chrome/browser/resources/downloads/icon_loader.js

// Copyright 2018 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.

import {assert} from 'chrome://resources/js/assert.m.js';
import {addSingletonGetter} from 'chrome://resources/js/cr.m.js';
import {getFileIconUrl} from 'chrome://resources/js/icon.m.js';
import {PromiseResolver} from 'chrome://resources/js/promise_resolver.m.js';

export class IconLoader {
  constructor() {
    /** @private {!Object<!PromiseResolver<boolean>>} */
    this.iconResolvers_ = {};

    /** @private {!Set<!HTMLImageElement>} */
    this.listeningImages_ = new Set();
  }

  /**
   * @param {!HTMLImageElement} imageEl
   * @param {string} filePath
   * @return {!Promise<boolean>} Whether or not the icon loaded successfully.
   */
  loadIcon(imageEl, filePath) {
    const url = getFileIconUrl(filePath);

    if (!this.iconResolvers_[url]) {
      this.iconResolvers_[url] = new PromiseResolver();
    }

    if (!this.listeningImages_.has(imageEl)) {
      imageEl.addEventListener('load', this.finishedLoading_.bind(this));
      imageEl.addEventListener('error', this.finishedLoading_.bind(this));
      this.listeningImages_.add(imageEl);
    }

    imageEl.src = url;

    return assert(this.iconResolvers_[url]).promise;
  }

  /**
   * @param {!Event} e
   * @private
   */
  finishedLoading_(e) {
    const resolver = assert(this.iconResolvers_[e.currentTarget.src]);
    if (!resolver.isFulfilled) {
      resolver.resolve(e.type === 'load');
    }
  }
}

addSingletonGetter(IconLoader);