public function output_user($user) {
        $out = fullname($user, $this->viewfullnames);
        if ($this->extrafields) {
            $displayfields = array();
            foreach ($this->extrafields as $field) {
                $displayfields[] = $user->{$field};
            }
            $out .= ' (' . implode(', ', $displayfields) . ')';
        }
        return $out;
    }