[mutter] clutter/actor: Use different view list when picking frame clock of stage

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

commit 9693462f3250336ca2a5dae316cfd358ca5b6fee
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Fri Dec 11 21:02:56 2020 +0100

    clutter/actor: Use different view list when picking frame clock of stage
    
    Apparently it can happen that a timeline tries to pick a frame clock
    from an actor that's on a stage, but the actor still doesn't find a
    frame clock and returns NULL.
    
    This probably is the case when starting a timeline right after attaching
    an actor to a newly created stage, so before the first stage-update
    cycle. In this case clutter_actor_update_stage_views() will not have run
    and the stage-actor will have priv->stage_views set to NULL even though
    there are stage views.
    
    To prevent this from happening, use the complete list of stage views
    maintained by the backend when picking a frame clock for the stage.
    
    This doesn't fix any issue appearing on master, but is correct
    nonetheless.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1631>

 clutter/clutter/clutter-actor.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
---
diff --git a/clutter/clutter/clutter-actor.c b/clutter/clutter/clutter-actor.c
index 5deeae6d0d..9f9a594623 100644
--- a/clutter/clutter/clutter-actor.c
+++ b/clutter/clutter/clutter-actor.c
@@ -15897,11 +15897,16 @@ clutter_actor_pick_frame_clock (ClutterActor  *self,
                                 ClutterActor **out_actor)
 {
   ClutterActorPrivate *priv = self->priv;
+  GList *stage_views_list;
   float max_refresh_rate = 0.0;
   ClutterStageView *best_view = NULL;
   GList *l;
 
-  if (!priv->stage_views)
+  stage_views_list = CLUTTER_IS_STAGE (self)
+    ? clutter_stage_peek_stage_views (CLUTTER_STAGE (self))
+    : priv->stage_views;
+
+  if (!stage_views_list)
     {
      if (priv->parent)
        return clutter_actor_pick_frame_clock (priv->parent, out_actor);
@@ -15909,7 +15914,7 @@ clutter_actor_pick_frame_clock (ClutterActor  *self,
        return NULL;
     }
 
-  for (l = priv->stage_views; l; l = l->next)
+  for (l = stage_views_list; l; l = l->next)
     {
       ClutterStageView *view = l->data;
       float refresh_rate;