clutter/actor: Add API to pick frame clock

The frame clock wouldn't be useable yet, but none the less, add API to
get the frame clock best suited for driving the actor. Currently this
translates to the fastest one, but that might change.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1285

clutter/clutter/clutter-actor.c

@@ -652,6 +652,7 @@
 #include "clutter-scriptable.h"
 #include "clutter-script-private.h"
 #include "clutter-stage-private.h"
+#include "clutter-stage-view-private.h"
 #include "clutter-timeline.h"
 #include "clutter-transition.h"
 #include "clutter-units.h"
@@ -16250,6 +16251,40 @@ clutter_actor_peek_stage_views (ClutterActor *self)
   return self->priv->stage_views;
 }
 
+/**
+ * clutter_actor_pick_frame_clock:
+ * @self: a #ClutterActor
+ *
+ * Pick the most suitable frame clock for driving animations for this actor.
+ *
+ * Returns: (transfer none): a #ClutterFrameClock
+ */
+ClutterFrameClock *
+clutter_actor_pick_frame_clock (ClutterActor *self)
+{
+  float max_refresh_rate = 0.0;
+  ClutterStageView *best_view = NULL;
+  GList *l;
+
+  for (l = self->priv->stage_views; l; l = l->next)
+    {
+      ClutterStageView *view = l->data;
+      float refresh_rate;
+
+      refresh_rate = clutter_stage_view_get_refresh_rate (view);
+      if (refresh_rate > max_refresh_rate)
+        {
+          best_view = view;
+          max_refresh_rate = refresh_rate;
+        }
+    }
+
+  if (best_view)
+    return clutter_stage_view_get_frame_clock (best_view);
+  else
+    return NULL;
+}
+
 /**
  * clutter_actor_has_overlaps:
  * @self: A #ClutterActor

clutter/clutter/clutter-actor.h

@@ -924,6 +924,9 @@ GList * clutter_actor_peek_stage_views (ClutterActor *self);
 CLUTTER_EXPORT
 void clutter_actor_invalidate_transform (ClutterActor *self);
 
+CLUTTER_EXPORT
+ClutterFrameClock * clutter_actor_pick_frame_clock (ClutterActor *self);
+
 G_END_DECLS
 
 #endif /* __CLUTTER_ACTOR_H__ */