/**
  *
  * @param Tracker_Artifact $artifact
  *
  * @return Tracker_FormElement_Field[]
  */
 public function getFields(Tracker_Artifact $artifact)
 {
     $diplayed_fields = array();
     $tracker_id = $artifact->getTrackerId();
     foreach ($this->displayed_fields as $diplayed_field_name) {
         $field = $this->form_element_factory->getUsedFieldByNameForUser($tracker_id, $diplayed_field_name, $this->user_manager->getCurrentUser());
         if ($field) {
             $diplayed_fields[] = $field;
         }
     }
     return $diplayed_fields;
 }