +7092,7 @@ void    ImGui::EndTabItem()
         window->IDStack.pop_back();
 }
 
-bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open, ImGuiTabItemFlags flags)
+bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open, ImGuiTabItemFlags flags, ImGuiWindow* docked_window)
 {
     // Layout whole tab bar if not already done
     if (tab_bar->WantLayout)
@@ -7023,6 +7107,7 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
     const ImGuiID id = TabBarCalcTabID(tab_bar, label);
 
     // If the user called us with *p_open == false, we early out and don't render. We make a dummy call to ItemAdd() so that attempts to use a contextual popup menu with an implicit ID won't use an older ID.
+    IMGUI_TEST_ENGINE_ITEM_INFO(id, label, window->DC.LastItemStatusFlags);
     if (p_open && !*p_open)
     {
         PushItemFlag(ImGuiItemFlags_NoNav | ImGuiItemFlags_NoNavDefaultFocus, true);
@@ -7059,10 +7144,20 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
     const bool tab_appearing = (tab->LastFrameVisible + 1 < g.FrameCount);
     tab->LastFrameVisible = g.FrameCount;
     tab->Flags = flags;
+    tab->Window = docked_window;
 
     // Append name with zero-terminator
-    tab->NameOffset = tab_bar->TabsNames.size();
-    tab_bar->TabsNames.append(label, label + strlen(label) + 1);
+    if (tab_bar->Flags & ImGuiTabBarFlags_DockNode)
+    {
+        IM_ASSERT(tab->Window != NULL);
+        tab->NameOffset = -1;
+    }
+    else
+    {
+        IM_ASSERT(tab->Window == NULL);
+        tab->NameOffset = tab_bar->TabsNames.size();
+        tab_bar->TabsNames.append(label, label + strlen(label) + 1); // Append name _with_ the zero-terminator.
+    }
 
     // If we are not reorderable, always reset offset based on submission order.
     // (We already handled layout and sizing using the previous known order, but sizing is not affected by order!)
@@ -7085,7 +7180,7 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
         tab_bar->VisibleTabWasSubmitted = true;
 
     // On the very first frame of a tab bar we let first tab contents be visible to minimize appearing glitches
-    if (!tab_contents_visible && tab_bar->SelectedTabId == 0 && tab_bar_appearing)
+    if (!tab_contents_visible && tab_bar->SelectedTabId == 0 && tab_bar_appearing && docked_window == NULL)
         if (tab_bar->Tabs.Size == 1 && !(tab_bar->Flags & ImGuiTabBarFlags_AutoSelectNewTabs))
             tab_contents_visible = true;
 
@@ -7128,7 +7223,7 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
 
     // Click to Select a tab
     ImGuiButtonFlags button_flags = (ImGuiButtonFlags_PressedOnClick | ImGuiButtonFlags_AllowItemOverlap);
-    if (g.DragDropActive)
+    if (g.DragDropActive && !g.DragDropPayload.IsDataType(IMGUI_PAYLOAD_TYPE_WINDOW))
         button_flags |= ImGuiButtonFlags_PressedOnDragDropHold;
     bool hovered, held;
     bool pressed = ButtonBehavior(bb, id, &hovered, &held, button_flags);
@@ -7140,23 +7235,66 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
     if (!held)
         SetItemAllowOverlap();
 
