1 files changed, 436 insertions, 0 deletions
diff --git a/webbrowser/modules/BrowserNewTabPreloader.jsm b/webbrowser/modules/BrowserNewTabPreloader.jsm
new file mode 100644
index 0000000..778698f
--- /dev/null
+++ b/webbrowser/modules/BrowserNewTabPreloader.jsm
@@ -0,0 +1,436 @@
+/* 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 = ["BrowserNewTabPreloader"];
+
+const Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.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 NEWTAB_URL = "about:newtab";
+const PREF_BRANCH = "browser.newtab.";
+
+// The interval between swapping in a preload docShell and kicking off the
+// next preload in the background.
+const PRELOADER_INTERVAL_MS = 600;
+// The initial delay before we start preloading our first new tab page. The
+// timer is started after the first 'browser-delayed-startup' has been sent.
+const PRELOADER_INIT_DELAY_MS = 5000;
+// The number of miliseconds we'll wait after we received a notification that
+// causes us to update our list of browsers and tabbrowser sizes. This acts as
+// kind of a damper when too many events are occuring in quick succession.
+const PRELOADER_UPDATE_DELAY_MS = 3000;
+
+const TOPIC_TIMER_CALLBACK = "timer-callback";
+const TOPIC_DELAYED_STARTUP = "browser-delayed-startup-finished";
+const TOPIC_XUL_WINDOW_CLOSED = "xul-window-destroyed";
+
+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.BrowserNewTabPreloader = {
+  init: function Preloader_init() {
+    Initializer.start();
+  },
+
+  uninit: function Preloader_uninit() {
+    Initializer.stop();
+    HostFrame.destroy();
+    Preferences.uninit();
+    HiddenBrowsers.uninit();
+  },
+
+  newTab: function Preloader_newTab(aTab) {
+    let win = aTab.ownerDocument.defaultView;
+    if (win.gBrowser) {
+      let utils = win.QueryInterface(Ci.nsIInterfaceRequestor)
+                     .getInterface(Ci.nsIDOMWindowUtils);
+
+      let {width, height} = utils.getBoundsWithoutFlushing(win.gBrowser);
+      let hiddenBrowser = HiddenBrowsers.get(width, height)
+      if (hiddenBrowser) {
+        return hiddenBrowser.swapWithNewTab(aTab);
+      }
+    }
+
+    return false;
+  }
+};
+
+Object.freeze(BrowserNewTabPreloader);
+
+var Initializer = {
+  _timer: null,
+  _observing: false,
+
+  start: function Initializer_start() {
+    Services.obs.addObserver(this, TOPIC_DELAYED_STARTUP, false);
+    this._observing = true;
+  },
+
+  stop: function Initializer_stop() {
+    this._timer = clearTimer(this._timer);
+
+    if (this._observing) {
+      Services.obs.removeObserver(this, TOPIC_DELAYED_STARTUP);
+      this._observing = false;
+    }
+  },
+
+  observe: function Initializer_observe(aSubject, aTopic, aData) {
+    if (aTopic == TOPIC_DELAYED_STARTUP) {
+      Services.obs.removeObserver(this, TOPIC_DELAYED_STARTUP);
+      this._observing = false;
+      this._startTimer();
+    } else if (aTopic == TOPIC_TIMER_CALLBACK) {
+      this._timer = null;
+      this._startPreloader();
+    }
+  },
+
+  _startTimer: function Initializer_startTimer() {
+    this._timer = createTimer(this, PRELOADER_INIT_DELAY_MS);
+  },
+
+  _startPreloader: function Initializer_startPreloader() {
+    Preferences.init();
+    if (Preferences.enabled) {
+      HiddenBrowsers.init();
+    }
+  }
+};
+
+var Preferences = {
+  _enabled: null,
+  _branch: null,
+
+  get enabled() {
+    if (this._enabled === null) {
+      this._enabled = this._branch.getBoolPref("preload") &&
+                      !this._branch.prefHasUserValue("url");
+    }
+
+    return this._enabled;
+  },
+
+  init: function Preferences_init() {
+    this._branch = Services.prefs.getBranch(PREF_BRANCH);
+    this._branch.addObserver("", this, false);
+  },
+
+  uninit: function Preferences_uninit() {
+    if (this._branch) {
+      this._branch.removeObserver("", this);
+      this._branch = null;
+    }
+  },
+
+  observe: function Preferences_observe() {
+    let prevEnabled = this._enabled;
+    this._enabled = null;
+
+    if (prevEnabled && !this.enabled) {
+      HiddenBrowsers.uninit();
+    } else if (!prevEnabled && this.enabled) {
+      HiddenBrowsers.init();
+    }
+  },
+};
+
+var HiddenBrowsers = {
+  _browsers: null,
+  _updateTimer: null,
+
+  _topics: [
+    TOPIC_DELAYED_STARTUP,
+    TOPIC_XUL_WINDOW_CLOSED
+  ],
+
+  init: function () {
+    this._browsers = new Map();
+    this._updateBrowserSizes();
+    this._topics.forEach(t => Services.obs.addObserver(this, t, false));
+  },
+
+  uninit: function () {
+    if (this._browsers) {
+      this._topics.forEach(t => Services.obs.removeObserver(this, t, false));
+      this._updateTimer = clearTimer(this._updateTimer);
+
+      for (let [key, browser] of this._browsers) {
+        browser.destroy();
+      }
+      this._browsers = null;
+    }
+  },
+
+  get: function (width, height) {
+    // We haven't been initialized, yet.
