Source: lib/polyfill/vttcue.js

  1. /**
  2.  * @license
  3.  * Copyright 2016 Google Inc.
  4.  *
  5.  * Licensed under the Apache License, Version 2.0 (the "License");
  6.  * you may not use this file except in compliance with the License.
  7.  * You may obtain a copy of the License at
  8.  *
  9.  *     http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  18. goog.provide('shaka.polyfill.VTTCue');
  20. goog.require('shaka.log');
  21. goog.require('shaka.polyfill.register');
  24. /**
  25.  * @namespace shaka.polyfill.VTTCue
  26.  *
  27.  * @summary A polyfill to provide VTTCue.
  28.  */
  31. /**
  32.  * Install the polyfill if needed.
  33.  */
  34. shaka.polyfill.VTTCue.install = function() {
  35.   if (window.VTTCue) {
  36.     shaka.log.info('Using native VTTCue.');
  37.     return;
  38.   }
  40.   if (!window.TextTrackCue) {
  41.     shaka.log.error('VTTCue not available.');
  42.     return;
  43.   }
  45.   let constructorLength = TextTrackCue.length;
  46.   if (constructorLength == 3) {
  47.     shaka.log.info('Using VTTCue polyfill from 3 argument TextTrackCue.');
  48.     window.VTTCue = shaka.polyfill.VTTCue.from3ArgsTextTrackCue_;
  49.   } else if (constructorLength == 6) {
  50.     shaka.log.info('Using VTTCue polyfill from 6 argument TextTrackCue.');
  51.     window.VTTCue = shaka.polyfill.VTTCue.from6ArgsTextTrackCue_;
  52.   } else if (shaka.polyfill.VTTCue.canUse3ArgsTextTrackCue_()) {
  53.     shaka.log.info('Using VTTCue polyfill from 3 argument TextTrackCue.');
  54.     window.VTTCue = shaka.polyfill.VTTCue.from3ArgsTextTrackCue_;
  55.   }
  56. };
  59. /**
  60.  * Draft spec TextTrackCue with 3 constructor arguments.
  61.  * @see {@link https://goo.gl/ZXBWZi W3C Working Draft 25 October 2012}.
  62.  *
  63.  * @param {number} startTime
  64.  * @param {number} endTime
  65.  * @param {string} text
  66.  * @return {TextTrackCue}
  67.  * @private
  68.  */
  69. shaka.polyfill.VTTCue.from3ArgsTextTrackCue_ = function(startTime, endTime,
  70.     text) {
  71.   return new window.TextTrackCue(startTime, endTime, text);
  72. };
  75. /**
  76.  * Draft spec TextTrackCue with 6 constructor arguments (5th & 6th are
  77.  * optional).
  78.  * @see {@link https://goo.gl/AYFqUh W3C Working Draft 29 March 2012}.
  79.  *
  80.  * @param {number} startTime
  81.  * @param {number} endTime
  82.  * @param {string} text
  83.  * @return {TextTrackCue}
  84.  * @private
  85.  */
  86. shaka.polyfill.VTTCue.from6ArgsTextTrackCue_ = function(startTime, endTime,
  87.     text) {
  88.   let id = startTime + '-' + endTime + '-' + text;
  89.   // Quoting the access to the TextTrackCue object to satisfy the compiler.
  90.   return new window['TextTrackCue'](id, startTime, endTime, text);
  91. };
  94. /**
  95.  * IE10, IE11 and Edge return TextTrackCue.length = 0, although they accept 3
  96.  * constructor arguments.
  97.  *
  98.  * @return {boolean}
  99.  * @private
  100.  */
  101. shaka.polyfill.VTTCue.canUse3ArgsTextTrackCue_ = function() {
  102.   try {
  103.     return !!shaka.polyfill.VTTCue.from3ArgsTextTrackCue_(1, 2, '');
  104.   } catch (error) {
  105.     return false;
  106.   }
  107. };
  110. shaka.polyfill.register(shaka.polyfill.VTTCue.install);