michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: "use strict";
michael@0: 
michael@0: this.EXPORTED_SYMBOLS = ["BrowserNewTabPreloader"];
michael@0: 
michael@0: const Cu = Components.utils;
michael@0: const Cc = Components.classes;
michael@0: const Ci = Components.interfaces;
michael@0: 
michael@0: Cu.import("resource://gre/modules/Services.jsm");
michael@0: Cu.import("resource://gre/modules/XPCOMUtils.jsm");
michael@0: Cu.import("resource://gre/modules/Promise.jsm");
michael@0: 
michael@0: const HTML_NS = "http://www.w3.org/1999/xhtml";
michael@0: const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
michael@0: const XUL_PAGE = "data:application/vnd.mozilla.xul+xml;charset=utf-8,<window%20id='win'/>";
michael@0: const NEWTAB_URL = "about:newtab";
michael@0: const PREF_BRANCH = "browser.newtab.";
michael@0: 
michael@0: // The interval between swapping in a preload docShell and kicking off the
michael@0: // next preload in the background.
michael@0: const PRELOADER_INTERVAL_MS = 600;
michael@0: // The initial delay before we start preloading our first new tab page. The
michael@0: // timer is started after the first 'browser-delayed-startup' has been sent.
michael@0: const PRELOADER_INIT_DELAY_MS = 5000;
michael@0: // The number of miliseconds we'll wait after we received a notification that
michael@0: // causes us to update our list of browsers and tabbrowser sizes. This acts as
michael@0: // kind of a damper when too many events are occuring in quick succession.
michael@0: const PRELOADER_UPDATE_DELAY_MS = 3000;
michael@0: 
michael@0: const TOPIC_TIMER_CALLBACK = "timer-callback";
michael@0: const TOPIC_DELAYED_STARTUP = "browser-delayed-startup-finished";
michael@0: const TOPIC_XUL_WINDOW_CLOSED = "xul-window-destroyed";
michael@0: 
michael@0: const FRAME_SCRIPT_URL = "chrome://browser/content/newtab/preloaderContent.js";
michael@0: 
michael@0: function createTimer(obj, delay) {
michael@0:   let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
michael@0:   timer.init(obj, delay, Ci.nsITimer.TYPE_ONE_SHOT);
michael@0:   return timer;
michael@0: }
michael@0: 
michael@0: function clearTimer(timer) {
michael@0:   if (timer) {
michael@0:     timer.cancel();
michael@0:   }
michael@0:   return null;
michael@0: }
michael@0: 
michael@0: this.BrowserNewTabPreloader = {
michael@0:   init: function Preloader_init() {
michael@0:     Initializer.start();
michael@0:   },
michael@0: 
michael@0:   uninit: function Preloader_uninit() {
michael@0:     Initializer.stop();
michael@0:     HostFrame.destroy();
michael@0:     Preferences.uninit();
michael@0:     HiddenBrowsers.uninit();
michael@0:   },
michael@0: 
michael@0:   newTab: function Preloader_newTab(aTab) {
michael@0:     let swapped = false;
michael@0:     let win = aTab.ownerDocument.defaultView;
michael@0:     if (win.gBrowser) {
michael@0:       let utils = win.QueryInterface(Ci.nsIInterfaceRequestor)
michael@0:                      .getInterface(Ci.nsIDOMWindowUtils);
michael@0: 
michael@0:       let {width, height} = utils.getBoundsWithoutFlushing(win.gBrowser);
michael@0:       let hiddenBrowser = HiddenBrowsers.get(width, height)
michael@0:       if (hiddenBrowser) {
michael@0:         swapped = hiddenBrowser.swapWithNewTab(aTab);
michael@0:       }
michael@0: 
michael@0:       // aTab's browser is now visible and is therefore allowed to make
michael@0:       // background captures.
