Add Keyboard Shortcuts Legend (#5823)

* Add Keyboard Shortcuts Legend

Adds a "Keyboard Shortcuts" legend (displayed in the rightmost column)
which is toggled via a new "?" hotkey. When subsequently pressed from
the Keyboard Shortcuts legend, "?" will navigate back to the previous
location.

* Add hidden table headings.

Makes the headings available for accessibility but hides them visually.

4 files changed, 105 insertions, 0 deletions

diff --git a/app/javascript/mastodon/features/keyboard_shortcuts/index.js b/app/javascript/mastodon/features/keyboard_shortcuts/index.js
new file mode 100644
index 000000000..00771b79c
--- /dev/null
+++ b/app/javascript/mastodon/features/keyboard_shortcuts/index.js
@@ -0,0 +1,68 @@
+import React from 'react';
+import Column from '../ui/components/column';
+import { defineMessages, injectIntl } from 'react-intl';
+import PropTypes from 'prop-types';
+import ImmutablePureComponent from 'react-immutable-pure-component';
+
+const messages = defineMessages({
+  heading: { id: 'keyboard_shortcuts.heading', defaultMessage: 'Keyboard Shortcuts' },
+  hotkey: { id: 'keyboard_shortcuts.hotkey', defaultMessage: 'Hotkey' },
+  description: { id: 'keyboard_shortcuts.description', defaultMessage: 'Description' },
+  reply: { id: 'keyboard_shortcuts.reply', defaultMessage: 'to reply' },
+  mention: { id: 'keyboard_shortcuts.mention', defaultMessage: 'to mention author' },
+  favourite: { id: 'keyboard_shortcuts.favourite', defaultMessage: 'to favourite' },
+  boost: { id: 'keyboard_shortcuts.boost', defaultMessage: 'to boost' },
+  enter: { id: 'keyboard_shortcuts.enter', defaultMessage: 'to open status' },
+  profile: { id: 'keyboard_shortcuts.profile', defaultMessage: 'to open author\'s profile' },
+  up: { id: 'keyboard_shortcuts.up', defaultMessage: 'to move up in the list' },
+  down: { id: 'keyboard_shortcuts.down', defaultMessage: 'to move down in the list' },
+  column: { id: 'keyboard_shortcuts.column', defaultMessage: 'to focus a status in one of the columns' },
+  compose: { id: 'keyboard_shortcuts.compose', defaultMessage: 'to focus the compose textarea' },
+  toot: { id: 'keyboard_shortcuts.toot', defaultMessage: 'to start a brand new toot' },
+  back: { id: 'keyboard_shortcuts.back', defaultMessage: 'to navigate back' },
+  search: { id: 'keyboard_shortcuts.search', defaultMessage: 'to focus search' },
+  unfocus: { id: 'keyboard_shortcuts.unfocus', defaultMessage: 'to un-focus compose textarea/search' },
+  legend: { id: 'keyboard_shortcuts.legend', defaultMessage: 'to display this legend' },
+});
+
+@injectIntl
+export default class KeyboardShortcuts extends ImmutablePureComponent {
+
+  static propTypes = {
+    intl: PropTypes.object.isRequired,
+    multiColumn: PropTypes.bool,
+  };
+
+  render () {
+    const { intl } = this.props;
+
+    return (
+      <Column icon='question' heading={intl.formatMessage(messages.heading)} hideHeadingOnMobile>
+        <div className='keyboard-shortcuts scrollable optionally-scrollable'>
+          <table>
+            <thead>
+              <tr><th>{intl.formatMessage(messages.hotkey)}</th><th>{intl.formatMessage(messages.description)}</th></tr>
+            </thead>
+            <tbody>
+              <tr><td><code>r</code></td><td>{intl.formatMessage(messages.reply)}</td></tr>
+              <tr><td><code>m</code></td><td>{intl.formatMessage(messages.mention)}</td></tr>
+              <tr><td><code>f</code></td><td>{intl.formatMessage(messages.favourite)}</td></tr>
+              <tr><td><code>b</code></td><td>{intl.formatMessage(messages.boost)}</td></tr>
+              <tr><td><code>enter</code></td><td>{intl.formatMessage(messages.enter)}</td></tr>
+              <tr><td><code>up</code></td><td>{intl.formatMessage(messages.up)}</td></tr>
+              <tr><td><code>down</code></td><td>{intl.formatMessage(messages.down)}</td></tr>
+              <tr><td><code>1</code>-<code>9</code></td><td>{intl.formatMessage(messages.column)}</td></tr>
+              <tr><td><code>n</code></td><td>{intl.formatMessage(messages.compose)}</td></tr>
+              <tr><td><code>alt</code>+<code>n</code></td><td>{intl.formatMessage(messages.toot)}</td></tr>
+              <tr><td><code>backspace</code></td><td>{intl.formatMessage(messages.back)}</td></tr>
+              <tr><td><code>s</code></td><td>{intl.formatMessage(messages.search)}</td></tr>
+              <tr><td><code>esc</code></td><td>{intl.formatMessage(messages.unfocus)}</td></tr>
+              <tr><td><code>?</code></td><td>{intl.formatMessage(messages.legend)}</td></tr>
+            </tbody>
+          </table>
+        </div>
+      </Column>
+    );
+  }
+
+}
diff --git a/app/javascript/mastodon/features/ui/index.js b/app/javascript/mastodon/features/ui/index.js
index 57289f519..361326961 100644
--- a/app/javascript/mastodon/features/ui/index.js
+++ b/app/javascript/mastodon/features/ui/index.js
@@ -19,6 +19,7 @@ import {
   Compose,
   Status,
   GettingStarted,
+  KeyboardShortcuts,
   PublicTimeline,
   CommunityTimeline,
   AccountTimeline,
@@ -56,6 +57,7 @@ const mapStateToProps = state => ({
 });
 
