xdg-shell: Take a xdg_surface as the parent surface

There is no other valid surface that we should be using here.

Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

clients/window.c

@@ -253,7 +253,7 @@ struct window {
 	struct xdg_popup *xdg_popup;
 
 	struct window *parent;
-	struct wl_surface *last_parent_surface;
+	struct window *last_parent;
 
 	struct ivi_surface *ivi_surface;
 
@@ -4031,21 +4031,21 @@ static const struct xdg_surface_listener xdg_surface_listener = {
 static void
 window_sync_parent(struct window *window)
 {
-	struct wl_surface *parent_surface;
+	struct xdg_surface *parent_surface;
 
 	if (!window->xdg_surface)
 		return;
 
+	if (window->parent == window->last_parent)
+		return;
+
 	if (window->parent)
-		parent_surface = window->parent->main_surface->surface;
+		parent_surface = window->parent->xdg_surface;
 	else
 		parent_surface = NULL;
 
-	if (parent_surface == window->last_parent_surface)
-		return;
-
 	xdg_surface_set_parent(window->xdg_surface, parent_surface);
-	window->last_parent_surface = parent_surface;
+	window->last_parent = window->parent;
 }
 
 static void

desktop-shell/shell.c

@@ -3717,14 +3717,14 @@ xdg_surface_set_parent(struct wl_client *client,
 		       struct wl_resource *parent_resource)
 {
 	struct shell_surface *shsurf = wl_resource_get_user_data(resource);
-	struct weston_surface *parent;
+	struct shell_surface *parent;
 
-	if (parent_resource)
+	if (parent_resource) {
 		parent = wl_resource_get_user_data(parent_resource);
-	else
+		shell_surface_set_parent(shsurf, parent->surface);
-		parent = NULL;
+	} else {
-
+		shell_surface_set_parent(shsurf, NULL);
-	shell_surface_set_parent(shsurf, parent);
+	}
 }
 
 static void

protocol/xdg-shell.xml

@@ -152,7 +152,7 @@
 	unmapped if the parent is unmapped too. They should not appear
 	on task bars and alt+tab.
       </description>
-      <arg name="parent" type="object" interface="wl_surface" allow-null="true"/>
+      <arg name="parent" type="object" interface="xdg_surface" allow-null="true"/>
     </request>
 
     <request name="set_title">