public function buildFilterParamsFor(BuildWidgetEvent $event)
{
if ($event->getEnvironment()->getDataDefinition()->getName() !== 'tl_metamodel_searchable_pages' || $event->getProperty()->getName() !== 'filterparams') {
return;
}
$model = $event->getModel();
$objFilterSettings = $this->getServiceContainer()->getFilterFactory()->createCollection($model->getProperty('filter'));
$extra = $event->getProperty()->getExtra();
$extra['subfields'] = $objFilterSettings->getParameterDCA();
$event->getProperty()->setExtra($extra);
}