1 files changed, 40 insertions, 3 deletions

diff --git a/source/blender/editors/interface/interface_panel.c b/source/blender/editors/interface/interface_panel.c
index 2ad1c25305c..04179721305 100644
--- a/source/blender/editors/interface/interface_panel.c
+++ b/source/blender/editors/interface/interface_panel.c
@@ -102,6 +102,7 @@ typedef struct uiHandlePanelData {
   double starttime;
 
   /* dragging */
+  bool is_drag_drop;
   int startx, starty;
   int startofsx, startofsy;
   int startsizex, startsizey;
@@ -743,7 +744,7 @@ void ui_draw_aligned_panel(uiStyle *style,
   /* an open panel */
   else {
     /* in some occasions, draw a border */
-    if (panel->flag & PNL_SELECT) {
+    if (panel->flag & PNL_SELECT && !is_subpanel) {
       if (panel->control & UI_PNL_SOLID) {
         UI_draw_roundbox_corner_set(UI_CNR_ALL);
       }
@@ -876,6 +877,16 @@ static int get_panel_real_ofsx(Panel *panel)
   }
 }
 
+bool UI_panel_is_dragging(const struct Panel *panel)
+{
+  uiHandlePanelData *data = panel->activedata;
+  if (!data) {
+    return false;
+  }
+
+  return data->is_drag_drop;
+}
+
 typedef struct PanelSort {
   Panel *panel, *orig;
 } PanelSort;
@@ -2458,6 +2469,24 @@ static void ui_handler_remove_panel(bContext *C, void *userdata)
   panel_activate_state(C, panel, PANEL_STATE_EXIT);
 }
 
+/**
+ * Set selection state for a panel and its subpanels. The subpanels need to know they are selected
+ * too so they can be drawn above their parent when it is dragged.
+ */
+static void set_panel_selection(Panel *panel, bool value)
+{
+  if (value) {
+    panel->flag |= PNL_SELECT;
+  }
+  else {
+    panel->flag &= ~PNL_SELECT;
+  }
+
+  LISTBASE_FOREACH (Panel *, child, &panel->children) {
+    set_panel_selection(child, value);
+  }
+}
+
 static void panel_activate_state(const bContext *C, Panel *panel, uiHandlePanelState state)
 {
   uiHandlePanelData *data = panel->activedata;
@@ -2468,6 +2497,8 @@ static void panel_activate_state(const bContext *C, Panel *panel, uiHandlePanelS
     return;
   }
 
+  bool was_drag_drop = (data && data->state == PANEL_STATE_DRAG);
+
   if (state == PANEL_STATE_EXIT || state == PANEL_STATE_ANIMATION) {
     if (data && data->state != PANEL_STATE_ANIMATION) {
       /* XXX:
@@ -2480,10 +2511,10 @@ static void panel_activate_state(const bContext *C, Panel *panel, uiHandlePanelS
       check_panel_overlap(region, NULL); /* clears */
     }
 
-    panel->flag &= ~PNL_SELECT;
+    set_panel_selection(panel, false);
   }
   else {
-    panel->flag |= PNL_SELECT;
+    set_panel_selection(panel, true);
   }
 
   if (data && data->animtimer) {
@@ -2519,6 +2550,12 @@ static void panel_activate_state(const bContext *C, Panel *panel, uiHandlePanelS
     data->startsizex = panel->sizex;
     data->startsizey = panel->sizey;
     data->starttime = PIL_check_seconds_timer();
+
+    /* Remember drag drop state even when animating to the aligned position after dragging. */
+    data->is_drag_drop = was_drag_drop;
+    if (state == PANEL_STATE_DRAG) {
+      data->is_drag_drop = true;
+    }
   }
 
   ED_region_tag_redraw(region);