1 files changed, 100 insertions, 0 deletions
diff --git a/web_src/js/features/aria.js b/web_src/js/features/aria.js
new file mode 100644
index 0000000000..162843678b
--- /dev/null
+++ b/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)));
+}