297 lines
10 KiB
Plaintext
297 lines
10 KiB
Plaintext
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0\r<>m<><6D> <00><><07> 3// Copyright 2013 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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/**
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* @fileoverview
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* This is a component extension that implements a text-to-speech (TTS)
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* engine powered by Google's speech synthesis API.
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*
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* This is a service worker, so it's not loaded when the API isn't being used,
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* and doesn't waste resources. When a web page or web app makes a speech
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* request and the parameters match one of the voices in this extension's
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* manifest, it makes a request to Google's API using Chrome's private key
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* and plays the resulting speech using HTML5 audio.
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*/
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/**
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* The main class for this extension. Adds listeners to
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* chrome.ttsEngine.onSpeak and chrome.ttsEngine.onStop and implements
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* them using Google's speech synthesis API.
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*/
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class TtsExtension {
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/**
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* Initializes data structures and adds event listeners.
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*/
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constructor() {
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/**
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* The url prefix of the speech server, including static query
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* parameters that don't change.
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* @type {string}
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* @const
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* @private
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*/
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this.SPEECH_SERVER_URL_ =
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'https://www.google.com/speech-api/v2/synthesize?' +
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'enc=mpeg&client=chromium';
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/**
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* A mapping from language and gender to voice name, hardcoded for now
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* until the speech synthesis server capabilities response provides this.
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* The key of this map is of the form '<lang>-<gender>'.
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* @type {Object<string>}
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* @private
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*/
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this.LANG_AND_GENDER_TO_VOICE_NAME_ = {
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'en-gb-male': 'rjs',
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'en-gb-female': 'fis',
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};
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/**
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* The arguments passed to the onSpeak event handler for the utterance
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* that's currently being spoken. Should be null when no object is
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* pending.
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*
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* @type {?{utterance: string, options: Object, callback: Function}}
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* @private
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*/
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this.currentUtterance_ = null;
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/**
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* A mapping from voice name to language and gender, derived from the
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* manifest file. This is used in case the speech synthesis request
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* specifies a voice name but doesn't specify a language code or gender.
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* @type {Object<{lang: string, gender: string}>}
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* @private
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*/
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this.voiceNameToLangAndGender_ = {};
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/** True when the offscreen document is in the progress of loading. */
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this.loading_ = true;
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/** Tracks the timeout callback which closes the offscreen document. */
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this.closeTimeoutId_ = null;
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// Get voices from manifest.
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const voices = chrome.runtime.getManifest().tts_engine.voices;
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for (let i = 0; i < voices.length; i++) {
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this.voiceNameToLangAndGender_[voices[i].voice_name] = {
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lang: voices[i].lang,
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gender: voices[i].gender,
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};
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}
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// Install event listeners for the ttsEngine API.
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chrome.ttsEngine.onSpeak.addListener(
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(utterance, options, callback) =>
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this.onSpeak_(utterance, options, callback));
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chrome.ttsEngine.onStop.addListener(() => this.onStop_());
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chrome.ttsEngine.onPause.addListener(() => this.onPause_());
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chrome.ttsEngine.onResume.addListener(() => this.onResume_());
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chrome.runtime.onMessage.addListener(message => {
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switch (message.command) {
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case 'loaded':
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// Speak an utterance spoken during load.
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if (this.loading_) {
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this.loading_ = false;
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if (this.currentUtterance_) {
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this.onSpeak_(
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this.currentUtterance_.utterance,
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this.currentUtterance_.options,
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this.currentUtterance_.callback);
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}
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}
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break;
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case 'onCanPlayThrough':
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chrome.metricsPrivate.recordEnumerationValue(
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'TextToSpeech.ExtensionNetworkSpeechSynthesis.Playback',
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/*can play through*/ 0, /*enum size*/ 2);
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if (this.currentUtterance_) {
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this.currentUtterance_.callback({'type': 'start', 'charIndex': 0});
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}
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break;
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case 'onEnded':
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chrome.metricsPrivate.recordEnumerationValue(
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'TextToSpeech.ExtensionNetworkSpeechSynthesis.Playback',
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/*ended*/ 1, /*enum size */ 2);
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this.onStop_(/* onEnded = */ true);
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break;
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}
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});
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}
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/**
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* Handler for the chrome.ttsEngine.onSpeak interface.
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* Gets Chrome's Google API key and then uses it to generate a request
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* url for the requested speech utterance. Sets that url as the source
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* of the HTML5 audio element.
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* @param {string} utterance The text to be spoken.
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* @param {Object} options Options to control the speech, as defined
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* in the Chrome ttsEngine extension API.
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* @private
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*/
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onSpeak_(utterance, options, callback) {
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// Ignore the utterance if it is empty. Continue such processing causes no
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// speech and fails all subsequent calls to process additional utterances.
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if (utterance.length === 0) {
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callback({'type': 'end', 'charIndex': 0});
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this.currentUtterance_ = null;
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return;
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}
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// Truncate the utterance if it's too long. Both Chrome's tts
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// extension api and the web speech api specify 32k as the
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// maximum limit for an utterance.
