WP_Customize_Nav_Menu_Item_Setting::preview(): bool

450	public function preview() {451		if ( $this->is_previewed ) {452			return false;453		}454 455		$undefined      = new stdClass();456		$is_placeholder = ( $this->post_id < 0 );457		$is_dirty       = ( $undefined !== $this->post_value( $undefined ) );458		if ( ! $is_placeholder && ! $is_dirty ) {459			return false;460		}461 462		$this->is_previewed              = true;463		$this->_original_value           = $this->value();464		$this->original_nav_menu_term_id = $this->_original_value['nav_menu_term_id'];465		$this->_previewed_blog_id        = get_current_blog_id();466 467		add_filter( 'wp_get_nav_menu_items', array( $this, 'filter_wp_get_nav_menu_items' ), 10, 3 );468 469		$sort_callback = array( __CLASS__, 'sort_wp_get_nav_menu_items' );470		if ( ! has_filter( 'wp_get_nav_menu_items', $sort_callback ) ) {471			add_filter( 'wp_get_nav_menu_items', array( __CLASS__, 'sort_wp_get_nav_menu_items' ), 1000, 3 );472		}473 474		// @todo Add get_post_metadata filters for plugins to add their data.475 476		return true;477	}