feat(): add aria live announcer

Fixes #106

Author: devversion

src/core/live-announcer/README.md

@@ -0,0 +1,30 @@
+# MdLiveAnnouncer
+`MdLiveAnnouncer` is a service, which announces messages to several screenreaders.
+
+### Methods
+
+| Name |  Description |
+| --- | --- |
+| `announce(message, politeness)` | This announces a text message to the supported screenreaders. <br><br>The politeness parameter sets the `aria-live` attribute on the announcer element |
+
+### Examples
+The service can be injected in a component.
+```ts
+@Component({
+  selector: 'my-component'
+  providers: [MdLiveAnnouncer]
+})
+export class MyComponent {
+
+ constructor(live: MdLiveAnnouncer) {
+   live.announce("Hey Google");
+ }
+
+}
+```
+
+### Supported Screenreaders
+- JAWS (Windows)
+- NVDA (Windows)
+- VoiceOver (OSX and iOS)
+- TalkBack (Android)

src/core/live-announcer/live-announcer.scss

@@ -0,0 +1,5 @@
+@import 'mixins';
+
+.md-live-announcer {
+  @include md-visually-hidden();
+}

src/core/live-announcer/live-announcer.spec.ts

@@ -0,0 +1,121 @@
+import {
+  inject,
+  TestComponentBuilder,
+  ComponentFixture,
+  fakeAsync,
+  flushMicrotasks,
+  tick,
+  beforeEachProviders
+} from 'angular2/testing';
+import {
+  it,
+  describe,
+  expect,
+  beforeEach,
+} from '../../core/facade/testing';
+import {Component} from 'angular2/core';
+import {By} from 'angular2/platform/browser';
+import {MdLiveAnnouncer} from './live-announcer';
+
+export function main() {
+  describe('MdLiveAnnouncer', () => {
+    let live: MdLiveAnnouncer;
+    let builder: TestComponentBuilder;
+    let liveEl: Element;
+
+    beforeEachProviders(() => [MdLiveAnnouncer]);
+
+    beforeEach(inject([TestComponentBuilder, MdLiveAnnouncer],
+      (tcb: TestComponentBuilder, _live: MdLiveAnnouncer) => {
+        builder = tcb;
+        live = _live;
+        liveEl = getLiveElement();
+    }));
+
+    afterEach(() => {
+      // In our tests we always remove the current live element, because otherwise we would have
+      // multiple live elements due multiple service instantiations.
+      liveEl.parentNode.removeChild(liveEl);
+    });
+
+    it('should correctly update the announce text', fakeAsyncTest(() => {
+      let appFixture: ComponentFixture = null;
+
+      builder.createAsync(TestApp).then(fixture => {
+        appFixture = fixture;
+      });
+
+      flushMicrotasks();
+
+      let buttonElement = appFixture.debugElement
+        .query(By.css('button')).nativeElement;
+
+      buttonElement.click();
+
+      // This flushes our 100ms timeout for the screenreaders.
+      tick(100);
+
+      expect(liveEl.textContent).toBe('Test');
+    }));
+
+    it('should correctly update the politeness attribute', fakeAsyncTest(() => {
+      let appFixture: ComponentFixture = null;
+
+      builder.createAsync(TestApp).then(fixture => {
+        appFixture = fixture;
+      });
+
+      flushMicrotasks();
+
+      live.announce('Hey Google', 'assertive');
+
+      // This flushes our 100ms timeout for the screenreaders.
+      tick(100);
+
+      expect(liveEl.textContent).toBe('Hey Google');
+      expect(liveEl.getAttribute('aria-live')).toBe('assertive');
+    }));
+
+    it('should apply the aria-live value polite by default', fakeAsyncTest(() => {
+      let appFixture: ComponentFixture = null;
+
+      builder.createAsync(TestApp).then(fixture => {
+        appFixture = fixture;
+      });
+
+      flushMicrotasks();
+
+      live.announce('Hey Google');
+
+      // This flushes our 100ms timeout for the screenreaders.
+      tick(100);
+
+      expect(liveEl.textContent).toBe('Hey Google');
+      expect(liveEl.getAttribute('aria-live')).toBe('polite');
+    }));
+
+  });
+}
+
+function fakeAsyncTest(fn: () => void) {
+  return inject([], fakeAsync(fn));
+}
+
+function getLiveElement(): Element {
+  return document.body.querySelector('.md-live-announcer');
+}
+
+@Component({
+  selector: 'test-app',
+  template: `<button (click)="announceText('Test')">Announce</button>`,
+})
+class TestApp {
+
+  constructor(private live: MdLiveAnnouncer) {};
+
+  announceText(message: string) {
+    this.live.announce(message);
+  }
+
+}
+