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if (utterance.length > 32768) {
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utterance = utterance.substr(0, 32768);
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}
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this.currentUtterance_ = {
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utterance: utterance,
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options: options,
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callback: callback,
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};
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if (this.loading_) {
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this.maybeCreateOffscreenDocument_();
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return;
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}
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// We're now committed to speaking something. Bump our timeout to keep the
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// offscreen doc open.
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clearTimeout(this.closeTimeoutId_);
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chrome.runtime.sendMessage({
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command: 'setCurrentUtterance',
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currentUtterance: this.currentUtterance_,
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});
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let lang = options.lang;
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let gender = options.gender;
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if (options.voiceName) {
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lang = this.voiceNameToLangAndGender_[options.voiceName].lang;
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gender = this.voiceNameToLangAndGender_[options.voiceName].gender;
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}
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if (!lang) {
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lang = navigator.language;
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}
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// Look up the specific voice name for this language and gender.
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// If it's not in the map, it doesn't matter - the language will
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// be used directly. This is only used for languages where more
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// than one gender is actually available.
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const key = lang.toLowerCase() + '-' + gender;
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const voiceName = this.LANG_AND_GENDER_TO_VOICE_NAME_[key];
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let url = this.SPEECH_SERVER_URL_;
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chrome.systemPrivate.getApiKey(key => {
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url += '&key=' + key;
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url += '&text=' + encodeURIComponent(utterance);
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url += '&lang=' + lang.toLowerCase();
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if (voiceName) {
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url += '&name=' + voiceName;
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}
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if (options.rate) {
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// Input rate is between 0.1 and 10.0 with a default of 1.0.
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// Output speed is between 0.0 and 1.0 with a default of 0.5.
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url += '&speed=' + (options.rate / 2.0);
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}
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if (options.pitch) {
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// Input pitch is between 0.0 and 2.0 with a default of 1.0.
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// Output pitch is between 0.0 and 1.0 with a default of 0.5.
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url += '&pitch=' + (options.pitch / 2.0);
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}
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// This begins loading the audio but does not play it.
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// When enough of the audio has loaded to begin playback,
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// the 'canplaythrough' handler will call this.onCanPlayThrough_,
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// which sends a start event to the ttsEngine callback and
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// then begins playing audio.
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chrome.runtime.sendMessage({command: 'setUrl', url});
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});
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}
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/**
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* Handler for the chrome.ttsEngine.onStop interface.
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* Called either when the ttsEngine API requests us to stop, or when
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* we reach the end of the audio stream. Pause the audio element to
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* silence it, and send a callback to the ttsEngine API to let it know
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* that we've completed. Note that the ttsEngine API manages callback
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* messages and will automatically replace the 'end' event with a
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* more specific callback like 'interrupted' when sending it to the
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* TTS client.
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* @param {boolean|undefined) onEnded
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* @private
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*/
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onStop_(onEnded) {
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if (this.currentUtterance_) {
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if (onEnded !== true) {
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chrome.runtime.sendMessage({command: 'pause'});
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}
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this.currentUtterance_.callback({
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'type': 'end',
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'charIndex': this.currentUtterance_.utterance.length,
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});
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this.currentUtterance_ = null;
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}
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this.maybeCloseOffscreenDocument_();
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}
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/**
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* Handler for the chrome.ttsEngine.onPause interface.
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* Pauses audio if we're in the middle of an utterance.
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* @private
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*/
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onPause_() {
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if (this.currentUtterance_) {
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chrome.runtime.sendMessage({command: 'pause'});
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}
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}
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/**
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* Handler for the chrome.ttsEngine.onPause interface.
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* Resumes audio if we're in the middle of an utterance.
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* @private
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*/
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onResume_() {
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if (this.currentUtterance_) {
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chrome.runtime.sendMessage({command: 'play'});
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}
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}
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async maybeCreateOffscreenDocument_() {
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const offscreenUrl = chrome.runtime.getURL('audio.html');
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const existingContexts = await chrome.runtime.getContexts(
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{contextTypes: ['OFFSCREEN_DOCUMENT'], documentUrls: [offscreenUrl]});
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if (existingContexts.length === 0) {
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const creating = chrome.offscreen.createDocument({
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url: offscreenUrl,
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// We use USER_MEDIA here instead of AUDIO_PLAYBACK because we need to
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// support pause/resume and need the offscreen document to exist without
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// audio playback. Once finished, we manually close the offscreen
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// document.
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reasons: ['USER_MEDIA'],
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justification: 'Use the audio element',
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});
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await creating;
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}
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}
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maybeCloseOffscreenDocument_() {
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// Clear any existing timeouts.
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clearTimeout(this.closeTimeoutId_);
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this.closeTimeoutId_ = setTimeout(async () => {
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await chrome.offscreen.closeDocument();
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this.loading_ = true;
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}, 30 * 1000);
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}
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}
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new TtsExtension();
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<EFBFBD>A
<0A>Eo<45><6F> <,<2C> <00> <00> q HTTP/1.1 200 OK Content-Security-Policy: script-src 'self'; Content-Length: 10084 Content-Type: text/javascript N@<40>b<EFBFBD>ۋ`<60><05><><EFBFBD><EFBFBD><EFBFBD><16>"0<>}<7D> d ~G)<29><><EFBFBD><EFBFBD>A
<0A>Eo<45><6F> <00><>N <20>
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