/**
  * Return the second row of the controls: colour + tool selectors.
  * @return string
  */
 protected function output_toolbar()
 {
     global $OUTPUT;
     $tools = '';
     // Choose comment colour.
     $titlestr = get_string('commentcolour', 'assignfeedback_pdf');
     $tools .= html_writer::empty_tag('input', array('type' => 'image', 'id' => 'choosecolour', 'style' => 'line-height:normal;', 'name' => 'choosecolour', 'value' => '', 'title' => $titlestr));
     $colours = array('red', 'yellow', 'green', 'blue', 'white', 'clear');
     $list = '';
     foreach ($colours as $colour) {
         $colourimg = html_writer::empty_tag('img', array('src' => $OUTPUT->pix_url($colour, 'assignfeedback_pdf')));
         $list .= html_writer::tag('li', $colourimg, array('class' => "choosecolour-{$colour}", 'value' => $colour));
     }
     $list = html_writer::tag('ul', $list, array('id' => 'choosecolourmenu', 'class' => 'dropmenu'));
     $tools .= $list;
     // Choose line colour.
     $titlestr = get_string('linecolour', 'assignfeedback_pdf');
     $tools .= html_writer::empty_tag('input', array('type' => 'image', 'id' => 'chooselinecolour', 'style' => 'line-height:normal;', 'name' => 'chooselinecolour', 'value' => '', 'title' => $titlestr));
     $colours = array('red', 'yellow', 'green', 'blue', 'white', 'black');
     $list = '';
     foreach ($colours as $colour) {
         $colourimg = html_writer::empty_tag('img', array('src' => $OUTPUT->pix_url("line{$colour}", 'assignfeedback_pdf')));
         $list .= html_writer::tag('li', $colourimg, array('class' => "choosecolour-{$colour}", 'value' => $colour));
     }
     $list = html_writer::tag('ul', $list, array('id' => 'chooselinecolourmenu', 'class' => 'dropmenu'));
     $tools .= $list;
     // Stamps.
     $titlestr = get_string('stamp', 'assignfeedback_pdf');
     $tools .= html_writer::empty_tag('input', array('type' => 'image', 'id' => 'choosestamp', 'style' => 'line-height:normal;', 'name' => 'choosestamp', 'width' => '32px', 'height' => '32px', 'value' => '', 'title' => $titlestr));
     $stamps = AssignPDFLib::get_stamps();
     $list = '';
     foreach ($stamps as $stamp => $filename) {
         $stampimg = html_writer::empty_tag('img', array('src' => $OUTPUT->pix_url("stamps/{$stamp}", 'assignfeedback_pdf'), 'width' => '32', 'height' => '32'));
         $list .= html_writer::tag('li', $stampimg, array('class' => "choosestamp-{$stamp}", 'value' => $stamp));
     }
     $list = html_writer::tag('ul', $list, array('id' => 'choosestampmenu', 'class' => 'dropmenu'));
     $tools .= $list;
     // Choose annotation type.
     $drawingtools = array('commenticon', 'lineicon', 'rectangleicon', 'ovalicon', 'freehandicon', 'highlighticon', 'stampicon', 'eraseicon');
     $list = '';
     foreach ($drawingtools as $drawingtool) {
         $item = html_writer::tag('button', '', array('name' => 'choosetoolradio', 'value' => $drawingtool, 'id' => $drawingtool, 'title' => get_string($drawingtool, 'assignfeedback_pdf')));
         $list .= $item;
     }
     $list = html_writer::tag('div', $list, array('id' => 'choosetoolgroup', 'class' => 'yui-buttongroup'));
     $tools .= $list;
     return $tools;
 }