chrome/renderer/resources/extensions/tts_custom_bindings.js

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // Custom binding for the tts API.
   6
   7 var binding = require('binding').Binding.create('tts');
   8
   9 var idGenerator = requireNative('id_generator');
  10 var sendRequest = require('sendRequest').sendRequest;
  11 var lazyBG = requireNative('lazy_background_page');
  12
  13 binding.registerCustomHook(function(api) {
  14   var apiFunctions = api.apiFunctions;
  15   var tts = api.compiledApi;
  16   var handlers = {};
  17
  18   function ttsEventListener(event) {
  19     var eventHandler = handlers[event.srcId];
  20     if (eventHandler) {
  21       eventHandler({
  22                      type: event.type,
  23                      charIndex: event.charIndex,
  24                      errorMessage: event.errorMessage
  25                    });
  26       if (event.isFinalEvent) {
  27         delete handlers[event.srcId];
  28         // Balanced in 'speak' handler.
  29         lazyBG.DecrementKeepaliveCount();
  30       }
  31     }
  32   }
  33
  34   // This file will get run if an extension needs the ttsEngine permission, but
  35   // it doesn't necessarily have the tts permission. If it doesn't, trying to
  36   // add a listener to chrome.tts.onEvent will fail.
  37   // See http://crbug.com/122474.
  38   try {
  39     tts.onEvent.addListener(ttsEventListener);
  40   } catch (e) {}
  41
  42   apiFunctions.setHandleRequest('speak', function() {
  43     var args = arguments;
  44     if (args.length > 1 && args[1] && args[1].onEvent) {
  45       var id = idGenerator.GetNextId();
  46       args[1].srcId = id;
  47       handlers[id] = args[1].onEvent;
  48       // Keep the page alive until the event finishes.
  49       // Balanced in eventHandler.
  50       lazyBG.IncrementKeepaliveCount();
  51     }
  52     sendRequest(this.name, args, this.definition.parameters);
  53     return id;
  54   });
  55 });
  56
  57 exports.binding = binding.generate();