[mutter] compositor: Update topmost window actor after visibility changes

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

commit bb76d6fcc3ea0e2a7ce98350b6b5200884c729f6
Author: Sebastian Keller <skeller gnome org>
Date:   Thu May 12 17:42:20 2022 +0200

    compositor: Update topmost window actor after visibility changes
    
    The compositor currently only updates the topmost window actor that is
    visible to it after stacking changes. The visibility of a window actor
    to the compositor however might only change via the display idle queue
    after the stacking changes. This could then lead to the topmost window
    actor being assumed to be NULL on Wayland after switching from an empty
    workspace or when opening the first window on an empty workspace. The
    result of this is direct scanout being disabled in these cases.
    
    To fix this also trigger the update when the visibility of windows
    changes.
    
    Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2269
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2413>

 src/compositor/compositor.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
---
diff --git a/src/compositor/compositor.c b/src/compositor/compositor.c
index 45c92d8cb6..6f4982553c 100644
--- a/src/compositor/compositor.c
+++ b/src/compositor/compositor.c
@@ -107,6 +107,7 @@ typedef struct _MetaCompositorPrivate
   gulong stage_presented_id;
   gulong before_paint_handler_id;
   gulong after_paint_handler_id;
+  gulong window_visibility_updated_id;
 
   int64_t server_time_query_time;
   int64_t server_time_offset;
@@ -1042,6 +1043,16 @@ on_after_paint (ClutterStage     *stage,
   meta_compositor_after_paint (compositor, stage_view);
 }
 
+static void
+on_window_visibility_updated (MetaDisplay    *display,
+                              GList          *unplaced,
+                              GList          *should_show,
+                              GList          *should_hide,
+                              MetaCompositor *compositor)
+{
+  update_top_window_actor (compositor);
+}
+
 static void
 meta_compositor_set_property (GObject      *object,
                               guint         prop_id,
@@ -1116,6 +1127,12 @@ meta_compositor_constructed (GObject *object)
                             G_CALLBACK (on_after_paint),
                             compositor);
 
+  priv->window_visibility_updated_id =
+    g_signal_connect (priv->display,
+                      "window-visibility-updated",
+                      G_CALLBACK (on_window_visibility_updated),
+                      compositor);
+
   priv->laters = meta_laters_new (compositor);
 
   G_OBJECT_CLASS (meta_compositor_parent_class)->constructed (object);
@@ -1134,6 +1151,7 @@ meta_compositor_dispose (GObject *object)
   g_clear_signal_handler (&priv->stage_presented_id, stage);
   g_clear_signal_handler (&priv->before_paint_handler_id, stage);
   g_clear_signal_handler (&priv->after_paint_handler_id, stage);
+  g_clear_signal_handler (&priv->window_visibility_updated_id, priv->display);
 
   g_clear_pointer (&priv->windows, g_list_free);