wayland/output: Set user data of xdg_output resource

mutter would randomly crash in `send_xdg_output_events()` when changing
the fractional scaling:

  wl_resource_post_event ()
  zxdg_output_v1_send_logical_size ()
  send_xdg_output_events ()
  wayland_output_update_for_output ()
  meta_wayland_compositor_update_outputs ()
  on_monitors_changed ()
  g_closure_invoke ()
  signal_emit_unlocked_R ()
  g_signal_emit_valist ()
  _signal_emit ()
  meta_monitor_manager_notify_monitors_changed ()
  meta_monitor_manager_rebuild ()

This is because the xdg-output resource got freed but wasn't removed
from the list of resources.

Fix this by setting the user data of the xdg-output resource to the
corresponding `MetaWaylandOutput` so that the xdg-output resource
destructor can remove it from the list of resources.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/538

1 files changed, 4 insertions, 4 deletions

diff --git a/src/wayland/meta-wayland-outputs.c b/src/wayland/meta-wayland-outputs.c
index 7695d86af..099e87ab9 100644
--- a/src/wayland/meta-wayland-outputs.c
+++ b/src/wayland/meta-wayland-outputs.c
@@ -624,14 +624,14 @@ meta_xdg_output_manager_get_xdg_output (struct wl_client   *client,
                                             wl_resource_get_version (resource),
                                             id);
 
-  wl_resource_set_implementation (xdg_output_resource,
-                                  &meta_xdg_output_interface,
-                                  NULL, meta_xdg_output_destructor);
-
   wayland_output = wl_resource_get_user_data (output);
   if (!wayland_output)
     return;
 
+  wl_resource_set_implementation (xdg_output_resource,
+                                  &meta_xdg_output_interface,
+                                  wayland_output, meta_xdg_output_destructor);
+
   wayland_output->xdg_output_resources =
     g_list_prepend (wayland_output->xdg_output_resources, xdg_output_resource);