+    if (!this._browsers) {
+      return null;
+    }
+
+    let key = width + "x" + height;
+    if (!this._browsers.has(key)) {
+      // Update all browsers' sizes if we can't find a matching one.
+      this._updateBrowserSizes();
+    }
+
+    // We should now have a matching browser.
+    if (this._browsers.has(key)) {
+      return this._browsers.get(key);
+    }
+
+    // We should never be here. Return the first browser we find.
+    Cu.reportError("NewTabPreloader: no matching browser found after updating");
+    for (let [size, browser] of this._browsers) {
+      return browser;
+    }
+
+    // We should really never be here.
+    Cu.reportError("NewTabPreloader: not even a single browser was found?");
+    return null;
+  },
+
+  observe: function (subject, topic, data) {
+    if (topic === TOPIC_TIMER_CALLBACK) {
+      this._updateTimer = null;
+      this._updateBrowserSizes();
+    } else {
+      this._updateTimer = clearTimer(this._updateTimer);
+      this._updateTimer = createTimer(this, PRELOADER_UPDATE_DELAY_MS);
+    }
+  },
+
+  _updateBrowserSizes: function () {
+    let sizes = this._collectTabBrowserSizes();
+    let toRemove = [];
+
+    // Iterate all browsers and check that they
+    // each can be assigned to one of the sizes.
+    for (let [key, browser] of this._browsers) {
+      if (sizes.has(key)) {
+        // We already have a browser for that size, great!
+        sizes.delete(key);
+      } else {
+        // This browser is superfluous or needs to be resized.
+        toRemove.push(browser);
+        this._browsers.delete(key);
+      }
+    }
+
+    // Iterate all sizes that we couldn't find a browser for.
+    for (let [key, {width, height}] of sizes) {
+      let browser;
+      if (toRemove.length) {
+        // Let's just resize one of the superfluous
+        // browsers and put it back into the map.
+        browser = toRemove.shift();
+        browser.resize(width, height);
+      } else {
+        // No more browsers to reuse, create a new one.
+        browser = new HiddenBrowser(width, height);
+      }
+
+      this._browsers.set(key, browser);
+    }
+
+    // Finally, remove all browsers we don't need anymore.
+    toRemove.forEach(b => b.destroy());
+  },
+
+  _collectTabBrowserSizes: function () {
+    let sizes = new Map();
+
+    function tabBrowserBounds() {
+      let wins = Services.ww.getWindowEnumerator("navigator:browser");
+      while (wins.hasMoreElements()) {
+        let win = wins.getNext();
+        if (win.gBrowser) {
+          let utils = win.QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIDOMWindowUtils);
+          yield utils.getBoundsWithoutFlushing(win.gBrowser);
+        }
+      }
+    }
+
+    // Collect the sizes of all <tabbrowser>s out there.
+    for (let {width, height} of tabBrowserBounds()) {
+      if (width > 0 && height > 0) {
+        let key = width + "x" + height;
+        if (!sizes.has(key)) {
+          sizes.set(key, {width: width, height: height});
+        }
+      }
+    }
+
+    return sizes;
+  }
+};
+
+function HiddenBrowser(width, height) {
+  this.resize(width, height);
+
+  HostFrame.get().then(aFrame => {
+    let doc = aFrame.document;
+    this._browser = doc.createElementNS(XUL_NS, "browser");
+    this._browser.setAttribute("type", "content");
+    this._browser.setAttribute("src", NEWTAB_URL);
+    this._applySize();
+    doc.getElementById("win").appendChild(this._browser);
+  });
+}
+
+HiddenBrowser.prototype = {
+  _width: null,
+  _height: null,
+  _timer: null,
+  _needsFrameScripts: true,
+
+  get isPreloaded() {
+    return this._browser &&
+           this._browser.contentDocument &&
+           this._browser.contentDocument.readyState === "complete" &&
+           this._browser.currentURI.spec === NEWTAB_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.
+    if (this._needsFrameScripts) {
+      this._needsFrameScripts = false;
+
+      let mm = aTab.linkedBrowser.messageManager;
+      mm.loadFrameScript("chrome://browser/content/content.js", true);
+      mm.loadFrameScript("chrome://browser/content/content-sessionStore.js", true);
+
+      if ("TabView" in win) {
+        mm.loadFrameScript("chrome://browser/content/tabview-content.js", true);
+      }
+    }
+
+    // Start a timer that will kick off preloading the next newtab page.
+    this._timer = createTimer(this, PRELOADER_INTERVAL_MS);
+
+    // Signal that we swapped docShells.
+    return true;
+  },
+
+  observe: function () {
+    this._timer = null;
+
+    // Start pre-loading the new tab page.
+    this._browser.loadURI(NEWTAB_URL);
+  },
+
+  resize: function (width, height) {
+    this._width = width;
+    this._height = height;
+    this._applySize();
+  },
+
+  _applySize: function () {
+    if (this._browser) {
+      this._browser.style.width = this._width + "px";
+      this._browser.style.height = this._height + "px";
+    }
+  },
+
+  destroy: function () {
+    if (this._browser) {
+      this._browser.remove();
+      this._browser = null;
+    }
+
+    this._timer = clearTimer(this._timer);
+  }
+};
+
+var 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);
+    }
+  }
+};