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";

 const { classes: Cc, interfaces: Ci, utils: Cu } = Components;

 this.EXPORTED_SYMBOLS = [ "switchToFloatingScrollbars", "switchToNativeScrollbars" ];

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

 let URL = Services.io.newURI("chrome://browser/skin/devtools/floating-scrollbars.css", null, null);

 let trackedTabs = new WeakMap();

 /**

  * Switch to floating scrollbars, à la mobile.

  *

  * @param aTab the targeted tab.

  *

  */

 this.switchToFloatingScrollbars = function switchToFloatingScrollbars(aTab) {

   let mgr = trackedTabs.get(aTab);

   if (!mgr) {

     mgr = new ScrollbarManager(aTab);

   }

   mgr.switchToFloating();

 }

 /**

  * Switch to original native scrollbars.

  *

  * @param aTab the targeted tab.

  *

  */

 this.switchToNativeScrollbars = function switchToNativeScrollbars(aTab) {

   let mgr = trackedTabs.get(aTab);

   if (mgr) {

     mgr.reset();

   }

 }

 function ScrollbarManager(aTab) {

   trackedTabs.set(aTab, this);

   this.attachedTab = aTab;

   this.attachedBrowser = aTab.linkedBrowser;

   this.reset = this.reset.bind(this);

   this.switchToFloating = this.switchToFloating.bind(this);

   this.attachedTab.addEventListener("TabClose", this.reset, true);

   this.attachedBrowser.addEventListener("DOMContentLoaded", this.switchToFloating, true);

 }

 ScrollbarManager.prototype = {

   get win() {

     return this.attachedBrowser.contentWindow;

   },

   /*

    * Change the look of the scrollbars.

    */

   switchToFloating: function() {

     let windows = this.getInnerWindows(this.win);

     windows.forEach(this.injectStyleSheet);

     this.forceStyle();

   },

   /*

    * Reset the look of the scrollbars.

    */

   reset: function() {

     let windows = this.getInnerWindows(this.win);

     windows.forEach(this.removeStyleSheet);

     this.forceStyle(this.attachedBrowser);

     this.attachedBrowser.removeEventListener("DOMContentLoaded", this.switchToFloating, true);

     this.attachedTab.removeEventListener("TabClose", this.reset, true);

     trackedTabs.delete(this.attachedTab);

   },

   /*

    * Toggle the display property of the window to force the style to be applied.

    */

   forceStyle: function() {

     let parentWindow = this.attachedBrowser.ownerDocument.defaultView;

     let display = parentWindow.getComputedStyle(this.attachedBrowser).display; // Save display value

     this.attachedBrowser.style.display = "none";

     parentWindow.getComputedStyle(this.attachedBrowser).display; // Flush

     this.attachedBrowser.style.display = display; // Restore

   },

   /*

    * return all the window objects present in the hiearchy of a window.

    */

   getInnerWindows: function(win) {

     let iframes = win.document.querySelectorAll("iframe");

     let innerWindows = [];

     for (let iframe of iframes) {

       innerWindows = innerWindows.concat(this.getInnerWindows(iframe.contentWindow));

     }

     return [win].concat(innerWindows);

   },

   /*

    * Append the new scrollbar style.

    */

   injectStyleSheet: function(win) {

     let winUtils = win.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);

     try {

       winUtils.loadSheet(URL, win.AGENT_SHEET);

     }catch(e) {}

   },

   /*

    * Remove the injected stylesheet.

    */

   removeStyleSheet: function(win) {

     let winUtils = win.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);

     try {

       winUtils.removeSheet(URL, win.AGENT_SHEET);

     }catch(e) {}

   },

 }