src/core/live-announcer/live-announcer.ts

@@ -0,0 +1,44 @@
+import {Injectable} from 'angular2/core';
+
+export type AriaLivePoliteness = 'off' | 'polite' | 'assertive';
+
+@Injectable()
+export class MdLiveAnnouncer {
+
+  private _liveElement: Element;
+
+  constructor() {
+    this._liveElement = this._createLiveElement();
+  }
+
+  /**
+   * @param message Message to be announced to the screenreader
+   * @param politeness The politeness of the announcer element.
+   */
+  announce(message: string, politeness: AriaLivePoliteness = 'polite'): void {
+    this._liveElement.textContent = '';
+
+    // TODO: ensure changing the politeness works on all environments we support.
+    this._liveElement.setAttribute('aria-live', politeness);
+
+    // This 100ms timeout is necessary for some browser + screen-reader combinations:
+    // - Both JAWS and NVDA over IE11 will not announce anything without a non-zero timeout.
+    // - With Chrome and IE11 with NVDA or JAWS, a repeated (identical) message won't be read a
+    //   second time without clearing and then using a non-zero delay.
+    // (using JAWS 17 at time of this writing).
+    setTimeout(() => this._liveElement.textContent = message, 100);
+  }
+
+  private _createLiveElement(): Element {
+    let liveEl = document.createElement('div');
+
+    liveEl.classList.add('md-live-announcer');
+    liveEl.setAttribute('aria-atomic', 'true');
+    liveEl.setAttribute('aria-live', 'polite');
+
+    document.body.appendChild(liveEl);
+
+    return liveEl;
+  }
+
+}

src/core/style/_mixins.scss

@@ -9,3 +9,19 @@
   // Use a transform to create a new stacking context.
   transform: translate3D(0, 0, 0);
 }
+
+/**
+ * This mixin hides an element visually.
+ * That means it's still accessible for screen-readers but not visible in view.
+ */
+@mixin md-visually-hidden {
+  border: 0;
+  clip: rect(0 0 0 0);
+  height: 1px;
+  margin: -1px;
+  overflow: hidden;
+  padding: 0;
+  position: absolute;
+  text-transform: none;
+  width: 1px;
+}

src/demo-app/demo-app.html

@@ -12,6 +12,7 @@ <h1>Angular Material2 Demos</h1>
     <li><a [routerLink]="['ToolbarDemo']">Toolbar demo</a></li>
     <li><a [routerLink]="['RadioDemo']">Radio demo</a></li>
     <li><a [routerLink]="['ListDemo']">List demo</a></li>
+    <li><a [routerLink]="['LiveAnnouncerDemo']">Live Announcer demo</a></li>
   </ul>
   <button md-raised-button (click)="root.dir = (root.dir == 'rtl' ? 'ltr' : 'rtl')">
     {{root.dir.toUpperCase()}}

src/demo-app/demo-app.ts

@@ -13,6 +13,7 @@ import {ToolbarDemo} from './toolbar/toolbar-demo';
 import {OverlayDemo} from './overlay/overlay-demo';
 import {ListDemo} from './list/list-demo';
 import {InputDemo} from './input/input-demo';
+import {LiveAnnouncerDemo} from './live-announcer/live-announcer-demo';
 
 
 @Component({
@@ -41,6 +42,7 @@ export class Home {}
   new Route({path: '/checkbox', name: 'CheckboxDemo', component: CheckboxDemo}),
   new Route({path: '/input', name: 'InputDemo', component: InputDemo}),
   new Route({path: '/toolbar', name: 'ToolbarDemo', component: ToolbarDemo}),
-  new Route({path: '/list', name: 'ListDemo', component: ListDemo})
+  new Route({path: '/list', name: 'ListDemo', component: ListDemo}),
+  new Route({path: '/live-announcer', name: 'LiveAnnouncerDemo', component: LiveAnnouncerDemo})
 ])
 export class DemoApp { }

src/demo-app/live-announcer/live-announcer-demo.html

@@ -0,0 +1,5 @@
+<div class="demo-live-announcer">
+
+  <button md-button (click)="announceText('Hey Google')">Announce Text</button>
+
+</div>

src/demo-app/live-announcer/live-announcer-demo.ts

@@ -0,0 +1,16 @@
+import {Component} from 'angular2/core';
+import {MdLiveAnnouncer} from '../../core/live-announcer/live-announcer';
+
+@Component({
+  selector: 'toolbar-demo',
+  templateUrl: 'demo-app/live-announcer/live-announcer-demo.html',
+})
+export class LiveAnnouncerDemo {
+
+  constructor(private live: MdLiveAnnouncer) {}
+
+  announceText(message: string) {
+    this.live.announce(message);
+  }
+
+}

src/main.scss

@@ -3,3 +3,4 @@
 // that are consumed across multiple components (and thus shouldn't be scoped).
 
 @import "core/overlay/overlay";
+@import "core/live-announcer/live-announcer";