VTTCue polyfill (#643)

This adds a VTTCue polyfill for IE/Edge (3-arg TextTrackCue) and
Toshiba dTV (6-arg TextTrackCue).

Closes #635

Author: jozefchutka

build/types/polyfill

@@ -8,3 +8,4 @@
 +../../lib/polyfill/patchedmediakeys_webkit.js
 +../../lib/polyfill/promise.js
 +../../lib/polyfill/videoplaybackquality.js
++../../lib/polyfill/vttcue.js

lib/media/text_engine.js

@@ -117,15 +117,10 @@ shaka.media.TextEngine.makeCue = function(startTime, endTime, payload) {
     return null;
   }
 
-  return new shaka.media.TextEngine.CueConstructor(
-      startTime, endTime, payload);
+  return new VTTCue(startTime, endTime, payload);
 };
 
 
-/** @type {function(new:TextTrackCue, number, number, string)} */
-shaka.media.TextEngine.CueConstructor = window.VTTCue || window.TextTrackCue;
-
-
 /** @override */
 shaka.media.TextEngine.prototype.destroy = function() {
   if (this.track_) {

lib/polyfill/vttcue.js

@@ -0,0 +1,111 @@
+/**
+ * @license
+ * Copyright 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+goog.provide('shaka.polyfill.VTTCue');
+
+goog.require('shaka.log');
+goog.require('shaka.polyfill.register');
+
+
+/**
+ * @namespace shaka.polyfill.VTTCue
+ *
+ * @summary A polyfill to provide VTTCue.
+ */
+
+
+/**
+ * Install the polyfill if needed.
+ */
+shaka.polyfill.VTTCue.install = function() {
+  if (window.VTTCue) {
+    shaka.log.info('Using native VTTCue.');
+    return;
+  }
+
+  if (!window.TextTrackCue) {
+    shaka.log.error('VTTCue not available.');
+    return;
+  }
+
+  var constructorLength = TextTrackCue.length;
+  if (constructorLength == 3) {
+    shaka.log.info('Using VTTCue polyfill from 3 argument TextTrackCue.');
+    window.VTTCue = shaka.polyfill.VTTCue.from3ArgsTextTrackCue_;
+  } else if (constructorLength == 6) {
+    shaka.log.info('Using VTTCue polyfill from 6 argument TextTrackCue.');
+    window.VTTCue = shaka.polyfill.VTTCue.from6ArgsTextTrackCue_;
+  } else if (shaka.polyfill.VTTCue.canUse3ArgsTextTrackCue_()) {
+    shaka.log.info('Using VTTCue polyfill from 3 argument TextTrackCue.');
+    window.VTTCue = shaka.polyfill.VTTCue.from3ArgsTextTrackCue_;
+  }
+};
+
+
+/**
+ * Draft spec TextTrackCue with 3 constructor arguments.
+ * See {@link https://goo.gl/ZXBWZi W3C Working Draft 25 October 2012}.
+ *
+ * @param {number} startTime
+ * @param {number} endTime
+ * @param {string} text
+ * @return {TextTrackCue}
+ * @private
+ */
+shaka.polyfill.VTTCue.from3ArgsTextTrackCue_ = function(startTime, endTime,
+    text) {
+  return new window.TextTrackCue(startTime, endTime, text);
+};
+
+
+/**
+ * Draft spec TextTrackCue with 6 constructor arguments (5th & 6th are
+ * optional).
+ * See {@link https://goo.gl/AYFqUh W3C Working Draft 29 March 2012}.
+ * Quoting the access to the TextTrackCue object to avoid the compiler
+ * complaining.
+ *
+ * @param {number} startTime
+ * @param {number} endTime
+ * @param {string} text
+ * @return {TextTrackCue}
+ * @private
+ */
+shaka.polyfill.VTTCue.from6ArgsTextTrackCue_ = function(startTime, endTime,
+    text) {
+  var id = startTime + '-' + endTime + '-' + text;
+  return new window['TextTrackCue'](id, startTime, endTime, text);
+};
+
+
+/**
+ * IE10, IE11 and Edge returns TextTrackCue.length = 0 although it accepts 3
+ * constructor arguments.
+ *
+ * @return {boolean}
+ * @private
+ */
+shaka.polyfill.VTTCue.canUse3ArgsTextTrackCue_ = function() {
+  try {
+    return !!shaka.polyfill.VTTCue.from3ArgsTextTrackCue_(1, 2, '');
+  } catch (error) {
+    return false;
+  }
+};
+
+
+shaka.polyfill.register(shaka.polyfill.VTTCue.install);

shaka-player.uncompiled.js

@@ -47,5 +47,6 @@ goog.require('shaka.polyfill.MediaKeys');
 goog.require('shaka.polyfill.MediaSource');
 goog.require('shaka.polyfill.Promise');
 goog.require('shaka.polyfill.VideoPlaybackQuality');
+goog.require('shaka.polyfill.VTTCue');
 goog.require('shaka.polyfill.installAll');
 goog.require('shaka.util.Error');

test/media/ttml_text_parser_unit.js

@@ -16,18 +16,18 @@
  */
 
 describe('TtmlTextParser', function() {
-  var originalCueConstructor;
+  var originalVTTCue;
 
   beforeAll(function() {
-    originalCueConstructor = shaka.media.TextEngine.CueConstructor;
+    originalVTTCue = window.VTTCue;
   });
 
   afterAll(function() {
-    shaka.media.TextEngine.CueConstructor = originalCueConstructor;
+    window.VTTCue = originalVTTCue;
   });
 
   beforeEach(function() {
-    shaka.media.TextEngine.CueConstructor = function(start, end, text) {
+    window.VTTCue = function(start, end, text) {
       this.startTime = start;
       this.endTime = end;
       this.text = text;
@@ -427,7 +427,7 @@ describe('TtmlTextParser', function() {
 
   it('uses a workaround for browsers not supporting align=center', function() {
 
-    shaka.media.TextEngine.CueConstructor = function(start, end, text) {
+    window.VTTCue = function(start, end, text) {
       var align = 'middle';
       Object.defineProperty(this, 'align', {
         get: function() { return align; },

test/media/vtt_text_parser_unit.js

@@ -17,22 +17,22 @@
 
 describe('VttTextParser', function() {
   var logWarningSpy;
-  var originalCueConstructor;
+  var originalVTTCue;
 
   beforeAll(function() {
-    originalCueConstructor = shaka.media.TextEngine.CueConstructor;
+    originalVTTCue = window.VTTCue;
 
     logWarningSpy = jasmine.createSpy('shaka.log.warning');
     shaka.log.warning = logWarningSpy;
   });
 
   afterAll(function() {
-    shaka.media.TextEngine.CueConstructor = originalCueConstructor;
+    window.VTTCue = originalVTTCue;
   });
 
   beforeEach(function() {
     logWarningSpy.calls.reset();
-    shaka.media.TextEngine.CueConstructor = function(start, end, text) {
+    window.VTTCue = function(start, end, text) {
       this.startTime = start;
       this.endTime = end;
       this.text = text;