private function isUsed(Tracker_Artifact_ChangesetValue $changeset_value)
 {
     $ugroup_ids = $changeset_value->getPerms();
     if (count($ugroup_ids) === 1 && (int) $ugroup_ids[0] === ProjectUGroup::ANONYMOUS) {
         return false;
     }
     return count($ugroup_ids) > 0;
 }
 /**
  * Fetch the html code to display the field value in tooltip
  * 
  * @param Tracker_Artifact $artifact
  * @param Tracker_Artifact_ChangesetValue_PermissionsOnArtifact $value The changeset value for this field
  * @return string
  */
 protected function fetchTooltipValue(Tracker_Artifact $artifact, Tracker_Artifact_ChangesetValue $value = null)
 {
     $html = '';
     if ($value && $artifact->useArtifactPermissions()) {
         $ugroup_dao = $this->getUGroupDao();
         $perms = $value->getPerms();
         $perms_name = array();
         foreach ($perms as $perm) {
             $row = $ugroup_dao->searchByUGroupId($perm)->getRow();
             $perms_name[] = util_translate_name_ugroup($row['name']);
         }
         $html .= implode(",", $perms_name);
     }
     return $html;
 }