ui/file_manager/image_loader/piex_loader.js

// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/**
 * @typedef {{
 *   fulfill: function(PiexLoaderResponse):undefined,
 *   reject: function(string):undefined}
 * }}
 */
var PiexRequestCallbacks;

/**
 * Color space.
 * @enum {string}
 */
var ColorSpace = {
  SRGB: 'sRgb',
  ADOBE_RGB: 'adobeRgb'
};

/**
 * @param {{id:number, thumbnail:!ArrayBuffer, orientation:number,
 *          colorSpace: ColorSpace}}
 *     data Data directly returned from NaCl module.
 * @constructor
 * @struct
 */
function PiexLoaderResponse(data) {
  /**
   * @public {number}
   * @const
   */
  this.id = data.id;

  /**
   * @public {!ArrayBuffer}
   * @const
   */
  this.thumbnail = data.thumbnail;

  /**
   * @public {!ImageOrientation}
   * @const
   */
  this.orientation =
      ImageOrientation.fromExifOrientation(data.orientation);

  /**
   * @public {ColorSpace}
   * @const
   */
  this.colorSpace = data.colorSpace;
}

/**
 * @constructor
 * @struct
 */
function PiexLoader() {
  /**
   * @private {!Element}
   * @const
   */
  this.naclModule_ = document.createElement('embed');

  /**
   * @private {!Promise}
   * @const
   */
  this.naclPromise_ = new Promise(function(fulfill) {
    chrome.fileManagerPrivate.isPiexLoaderEnabled(fulfill);
  }).then(function(enabled) {
    if (!enabled)
      return Promise.reject('PiexLoader is not enabled for chromium build.');
    return new Promise(function(fulfill, reject) {
      var embed = this.naclModule_;
      embed.setAttribute('type', 'application/x-pnacl');
      // The extension nmf is not allowed to load. We uses .nmf.js instead.
      embed.setAttribute('src', '/piex/piex.nmf.txt');
      embed.width = 0;
      embed.height = 0;

      // The <EMBED> element is wrapped inside a <DIV>, which has both a 'load'
      // and a 'message' event listener attached.  This wrapping method is used
      // instead of attaching the event listeners directly to the <EMBED>
      // element to ensure that the listeners are active before the NaCl module
      // 'load' event fires.
      var listenerContainer = document.createElement('div');
      listenerContainer.appendChild(embed);
      listenerContainer.addEventListener('load', fulfill, true);
      listenerContainer.addEventListener(
          'message', this.onMessage_.bind(this), true);
      listenerContainer.addEventListener('error', function() {
        reject(embed['lastError']);
      }.bind(this), true);
      listenerContainer.addEventListener('crash', function() {
        reject('PiexLoader crashed.');
      }.bind(this), true);
      listenerContainer.style.height = '0px';
      document.body.appendChild(listenerContainer);
    }.bind(this));
  }.bind(this));

  /**
   * @private {!Object<number, PiexRequestCallbacks>}
   * @const
   */
  this.requests_ = {};

  /**
   * @private {number}
   */
  this.requestIdCount_ = 0;
}

/**
 * @param {Event} event
 * @private
 */
PiexLoader.prototype.onMessage_ = function(event) {
  var id = event.data.id;
  if (!event.data.error) {
    var response = new PiexLoaderResponse(event.data);
    this.requests_[id].fulfill(response);
  } else {
    this.requests_[id].reject(event.data.error);
  }
  delete this.requests_[id];
};

/**
 * Starts to load RAW image.
 * @param {string} url
 * @return {!Promise<!PiexLoaderResponse>}
 */
PiexLoader.prototype.load = function(url) {
  return this.naclPromise_.then(function() {
    var message = {
      id: this.requestIdCount_++,
      name: 'loadThumbnail',
      url: url
    };
    this.naclModule_.postMessage(message);
    return new Promise(function(fulfill, reject) {
      this.requests_[message.id] = {fulfill: fulfill, reject: reject};
    }.bind(this));
  }.bind(this));
};