public static function admin_bar_menu( $wp_admin_bar ) {
		$themes  = self::get_allowed_themes();
		$current = empty( self::$theme ) ? wp_get_theme() : self::$theme;
		unset( $themes[ $current->get( 'Name' ) ] );
		uksort( $themes, array( __CLASS__, 'sort_core_themes' ) );

		$title = apply_filters( 'tts_root_title', sprintf( __( 'Theme: %s', 'toolbar-theme-switcher' ), $current->display( 'Name' ) ) );

		$wp_admin_bar->add_menu( array(
			'id'    => 'toolbar_theme_switcher',
			'title' => $title,
			'href'  => admin_url( 'themes.php' ),
		) );

		$ajax_url = admin_url( 'admin-ajax.php' );

		foreach ( $themes as $theme ) {

			$href = add_query_arg( array(
				'action' => 'tts_set_theme',
				'theme'  => urlencode( $theme->get_stylesheet() ),
			), $ajax_url );

			$wp_admin_bar->add_menu( array(
				'id'     => $theme['Stylesheet'],
				'title'  => $theme->display( 'Name' ),
				'href'   => $href,
				'parent' => 'toolbar_theme_switcher',
			) );
		}
	}