public static function sidebar($app = null)
{
global $registry;
if (empty($app)) {
$app = $registry->getApp();
}
$menu = new Horde_Menu();
$registry->callAppMethod($app, 'menu', array('args' => array($menu)));
$sidebar = $menu->render();
$registry->callAppMethod($app, 'sidebar', array('args' => array($sidebar)));
return $sidebar;
}