intern/ghost/GHOST_C-api.h

@@ -256,7 +256,10 @@ extern GHOST_TSuccess GHOST_EndFullScreen(GHOST_SystemHandle systemhandle);
 extern bool GHOST_GetFullScreen(GHOST_SystemHandle systemhandle);
 
 /**
- * Get the Window under the cursor.
+ * Get the Window under the cursor. Although coordinates of the mouse are supplied, platform-
+ * specific implementations are free to ignore these and query the mouse location themselves, due
+ * to them possibly being incorrect under certain conditions, for example when using multiple
+ * monitors that vary in scale and/or DPI.
  * \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.

intern/ghost/GHOST_ISystem.hh

@@ -332,7 +332,10 @@ class GHOST_ISystem {
   virtual void setAutoFocus(const bool auto_focus) = 0;
 
   /**
-   * Get the Window under the cursor.
+   * Get the Window under the cursor. Although coordinates of the mouse are supplied, platform-
+   * specific implementations are free to ignore these and query the mouse location themselves, due
+   * to them possibly being incorrect under certain conditions, for example when using multiple
+   * monitors that vary in scale and/or DPI.
    * \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.

intern/ghost/intern/GHOST_SystemWin32.cc

@@ -473,6 +473,23 @@ GHOST_TSuccess GHOST_SystemWin32::getPixelAtCursor(float r_color[3]) const
   return GHOST_kSuccess;
 }
 
+GHOST_IWindow *GHOST_SystemWin32::getWindowUnderCursor(int32_t /*x*/, int32_t /*y*/)
+{
+  /* Get cursor position from the OS. Do not use the supplied positions as those
+   * could be incorrect, especially if using multiple windows of differing OS scale. */
+  POINT point;
+  if (!GetCursorPos(&point)) {
+    return nullptr;
+  }
+
+  HWND win = WindowFromPoint(point);
+  if (win == NULL) {
+    return nullptr;
+  }
+
+  return m_windowManager->getWindowAssociatedWithOSWindow((void *)win);
+}
+
 GHOST_TSuccess GHOST_SystemWin32::getModifierKeys(GHOST_ModifierKeys &keys) const
 {
   /* `GetAsyncKeyState` returns the current interrupt-level state of the hardware, which is needed

intern/ghost/intern/GHOST_SystemWin32.hh

@@ -151,6 +151,12 @@ class GHOST_SystemWin32 : public GHOST_System {
    */
   static GHOST_TSuccess disposeContextD3D(GHOST_ContextD3D *context);
 
+  /**
+   * Get the Window under the mouse cursor. Location obtained from the OS.
+   * \return The window under the cursor or nullptr if none.
+   */
+  GHOST_IWindow *getWindowUnderCursor(int32_t /*x*/, int32_t /*y*/);
+
   /***************************************************************************************
    ** Event management functionality
    ***************************************************************************************/

intern/ghost/intern/GHOST_WindowWin32.cc

@@ -361,6 +361,11 @@ HWND GHOST_WindowWin32::getHWND() const
   return m_hWnd;
 }
 
+void *GHOST_WindowWin32::getOSWindow() const
+{
+  return (void *)m_hWnd;
+}
+
 void GHOST_WindowWin32::setTitle(const char *title)
 {
   wchar_t *title_16 = alloc_utf16_from_8((char *)title, 0);

intern/ghost/intern/GHOST_WindowWin32.hh

@@ -107,6 +107,12 @@ class GHOST_WindowWin32 : public GHOST_Window {
    */
   HWND getHWND() const;
 
+  /**
+   * Returns the handle of the window.
+   * \return The handle of the window.
+   */
+  void *getOSWindow() const;
+
   /**
    * Sets the title displayed in the title bar.
    * \param title: The title to display in the title bar.