michael@0:       let msgMan = aTab.linkedBrowser.messageManager;
michael@0:       msgMan.loadFrameScript(FRAME_SCRIPT_URL, false);
michael@0:       msgMan.sendAsyncMessage("BrowserNewTabPreloader:allowBackgroundCaptures");
michael@0:     }
michael@0: 
michael@0:     return swapped;
michael@0:   }
michael@0: };
michael@0: 
michael@0: Object.freeze(BrowserNewTabPreloader);
michael@0: 
michael@0: let Initializer = {
michael@0:   _timer: null,
michael@0:   _observing: false,
michael@0: 
michael@0:   start: function Initializer_start() {
michael@0:     Services.obs.addObserver(this, TOPIC_DELAYED_STARTUP, false);
michael@0:     this._observing = true;
michael@0:   },
michael@0: 
michael@0:   stop: function Initializer_stop() {
michael@0:     this._timer = clearTimer(this._timer);
michael@0: 
michael@0:     if (this._observing) {
michael@0:       Services.obs.removeObserver(this, TOPIC_DELAYED_STARTUP);
michael@0:       this._observing = false;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   observe: function Initializer_observe(aSubject, aTopic, aData) {
michael@0:     if (aTopic == TOPIC_DELAYED_STARTUP) {
michael@0:       Services.obs.removeObserver(this, TOPIC_DELAYED_STARTUP);
michael@0:       this._observing = false;
michael@0:       this._startTimer();
michael@0:     } else if (aTopic == TOPIC_TIMER_CALLBACK) {
michael@0:       this._timer = null;
michael@0:       this._startPreloader();
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   _startTimer: function Initializer_startTimer() {
michael@0:     this._timer = createTimer(this, PRELOADER_INIT_DELAY_MS);
michael@0:   },
michael@0: 
michael@0:   _startPreloader: function Initializer_startPreloader() {
michael@0:     Preferences.init();
michael@0:     if (Preferences.enabled) {
michael@0:       HiddenBrowsers.init();
michael@0:     }
michael@0:   }
michael@0: };
michael@0: 
michael@0: let Preferences = {
michael@0:   _enabled: null,
michael@0:   _branch: null,
michael@0: 
michael@0:   get enabled() {
michael@0:     if (this._enabled === null) {
michael@0:       this._enabled = this._branch.getBoolPref("preload") &&
michael@0:                       !this._branch.prefHasUserValue("url");
michael@0:     }
michael@0: 
michael@0:     return this._enabled;
michael@0:   },
michael@0: 
michael@0:   init: function Preferences_init() {
michael@0:     this._branch = Services.prefs.getBranch(PREF_BRANCH);
michael@0:     this._branch.addObserver("", this, false);
michael@0:   },
michael@0: 
michael@0:   uninit: function Preferences_uninit() {
michael@0:     if (this._branch) {
michael@0:       this._branch.removeObserver("", this);
michael@0:       this._branch = null;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   observe: function Preferences_observe() {
michael@0:     let prevEnabled = this._enabled;
michael@0:     this._enabled = null;
michael@0: 
michael@0:     if (prevEnabled && !this.enabled) {
michael@0:       HiddenBrowsers.uninit();
michael@0:     } else if (!prevEnabled && this.enabled) {
michael@0:       HiddenBrowsers.init();
michael@0:     }
michael@0:   },
michael@0: };
michael@0: 
michael@0: let HiddenBrowsers = {
michael@0:   _browsers: null,
michael@0:   _updateTimer: null,
michael@0: 
michael@0:   _topics: [
michael@0:     TOPIC_DELAYED_STARTUP,
michael@0:     TOPIC_XUL_WINDOW_CLOSED
michael@0:   ],
michael@0: 
michael@0:   init: function () {
michael@0:     this._browsers = new Map();
michael@0:     this._updateBrowserSizes();
michael@0:     this._topics.forEach(t => Services.obs.addObserver(this, t, false));
michael@0:   },
michael@0: 
michael@0:   uninit: function () {
michael@0:     if (this._browsers) {
michael@0:       this._topics.forEach(t => Services.obs.removeObserver(this, t, false));
michael@0:       this._updateTimer = clearTimer(this._updateTimer);
michael@0: 
michael@0:       for (let [key, browser] of this._browsers) {
michael@0:         browser.destroy();
michael@0:       }
michael@0:       this._browsers = null;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   get: function (width, height) {
michael@0:     // We haven't been initialized, yet.
michael@0:     if (!this._browsers) {
michael@0:       return null;
michael@0:     }
michael@0: 
michael@0:     let key = width + "x" + height;
michael@0:     if (!this._browsers.has(key)) {
michael@0:       // Update all browsers' sizes if we can't find a matching one.
michael@0:       this._updateBrowserSizes();
michael@0:     }
michael@0: 
michael@0:     // We should now have a matching browser.
michael@0:     if (this._browsers.has(key)) {
michael@0:       return this._browsers.get(key);
michael@0:     }
michael@0: 
michael@0:     // We should never be here. Return the first browser we find.
