protected function get_sort_icon($reverse) {
        global $OUTPUT;
        if ($reverse) {
            return $OUTPUT->pix_icon('t/sort_desc', get_string('desc'), '', array('class' => 'iconsort'));
        } else {
            return $OUTPUT->pix_icon('t/sort_asc', get_string('asc'), '', array('class' => 'iconsort'));
        }
    }