-    // Drag and drop: re-order tabs
-    if (held && !tab_appearing && IsMouseDragging(0))
+    // Drag and drop a single floating window node moves it
+    ImGuiDockNode* node = docked_window ? docked_window->DockNode : NULL;
+    const bool single_floating_window_node = node && node->IsFloatingNode() && (node->Windows.Size == 1);
+    if (held && single_floating_window_node && IsMouseDragging(0, 0.0f))
     {
-        if (!g.DragDropActive && (tab_bar->Flags & ImGuiTabBarFlags_Reorderable))
+        // Move
+        StartMouseMovingWindow(docked_window);
+    }
+    else if (held && !tab_appearing && IsMouseDragging(0))
+    {
+        // Drag and drop: re-order tabs
+        float drag_distance_from_edge_x = 0.0f;
+        if (!g.DragDropActive && ((tab_bar->Flags & ImGuiTabBarFlags_Reorderable) || (docked_window != NULL)))
         {
             // While moving a tab it will jump on the other side of the mouse, so we also test for MouseDelta.x
             if (g.IO.MouseDelta.x < 0.0f && g.IO.MousePos.x < bb.Min.x)
             {
+                drag_distance_from_edge_x = bb.Min.x - g.IO.MousePos.x;
                 if (tab_bar->Flags & ImGuiTabBarFlags_Reorderable)
                     TabBarQueueChangeTabOrder(tab_bar, tab, -1);
             }
             else if (g.IO.MouseDelta.x > 0.0f && g.IO.MousePos.x > bb.Max.x)
             {
+                drag_distance_from_edge_x = g.IO.MousePos.x - bb.Max.x;
                 if (tab_bar->Flags & ImGuiTabBarFlags_Reorderable)
                     TabBarQueueChangeTabOrder(tab_bar, tab, +1);
             }
         }
+
+        // Extract a Dockable window out of it's tab bar
+        if (docked_window != NULL && !(docked_window->Flags & ImGuiWindowFlags_NoMove))
+        {
+            // We use a variable threshold to distinguish dragging tabs within a tab bar and extracting them out of the tab bar
+            bool undocking_tab = (g.DragDropActive && g.DragDropPayload.SourceId == id);
+
+            if (!undocking_tab) //&& (!g.IO.ConfigDockingWithShift || g.IO.KeyShift)
+            {
+                float threshold_base = g.FontSize;
+                //float threshold_base = g.IO.ConfigDockingWithShift ? g.FontSize * 0.5f : g.FontSize;
+                float threshold_x = (threshold_base * 2.2f);
+                float threshold_y = (threshold_base * 1.5f) + ImClamp((ImFabs(g.IO.MouseDragMaxDistanceAbs[0].x) - threshold_base * 2.0f) * 0.20f, 0.0f, threshold_base * 4.0f);
+                //GetForegroundDrawList()->AddRect(ImVec2(bb.Min.x - threshold_x, bb.Min.y - threshold_y), ImVec2(bb.Max.x + threshold_x, bb.Max.y + threshold_y), IM_COL32_WHITE); // [DEBUG]
+
+                float distance_from_edge_y = ImMax(bb.Min.y - g.IO.MousePos.y, g.IO.MousePos.y - bb.Max.y);
+                if (distance_from_edge_y >= threshold_y)
+                    undocking_tab = true;
+                else if (drag_distance_from_edge_x > threshold_x)
+                    if ((tab_bar->ReorderRequestDir < 0 && tab_bar->GetTabOrder(tab) == 0) || (tab_bar->ReorderRequestDir > 0 && tab_bar->GetTabOrder(tab) == tab_bar->Tabs.Size - 1))
+                        undocking_tab = true;
+            }
+
+            if (undocking_tab)
+            {
+                // Undock
+                DockContextQueueUndockWindow(&g, docked_window);
+                g.MovingWindow = docked_window;
+                g.ActiveId = g.MovingWindow->MoveId;
+                g.ActiveIdClickOffset -= g.MovingWindow->Pos - bb.Min;
+            }
+        }
     }
 
 #if 0
@@ -7219,6 +7357,16 @@ void    ImGui::SetTabItemClosed(const char* label)
         ImGuiID tab_id = TabBarCalcTabID(tab_bar, label);
         TabBarRemoveTab(tab_bar, tab_id);
     }
+    else if (ImGuiWindow* window = FindWindowByName(label))
+    {
+        if (window->DockIsActive)
+            if (ImGuiDockNode* node = window->DockNode)
+            {
+                ImGuiID tab_id = TabBarCalcTabID(node->TabBar, label);
+                TabBarRemoveTab(node->TabBar, tab_id);
+                window->DockTabWantClose = true;
+            }
+    }
 }
 
 ImVec2 ImGui::TabItemCalcSize(const char* label, bool has_close_button)
@@ -7242,7 +7390,7 @@ void ImGui::TabItemBackground(ImDrawList* draw_list, const ImRect& bb, ImGuiTabI
     IM_ASSERT(width > 0.0f);
     const float rounding = ImMax(0.0f, ImMin(g.Style.TabRounding, width * 0.5f - 1.0f));
     const float y1 = bb.Min.y + 1.0f;
-    const float y2 = bb.Max.y - 1.0f;
+    const float y2 = bb.Max.y + ((flags & ImGuiTabItemFlags_Preview) ? 0.0f : -1.0f);
     draw_list->PathLineTo(ImVec2(bb.Min.x, y2));
     draw_list->PathArcToFast(ImVec2(bb.Min.x + rounding, y1 + rounding), rounding, 6, 9);
     draw_list->PathArcToFast(ImVec2(bb.Max.x - rounding, y1 + rounding), rounding, 9, 12);