Add "skip to content", "skip to navigation" links (#38006)

app/javascript/mastodon/features/ui/components/columns_area.jsx

@@ -1,5 +1,5 @@
 import PropTypes from 'prop-types';
-import { Children, cloneElement, useCallback } from 'react';
+import { Children, cloneElement, createContext, useContext, useCallback } from 'react';
 
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import ImmutablePureComponent from 'react-immutable-pure-component';
@@ -53,6 +53,13 @@ const TabsBarPortal = () => {
   return <div id='tabs-bar__portal' ref={setRef} />;
 };
 
+// Simple context to allow column children to know which column they're in
+export const ColumnIndexContext = createContext(1);
+/**
+ * @returns {number}
+ */
+export const useColumnIndexContext = () => useContext(ColumnIndexContext);
+
 export default class ColumnsArea extends ImmutablePureComponent {
   static propTypes = {
     columns: ImmutablePropTypes.list.isRequired,
@@ -140,18 +147,22 @@ export default class ColumnsArea extends ImmutablePureComponent {
 
     return (
       <div className={`columns-area ${ isModalOpen ? 'unscrollable' : '' }`} ref={this.setRef}>
-        {columns.map(column => {
+        {columns.map((column, index) => {
           const params = column.get('params', null) === null ? null : column.get('params').toJS();
           const other  = params && params.other ? params.other : {};
 
           return (
-            <Bundle key={column.get('uuid')} fetchComponent={componentMap[column.get('id')]} loading={this.renderLoading(column.get('id'))} error={this.renderError}>
-              {SpecificComponent => <SpecificComponent columnId={column.get('uuid')} params={params} multiColumn {...other} />}
-            </Bundle>
+            <ColumnIndexContext.Provider value={index} key={column.get('uuid')}>
+              <Bundle fetchComponent={componentMap[column.get('id')]} loading={this.renderLoading(column.get('id'))} error={this.renderError}>
+                {SpecificComponent => <SpecificComponent columnId={column.get('uuid')} params={params} multiColumn {...other} />}
+              </Bundle>
+            </ColumnIndexContext.Provider>
           );
         })}
 
-        {Children.map(children, child => cloneElement(child, { multiColumn: true }))}
+        <ColumnIndexContext.Provider value={columns.size}>
+          {Children.map(children, child => cloneElement(child, { multiColumn: true }))}
+        </ColumnIndexContext.Provider>
       </div>
     );
   }

app/javascript/mastodon/features/ui/components/skip_links/index.tsx

@@ -0,0 +1,84 @@
+import { useCallback, useId } from 'react';
+
+import { useIntl } from 'react-intl';
+
+import { useAppSelector } from 'mastodon/store';
+
+import classes from './skip_links.module.scss';
+
+export const getNavigationSkipLinkId = () => 'skip-link-target-nav';
+export const getColumnSkipLinkId = (index: number) =>
+  `skip-link-target-content-${index}`;
+
+export const SkipLinks: React.FC<{
+  multiColumn: boolean;
+  onFocusGettingStartedColumn: () => void;
+}> = ({ multiColumn, onFocusGettingStartedColumn }) => {
+  const intl = useIntl();
+  const columnCount = useAppSelector((state) => {
+    const settings = state.settings as Immutable.Collection<string, unknown>;
+    return (settings.get('columns') as Immutable.Map<number, unknown>).size;
+  });
+
+  const focusMultiColumnNavbar = useCallback(
+    (e: React.MouseEvent) => {
+      e.preventDefault();
+      onFocusGettingStartedColumn();
+    },
+    [onFocusGettingStartedColumn],
+  );
+
+  return (
+    <ul className={classes.list}>
+      <li className={classes.listItem}>
+        <SkipLink target={getColumnSkipLinkId(1)} hotkey='1'>
+          {intl.formatMessage({
+            id: 'skip_links.skip_to_content',
+            defaultMessage: 'Skip to main content',
+          })}
+        </SkipLink>
+      </li>
+      <li className={classes.listItem}>
+        <SkipLink
+          target={multiColumn ? `/getting-started` : getNavigationSkipLinkId()}
+          onRouterLinkClick={multiColumn ? focusMultiColumnNavbar : undefined}
+          hotkey={multiColumn ? `${columnCount}` : '2'}
+        >
+          {intl.formatMessage({
+            id: 'skip_links.skip_to_navigation',
+            defaultMessage: 'Skip to main navigation',
+          })}
+        </SkipLink>
+      </li>
+    </ul>
+  );
+};
+
+const SkipLink: React.FC<{
+  children: string;
+  target: string;
+  onRouterLinkClick?: React.MouseEventHandler;
+  hotkey: string;
+}> = ({ children, hotkey, target, onRouterLinkClick }) => {
+  const intl = useIntl();
+  const id = useId();
+  return (
+    <>
+      <a href={`#${target}`} aria-describedby={id} onClick={onRouterLinkClick}>
+        {children}
+      </a>
+      <span id={id} className={classes.hotkeyHint}>
+        {intl.formatMessage(
+          {
+            id: 'skip_links.hotkey',
+            defaultMessage: '<span>Hotkey</span> {hotkey}',
+          },
+          {
+            hotkey,
+            span: (text) => <span className='sr-only'>{text}</span>,
+          },
+        )}
+      </span>
+    </>
+  );
+};

app/javascript/mastodon/features/ui/components/skip_links/skip_links.module.scss

@@ -0,0 +1,64 @@
+.list {
+  position: fixed;
+  z-index: 100;
+  margin: 10px;
+  padding: 10px 16px;
+  border-radius: 10px;
+  font-size: 15px;
+  color: var(--color-text-primary);
+  background: var(--color-bg-primary);
+  box-shadow: var(--dropdown-shadow);
+
+  /* Hide visually when not focused */
+  &:not(:focus-within) {
+    width: 1px;
+    height: 1px;
+    margin: 0;
+    padding: 0;
+    clip-path: inset(50%);
+    overflow: hidden;
+  }
+}
+
+.listItem {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding-inline-end: 4px;
+  border-radius: 4px;
+
+  &:not(:first-child) {
+    margin-top: 2px;
+  }
+
+  &:focus-within {
+    outline: var(--outline-focus-default);
+    background: var(--color-bg-brand-softer);
+  }
+
+  :any-link {
+    display: block;
+    padding: 8px;
+    color: inherit;
+    text-decoration-color: var(--color-text-secondary);
+    text-underline-offset: 0.2em;
+
+    &:focus,
+    &:focus-visible {
+      outline: none;
+    }
+  }
+}
+
+.hotkeyHint {
+  display: inline-block;
+  box-sizing: border-box;
+  min-width: 2.5ch;
+  margin-inline-start: auto;
+  padding: 3px 5px;
+  font-family: 'Courier New', Courier, monospace;
+  text-align: center;
+  background: var(--color-bg-primary);
+  border: 1px solid var(--color-border-primary);
+  border-radius: 4px;
+}