[mutter] xwayland: Don't crash when the window disappears from under us

[Jasper St. Pierre <jstpierre src gnome org>]

commit 9c4908b44ac5e1925f28f24c0f62d9f4d6d0d794
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Sun May 4 15:48:41 2014 -0400

    xwayland: Don't crash when the window disappears from under us
    
    If we attach to a MetaWindow that disappears before the idle fires,
    we'll notice that we can't associate the window properly again and
    try to access data on the MetaWindow struct, which might crash.
    
    Install a weak ref that ties the lifetime of the idle to the lifetime
    of the MetaWindow.
    
    It seems every GTK+ app does this for some reason at startup. This
    is really unfortunate, since we'll have to create and destroy a new
    MetaWindow really quickly.

 src/wayland/meta-xwayland.c |   19 +++++++++++++++----
 1 files changed, 15 insertions(+), 4 deletions(-)
---
diff --git a/src/wayland/meta-xwayland.c b/src/wayland/meta-xwayland.c
index 66d3c70..1910f79 100644
--- a/src/wayland/meta-xwayland.c
+++ b/src/wayland/meta-xwayland.c
@@ -76,8 +76,18 @@ typedef struct {
   MetaXWaylandManager *manager;
   MetaWindow *window;
   guint32 surface_id;
+  guint idle_id;
 } AssociateWindowWithSurfaceOp;
 
+static void
+associate_window_with_surface_window_destroyed (gpointer  user_data,
+                                                GObject  *obj)
+{
+  AssociateWindowWithSurfaceOp *op = user_data;
+  g_source_remove (op->idle_id);
+  g_free (op);
+}
+
 static gboolean
 associate_window_with_surface_idle (gpointer user_data)
 {
@@ -87,6 +97,7 @@ associate_window_with_surface_idle (gpointer user_data)
       /* Not here? Oh well... nothing we can do */
       g_warning ("Unknown surface ID %d (from window %s)", op->surface_id, op->window->desc);
     }
+  g_object_weak_unref (G_OBJECT (op->window), associate_window_with_surface_window_destroyed, op);
   g_free (op);
 
   return G_SOURCE_REMOVE;
@@ -101,8 +112,6 @@ meta_xwayland_handle_wl_surface_id (MetaWindow *window,
 
   if (!associate_window_with_surface_id (manager, window, surface_id))
     {
-      guint id;
-
       /* No surface ID yet... it should arrive after the next
        * iteration through the loop, so queue an idle and see
        * what happens.
@@ -111,8 +120,10 @@ meta_xwayland_handle_wl_surface_id (MetaWindow *window,
       op->manager = manager;
       op->window = window;
       op->surface_id = surface_id;
-      id = g_idle_add (associate_window_with_surface_idle, op);
-      g_source_set_name_by_id (id, "[mutter] associate_window_with_surface_idle");
+      op->idle_id = g_idle_add (associate_window_with_surface_idle, op);
+      g_source_set_name_by_id (op->idle_id, "[mutter] associate_window_with_surface_idle");
+
+      g_object_weak_ref (G_OBJECT (op->window), associate_window_with_surface_window_destroyed, op);
     }
 }