 const keyMap = {
+  help: '?',
   new: 'n',
   search: 's',
   forceNew: 'option+n',
@@ -298,6 +300,14 @@ export default class UI extends React.Component {
     this.hotkeys = c;
   }
 
+  handleHotkeyToggleHelp = () => {
+    if (this.props.location.pathname === '/keyboard-shortcuts') {
+      this.context.router.history.goBack();
+    } else {
+      this.context.router.history.push('/keyboard-shortcuts');
+    }
+  }
+
   handleHotkeyGoToHome = () => {
     this.context.router.history.push('/timelines/home');
   }
@@ -343,6 +353,7 @@ export default class UI extends React.Component {
     const { children } = this.props;
 
     const handlers = {
+      help: this.handleHotkeyToggleHelp,
       new: this.handleHotkeyNew,
       search: this.handleHotkeySearch,
       forceNew: this.handleHotkeyForceNew,
@@ -369,6 +380,7 @@ export default class UI extends React.Component {
             <WrappedSwitch>
               <Redirect from='/' to='/getting-started' exact />
               <WrappedRoute path='/getting-started' component={GettingStarted} content={children} />
+              <WrappedRoute path='/keyboard-shortcuts' component={KeyboardShortcuts} content={children} />
               <WrappedRoute path='/timelines/home' component={HomeTimeline} content={children} />
               <WrappedRoute path='/timelines/public' exact component={PublicTimeline} content={children} />
               <WrappedRoute path='/timelines/public/local' component={CommunityTimeline} content={children} />
diff --git a/app/javascript/mastodon/features/ui/util/async-components.js b/app/javascript/mastodon/features/ui/util/async-components.js
index ec1630ed6..b741f668e 100644
--- a/app/javascript/mastodon/features/ui/util/async-components.js
+++ b/app/javascript/mastodon/features/ui/util/async-components.js
@@ -38,6 +38,10 @@ export function GettingStarted () {
   return import(/* webpackChunkName: "features/getting_started" */'../../getting_started');
 }
 
+export function KeyboardShortcuts () {
+  return import(/* webpackChunkName: "features/keyboard_shortcuts" */'../../keyboard_shortcuts');
+}
+
 export function PinnedStatuses () {
   return import(/* webpackChunkName: "features/pinned_statuses" */'../../pinned_statuses');
 }
diff --git a/app/javascript/styles/mastodon/components.scss b/app/javascript/styles/mastodon/components.scss
index f4ad66271..80060a00f 100644
--- a/app/javascript/styles/mastodon/components.scss
+++ b/app/javascript/styles/mastodon/components.scss
@@ -2099,6 +2099,27 @@
   }
 }
 
+.keyboard-shortcuts {
+  padding: 8px 0 0;
+  overflow: hidden;
+
+  thead {
+    position: absolute;
+    left: -9999px;
+  }
+
+  td {
+    padding: 0 10px 8px;
+  }
+
+  code {
+    display: inline-block;
+    padding: 3px 5px;
+    background-color: lighten($ui-base-color, 8%);
+    border: 1px solid darken($ui-base-color, 4%);
+  }
+}
+
 .setting-text {
   color: $ui-primary-color;
   background: transparent;