tor-browser

Screenshots.sys.mjs (5118B)

---

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// We use importESModule here instead of static import so that
// the Karma test environment won't choke on this module. This
// is because the Karma test environment already stubs out
// XPCOMUtils, and overrides importESModule to be a no-op (which
// can't be done for a static import statement).

// eslint-disable-next-line mozilla/use-static-import
const { XPCOMUtils } = ChromeUtils.importESModule(
 "resource://gre/modules/XPCOMUtils.sys.mjs"
);

const lazy = {};

ChromeUtils.defineESModuleGetters(lazy, {
 BackgroundPageThumbs: "resource://gre/modules/BackgroundPageThumbs.sys.mjs",
 PageThumbs: "resource://gre/modules/PageThumbs.sys.mjs",
 PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
});

const GREY_10 = "#F9F9FA";

XPCOMUtils.defineLazyPreferenceGetter(
 lazy,
 "gPrivilegedAboutProcessEnabled",
 "browser.tabs.remote.separatePrivilegedContentProcess",
 false
);

export const Screenshots = {
 /**
  * Get a screenshot / thumbnail for a url. Either returns the disk cached
  * image or initiates a background request for the url.
  *
  * @param url {string} The url to get a thumbnail
  * @return {Promise} Resolves a custom object or null if failed
  */
 async getScreenshotForURL(url) {
   try {
     await lazy.BackgroundPageThumbs.captureIfMissing(url, {
       backgroundColor: GREY_10,
     });

     // The privileged about content process is able to use the moz-page-thumb
     // protocol, so if it's enabled, send that down.
     if (lazy.gPrivilegedAboutProcessEnabled) {
       return lazy.PageThumbs.getThumbnailURL(url);
     }

     // Otherwise, for normal content processes, we fallback to using
     // Blob URIs for the screenshots.
     const imgPath = lazy.PageThumbs.getThumbnailPath(url);

     const filePathResponse = await fetch(`file://${imgPath}`);
     const fileContents = await filePathResponse.blob();

     // Check if the file is empty, which indicates there isn't actually a
     // thumbnail, so callers can show a failure state.
     if (fileContents.size === 0) {
       return null;
     }

     return { path: imgPath, data: fileContents };
   } catch (err) {
     console.error(`getScreenshot(${url}) failed:`, err);
   }

   // We must have failed to get the screenshot, so persist the failure by
   // storing an empty file. Future calls will then skip requesting and return
   // failure, so do the same thing here. The empty file should not expire with
   // the usual filtering process to avoid repeated background requests, which
   // can cause unwanted high CPU, network and memory usage - Bug 1384094
   try {
     await lazy.PageThumbs._store(url, url, null, true);
   } catch (err) {
     // Probably failed to create the empty file, but not much more we can do.
   }
   return null;
 },

 /**
  * Checks if all the open windows are private browsing windows. If so, we do not
  * want to collect screenshots. If there exists at least 1 non-private window,
  * we are ok to collect screenshots.
  */
 _shouldGetScreenshots() {
   for (let win of Services.wm.getEnumerator("navigator:browser")) {
     if (!lazy.PrivateBrowsingUtils.isWindowPrivate(win)) {
       // As soon as we encounter 1 non-private window, screenshots are fair game.
       return true;
     }
   }
   return false;
 },

 /**
  * Conditionally get a screenshot for a link if there's no existing pending
  * screenshot. Updates the cached link's desired property with the result.
  *
  * @param link {object} Link object to update
  * @param url {string} Url to get a screenshot of
  * @param property {string} Name of property on object to set
  @ @param onScreenshot {function} Callback for when the screenshot loads
  */
 async maybeCacheScreenshot(link, url, property, onScreenshot) {
   // If there are only private windows open, do not collect screenshots
   if (!this._shouldGetScreenshots()) {
     return;
   }
   // __sharedCache may not exist yet for links from default top sites that
   // don't have a default tippy top icon.
   if (!link.__sharedCache) {
     link.__sharedCache = {
       updateLink(prop, val) {
         link[prop] = val;
       },
     };
   }
   const cache = link.__sharedCache;
   // Nothing to do if we already have a pending screenshot or
   // if a previous request failed and returned null.
   if (cache.fetchingScreenshot || link[property] !== undefined) {
     return;
   }

   // Save the promise to the cache so other links get it immediately
   cache.fetchingScreenshot = this.getScreenshotForURL(url);

   // Clean up now that we got the screenshot
   const screenshot = await cache.fetchingScreenshot;
   delete cache.fetchingScreenshot;

   // Update the cache for future links and call back for existing content
   cache.updateLink(property, screenshot);
   onScreenshot(screenshot);
 },
};