make sections collapsible

amd/src/collapse.js

@@ -0,0 +1,34 @@
+// WWU Addon. Allows collapsing of topics in courses.
+// Robin Tschudi
+
+define(['jquery'], function ($) {
+
+    const collapsed_url = M.util.image_url("t/collapsed", "core");
+    const expanded_url = M.util.image_url("t/expanded", "core");
+
+    var hide = function (section) {
+        $("#section-" + section).find(".content").each(function (index, element) {
+            element.hidden = true;
+        });
+        let arrow = $("#collapseicon" + section);
+        arrow.attr("src", collapsed_url);
+        arrow.click(function () { arrow.unbind("click"); show(section); });
+    };
+
+    var show = function (section) {
+        $("#section-" + section).find(".content").each(function (index, element) {
+            element.hidden = false;
+        });
+        let arrow = $("#collapseicon" + section);
+        arrow.attr("src", expanded_url);
+        arrow.click(function () { arrow.unbind("click"); hide(section); });
+    };
+
+    var init = function (sectionindex) {
+        let arrow = $("#collapseicon" + sectionindex);
+        arrow.click(function () {arrow.unbind("click"); hide(sectionindex);});
+    };
+    return {
+        init: init,
+    };
+});

classes/output/wwu_format_trait.php

@@ -75,6 +75,11 @@ public function wwu_section_header($section, $course, $onsectionpage) {
         $leftcontent = $this->section_left_content($section, $course, $onsectionpage);
         $o .= html_writer::tag('div', $leftcontent, array('class' => 'left side'));
 
+        global $OUTPUT;
+        $arrowurl = $OUTPUT->image_url("t/expanded", "core");
+        $o .= html_writer::img($arrowurl, "collapse", array("id" => "collapseicon" . $section->section));
+        $this->page->requires->js_call_amd('theme_wwu2019/collapse', 'init', array($section->section));
+
         $sectionname = html_writer::tag('span', $this->section_title($section, $course));
         $o .= $this->output->heading($sectionname, 3, 'sectionname');