Remove customized (unmaintained) dropdown, improve aria a11y for dropdown (#19861)

* Remove customized (unmaintained) dropdown, improve aria a11y for dropdown

* fix repo permission

* use action instead of onChange

* re-order the CSS selector

* fix dropdown behavior for repo permissions, make elements inside menu item non-focusable

* use menu/menuitem instead of combobox/option. use tooltip(data-content) for aria-label, prevent from repeated attaching

* click menu item when pressing Enter

* code format

* fix repo permission

* repo setting: prevent from misleading users when error occurs

* fine tune the repo collaboration access mode dropdown (in case the access mode is undefined in the template)

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

web_src/js/features/aria.js

@@ -0,0 +1,100 @@
+import $ from 'jquery';
+
+let ariaIdCounter = 0;
+
+function generateAriaId() {
+  return `_aria_auto_id_${ariaIdCounter++}`;
+}
+
+// make the item has role=option, and add an id if there wasn't one yet.
+function prepareMenuItem($item) {
+  if (!$item.attr('id')) $item.attr('id', generateAriaId());
+  $item.attr({'role': 'menuitem', 'tabindex': '-1'});
+  $item.find('a').attr('tabindex', '-1'); // as above, the elements inside the dropdown menu item should not be focusable, the focus should always be on the dropdown primary element.
+}
+
+// when the menu items are loaded from AJAX requests, the items are created dynamically
+const defaultCreateDynamicMenu = $.fn.dropdown.settings.templates.menu;
+$.fn.dropdown.settings.templates.menu = function(response, fields, preserveHTML, className) {
+  const ret = defaultCreateDynamicMenu(response, fields, preserveHTML, className);
+  const $wrapper = $('<div>').append(ret);
+  const $items = $wrapper.find('> .item');
+  $items.each((_, item) => {
+    prepareMenuItem($(item));
+  });
+  return $wrapper.html();
+};
+
+function attachOneDropdownAria($dropdown) {
+  if ($dropdown.attr('data-aria-attached')) return;
+  $dropdown.attr('data-aria-attached', 1);
+
+  const $textSearch = $dropdown.find('input.search').eq(0);
+  const $focusable = $textSearch.length ? $textSearch : $dropdown; // see comment below
+  if (!$focusable.length) return;
+
+  // prepare menu list
+  const $menu = $dropdown.find('> .menu');
+  if (!$menu.attr('id')) $menu.attr('id', generateAriaId());
+
+  // dropdown has 2 different focusing behaviors
+  // * with search input: the input is focused, and it works perfectly with aria-activedescendant pointing another sibling element.
+  // * without search input (but the readonly text), the dropdown itself is focused. then the aria-activedescendant points to the element inside dropdown
+
+  // expected user interactions for dropdown with aria support:
+  // * user can use Tab to focus in the dropdown, then the dropdown menu (list) will be shown
+  // * user presses Tab on the focused dropdown to move focus to next sibling focusable element (but not the menu item)
+  // * user can use arrow key Up/Down to navigate between menu items
+  // * when user presses Enter:
+  //    - if the menu item is clickable (eg: <a>), then trigger the click event
+  //    - otherwise, the dropdown control (low-level code) handles the Enter event, hides the dropdown menu
+
+  // TODO: multiple selection is not supported yet.
+
+  $focusable.attr({
+    'role': 'menu',
+    'aria-haspopup': 'menu',
+    'aria-controls': $menu.attr('id'),
+    'aria-expanded': 'false',
+  });
+
+  if ($dropdown.attr('data-content') && !$dropdown.attr('aria-label')) {
+    $dropdown.attr('aria-label', $dropdown.attr('data-content'));
+  }
+
+  $menu.find('> .item').each((_, item) => {
+    prepareMenuItem($(item));
+  });
+
+  // update aria attributes according to current active/selected item
+  const refreshAria = () => {
+    const isMenuVisible = !$menu.is('.hidden') && !$menu.is('.animating.out');
+    $focusable.attr('aria-expanded', isMenuVisible ? 'true' : 'false');
+
+    let $active = $menu.find('> .item.active');
+    if (!$active.length) $active = $menu.find('> .item.selected'); // it's strange that we need this fallback at the moment
+
+    // if there is an active item, use its id. if no active item, then the empty string is set
+    $focusable.attr('aria-activedescendant', $active.attr('id'));
+  };
+
+  $dropdown.on('keydown', (e) => {
+    // here it must use keydown event before dropdown's keyup handler, otherwise there is no Enter event in our keyup handler
+    if (e.key === 'Enter') {
+      const $item = $dropdown.dropdown('get item', $dropdown.dropdown('get value'));
+      // if the selected item is clickable, then trigger the click event. in the future there could be a special CSS class for it.
+      if ($item && $item.is('a')) $item[0].click();
+    }
+  });
+
+  // use setTimeout to run the refreshAria in next tick (to make sure the Fomantic UI code has finished its work)
+  const deferredRefreshAria = () => { setTimeout(refreshAria, 0) }; // do not return any value, jQuery has return-value related behaviors.
+  $focusable.on('focus', deferredRefreshAria);
+  $focusable.on('mouseup', deferredRefreshAria);
+  $focusable.on('blur', deferredRefreshAria);
+  $dropdown.on('keyup', (e) => { if (e.key.startsWith('Arrow')) deferredRefreshAria(); });
+}
+
+export function attachDropdownAria($dropdowns) {
+  $dropdowns.each((_, e) => attachOneDropdownAria($(e)));
+}

