8 files changed, 82 insertions, 0 deletions
diff --git a/intern/ghost/GHOST_C-api.h b/intern/ghost/GHOST_C-api.h
index 98094cc0669..a2eef91c704 100644
--- a/intern/ghost/GHOST_C-api.h
+++ b/intern/ghost/GHOST_C-api.h
@@ -265,6 +265,16 @@ extern GHOST_TSuccess GHOST_EndFullScreen(GHOST_SystemHandle systemhandle);
  */
 extern int GHOST_GetFullScreen(GHOST_SystemHandle systemhandle);
 
+/**
+ * Get the Window under the cursor.
+ * \param x: The x-coordinate of the cursor.
+ * \param y: The y-coordinate of the cursor.
+ * @return The window under the cursor or nullptr in none.
+ */
+extern GHOST_WindowHandle GHOST_GetWindowUnderCursor(GHOST_SystemHandle systemhandle,
+                                                     int32_t x,
+                                                     int32_t y);
+
 /***************************************************************************************
  * Event management functionality
  ***************************************************************************************/
diff --git a/intern/ghost/GHOST_ISystem.h b/intern/ghost/GHOST_ISystem.h
index 05c6c9d907f..4c568a0cc02 100644
--- a/intern/ghost/GHOST_ISystem.h
+++ b/intern/ghost/GHOST_ISystem.h
@@ -325,6 +325,14 @@ class GHOST_ISystem {
    */
   virtual void useWindowFocus(const bool use_focus) = 0;
 
+  /**
+   * Get the Window under the cursor.
+   * \param x: The x-coordinate of the cursor.
+   * \param y: The y-coordinate of the cursor.
+   * @return The window under the cursor or nullptr if none.
+   */
+  virtual GHOST_IWindow *getWindowUnderCursor(int32_t x, int32_t y) = 0;
+
   /***************************************************************************************
    * Event management functionality
    ***************************************************************************************/
diff --git a/intern/ghost/intern/GHOST_C-api.cpp b/intern/ghost/intern/GHOST_C-api.cpp
index a21c3a90c06..3d8411a8268 100644
--- a/intern/ghost/intern/GHOST_C-api.cpp
+++ b/intern/ghost/intern/GHOST_C-api.cpp
@@ -249,6 +249,16 @@ int GHOST_GetFullScreen(GHOST_SystemHandle systemhandle)
   return (int)system->getFullScreen();
 }
 
+GHOST_WindowHandle GHOST_GetWindowUnderCursor(GHOST_SystemHandle systemhandle,
+                                              int32_t x,
+                                              int32_t y)
+{
+  GHOST_ISystem *system = (GHOST_ISystem *)systemhandle;
+  GHOST_IWindow *window = system->getWindowUnderCursor(x, y);
+
+  return (GHOST_WindowHandle)window;
+}
+
 bool GHOST_ProcessEvents(GHOST_SystemHandle systemhandle, bool waitForEvent)
 {
   GHOST_ISystem *system = (GHOST_ISystem *)systemhandle;
diff --git a/intern/ghost/intern/GHOST_System.cpp b/intern/ghost/intern/GHOST_System.cpp
index d09c167cb95..17f74003805 100644
--- a/intern/ghost/intern/GHOST_System.cpp
+++ b/intern/ghost/intern/GHOST_System.cpp
@@ -205,6 +205,25 @@ bool GHOST_System::getFullScreen(void)
   return fullScreen;
 }
 
