96 lines
3.3 KiB
JavaScript
96 lines
3.3 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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"use strict";
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this.EXPORTED_SYMBOLS = ["Screenshots"];
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const {utils: Cu} = Components;
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Cu.import("resource://gre/modules/XPCOMUtils.jsm");
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XPCOMUtils.defineLazyModuleGetter(this, "BackgroundPageThumbs",
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"resource://gre/modules/BackgroundPageThumbs.jsm");
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XPCOMUtils.defineLazyModuleGetter(this, "PageThumbs",
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"resource://gre/modules/PageThumbs.jsm");
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XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
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"resource://gre/modules/FileUtils.jsm");
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XPCOMUtils.defineLazyServiceGetter(this, "MIMEService",
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"@mozilla.org/mime;1", "nsIMIMEService");
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XPCOMUtils.defineLazyModuleGetter(this, "OS",
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"resource://gre/modules/osfile.jsm");
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const GREY_10 = "#F9F9FA";
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this.Screenshots = {
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/**
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* Convert bytes to a string using extremely fast String.fromCharCode without
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* exceeding the max number of arguments that can be provided to a function.
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*/
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_bytesToString(bytes) {
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// NB: This comes from js/src/vm/ArgumentsObject.h ARGS_LENGTH_MAX
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const ARGS_LENGTH_MAX = 500 * 1000;
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let i = 0;
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let str = "";
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let {length} = bytes;
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while (i < length) {
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const start = i;
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i += ARGS_LENGTH_MAX;
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str += String.fromCharCode.apply(null, bytes.slice(start, i));
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}
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return str;
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},
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async getScreenshotForURL(url) {
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let screenshot = null;
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try {
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await BackgroundPageThumbs.captureIfMissing(url, {backgroundColor: GREY_10});
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const imgPath = PageThumbs.getThumbnailPath(url);
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// OS.File object used to easily read off-thread
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const file = await OS.File.open(imgPath, {read: true, existing: true});
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// nsIFile object needed for MIMEService
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const nsFile = FileUtils.File(imgPath);
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const contentType = MIMEService.getTypeFromFile(nsFile);
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const bytes = await file.read();
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const encodedData = btoa(this._bytesToString(bytes));
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file.close();
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screenshot = `data:${contentType};base64,${encodedData}`;
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} catch (err) {
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Cu.reportError(`getScreenshot error: ${err}`);
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}
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return screenshot;
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},
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/**
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* Conditionally get a screenshot for a link if there's no existing pending
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* screenshot. Updates the cached link's desired property with the result.
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*
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* @param link {object} Link object to update
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* @param url {string} Url to get a screenshot of
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* @param property {string} Name of property on object to set
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@ @param onScreenshot {function} Callback for when the screenshot loads
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*/
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async maybeCacheScreenshot(link, url, property, onScreenshot) {
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// Nothing to do if we already have a pending screenshot
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const cache = link.__sharedCache;
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if (cache.fetchingScreenshot) {
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return;
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}
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// Save the promise to the cache so other links get it immediately
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cache.fetchingScreenshot = this.getScreenshotForURL(url);
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// Clean up now that we got the screenshot
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const screenshot = await cache.fetchingScreenshot;
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delete cache.fetchingScreenshot;
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// Update the cache for future links and call back for existing content
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if (screenshot) {
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cache.updateLink(property, screenshot);
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onScreenshot(screenshot);
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}
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}
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};
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