The Tor Browser / file revision

 /* 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/. */

 "use strict";

 this.EXPORTED_SYMBOLS = ["CustomizationTabPreloader"];

 const Cu = Components.utils;

 const Cc = Components.classes;

 const Ci = Components.interfaces;

 Cu.import("resource://gre/modules/Services.jsm");

 Cu.import("resource://gre/modules/Promise.jsm");

 const HTML_NS = "http://www.w3.org/1999/xhtml";

 const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";

 const XUL_PAGE = "data:application/vnd.mozilla.xul+xml;charset=utf-8,<window%20id='win'/>";

 const CUSTOMIZATION_URL = "about:customizing";

 // The interval between swapping in a preload docShell and kicking off the

 // next preload in the background.

 const PRELOADER_INTERVAL_MS = 600;

 function createTimer(obj, delay) {

   let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);

   timer.init(obj, delay, Ci.nsITimer.TYPE_ONE_SHOT);

   return timer;

 }

 function clearTimer(timer) {

   if (timer) {

     timer.cancel();

   }

   return null;

 }

 this.CustomizationTabPreloader = {

   uninit: function () {

     CustomizationTabPreloaderInternal.uninit();

   },

   newTab: function (aTab) {

     return CustomizationTabPreloaderInternal.newTab(aTab);

   },

   /**

    * ensurePreloading starts the preloading of the about:customizing

    * content page. This function is idempotent (until a call to uninit),

    * so multiple calls to it are fine.

    */

   ensurePreloading: function() {

     CustomizationTabPreloaderInternal.ensurePreloading();

   },

 };

 Object.freeze(CustomizationTabPreloader);

 this.CustomizationTabPreloaderInternal = {

   _browser: null,

   uninit: function () {

     HostFrame.destroy();

     if (this._browser) {

       this._browser.destroy();

       this._browser = null;

     }

   },

   newTab: function (aTab) {

     let win = aTab.ownerDocument.defaultView;

     if (win.gBrowser && this._browser) {

       return this._browser.swapWithNewTab(aTab);

     }

     return false;

   },

   ensurePreloading: function () {

     if (!this._browser) {

       this._browser = new HiddenBrowser();

     }

   }

 };

 function HiddenBrowser() {

   this._createBrowser();

 }

 HiddenBrowser.prototype = {

   _timer: null,

   get isPreloaded() {

     return this._browser &&

            this._browser.contentDocument &&

            this._browser.contentDocument.readyState === "complete" &&

            this._browser.currentURI.spec === CUSTOMIZATION_URL;

   },

   swapWithNewTab: function (aTab) {

     if (!this.isPreloaded || this._timer) {

       return false;

     }

     let win = aTab.ownerDocument.defaultView;

     let tabbrowser = win.gBrowser;

     if (!tabbrowser) {

       return false;

     }

     // Swap docShells.

     tabbrowser.swapNewTabWithBrowser(aTab, this._browser);

     // Load all default frame scripts attached to the target window.

     let mm = aTab.linkedBrowser.messageManager;

     let scripts = win.messageManager.getDelayedFrameScripts();

     Array.forEach(scripts, ([script, runGlobal]) => mm.loadFrameScript(script, true, runGlobal));

     // Remove the browser, it will be recreated by a timer.

     this._removeBrowser();

     // Start a timer that will kick off preloading the next page.

     this._timer = createTimer(this, PRELOADER_INTERVAL_MS);

     // Signal that we swapped docShells.

     return true;

   },

   observe: function () {

     this._timer = null;

     // Start pre-loading the customization page.

     this._createBrowser();

   },

   destroy: function () {

     this._removeBrowser();

     this._timer = clearTimer(this._timer);

   },

   _createBrowser: function () {

     HostFrame.get().then(aFrame => {

       let doc = aFrame.document;

       this._browser = doc.createElementNS(XUL_NS, "browser");

       this._browser.setAttribute("type", "content");

       this._browser.setAttribute("src", CUSTOMIZATION_URL);

       this._browser.style.width = "400px";

       this._browser.style.height = "400px";

       doc.getElementById("win").appendChild(this._browser);

     });

   },

   _removeBrowser: function () {

     if (this._browser) {

       this._browser.remove();

       this._browser = null;

     }

   }

 };

 let HostFrame = {

   _frame: null,

   _deferred: null,

   get hiddenDOMDocument() {

     return Services.appShell.hiddenDOMWindow.document;

   },

   get isReady() {

     return this.hiddenDOMDocument.readyState === "complete";

   },

   get: function () {

     if (!this._deferred) {

       this._deferred = Promise.defer();

       this._create();

     }

     return this._deferred.promise;

   },

   destroy: function () {

     if (this._frame) {

       if (!Cu.isDeadWrapper(this._frame)) {

         this._frame.removeEventListener("load", this, true);

         this._frame.remove();

       }

       this._frame = null;

       this._deferred = null;

     }

   },

   handleEvent: function () {

     let contentWindow = this._frame.contentWindow;

     if (contentWindow.location.href === XUL_PAGE) {

       this._frame.removeEventListener("load", this, true);

       this._deferred.resolve(contentWindow);

     } else {

       contentWindow.location = XUL_PAGE;

     }

   },

   _create: function () {

     if (this.isReady) {

       let doc = this.hiddenDOMDocument;

       this._frame = doc.createElementNS(HTML_NS, "iframe");

       this._frame.addEventListener("load", this, true);

       doc.documentElement.appendChild(this._frame);

     } else {

       let flags = Ci.nsIThread.DISPATCH_NORMAL;

       Services.tm.currentThread.dispatch(() => this._create(), flags);

     }

   }

 };