/**
  * Handle the page fields.
  *
  * @param PageFormBuilder $builder
  */
 public function handle(PageFormBuilder $builder)
 {
     $type = $builder->getType();
     $parent = $builder->getParent();
     /* @var PageInterface $entry */
     if (!$parent && ($entry = $builder->getFormEntry())) {
         $parent = $entry->getParent();
     }
     $builder->setFields(['*', 'slug' => ['config' => ['prefix' => ($parent ? url($this->dispatch(new GetRealPath($parent))) : url()) . '/']], 'theme_layout' => ['config' => ['default_value' => $type ? $type->getThemeLayout() : null]]]);
 }