From db297e7fdb08e80583c39bd6c59ddf05805f67ec Mon Sep 17 00:00:00 2001
From: "Owen W. Taylor" <otaylor@fishsoup.net>
Date: Wed, 7 Oct 2015 22:56:11 -0400
Subject: [PATCH] Don't crash on accesses to stale window-backed apps

The JS code could still be holding on to a reference to a window-backed app
after all windows have vanished. (For example, the dash queues an idle to
refetch apps and display them.) Avoid dying with an error message if we
attempt to activate or otherwise manipulate such a window.

https://bugzilla.gnome.org/show_bug.cgi?id=674799
---
 src/shell-app.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/src/shell-app.c b/src/shell-app.c
index 4f1fe10f7..afc45cb65 100644
--- a/src/shell-app.c
+++ b/src/shell-app.c
@@ -156,16 +156,20 @@ static MetaWindow *
 window_backed_app_get_window (ShellApp     *app)
 {
   g_assert (app->info == NULL);
-  g_assert (app->running_state);
-  g_assert (app->running_state->windows);
-  return app->running_state->windows->data;
+  if (app->running_state)
+    {
+      g_assert (app->running_state->windows);
+      return app->running_state->windows->data;
+    }
+  else
+    return NULL;
 }
 
 static ClutterActor *
 window_backed_app_get_icon (ShellApp *app,
                             int       size)
 {
-  MetaWindow *window;
+  MetaWindow *window = NULL;
   ClutterActor *actor;
   gint scale;
   ShellGlobal *global;
@@ -181,14 +185,16 @@ window_backed_app_get_icon (ShellApp *app,
    * window-backend apps, it's possible we get a request for the icon.
    * Avoid asserting here and just return an empty image.
    */
-  if (app->running_state == NULL)
+  if (app->running_state != NULL)
+    window = window_backed_app_get_window (app);
+
+  if (window == NULL)
     {
       actor = clutter_texture_new ();
       g_object_set (actor, "opacity", 0, "width", (float) size, "height", (float) size, NULL);
       return actor;
     }
 
-  window = window_backed_app_get_window (app);
   actor = st_texture_cache_bind_cairo_surface_property (st_texture_cache_get_default (),
                                                         G_OBJECT (window),
                                                         "icon");
@@ -232,9 +238,10 @@ shell_app_get_name (ShellApp *app)
   else
     {
       MetaWindow *window = window_backed_app_get_window (app);
-      const char *name;
+      const char *name = NULL;
 
-      name = meta_window_get_wm_class (window);
+      if (window)
+        name = meta_window_get_wm_class (window);
       if (!name)
         name = C_("program", "Unknown");
       return name;
@@ -1154,7 +1161,13 @@ shell_app_launch (ShellApp     *app,
   if (app->info == NULL)
     {
       MetaWindow *window = window_backed_app_get_window (app);
-      meta_window_activate (window, timestamp);
+      /* We don't use an error return if there no longer any windows, because the
+       * user attempting to activate a stale window backed app isn't something
+       * we would expect the caller to meaningfully handle or display an error
+       * message to the user.
+       */
+      if (window)
+        meta_window_activate (window, timestamp);
       return TRUE;
     }