[mutter] window-actor: Add API to get a MetaWindowActor from a ClutterActor

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 73bc3c4426776c85177413762498d7e9bd1e059d
Author: Robert Mader <robert mader posteo de>
Date:   Thu Jun 13 20:16:37 2019 +0200

    window-actor: Add API to get a MetaWindowActor from a ClutterActor
    
    Make it so it returns the closest ancestry MetaWindowActor if it
    is a MetaSurfaceActor.
    We need this for Wayland subsurfaces, so we can support actions like
    Meta+Drag on them.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/604

 src/compositor/meta-window-actor-private.h |  1 +
 src/compositor/meta-window-actor.c         | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)
---
diff --git a/src/compositor/meta-window-actor-private.h b/src/compositor/meta-window-actor-private.h
index 396e84a8a..24a4cfcb6 100644
--- a/src/compositor/meta-window-actor-private.h
+++ b/src/compositor/meta-window-actor-private.h
@@ -86,5 +86,6 @@ void meta_window_actor_assign_surface_actor (MetaWindowActor  *self,
                                              MetaSurfaceActor *surface_actor);
 
 MetaWindowActor *meta_window_actor_from_window (MetaWindow *window);
+MetaWindowActor *meta_window_actor_from_actor (ClutterActor *actor);
 
 #endif /* META_WINDOW_ACTOR_PRIVATE_H */
diff --git a/src/compositor/meta-window-actor.c b/src/compositor/meta-window-actor.c
index f558bfd1b..84c282e18 100644
--- a/src/compositor/meta-window-actor.c
+++ b/src/compositor/meta-window-actor.c
@@ -2035,3 +2035,21 @@ screen_cast_window_iface_init (MetaScreenCastWindowInterface *iface)
   iface->capture_into = meta_window_actor_capture_into;
   iface->has_damage = meta_window_actor_has_damage;
 }
+
+MetaWindowActor *
+meta_window_actor_from_actor (ClutterActor *actor)
+{
+  if (!META_IS_SURFACE_ACTOR (actor))
+    return NULL;
+
+  do
+    {
+      actor = clutter_actor_get_parent (actor);
+
+      if (META_IS_WINDOW_ACTOR (actor))
+        return META_WINDOW_ACTOR (actor);
+    }
+  while (actor != NULL);
+
+  return NULL;
+}