src/chrome/browser/resources/chromeos/wallpaper_manager/js/progress_manager.js

   1 // Copyright (c) 2013 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 /**
   6  * Monitor the downloading progress of a XMLHttpRequest |xhr_| and shows the
   7  * progress on |progressBar_|.
   8  * @constructor
   9  */
  10 function ProgressManager() {
  11   this.xhr_ = null;
  12   this.progressBar_ = document.querySelector('.progress-bar');
  13   this.selectedGridItem_ = null;
  14 }
  15
  16 /**
  17  * Sets the XMLHttpRequest |xhr| to monitor, and the wallpaper thumbnail grid
  18  * item |selectedGridItem| to show a progress bar for. Cancels previous xhr and
  19  * hides/removes previous progress bar if any.
  20  * Note: this must be called before xhr.send() function. Otherwise, we wont get
  21  * loadstart event.
  22  * @param {XMLHttpRequest} xhr The XMLHttpRequest.
  23  * @param {WallpaperThumbnailsGridItem} selectedGridItem The wallpaper thumbnail
  24  *     grid item. It extends from cr.ui.ListItem.
  25  */
  26 ProgressManager.prototype.reset = function(xhr, selectedGridItem) {
  27   if (this.xhr_)
  28     this.removeEventListeners_();
  29   this.hideProgressBar(this.selectedGridItem_);
  30   this.xhr_ = xhr;
  31   this.selectedGridItem_ = selectedGridItem;
  32   this.xhrListeners_ = {
  33     'loadstart': this.onDownloadStart_.bind(this),
  34     'progress': this.onDownloadProgress_.bind(this),
  35     'abort': this.onDownloadErrorOrAbort_.bind(this),
  36     'error': this.onDownloadErrorOrAbort_.bind(this),
  37     'load': this.onDownloadComplete_.bind(this)
  38   };
  39   for (var eventType in this.xhrListeners_)
  40     this.xhr_.addEventListener(eventType, this.xhrListeners_[eventType]);
  41 };
  42
  43 /**
  44  * Removes all event listeners progress manager currently registered.
  45  * @private
  46  */
  47 ProgressManager.prototype.removeEventListeners_ = function() {
  48   for (var eventType in this.xhrListeners_)
  49     this.xhr_.removeEventListener(eventType, this.xhrListeners_[eventType]);
  50 };
  51
  52 /**
  53  * Removes the progress bar in |selectedGridItem| if any. May be called
  54  * asynchronously.
  55  * @param {WallpaperThumbnailsGridItem} selectedGridItem The wallpaper thumbnail
  56        grid item. It extends from cr.ui.ListItem.
  57  */
  58 ProgressManager.prototype.hideProgressBar = function(selectedGridItem) {
  59   if (selectedGridItem && selectedGridItem.querySelector('.progress-bar')) {
  60     this.progressBar_.hidden = true;
  61     selectedGridItem.removeChild(this.progressBar_);
  62   }
  63 };
  64
  65 /**
  66  * Calculates and updates the width of progress track.
  67  * @private
  68  * @param {float} percentComplete The percent of loaded content.
  69  */
  70 ProgressManager.prototype.setProgress_ = function(percentComplete) {
  71   this.progressBar_.querySelector('.progress-track').style.width =
  72       (percentComplete * 100) + '%';
  73 };
  74
  75 /**
  76  * Shows a 0% progress bar to indicate downloading starts.
  77  * @private
  78  * @param {Event} e A loadstart ProgressEvent from XMLHttpRequest.
  79  */
  80 ProgressManager.prototype.onDownloadStart_ = function(e) {
  81   this.setProgress_(0);
  82   this.selectedGridItem_.appendChild(this.progressBar_);
  83   this.progressBar_.hidden = false;
  84 };
  85
  86 /**
  87  * Hides progress bar when progression is terminated.
  88  * @private
  89  * @param {Event} e An error/abort ProgressEvent from XMLHttpRequest.
  90  */
  91 ProgressManager.prototype.onDownloadErrorOrAbort_ = function(e) {
  92   this.removeEventListeners_();
  93   this.xhr_ = null;
  94   this.hideProgressBar(this.selectedGridItem_);
  95 };
  96
  97 /**
  98  * Download completed successfully. Shows a 100% progress bar and clears |xhr_|.
  99  * @private
 100  * @param {Event} e A load ProgressEvent from XMLHttpRequest.
 101  */
 102 ProgressManager.prototype.onDownloadComplete_ = function(e) {
 103   this.setProgress_(1);
 104   this.removeEventListeners_();
 105   this.xhr_ = null;
 106 };
 107
 108 /**
 109  * Calculates downloading percentage and shows downloading progress.
 110  * @private
 111  * @param {Event} e A progress ProgressEvent from XMLHttpRequest.
 112  */
 113 ProgressManager.prototype.onDownloadProgress_ = function(e) {
 114   if (e.lengthComputable)
 115     this.setProgress_(e.loaded / e.total);
 116 };