[gtk/fix-3798] GDK-Win32: Fix drag surface positioning

[Chun-wei Fan <fanchunwei src gnome org>]

commit eca4180116172f1db364087ef32eff882f77a61c
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri Jun 11 10:17:07 2021 +0800

    GDK-Win32: Fix drag surface positioning
    
    Adjust the coordinates of where the drag surface using
    gdk_win32_surface_get_root_coords(), so that drag surfaces are
    positioned correctly.
    
    Fixes issue #3798.

 gdk/win32/gdksurface-win32.c | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/gdk/win32/gdksurface-win32.c b/gdk/win32/gdksurface-win32.c
index 1d0f12771a..e5ea17546c 100644
--- a/gdk/win32/gdksurface-win32.c
+++ b/gdk/win32/gdksurface-win32.c
@@ -5021,6 +5021,11 @@ gdk_win32_drag_surface_present (GdkDragSurface *drag_surface,
 {
   GdkSurface *surface = GDK_SURFACE (drag_surface);
 
+  gdk_win32_surface_get_root_coords (surface,
+                                     surface->x,
+                                     surface->y,
+                                    &surface->x,
+                                     &surface->y);
   gdk_win32_surface_resize (surface, width, height);  
   gdk_win32_surface_show (surface, FALSE);
   maybe_notify_mapped (surface);