protected function definition_draggable_items($mform, $itemrepeatsatstart) {
        $mform->addElement('header', 'draggableitemheader',
                                get_string('draggableitems', 'qtype_ddimageortext'));
        $mform->addElement('advcheckbox', 'shuffleanswers', ' ',
                                get_string('shuffleimages', 'qtype_'.$this->qtype()));
        $mform->setDefault('shuffleanswers', 0);
        $this->repeat_elements($this->draggable_item($mform), $itemrepeatsatstart,
                $this->draggable_items_repeated_options(),
                'noitems', 'additems', self::ADD_NUM_ITEMS,
                get_string('addmoreimages', 'qtype_ddimageortext'), true);
    }