+GHOST_IWindow *GHOST_System::getWindowUnderCursor(int32_t x, int32_t y)
+{
+  /* TODO: This solution should follow the order of the activated windows (Z-order).
+   * It is imperfect but usable in most cases. */
+  for (GHOST_IWindow *iwindow : m_windowManager->getWindows()) {
+    if (iwindow->getState() == GHOST_kWindowStateMinimized) {
+      continue;
+    }
+
+    GHOST_Rect bounds;
+    iwindow->getClientBounds(bounds);
+    if (bounds.isInside(x, y)) {
+      return iwindow;
+    }
+  }
+
+  return NULL;
+}
+
 void GHOST_System::dispatchEvents()
 {
 #ifdef WITH_INPUT_NDOF
diff --git a/intern/ghost/intern/GHOST_System.h b/intern/ghost/intern/GHOST_System.h
index 16c34ff1a6d..692e483be2a 100644
--- a/intern/ghost/intern/GHOST_System.h
+++ b/intern/ghost/intern/GHOST_System.h
@@ -173,6 +173,14 @@ class GHOST_System : public GHOST_ISystem {
   void useWindowFocus(const bool use_focus);
   bool m_windowFocus;
 
+  /**
+   * Get the Window under the cursor.
+   * \param x: The x-coordinate of the cursor.
+   * \param y: The y-coordinate of the cursor.
+   * @return The window under the cursor or nullptr if none.
+   */
+  GHOST_IWindow *getWindowUnderCursor(int32_t x, int32_t y);
+
   /***************************************************************************************
    * Event management functionality
    ***************************************************************************************/
diff --git a/intern/ghost/intern/GHOST_SystemCocoa.h b/intern/ghost/intern/GHOST_SystemCocoa.h
index 5950da6813d..37cba8b8559 100644
--- a/intern/ghost/intern/GHOST_SystemCocoa.h
+++ b/intern/ghost/intern/GHOST_SystemCocoa.h
@@ -125,6 +125,14 @@ class GHOST_SystemCocoa : public GHOST_System {
    */
   GHOST_TSuccess disposeContext(GHOST_IContext *context);
 
+  /**
+   * Get the Window under the cursor.
+   * \param x: The x-coordinate of the cursor.
+   * \param y: The y-coordinate of the cursor.
+   * @return The window under the cursor or nullptr if none.
+   */
+  GHOST_IWindow *getWindowUnderCursor(int32_t x, int32_t y);
+
   /***************************************************************************************
    * Event management functionality
    ***************************************************************************************/
diff --git a/intern/ghost/intern/GHOST_SystemCocoa.mm b/intern/ghost/intern/GHOST_SystemCocoa.mm
index a53c3d8f2ab..b54bfab5547 100644
--- a/intern/ghost/intern/GHOST_SystemCocoa.mm
+++ b/intern/ghost/intern/GHOST_SystemCocoa.mm
@@ -788,6 +788,20 @@ GHOST_TSuccess GHOST_SystemCocoa::disposeContext(GHOST_IContext *context)
   return GHOST_kSuccess;
 }
 
+GHOST_IWindow *GHOST_SystemCocoa::getWindowUnderCursor(int32_t x, int32_t y)
+{
+  NSPoint scr_co = NSMakePoint(x, y);
+
+  int windowNumberAtPoint = [NSWindow windowNumberAtPoint:scr_co belowWindowWithWindowNumber:0];
+  NSWindow *nswindow = [NSApp windowWithWindowNumber:windowNumberAtPoint];
+
+  if (nswindow == nil) {
+    return nil;
+  }
+
+  return m_windowManager->getWindowAssociatedWithOSWindow((void *)nswindow);
+}
+
 /**
  * \note : returns coordinates in Cocoa screen coordinates
  */
diff --git a/intern/ghost/intern/GHOST_SystemNULL.h b/intern/ghost/intern/GHOST_SystemNULL.h
index 5dbc42b53a2..43bbc788113 100644
--- a/intern/ghost/intern/GHOST_SystemNULL.h
+++ b/intern/ghost/intern/GHOST_SystemNULL.h
@@ -128,4 +128,9 @@ class GHOST_SystemNULL : public GHOST_System {
                                 type,
                                 ((glSettings.flags & GHOST_glStereoVisual) != 0));
   }
+
+  GHOST_IWindow *getWindowUnderCursor(int32_t x, int32_t y)
+  {
+    return NULL;
+  }
 };