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.

ref: https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2299

Fixes linuxmint/cinnamon#11086.

Author: jonas2515

clutter/clutter/clutter-actor.c

@@ -1413,6 +1413,10 @@ 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);
@@ -1423,6 +1427,8 @@ 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

clutter/clutter/clutter-private.h

@@ -72,6 +72,7 @@ typedef struct _ClutterVertex4          ClutterVertex4;
 #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)
@@ -109,6 +110,8 @@ typedef enum
 
   /* Used to avoid recursion */
   CLUTTER_IN_RELAYOUT    = 1 << 7,
+
+  CLUTTER_IN_MAP_UNMAP   = 1 << 8,
 } ClutterPrivateFlags;
 
 /*