web_src/js/features/aria.md

@@ -0,0 +1,46 @@
+**This document is used as aria/a11y reference for future developers**
+
+## ARIA Dropdown
+
+There are different solutions: 
+* combobox + listbox + option
+* menu + menuitem
+
+At the moment, `menu + menuitem` seems to work better with Fomantic UI Dropdown, so we only use it now.
+
+```html
+<div>
+  <input role="combobox" aria-haspopup="listbox" aria-expanded="false" aria-controls="the-menu-listbox" aria-activedescendant="item-id-123456">
+  <ul id="the-menu-listbox" role="listbox">
+    <li role="option" id="item-id-123456" aria-selected="true">
+      <a tabindex="-1" href="....">....</a>
+    </li>
+  </ul>
+</div>
+```
+
+
+## Fomantic UI Dropdown
+
+```html
+<!-- read-only dropdown -->
+<div class="ui dropdown"> <!-- focused here, then it's not perfect to use aria-activedescendant to point to the menu item -->
+  <input type="hidden" ...>
+  <div class="text">Default</div>
+  <div class="menu transition hidden" tabindex="-1">
+    <div class="item active selected">Default</div>
+    <div class="item">...</div>
+  </div>
+</div>
+
+<!-- search input dropdown -->
+<div class="ui dropdown">
+  <input type="hidden" ...>
+  <input class="search" autocomplete="off" tabindex="0"> <!-- focused here -->
+  <div class="text"></div>
+  <div class="menu transition visible" tabindex="-1">
+    <div class="item selected">...</div>
+    <div class="item">...</div>
+  </div>
+</div>
+```

web_src/js/features/common-global.js

@@ -4,6 +4,7 @@ import {mqBinarySearch} from '../utils.js';
 import createDropzone from './dropzone.js';
 import {initCompColorPicker} from './comp/ColorPicker.js';
 import {showGlobalErrorMessage} from '../bootstrap.js';
+import {attachDropdownAria} from './aria.js';
 
 const {appUrl, csrfToken} = window.config;
 
@@ -97,24 +98,27 @@ export function initGlobalCommon() {
   }
 
   // Semantic UI modules.
-  $('.dropdown:not(.custom)').dropdown({
+  const $uiDropdowns = $('.ui.dropdown');
+  $uiDropdowns.filter(':not(.custom)').dropdown({
     fullTextSearch: 'exact'
   });
-  $('.jump.dropdown').dropdown({
+  $uiDropdowns.filter('.jump').dropdown({
     action: 'hide',
     onShow() {
       $('.tooltip').popup('hide');
     },
     fullTextSearch: 'exact'
   });
-  $('.slide.up.dropdown').dropdown({
+  $uiDropdowns.filter('.slide.up').dropdown({
     transition: 'slide up',
     fullTextSearch: 'exact'
   });
-  $('.upward.dropdown').dropdown({
+  $uiDropdowns.filter('.upward').dropdown({
     direction: 'upward',
     fullTextSearch: 'exact'
   });
+  attachDropdownAria($uiDropdowns);
+
   $('.ui.checkbox').checkbox();
 
   // init popups

web_src/js/features/repo-settings.js

@@ -6,12 +6,37 @@ const {appSubUrl, csrfToken} = window.config;
 
 export function initRepoSettingsCollaboration() {
   // Change collaborator access mode
-  $('.access-mode.menu .item').on('click', function () {
-    const $menu = $(this).parent();
-    $.post($menu.data('url'), {
-      _csrf: csrfToken,
-      uid: $menu.data('uid'),
-      mode: $(this).data('value')
+  $('.page-content.repository .ui.dropdown.access-mode').each((_, e) => {
+    const $dropdown = $(e);
+    const $text = $dropdown.find('> .text');
+    $dropdown.dropdown({
+      action(_text, value) {
+        const lastValue = $dropdown.attr('data-last-value');
+        $.post($dropdown.attr('data-url'), {
+          _csrf: csrfToken,
+          uid: $dropdown.attr('data-uid'),
+          mode: value,
+        }).fail(() => {
+          $text.text('(error)'); // prevent from misleading users when error occurs
+          $dropdown.attr('data-last-value', lastValue);
+        });
+        $dropdown.attr('data-last-value', value);
+        $dropdown.dropdown('hide');
+      },
+      onChange(_value, text, _$choice) {
+        $text.text(text); // update the text when using keyboard navigating
+      },
+      onHide() {
+        // set to the really selected value, defer to next tick to make sure `action` has finished its work because the calling order might be onHide -> action
+        setTimeout(() => {
+          const $item = $dropdown.dropdown('get item', $dropdown.attr('data-last-value'));
+          if ($item) {
+            $dropdown.dropdown('set selected', $dropdown.attr('data-last-value'));
+          } else {
+            $text.text('(N/A)'); // prevent from misleading users when the access mode is undefined
+          }
+        }, 0);
+      }
     });
   });
 }