[mutter] window/x11: Keep buffer size if resize is not allowed

[Marge Bot <marge-bot src gnome org>]

commit a2a161eb1e21b0919291da9eb7ccb553f1ea97ab
Author: Olivier Fourdan <ofourdan redhat com>
Date:   Fri Mar 12 16:18:07 2021 +0100

    window/x11: Keep buffer size if resize is not allowed
    
    Mutter would deny the application the right to resize itself during an
    interactive resize, to avoid the user and the client to fight for the
    size.
    
    When the client is not allowed to resize, it would use the client rect
    rather than the buffer rect.
    
    As a result, the client window with client side decorations would
    quickly shrink to its minimum size.
    
    Use the buffer rect instead, so that the size really remains the same.
    
    https://gitlab.gnome.org/GNOME/mutter/-/issues/1674
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1777>

 src/x11/window-x11.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/src/x11/window-x11.c b/src/x11/window-x11.c
index 3f136af4f7..204b49e93e 100644
--- a/src/x11/window-x11.c
+++ b/src/x11/window-x11.c
@@ -2502,6 +2502,7 @@ meta_window_move_resize_request (MetaWindow  *window,
   gboolean allow_position_change;
   gboolean in_grab_op;
   MetaMoveResizeFlags flags;
+  MetaRectangle buffer_rect;
 
   /* We ignore configure requests while the user is moving/resizing
    * the window, since these represent the app sucking and fighting
@@ -2573,8 +2574,9 @@ meta_window_move_resize_request (MetaWindow  *window,
                  window->type);
     }
 
-  width = window->rect.width;
-  height = window->rect.height;
+  meta_window_get_buffer_rect (window, &buffer_rect);
+  width = buffer_rect.width;
+  height = buffer_rect.height;
   if (!in_grab_op || !meta_grab_op_is_resizing (window->display->grab_op))
     {
       if (value_mask & CWWidth)