New APIs: GetWindowSurfaceBufferFD() and CreateMemDCFromSurfaceBufferFD() for compositing schema.

include/gdi.h

@@ -1704,6 +1704,27 @@ MG_EXPORT BOOL GUIAPI IsScreenDC (HDC hdc);
  */
 MG_EXPORT BOOL GUIAPI IsWindowDC (HDC hdc);
 
+#ifdef _MGSCHEMA_COMPOSITING
+/**
+ * \fn HDC GUIAPI CreateMemDCFromSurfaceBufferFD (int fd);
+ * \brief Creates a memory DC from a file descriptor of a surface buffer.
+ *
+ * This function creates a memory DC from the specified file descriptor \a fd,
+ * which represents a surface buffer.
+ *
+ * \param fd The file descriptor which represents a surface buffer.
+ *
+ * \return The handle to a new memory DC, HDC_INVALID indicates an error.
+ *
+ * \note This function only available when _MGSCHEMA_COMPOSITING is defined.
+ *
+ * \sa GetWindowSurfaceBufferFD
+ *
+ * Since 5.0.13
+ */
+MG_EXPORT HDC GUIAPI CreateMemDCFromSurfaceBufferFD (int fd);
+#endif /* _MGSCHEMA_COMPOSITING */
+
 /**
  * \fn HDC GUIAPI CreateMemDCEx (int width, int height, int depth, DWORD flags, \
  Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask,

include/window.h

@@ -7237,6 +7237,29 @@ MG_EXPORT BOOL GUIAPI SetMainWindowGestureFlags (HWND hWnd, DWORD dwFlags);
 
 #ifdef _MGSCHEMA_COMPOSITING
 
+/**
+ * \fn int GUIAPI GetWindowSurfaceBufferFD (HWND hwnd)
+ * \brief Gets the file descriptor of the surface buffer for a window or
+ * the main window it locates.
+ *
+ * This function gets the file descriptor of the surface buffer for
+ * the specified window if it is a main window or the main window it locates.
+ * Note that if the window is a control that has the style `WS_EX_CTRLASMAINWIN`,
+ * the window will have a separate surface buffer.
+ *
+ * \param hwnd The handle to the window.
+ *
+ * \return An integer larger than or equal to 0 for a valid file descriptor,
+ *      otherwise a negative value.
+ *
+ * \note This function only available when _MGSCHEMA_COMPOSITING is defined.
+ *
+ * \sa CreateMemDCFromSurfaceBufferFD
+ *
+ * Since 5.0.13
+ */
+MG_EXPORT int GUIAPI GetWindowSurfaceBufferFD (HWND hWnd);
+
 /**
  * \fn BOOL GUIAPI SetMainWindowCompositing (HWND hWnd,
         int type, DWORD arg)