michael@0:     Cu.reportError("NewTabPreloader: no matching browser found after updating");
michael@0:     for (let [size, browser] of this._browsers) {
michael@0:       return browser;
michael@0:     }
michael@0: 
michael@0:     // We should really never be here.
michael@0:     Cu.reportError("NewTabPreloader: not even a single browser was found?");
michael@0:     return null;
michael@0:   },
michael@0: 
michael@0:   observe: function (subject, topic, data) {
michael@0:     if (topic === TOPIC_TIMER_CALLBACK) {
michael@0:       this._updateTimer = null;
michael@0:       this._updateBrowserSizes();
michael@0:     } else {
michael@0:       this._updateTimer = clearTimer(this._updateTimer);
michael@0:       this._updateTimer = createTimer(this, PRELOADER_UPDATE_DELAY_MS);
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   _updateBrowserSizes: function () {
michael@0:     let sizes = this._collectTabBrowserSizes();
michael@0:     let toRemove = [];
michael@0: 
michael@0:     // Iterate all browsers and check that they
michael@0:     // each can be assigned to one of the sizes.
michael@0:     for (let [key, browser] of this._browsers) {
michael@0:       if (sizes.has(key)) {
michael@0:         // We already have a browser for that size, great!
michael@0:         sizes.delete(key);
michael@0:       } else {
michael@0:         // This browser is superfluous or needs to be resized.
michael@0:         toRemove.push(browser);
michael@0:         this._browsers.delete(key);
michael@0:       }
michael@0:     }
michael@0: 
michael@0:     // Iterate all sizes that we couldn't find a browser for.
michael@0:     for (let [key, {width, height}] of sizes) {
michael@0:       let browser;
michael@0:       if (toRemove.length) {
michael@0:         // Let's just resize one of the superfluous
michael@0:         // browsers and put it back into the map.
michael@0:         browser = toRemove.shift();
michael@0:         browser.resize(width, height);
michael@0:       } else {
michael@0:         // No more browsers to reuse, create a new one.
michael@0:         browser = new HiddenBrowser(width, height);
michael@0:       }
michael@0: 
michael@0:       this._browsers.set(key, browser);
michael@0:     }
michael@0: 
michael@0:     // Finally, remove all browsers we don't need anymore.
michael@0:     toRemove.forEach(b => b.destroy());
michael@0:   },
michael@0: 
michael@0:   _collectTabBrowserSizes: function () {
michael@0:     let sizes = new Map();
michael@0: 
michael@0:     function tabBrowserBounds() {
michael@0:       let wins = Services.ww.getWindowEnumerator("navigator:browser");
michael@0:       while (wins.hasMoreElements()) {
michael@0:         let win = wins.getNext();
michael@0:         if (win.gBrowser) {
michael@0:           let utils = win.QueryInterface(Ci.nsIInterfaceRequestor)
michael@0:                          .getInterface(Ci.nsIDOMWindowUtils);
michael@0:           yield utils.getBoundsWithoutFlushing(win.gBrowser);
michael@0:         }
michael@0:       }
michael@0:     }
michael@0: 
michael@0:     // Collect the sizes of all <tabbrowser>s out there.
michael@0:     for (let {width, height} of tabBrowserBounds()) {
michael@0:       if (width > 0 && height > 0) {
michael@0:         let key = width + "x" + height;
michael@0:         if (!sizes.has(key)) {
michael@0:           sizes.set(key, {width: width, height: height});
michael@0:         }
michael@0:       }
michael@0:     }
michael@0: 
michael@0:     return sizes;
michael@0:   }
michael@0: };
michael@0: 
michael@0: function HiddenBrowser(width, height) {
michael@0:   this.resize(width, height);
michael@0:   this._createBrowser();
michael@0: }
michael@0: 
michael@0: HiddenBrowser.prototype = {
michael@0:   _width: null,
michael@0:   _height: null,
michael@0:   _timer: null,
michael@0: 
michael@0:   get isPreloaded() {
michael@0:     return this._browser &&
michael@0:            this._browser.contentDocument &&
michael@0:            this._browser.contentDocument.readyState === "complete" &&
michael@0:            this._browser.currentURI.spec === NEWTAB_URL;
michael@0:   },
michael@0: 
michael@0:   swapWithNewTab: function (aTab) {
michael@0:     if (!this.isPreloaded || this._timer) {
michael@0:       return false;
michael@0:     }
michael@0: 
michael@0:     let win = aTab.ownerDocument.defaultView;
michael@0:     let tabbrowser = win.gBrowser;
michael@0: 
michael@0:     if (!tabbrowser) {
michael@0:       return false;
michael@0:     }
michael@0: 
michael@0:     // Swap docShells.
