[mutter/wip/carlosg/activation-surface-listener] wayland: Add destruction listener to activation token surface

[Carlos Garnacho <carlosg src gnome org>]

commit 256122d901c0bac9a5a7c5894e375e6df1146bc3
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue Aug 23 21:56:02 2022 +0200

    wayland: Add destruction listener to activation token surface
    
    In the timespan between an activation token being created and the
    token being used by the activated application, the surface that started
    the activation request may end up destroyed/disposed.
    
    In that case, the token would be left with a stale surface pointer,
    maybe causing crashes later on. Set up a destroy notification listener
    so that we do know to unset the token surface if that situation arises,
    this will result in Mutter not considering the token activatable, thus
    maybe issuing the "Application needs attention" if the activated surface
    did not immediately get focus. In any case this is better than a
    compositor crash.
    
    A typical situation where this may happen is "Open With..." dialogs,
    since those don't live long after launching the application.
    
    Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2390

 src/wayland/meta-wayland-activation.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
---
diff --git a/src/wayland/meta-wayland-activation.c b/src/wayland/meta-wayland-activation.c
index 73faa19142..5fe2964dba 100644
--- a/src/wayland/meta-wayland-activation.c
+++ b/src/wayland/meta-wayland-activation.c
@@ -47,6 +47,7 @@ struct _MetaXdgActivationToken
   MetaWaylandSeat *seat;
   MetaWaylandActivation *activation;
   MetaStartupSequence *sequence;
+  struct wl_listener surface_listener;
   char *app_id;
   char *token;
   uint32_t serial;
@@ -94,6 +95,8 @@ token_set_surface (struct wl_client   *client,
   MetaWaylandSurface *surface = wl_resource_get_user_data (surface_resource);
 
   token->surface = surface;
+  wl_resource_add_destroy_listener (surface_resource,
+                                    &token->surface_listener);
 }
 
 static void
@@ -216,6 +219,17 @@ meta_xdg_activation_token_free (MetaXdgActivationToken *token)
   g_free (token);
 }
 
+static void
+token_handle_surface_destroy (struct wl_listener *listener,
+                              void               *data)
+{
+  MetaXdgActivationToken *token = wl_container_of (listener, token,
+                                                   surface_listener);
+
+  token->surface = NULL;
+  wl_list_remove (&token->surface_listener.link);
+}
+
 static void
 meta_wayland_activation_token_create_new_resource (MetaWaylandActivation *activation,
                                                    struct wl_client      *client,
@@ -237,6 +251,8 @@ meta_wayland_activation_token_create_new_resource (MetaWaylandActivation *activa
   wl_resource_set_user_data (token_resource, token);
   wl_list_insert (&activation->token_list,
                   wl_resource_get_link (token_resource));
+  token->surface_listener.notify = token_handle_surface_destroy;
+
 }
 
 static void