[mutter] wayland/subsurface: Move actor unparenting back to rebuild_surface_tree()

[Robert Mader <rmader src gnome org>]

commit 57881ba612f1571f2bf3f1642f416741fc4d3610
Author: Robert Mader <robert mader posteo de>
Date:   Fri Jul 8 21:03:52 2022 +0200

    wayland/subsurface: Move actor unparenting back to rebuild_surface_tree()
    
    Unparenting the surface actor when the subsurface object is destroyed
    has several issues:
     - subsurface actors can be unparented while a close animation is
       still ongoing, breaking the animation for e.g. Firefox.
     - adding and removing the actor to/from the parent is not handled in
       one place, making the code harder to follow.
     - if the destroyed subsurface had children of its own, they potentially
       stick around until a surface-tree rebuild. This makes the Firefox
       hamburger menu not close with the "compositor" backend.
    
    Move the unparenting back to
    `meta_window_actor_wayland_rebuild_surface_tree()` and instead just
    notify the parent of a state change, if it still exist. This will ensure
    a correct mapping between the subsurface node tree and the flat surface
    actor list. In case of the closing animation the parent will already be
    removed and the call is skipped.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2501>

 src/compositor/meta-window-actor-wayland.c | 32 ++++++++++++++++++++++++++++++
 src/wayland/meta-wayland-subsurface.c      | 17 +---------------
 2 files changed, 33 insertions(+), 16 deletions(-)
---
diff --git a/src/compositor/meta-window-actor-wayland.c b/src/compositor/meta-window-actor-wayland.c
index e1f3410483..09205de5e4 100644
--- a/src/compositor/meta-window-actor-wayland.c
+++ b/src/compositor/meta-window-actor-wayland.c
@@ -38,6 +38,18 @@ typedef struct _SurfaceTreeTraverseData
   int index;
 } SurfaceTreeTraverseData;
 
+static gboolean
+get_surface_actor_list (GNode    *node,
+                        gpointer  data)
+{
+  MetaWaylandSurface *surface = node->data;
+  MetaSurfaceActor *surface_actor = meta_wayland_surface_get_actor (surface);
+  GList **surface_actors = data;
+
+  *surface_actors = g_list_prepend (*surface_actors, surface_actor);
+  return FALSE;
+}
+
 static gboolean
 set_surface_actor_index (GNode    *node,
                          gpointer  data)
@@ -74,8 +86,28 @@ meta_window_actor_wayland_rebuild_surface_tree (MetaWindowActor *actor)
   MetaWaylandSurface *surface = meta_surface_actor_wayland_get_surface (
     META_SURFACE_ACTOR_WAYLAND (surface_actor));
   GNode *root_node = surface->subsurface_branch_node;
+  g_autoptr (GList) surface_actors = NULL;
+  g_autoptr (GList) children = NULL;
+  GList *l;
   SurfaceTreeTraverseData traverse_data;
 
+  g_node_traverse (root_node,
+                   G_IN_ORDER,
+                   G_TRAVERSE_LEAVES,
+                   -1,
+                   get_surface_actor_list,
+                   &surface_actors);
+
+  children = clutter_actor_get_children (CLUTTER_ACTOR (actor));
+  for (l = children; l; l = l->next)
+    {
+      ClutterActor *child_actor = l->data;
+
+      if (META_IS_SURFACE_ACTOR_WAYLAND (child_actor) &&
+          !g_list_find (surface_actors, child_actor))
+        clutter_actor_remove_child (CLUTTER_ACTOR (actor), child_actor);
+    }
+
   traverse_data = (SurfaceTreeTraverseData) {
     .window_actor = actor,
     .index = 0,
diff --git a/src/wayland/meta-wayland-subsurface.c b/src/wayland/meta-wayland-subsurface.c
index bc30bc7794..ef6f6657bf 100644
--- a/src/wayland/meta-wayland-subsurface.c
+++ b/src/wayland/meta-wayland-subsurface.c
@@ -292,31 +292,16 @@ meta_wayland_subsurface_class_init (MetaWaylandSubsurfaceClass *klass)
     meta_wayland_subsurface_sync_actor_state;
 }
 
-static void
-unparent_actor (MetaWaylandSurface *surface)
-{
-  ClutterActor *actor;
-  ClutterActor *parent_actor;
-
-  actor = CLUTTER_ACTOR (meta_wayland_surface_get_actor (surface));
-  if (!actor)
-    return;
-
-  parent_actor = clutter_actor_get_parent (actor);
-  if (parent_actor)
-    clutter_actor_remove_child (parent_actor, actor);
-}
-
 static void
 wl_subsurface_destructor (struct wl_resource *resource)
 {
   MetaWaylandSurface *surface = wl_resource_get_user_data (resource);
 
   g_node_unlink (surface->subsurface_branch_node);
-  unparent_actor (surface);
 
   if (surface->sub.parent)
     {
+      meta_wayland_surface_notify_subsurface_state_changed (surface->sub.parent);
       wl_list_remove (&surface->sub.parent_destroy_listener.link);
       surface->sub.parent = NULL;
     }