[mutter] clutter: Bail out and warn on reentry into mapping/unmapping cycle

[Marge Bot <marge-bot src gnome org>]

commit c64803770e742f3d1ddd0f51c4a520b6059ad7d0
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Wed Feb 16 22:34:12 2022 +0100

    clutter: Bail out and warn on reentry into mapping/unmapping cycle
    
    There's a bunch of crashes right now where the assertions in
    clutter_actor_set_mapped() after calling the map/unmap() vfuncs are
    failing. The only way this can happen is by re-entering
    clutter_actor_set_mapped() during the map/unmap recursion.
    
    The reason for those crashes is that the shell hides/shows some actors
    in response to crossing events and key-focus changes. These in turn get
    triggered by the newly introduced ungrabbing of ClutterGrabs when an
    actor gets unmapped, which triggers GRAB_NOTIFY crossing events and
    key-focus changes.
    
    Since these situations are hardly avoidable (it's a valid use-case to
    hide/show something in response to a crossing/key-focus event), catch
    the set_mapped() call early while we reenter the mapping machinery and
    log a warning instead of crashing.
    
    Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3165
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2299>

 clutter/clutter/clutter-actor.c   | 6 ++++++
 clutter/clutter/clutter-private.h | 3 +++
 2 files changed, 9 insertions(+)
---
diff --git a/clutter/clutter/clutter-actor.c b/clutter/clutter/clutter-actor.c
index 23ef03dc1f..4279d3476c 100644
--- a/clutter/clutter/clutter-actor.c
+++ b/clutter/clutter/clutter-actor.c
@@ -1264,6 +1264,10 @@ clutter_actor_set_mapped (ClutterActor *self,
   if (CLUTTER_ACTOR_IS_MAPPED (self) == mapped)
     return;
 
+  g_return_if_fail (!CLUTTER_ACTOR_IN_MAP_UNMAP (self));
+
+  CLUTTER_SET_PRIVATE_FLAGS (self, CLUTTER_IN_MAP_UNMAP);
+
   if (mapped)
     {
       CLUTTER_ACTOR_GET_CLASS (self)->map (self);
@@ -1274,6 +1278,8 @@ clutter_actor_set_mapped (ClutterActor *self,
       CLUTTER_ACTOR_GET_CLASS (self)->unmap (self);
       g_assert (!CLUTTER_ACTOR_IS_MAPPED (self));
     }
+
+  CLUTTER_UNSET_PRIVATE_FLAGS (self, CLUTTER_IN_MAP_UNMAP);
 }
 
 /* this function updates the mapped and realized states according to
diff --git a/clutter/clutter/clutter-private.h b/clutter/clutter/clutter-private.h
index 377b318798..117902a35f 100644
--- a/clutter/clutter/clutter-private.h
+++ b/clutter/clutter/clutter-private.h
@@ -69,6 +69,7 @@ typedef struct _ClutterMainContext      ClutterMainContext;
 #define CLUTTER_ACTOR_IN_PREF_WIDTH(a)          ((CLUTTER_PRIVATE_FLAGS (a) & CLUTTER_IN_PREF_WIDTH) != 
FALSE)
 #define CLUTTER_ACTOR_IN_PREF_HEIGHT(a)         ((CLUTTER_PRIVATE_FLAGS (a) & CLUTTER_IN_PREF_HEIGHT) != 
FALSE)
 #define CLUTTER_ACTOR_IN_PREF_SIZE(a)           ((CLUTTER_PRIVATE_FLAGS (a) & 
(CLUTTER_IN_PREF_HEIGHT|CLUTTER_IN_PREF_WIDTH)) != FALSE)
+#define CLUTTER_ACTOR_IN_MAP_UNMAP(a)           ((CLUTTER_PRIVATE_FLAGS (a) & CLUTTER_IN_MAP_UNMAP) != FALSE)
 
 #define CLUTTER_PARAM_READABLE  (G_PARAM_READABLE | G_PARAM_STATIC_STRINGS)
 #define CLUTTER_PARAM_WRITABLE  (G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS)
@@ -105,6 +106,8 @@ typedef enum
 
   /* Used to avoid recursion */
   CLUTTER_IN_RELAYOUT    = 1 << 7,
+
+  CLUTTER_IN_MAP_UNMAP   = 1 << 8,
 } ClutterPrivateFlags;
 
 /*