From fb9bbdec67d2c48fbce2c797346526ad981f3b0c Mon Sep 17 00:00:00 2001
From: Zander Brown <zbrown@gnome.org>
Date: Wed, 9 Aug 2023 04:48:19 +0100
Subject: [PATCH] shell/window-preview-layout: Ensure we don't touch dead
 objects

We were assuming the lifetime of the MetaWindow worked out in our
favour, and further hoping the GC didn't work against us

Avoid this by taking an explict weak ref, and checking the object is
live before removing handlers

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/6570
---
 src/shell-window-preview-layout.c | 68 ++++++++++++++++++-------------
 1 file changed, 39 insertions(+), 29 deletions(-)

diff --git a/src/shell-window-preview-layout.c b/src/shell-window-preview-layout.c
index 28676d7ce..f4bffcb5f 100644
--- a/src/shell-window-preview-layout.c
+++ b/src/shell-window-preview-layout.c
@@ -33,6 +33,7 @@ typedef struct _WindowInfo
 {
   MetaWindow *window;
   ClutterActor *window_actor;
+  ClutterActor *window_clone;
 
   gulong size_changed_id;
   gulong position_changed_id;
@@ -40,6 +41,30 @@ typedef struct _WindowInfo
   gulong destroy_id;
 } WindowInfo;
 
+static void
+window_info_free (WindowInfo *info)
+{
+  if (G_LIKELY (info->window))
+    {
+      g_clear_signal_handler (&info->size_changed_id, info->window);
+      g_clear_signal_handler (&info->position_changed_id, info->window);
+    }
+
+  if (G_LIKELY (info->window_actor))
+    g_clear_signal_handler (&info->window_actor_destroy_id, info->window_actor);
+
+  if (G_LIKELY (info->window_clone))
+    g_clear_signal_handler (&info->destroy_id, info->window_clone);
+
+  g_clear_weak_pointer (&info->window);
+  g_clear_weak_pointer (&info->window_actor);
+  g_clear_weak_pointer (&info->window_clone);
+
+  g_free (info);
+}
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC (WindowInfo, window_info_free);
+
 static void
 shell_window_preview_layout_get_property (GObject      *object,
                                           unsigned int  property_id,
@@ -271,23 +296,13 @@ shell_window_preview_layout_dispose (GObject *gobject)
   ShellWindowPreviewLayout *self = SHELL_WINDOW_PREVIEW_LAYOUT (gobject);
   ShellWindowPreviewLayoutPrivate *priv;
   GHashTableIter iter;
-  gpointer key, value;
+  gpointer actor;
 
   priv = shell_window_preview_layout_get_instance_private (self);
 
   g_hash_table_iter_init (&iter, priv->windows);
-  while (g_hash_table_iter_next (&iter, &key, &value))
-    {
-      ClutterActor *actor = key;
-      WindowInfo *info = value;
-
-      g_clear_signal_handler (&info->size_changed_id, info->window);
-      g_clear_signal_handler (&info->position_changed_id, info->window);
-      g_clear_signal_handler (&info->window_actor_destroy_id, info->window_actor);
-      g_clear_signal_handler (&info->destroy_id, actor);
-
-      clutter_actor_remove_child (priv->container, actor);
-    }
+  while (g_hash_table_iter_next (&iter, &actor, NULL))
+    clutter_actor_remove_child (priv->container, actor);
 
   g_hash_table_remove_all (priv->windows);
 
@@ -314,8 +329,9 @@ shell_window_preview_layout_init (ShellWindowPreviewLayout *self)
 
   priv = shell_window_preview_layout_get_instance_private (self);
 
-  priv->windows = g_hash_table_new_full (NULL, NULL, NULL,
-                                         (GDestroyNotify) g_free);
+  priv->windows = g_hash_table_new_full (NULL, NULL,
+                                         g_object_unref,
+                                         (GDestroyNotify) window_info_free);
 }
 
 static void
@@ -387,8 +403,9 @@ shell_window_preview_layout_add_window (ShellWindowPreviewLayout *self,
 
   window_info = g_new0 (WindowInfo, 1);
 
-  window_info->window = window;
-  window_info->window_actor = window_actor;
+  g_set_weak_pointer (&window_info->window, window);
+  g_set_weak_pointer (&window_info->window_actor, window_actor);
+  g_set_weak_pointer (&window_info->window_clone, actor);
   window_info->size_changed_id =
     g_signal_connect (window, "size-changed",
                       G_CALLBACK (on_window_size_position_changed), self);
@@ -402,7 +419,7 @@ shell_window_preview_layout_add_window (ShellWindowPreviewLayout *self,
     g_signal_connect (actor, "destroy",
                       G_CALLBACK (on_actor_destroyed), self);
 
-  g_hash_table_insert (priv->windows, actor, window_info);
+  g_hash_table_insert (priv->windows, g_object_ref (actor), window_info);
 
   clutter_actor_add_child (priv->container, actor);
 
@@ -425,8 +442,7 @@ shell_window_preview_layout_remove_window (ShellWindowPreviewLayout *self,
                                            MetaWindow               *window)
 {
   ShellWindowPreviewLayoutPrivate *priv;
-  ClutterActor *actor;
-  WindowInfo *window_info = NULL;
+  g_autoptr (ClutterActor) actor = NULL;
   GHashTableIter iter;
   gpointer key, value;
 
@@ -442,22 +458,16 @@ shell_window_preview_layout_remove_window (ShellWindowPreviewLayout *self,
 
       if (info->window == window)
         {
+          g_hash_table_iter_steal (&iter);
           actor = CLUTTER_ACTOR (key);
-          window_info = info;
+          window_info_free (info);
           break;
         }
     }
 
-  if (window_info == NULL)
+  if (actor == NULL)
     return;
 
-  g_clear_signal_handler (&window_info->size_changed_id, window);
-  g_clear_signal_handler (&window_info->position_changed_id, window);
-  g_clear_signal_handler (&window_info->window_actor_destroy_id, window_info->window_actor);
-  g_clear_signal_handler (&window_info->destroy_id, actor);
-
-  g_hash_table_remove (priv->windows, actor);
-
   clutter_actor_remove_child (priv->container, actor);
 
   on_layout_changed (self);