public function renderBlock(FormView $view, $resource, $blockName, array $variables = array())
{
$cacheKey = $view->vars[self::CACHE_KEY_VAR];
$context = $this->environment->mergeGlobals($variables);
ob_start();
// By contract,This method can only be called after getting the resource
// (which is passed to the method). Getting a resource for the first time
// (with an empty cache) is guaranteed to invoke loadResourcesFromTheme(),
// where the property $template is initialized.
// We do not call renderBlock here to avoid too many nested level calls
// (XDebug limits the level to 100 by default)
$this->template->displayBlock($blockName, $context, $this->resources[$cacheKey]);
return ob_get_clean();
}