michael@0:     tabbrowser.swapNewTabWithBrowser(aTab, this._browser);
michael@0: 
michael@0:     // Load all default frame scripts attached to the target window.
michael@0:     let mm = aTab.linkedBrowser.messageManager;
michael@0:     let scripts = win.messageManager.getDelayedFrameScripts();
michael@0:     Array.forEach(scripts, ([script, runGlobal]) => mm.loadFrameScript(script, true, runGlobal));
michael@0: 
michael@0:     // Remove the browser, it will be recreated by a timer.
michael@0:     this._removeBrowser();
michael@0: 
michael@0:     // Start a timer that will kick off preloading the next newtab page.
michael@0:     this._timer = createTimer(this, PRELOADER_INTERVAL_MS);
michael@0: 
michael@0:     // Signal that we swapped docShells.
michael@0:     return true;
michael@0:   },
michael@0: 
michael@0:   observe: function () {
michael@0:     this._timer = null;
michael@0: 
michael@0:     // Start pre-loading the new tab page.
michael@0:     this._createBrowser();
michael@0:   },
michael@0: 
michael@0:   resize: function (width, height) {
michael@0:     this._width = width;
michael@0:     this._height = height;
michael@0:     this._applySize();
michael@0:   },
michael@0: 
michael@0:   destroy: function () {
michael@0:     this._removeBrowser();
michael@0:     this._timer = clearTimer(this._timer);
michael@0:   },
michael@0: 
michael@0:   _applySize: function () {
michael@0:     if (this._browser) {
michael@0:       this._browser.style.width = this._width + "px";
michael@0:       this._browser.style.height = this._height + "px";
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   _createBrowser: function () {
michael@0:     HostFrame.get().then(aFrame => {
michael@0:       let doc = aFrame.document;
michael@0:       this._browser = doc.createElementNS(XUL_NS, "browser");
michael@0:       this._browser.setAttribute("type", "content");
michael@0:       this._browser.setAttribute("src", NEWTAB_URL);
michael@0:       this._applySize();
michael@0:       doc.getElementById("win").appendChild(this._browser);
michael@0:     });
michael@0:   },
michael@0: 
michael@0:   _removeBrowser: function () {
michael@0:     if (this._browser) {
michael@0:       this._browser.remove();
michael@0:       this._browser = null;
michael@0:     }
michael@0:   }
michael@0: };
michael@0: 
michael@0: let HostFrame = {
michael@0:   _frame: null,
michael@0:   _deferred: null,
michael@0: 
michael@0:   get hiddenDOMDocument() {
michael@0:     return Services.appShell.hiddenDOMWindow.document;
michael@0:   },
michael@0: 
michael@0:   get isReady() {
michael@0:     return this.hiddenDOMDocument.readyState === "complete";
michael@0:   },
michael@0: 
michael@0:   get: function () {
michael@0:     if (!this._deferred) {
michael@0:       this._deferred = Promise.defer();
michael@0:       this._create();
michael@0:     }
michael@0: 
michael@0:     return this._deferred.promise;
michael@0:   },
michael@0: 
michael@0:   destroy: function () {
michael@0:     if (this._frame) {
michael@0:       if (!Cu.isDeadWrapper(this._frame)) {
michael@0:         this._frame.removeEventListener("load", this, true);
michael@0:         this._frame.remove();
michael@0:       }
michael@0: 
michael@0:       this._frame = null;
michael@0:       this._deferred = null;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   handleEvent: function () {
michael@0:     let contentWindow = this._frame.contentWindow;
michael@0:     if (contentWindow.location.href === XUL_PAGE) {
michael@0:       this._frame.removeEventListener("load", this, true);
michael@0:       this._deferred.resolve(contentWindow);
michael@0:     } else {
michael@0:       contentWindow.location = XUL_PAGE;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   _create: function () {
michael@0:     if (this.isReady) {
michael@0:       let doc = this.hiddenDOMDocument;
michael@0:       this._frame = doc.createElementNS(HTML_NS, "iframe");
michael@0:       this._frame.addEventListener("load", this, true);
michael@0:       doc.documentElement.appendChild(this._frame);
michael@0:     } else {
michael@0:       let flags = Ci.nsIThread.DISPATCH_NORMAL;
michael@0:       Services.tm.currentThread.dispatch(() => this._create(), flags);
michael@0:     }
michael@0:   }
michael@0: };