tinywl: use xdg-shell v3

tinywl/tinywl.c

@@ -860,14 +860,14 @@ int main(int argc, char *argv[]) {
 	server.scene = wlr_scene_create();
 	wlr_scene_attach_output_layout(server.scene, server.output_layout);
 
-	/* Set up xdg-shell version 2. The xdg-shell is a Wayland protocol which is
+	/* Set up xdg-shell version 3. The xdg-shell is a Wayland protocol which is
 	 * used for application windows. For more detail on shells, refer to my
 	 * article:
 	 *
 	 * https://drewdevault.com/2018/07/29/Wayland-shells.html
 	 */
 	wl_list_init(&server.views);
-	server.xdg_shell = wlr_xdg_shell_create(server.wl_display, 2);
+	server.xdg_shell = wlr_xdg_shell_create(server.wl_display, 3);
 	server.new_xdg_surface.notify = server_new_xdg_surface;
 	wl_signal_add(&server.xdg_shell->events.new_surface,
 			&server.new_xdg_surface);