[mutter] window-actor/wayland: Only use scanout for opaque non-fullscreen windows

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

commit 54ba64b9f22f02893bc8c593358d6ace842be40c
Author: Sebastian Keller <skeller gnome org>
Date:   Wed May 11 22:49:08 2022 +0200

    window-actor/wayland: Only use scanout for opaque non-fullscreen windows
    
    This could for example happen with the client window created by the
    desktop-icons-ng extension which spans the entire desktop, but is not a
    fullscreen window and uses transparency
    
    On Wayland only opaque surfaces or transparent surfaces of fullscreen
    windows can be used for direct scanout.
    
    Related: https://gitlab.gnome.org/GNOME/mutter/-/issues/2263
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2409>

 src/compositor/meta-window-actor-wayland.c | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/src/compositor/meta-window-actor-wayland.c b/src/compositor/meta-window-actor-wayland.c
index 4b87fd11fb..e1f3410483 100644
--- a/src/compositor/meta-window-actor-wayland.c
+++ b/src/compositor/meta-window-actor-wayland.c
@@ -93,6 +93,7 @@ meta_window_actor_wayland_get_scanout_candidate (MetaWindowActor *actor)
 {
   ClutterActor *child_actor;
   MetaSurfaceActor *topmost_surface_actor;
+  MetaWindow *window;
 
   child_actor = clutter_actor_get_last_child (CLUTTER_ACTOR (actor));
   if (!child_actor || !META_IS_SURFACE_ACTOR_WAYLAND (child_actor))
@@ -100,6 +101,11 @@ meta_window_actor_wayland_get_scanout_candidate (MetaWindowActor *actor)
 
   topmost_surface_actor = META_SURFACE_ACTOR (child_actor);
 
+  window = meta_window_actor_get_meta_window (actor);
+  if (!meta_window_is_fullscreen (window) &&
+      !meta_surface_actor_is_opaque (topmost_surface_actor))
+    return NULL;
+
   return topmost_surface_actor;
 }