winex11: Clip out children window when repainting the desktop.

dlls/winex11.drv/window.c

@@ -1532,6 +1532,7 @@ void X11DRV_GetDC( HDC hdc, HWND hwnd, HWND top, const RECT *win_rect,
         escape.fbconfig_id = data ? data->fbconfig_id : (XID)GetPropA( hwnd, fbconfig_id_prop );
         escape.gl_drawable = data ? data->gl_drawable : (Drawable)GetPropA( hwnd, gl_drawable_prop );
         escape.pixmap      = data ? data->pixmap : (Pixmap)GetPropA( hwnd, pixmap_prop );
+        if (flags & DCX_CLIPCHILDREN) escape.mode = ClipByChildren;
     }
 
     escape.dc_rect.left         = win_rect->left - top_rect->left;