/**
  * Return random question form.
  * @param \moodle_url $thispageurl the canonical URL of this page.
  * @param \question_edit_contexts $contexts the relevant question bank contexts.
  * @param array $pagevars the variables from {@link \question_edit_setup()}.
  * @return string HTML to output.
  */
 protected function random_question_form(\moodle_url $thispageurl, \question_edit_contexts $contexts, array $pagevars)
 {
     if (!$contexts->have_cap('moodle/question:useall')) {
         return '';
     }
     $randomform = new \quiz_add_random_form(new \moodle_url('/mod/quiz/addrandom.php'), array('contexts' => $contexts, 'cat' => $pagevars['cat']));
     $randomform->set_data(array('category' => $pagevars['cat'], 'returnurl' => $thispageurl->out_as_local_url(true), 'randomnumber' => 1, 'cmid' => $thispageurl->param('cmid')));
     return html_writer::div($randomform->render(), 'randomquestionformforpopup');
 }