[mutter] clutter/actor: Replace ABSOLUTE_ORIGIN_CHANGED flag with a property

[verdre <jonasd src gnome org>]

commit dc8e5c7f8be1cc348781d8fd3348e7ad8326dfd2
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Sat May 9 19:53:02 2020 +0200

    clutter/actor: Replace ABSOLUTE_ORIGIN_CHANGED flag with a property
    
    The ABSOLUTE_ORIGIN_CHANGED allocation flag is only really useful to
    propagate the information of the absolute origin of an actor having
    changed inside Clutter. It wasn't used anywhere else besides for some
    debug messages and it probably shouldn't be used in custom layout
    implementations anyway since 1) actors shouldn't have to be aware of
    absolute allocation changes and 2) it doesn't factor in changes to the
    transformation matrix of a parent.
    
    Also the propagation of absolute origin changes using this flag broke
    with commit 0eab73dc2e and now hidden actors are no longer notified
    about those changes.
    
    Additionally, this flag gets in the way of a few potential optimizations
    since it has to be propagated even if the allocation box of the child
    hasn't changed, forcing a reallocation of the child.
    
    So replace this flag with a simple new private property of ClutterActor
    absolute_origin_changed, but keep the exact same behavior for now.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1245

 clutter/clutter/clutter-actor.c | 29 +++++++++++------------------
 clutter/clutter/clutter-enums.h |  4 ----
 2 files changed, 11 insertions(+), 22 deletions(-)
---
diff --git a/clutter/clutter/clutter-actor.c b/clutter/clutter/clutter-actor.c
index e04896cfd8..571ee6a812 100644
--- a/clutter/clutter/clutter-actor.c
+++ b/clutter/clutter/clutter-actor.c
@@ -854,6 +854,7 @@ struct _ClutterActorPrivate
   guint needs_paint_volume_update   : 1;
   guint had_effects_on_last_paint_volume_update : 1;
   guint needs_compute_resource_scale : 1;
+  guint absolute_origin_changed     : 1;
 };
 
 enum
@@ -10163,7 +10164,7 @@ clutter_actor_allocate (ClutterActor           *self,
                         ClutterAllocationFlags  flags)
 {
   ClutterActorBox old_allocation, real_allocation;
-  gboolean origin_changed, child_moved, size_changed;
+  gboolean origin_changed, size_changed;
   gboolean stage_allocation_changed;
   ClutterActorPrivate *priv;
 
@@ -10206,18 +10207,19 @@ clutter_actor_allocate (ClutterActor           *self,
   real_allocation.x2 = MAX (real_allocation.x2, real_allocation.x1);
   real_allocation.y2 = MAX (real_allocation.y2, real_allocation.y1);
 
-  origin_changed = (flags & CLUTTER_ABSOLUTE_ORIGIN_CHANGED);
-
-  child_moved = (real_allocation.x1 != old_allocation.x1 ||
-                 real_allocation.y1 != old_allocation.y1);
+  origin_changed = (real_allocation.x1 != old_allocation.x1 ||
+                    real_allocation.y1 != old_allocation.y1);
 
   size_changed = (real_allocation.x2 != old_allocation.x2 ||
                   real_allocation.y2 != old_allocation.y2);
 
-  if (origin_changed || child_moved || size_changed)
-    stage_allocation_changed = TRUE;
-  else
-    stage_allocation_changed = FALSE;
+  priv->absolute_origin_changed = priv->parent
+                                ? priv->parent->priv->absolute_origin_changed
+                                : FALSE;
+
+  priv->absolute_origin_changed |= origin_changed;
+
+  stage_allocation_changed = priv->absolute_origin_changed || size_changed;
 
   /* If we get an allocation "out of the blue"
    * (we did not queue relayout), then we want to
@@ -10251,15 +10253,6 @@ clutter_actor_allocate (ClutterActor           *self,
       return;
     }
 
-  /* When ABSOLUTE_ORIGIN_CHANGED is passed in to
-   * clutter_actor_allocate(), it indicates whether the parent has its
-   * absolute origin moved; when passed in to ClutterActor::allocate()
-   * virtual method though, it indicates whether the child has its
-   * absolute origin moved.  So we set it when child_moved is TRUE
-   */
-  if (child_moved)
-    flags |= CLUTTER_ABSOLUTE_ORIGIN_CHANGED;
-
   /* store the flags here, so that they can be propagated by the
    * transition code
    */
diff --git a/clutter/clutter/clutter-enums.h b/clutter/clutter/clutter-enums.h
index 5c4e3a5dc2..aed8e90481 100644
--- a/clutter/clutter/clutter-enums.h
+++ b/clutter/clutter/clutter-enums.h
@@ -557,9 +557,6 @@ typedef enum /*< prefix=CLUTTER_OFFSCREEN_REDIRECT >*/
 /**
  * ClutterAllocationFlags:
  * @CLUTTER_ALLOCATION_NONE: No flag set
- * @CLUTTER_ABSOLUTE_ORIGIN_CHANGED: Whether the absolute origin of the
- *   actor has changed; this implies that any ancestor of the actor has
- *   been moved.
  *
  * Flags passed to the #ClutterActorClass.allocate() virtual function
  * and to the clutter_actor_allocate() function.
@@ -569,7 +566,6 @@ typedef enum /*< prefix=CLUTTER_OFFSCREEN_REDIRECT >*/
 typedef enum
 {
   CLUTTER_ALLOCATION_NONE         = 0,
-  CLUTTER_ABSOLUTE_ORIGIN_CHANGED = 1 << 1,
 } ClutterAllocationFlags;
 
 /**