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

Makefile

@@ -703,7 +703,6 @@ fomantic:
 	cd $(FOMANTIC_WORK_DIR) && npm install --no-save
 	cp -f $(FOMANTIC_WORK_DIR)/theme.config.less $(FOMANTIC_WORK_DIR)/node_modules/fomantic-ui/src/theme.config
 	cp -rf $(FOMANTIC_WORK_DIR)/_site $(FOMANTIC_WORK_DIR)/node_modules/fomantic-ui/src/
-	cp -f web_src/js/vendor/dropdown.js $(FOMANTIC_WORK_DIR)/node_modules/fomantic-ui/src/definitions/modules
 	cd $(FOMANTIC_WORK_DIR) && npx gulp -f node_modules/fomantic-ui/gulpfile.js build
 	rm -f $(FOMANTIC_WORK_DIR)/build/*.min.*
 

templates/repo/settings/collaboration.tmpl

@@ -19,13 +19,13 @@
 					</div>
 					<div class="ui eight wide column">
 						{{svg "octicon-shield-lock"}}
-						<div class="ui inline dropdown">
+						<div class="ui inline dropdown access-mode" data-url="{{$.Link}}/access_mode" data-uid="{{.ID}}" data-last-value="{{printf "%d" .Collaboration.Mode}}">
 							<div class="text">{{if eq .Collaboration.Mode 1}}{{$.i18n.Tr "repo.settings.collaboration.read"}}{{else if eq .Collaboration.Mode 2}}{{$.i18n.Tr "repo.settings.collaboration.write"}}{{else if eq .Collaboration.Mode 3}}{{$.i18n.Tr "repo.settings.collaboration.admin"}}{{else}}{{$.i18n.Tr "repo.settings.collaboration.undefined"}}{{end}}</div>
 							{{svg "octicon-triangle-down" 14 "dropdown icon"}}
-							<div class="access-mode menu" data-url="{{$.Link}}/access_mode" data-uid="{{.ID}}">
-							<div class="item" data-text="{{$.i18n.Tr "repo.settings.collaboration.admin"}}" data-value="3">{{$.i18n.Tr "repo.settings.collaboration.admin"}}</div>
-							<div class="item" data-text="{{$.i18n.Tr "repo.settings.collaboration.write"}}" data-value="2">{{$.i18n.Tr "repo.settings.collaboration.write"}}</div>
-							<div class="item" data-text="{{$.i18n.Tr "repo.settings.collaboration.read"}}" data-value="1">{{$.i18n.Tr "repo.settings.collaboration.read"}}</div>
+							<div class="menu">
+								<div class="item" data-text="{{$.i18n.Tr "repo.settings.collaboration.admin"}}" data-value="3">{{$.i18n.Tr "repo.settings.collaboration.admin"}}</div>
+								<div class="item" data-text="{{$.i18n.Tr "repo.settings.collaboration.write"}}" data-value="2">{{$.i18n.Tr "repo.settings.collaboration.write"}}</div>
+								<div class="item" data-text="{{$.i18n.Tr "repo.settings.collaboration.read"}}" data-value="1">{{$.i18n.Tr "repo.settings.collaboration.read"}}</div>
 							</div>
 						</div>
 					</div>

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>
+```