[mutter/gnome-3-38] clutter/actor: Handle getting (un-)mapped during painting differently

[verdre <jonasd src gnome org>]

commit 078ef8acd08d0c33d7fd428a062fe3f5f8042e9f
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Wed Jul 8 12:38:57 2020 +0000

    clutter/actor: Handle getting (un-)mapped during painting differently
    
    We currently support only one case where an actor can get mapped or
    unmapped during painting, that is using
    _clutter_actor_enable_paint_unmapped() (although we could arguably do a
    better job explicitely forbidding it in other cases). This function is
    called when painting ClutterClone or MetaWindowActors during
    screensharing. It temporarily (fake) realizes and maps the actor and all
    its children so it can get painted.
    
    Now a problem will appear when we'll start coupling layout and the
    mapped state of actors more closely with the next commit: Since
    enable_paint_unmapped() is meant to be enabled and disabled during every
    clone paint, we also notify the "mapped" property twice on every clone
    paint. That means with the next commit we would queue a relayout for the
    source actor on every clone paint.
    
    To avoid this unnecessary work, check whether we're being painted while
    unmapped using the new unmapped_paint_branch_counter. Then avoid queuing
    relayouts or invalidating paint volumes in that case.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1366
    
    
    (cherry picked from commit 9b502150088de067ce6625f262cb7fd402074997)

 clutter/clutter/clutter-actor.c | 38 ++++++++++++++++++++++----------------
 1 file changed, 22 insertions(+), 16 deletions(-)
---
diff --git a/clutter/clutter/clutter-actor.c b/clutter/clutter/clutter-actor.c
index d06138b576..db3bcc06af 100644
--- a/clutter/clutter/clutter-actor.c
+++ b/clutter/clutter/clutter-actor.c
@@ -1609,18 +1609,21 @@ clutter_actor_real_map (ClutterActor *self)
 
   CLUTTER_ACTOR_SET_FLAGS (self, CLUTTER_ACTOR_MAPPED);
 
-  self->priv->needs_paint_volume_update = TRUE;
-
-  /* We skip unmapped actors when updating the stage-views list, so if
-   * an actors list got invalidated while it was unmapped make sure to
-   * set priv->needs_update_stage_views to TRUE for all actors up the
-   * hierarchy now.
-   */
-  if (self->priv->needs_update_stage_views)
+  if (self->priv->unmapped_paint_branch_counter == 0)
     {
-      /* Avoid the early return in queue_update_stage_views() */
-      self->priv->needs_update_stage_views = FALSE;
-      queue_update_stage_views (self);
+      self->priv->needs_paint_volume_update = TRUE;
+
+      /* We skip unmapped actors when updating the stage-views list, so if
+       * an actors list got invalidated while it was unmapped make sure to
+       * set priv->needs_update_stage_views to TRUE for all actors up the
+       * hierarchy now.
+       */
+      if (self->priv->needs_update_stage_views)
+        {
+          /* Avoid the early return in queue_update_stage_views() */
+          self->priv->needs_update_stage_views = FALSE;
+          queue_update_stage_views (self);
+        }
     }
 
   /* notify on parent mapped before potentially mapping
@@ -1721,11 +1724,14 @@ clutter_actor_real_unmap (ClutterActor *self)
 
   CLUTTER_ACTOR_UNSET_FLAGS (self, CLUTTER_ACTOR_MAPPED);
 
-  /* clear the contents of the last paint volume, so that hiding + moving +
-   * showing will not result in the wrong area being repainted
-   */
-  _clutter_paint_volume_init_static (&priv->last_paint_volume, NULL);
-  priv->last_paint_volume_valid = TRUE;
+  if (self->priv->unmapped_paint_branch_counter == 0)
+    {
+      /* clear the contents of the last paint volume, so that hiding + moving +
+       * showing will not result in the wrong area being repainted
+       */
+     _clutter_paint_volume_init_static (&priv->last_paint_volume, NULL);
+      priv->last_paint_volume_valid = TRUE;
+    }
 
   /* notify on parent mapped after potentially unmapping
    * children, so apps see a bottom-up notification.