wayland/xdg-shell: Handle requests after toplevel was unmanaged

A window can be unmanaged without asking the client to do it, for
example as a side effect of a parent window being unmanaged, if the
child window was a attached dialog.

This means that the client might still make requests post updates to it
after that it was unmapped. Handle this gracefully by NULL-checking the
surface's MetaWindow pointer. We're not loosing any state due to this,
as if the client wants to map the same surface again, it needs to either
reassign it the toplevel role, or reset the xdg-toplevel, both resulting
in all state being lost anyway.

https://gitlab.gnome.org/GNOME/mutter/issues/240

src/wayland/meta-wayland-xdg-shell.c

@@ -191,6 +191,11 @@ xdg_toplevel_set_parent (struct wl_client   *client,
 {
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
   MetaWindow *transient_for = NULL;
+  MetaWindow *window;
+
+  window = surface->window;
+  if (!window)
+    return;
 
   if (parent_resource)
     {
@@ -200,7 +205,7 @@ xdg_toplevel_set_parent (struct wl_client   *client,
       transient_for = parent_surface->window;
     }
 
-  meta_window_set_transient_for (surface->window, transient_for);
+  meta_window_set_transient_for (window, transient_for);
 }
 
 static void
@@ -209,11 +214,16 @@ xdg_toplevel_set_title (struct wl_client   *client,
                         const char         *title)
 {
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
+  MetaWindow *window;
+
+  window = surface->window;
+  if (!window)
+    return;
 
   if (!g_utf8_validate (title, -1, NULL))
     title = "";
 
-  meta_window_set_title (surface->window, title);
+  meta_window_set_title (window, title);
 }
 
 static void
@@ -222,11 +232,16 @@ xdg_toplevel_set_app_id (struct wl_client   *client,
                          const char         *app_id)
 {
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
+  MetaWindow *window;
+
+  window = surface->window;
+  if (!window)
+    return;
 
   if (!g_utf8_validate (app_id, -1, NULL))
     app_id = "";
 
-  meta_window_set_wm_class (surface->window, app_id, app_id);
+  meta_window_set_wm_class (window, app_id, app_id);
 }
 
 static void
@@ -239,15 +254,20 @@ xdg_toplevel_show_window_menu (struct wl_client   *client,
 {
   MetaWaylandSeat *seat = wl_resource_get_user_data (seat_resource);
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
+  MetaWindow *window;
   int monitor_scale;
 
+  window = surface->window;
+  if (!window)
+    return;
+
   if (!meta_wayland_seat_get_grab_info (seat, surface, serial, FALSE, NULL, NULL))
     return;
 
-  monitor_scale = surface->window->monitor->scale;
+  monitor_scale = window->monitor->scale;
-  meta_window_show_menu (surface->window, META_WINDOW_MENU_WM,
+  meta_window_show_menu (window, META_WINDOW_MENU_WM,
-                         surface->window->buffer_rect.x + (x * monitor_scale),
+                         window->buffer_rect.x + (x * monitor_scale),
-                         surface->window->buffer_rect.y + (y * monitor_scale));
+                         window->buffer_rect.y + (y * monitor_scale));
 }
 
 static void
@@ -258,8 +278,13 @@ xdg_toplevel_move (struct wl_client   *client,
 {
   MetaWaylandSeat *seat = wl_resource_get_user_data (seat_resource);
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
+  MetaWindow *window;
   float x, y;
 
+  window = surface->window;
+  if (!window)
+    return;
+
   if (!meta_wayland_seat_get_grab_info (seat, surface, serial, TRUE, &x, &y))
     return;
 
@@ -298,9 +323,14 @@ xdg_toplevel_resize (struct wl_client   *client,
 {
   MetaWaylandSeat *seat = wl_resource_get_user_data (seat_resource);
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
+  MetaWindow *window;
   gfloat x, y;
   MetaGrabOp grab_op;
 
+  window = surface->window;
+  if (!window)
+    return;
+
   if (!meta_wayland_seat_get_grab_info (seat, surface, serial, TRUE, &x, &y))
     return;
 
@@ -357,7 +387,11 @@ xdg_toplevel_set_maximized (struct wl_client   *client,
                             struct wl_resource *resource)
 {
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
-  MetaWindow *window = surface->window;
+  MetaWindow *window;
+
+  window = surface->window;
+  if (!window)
+    return;
 
   meta_window_force_placement (window, TRUE);
   meta_window_maximize (window, META_MAXIMIZE_BOTH);
@@ -368,8 +402,13 @@ xdg_toplevel_unset_maximized (struct wl_client   *client,
                               struct wl_resource *resource)
 {
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
+  MetaWindow *window;
 
-  meta_window_unmaximize (surface->window, META_MAXIMIZE_BOTH);
+  window = surface->window;
+  if (!window)
+    return;
+
+  meta_window_unmaximize (window, META_MAXIMIZE_BOTH);
 }
 
 static void
@@ -378,6 +417,11 @@ xdg_toplevel_set_fullscreen (struct wl_client   *client,
                              struct wl_resource *output_resource)
 {
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
+  MetaWindow *window;
+
+  window = surface->window;
+  if (!window)
+    return;
 
   if (output_resource)
     {
@@ -385,12 +429,12 @@ xdg_toplevel_set_fullscreen (struct wl_client   *client,
 
       if (output)
         {
-          meta_window_move_to_monitor (surface->window,
+          meta_window_move_to_monitor (window,
                                        output->logical_monitor->number);
         }
     }
 
-  meta_window_make_fullscreen (surface->window);
+  meta_window_make_fullscreen (window);
 }
 
 static void
@@ -398,8 +442,13 @@ xdg_toplevel_unset_fullscreen (struct wl_client   *client,
                                struct wl_resource *resource)
 {
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
+  MetaWindow *window;
 
-  meta_window_unmake_fullscreen (surface->window);
+  window = surface->window;
+  if (!window)
+    return;
+
+  meta_window_unmake_fullscreen (window);
 }
 
 static void
@@ -407,8 +456,13 @@ xdg_toplevel_set_minimized (struct wl_client   *client,
                             struct wl_resource *resource)
 {
   MetaWaylandSurface *surface = surface_from_xdg_toplevel_resource (resource);
+  MetaWindow *window;
 
-  meta_window_minimize (surface->window);
+  window = surface->window;
+  if (!window)
+    return;
+
+  meta_window_minimize (window);
 }
 
 static const struct xdg_toplevel_interface meta_wayland_xdg_toplevel_interface = {