MDL-69116 qtype_multichoice: accessibility improvement

- Screen-readers should not see 'clear my choice' when it is not visible
- 'clear my choice' option should only become visible when a choice is
selected

question/type/multichoice/amd/src/clearchoice.js

@@ -55,7 +55,10 @@ define(['jquery', 'core/custom_interaction_events'], function($, CustomEvents) {
      * @param {Object} clearChoiceContainer The clear choice option container.
      */
     var hideClearChoiceOption = function(clearChoiceContainer) {
+        // We are using .sr-only and aria-hidden together so while the element is hidden
+        // from both the monitor and the screen-reader, it is still tabbable.
         clearChoiceContainer.addClass('sr-only');
+        clearChoiceContainer.attr('aria-hidden', true);
         clearChoiceContainer.find(SELECTORS.LINK).attr('tabindex', -1);
     };
 
@@ -66,6 +69,7 @@ define(['jquery', 'core/custom_interaction_events'], function($, CustomEvents) {
      */
     var showClearChoiceOption = function(clearChoiceContainer) {
         clearChoiceContainer.removeClass('sr-only');
+        clearChoiceContainer.removeAttr('aria-hidden');
         clearChoiceContainer.find(SELECTORS.LINK).attr('tabindex', 0);
         clearChoiceContainer.find(SELECTORS.RADIO).prop('disabled', true);
     };
@@ -89,7 +93,7 @@ define(['jquery', 'core/custom_interaction_events'], function($, CustomEvents) {
                 data.originalEvent.preventDefault();
         });
 
-        root.on(CustomEvents.events.activate, SELECTORS.CHOICE_ELEMENT, function() {
+        root.on('change', SELECTORS.CHOICE_ELEMENT, function() {
             // If the event has been triggered by any other choice, show the clear choice option.
             showClearChoiceOption(clearChoiceContainer);
         });

question/type/multichoice/renderer.php

@@ -293,14 +293,21 @@ public function after_choices(question_attempt $qa, question_display_options $op
             'name' => $qa->get_qt_field_name('answer'),
             'id' => $clearchoiceid,
             'value' => -1,
-            'class' => 'sr-only'
+            'class' => 'sr-only',
+            'aria-hidden' => 'true'
+        ];
+        $clearchoicewrapperattrs = [
+            'id' => $clearchoicefieldname,
+            'class' => 'qtype_multichoice_clearchoice',
         ];
 
-        $cssclass = 'qtype_multichoice_clearchoice';
         // When no choice selected during rendering, then hide the clear choice option.
+        // We are using .sr-only and aria-hidden together so while the element is hidden
+        // from both the monitor and the screen-reader, it is still tabbable.
         $linktabindex = 0;
         if (!$hascheckedchoice && $response == -1) {
-            $cssclass .= ' sr-only';
+            $clearchoicewrapperattrs['class'] .= ' sr-only';
+            $clearchoicewrapperattrs['aria-hidden'] = 'true';
             $clearchoiceradioattrs['checked'] = 'checked';
             $linktabindex = -1;
         }
@@ -311,7 +318,7 @@ public function after_choices(question_attempt $qa, question_display_options $op
             'class' => 'btn btn-link ml-4 pl-1 mt-2']);
 
         // Now wrap the radio and label inside a div.
-        $result = html_writer::tag('div', $clearchoiceradio, ['id' => $clearchoicefieldname, 'class' => $cssclass]);
+        $result = html_writer::tag('div', $clearchoiceradio, $clearchoicewrapperattrs);
 
         // Load required clearchoice AMD module.
         $this->page->requires->js_call_amd('qtype_multichoice/clearchoice', 'init',