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// 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 {{img: HTMLImageElement, url: string}} */
var LoadIconRequest;
cr.define('downloads', function() {
/**
* @param {number} maxAllowed The maximum number of simultaneous downloads
* allowed.
* @constructor
*/
function ThrottledIconLoader(maxAllowed) {
assert(maxAllowed > 0);
/** @private {number} */
this.maxAllowed_ = maxAllowed;
/** @private {!Array<!LoadIconRequest>} */
this.requests_ = [];
}
ThrottledIconLoader.prototype = {
/** @private {number} */
loading_: 0,
/**
* Load the provided |url| into |img.src| after appending ?scale=.
* @param {!HTMLImageElement} img An <img> to show the loaded image in.
* @param {string} url A remote image URL to load.
*/
loadScaledIcon: function(img, url) {
var scaledUrl = url + '?scale=' + window.devicePixelRatio + 'x';
if (img.src == scaledUrl)
return;
this.requests_.push({img: img, url: scaledUrl});
this.loadNextIcon_();
},
/** @private */
loadNextIcon_: function() {
if (this.loading_ > this.maxAllowed_ || !this.requests_.length)
return;
var request = this.requests_.shift();
var img = request.img;
img.onabort = img.onerror = img.onload = function() {
this.loading_--;
this.loadNextIcon_();
}.bind(this);
this.loading_++;
img.src = request.url;
},
};
return {ThrottledIconLoader: ThrottledIconLoader};
});
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