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diff --git a/browser/components/newtab/lib/Screenshots.sys.mjs b/browser/components/newtab/lib/Screenshots.sys.mjs
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+/* 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);
+ },
+};