The Tor Browser / file revision

 // -*- Mode: js2; tab-width: 2; indent-tabs-mode: nil; js2-basic-offset: 2; js2-skip-preprocessor-directives: t; -*-

 /* 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/. */

 let Cc = Components.classes;

 let Ci = Components.interfaces;

 let Cu = Components.utils;

 let Cr = Components.results;

 /**

  * Misc. front end utilities for apzc management.

  * the pref: layers.async-pan-zoom.enabled is true.

  */

 var APZCObserver = {

   _debugEvents: false,

   _enabled: false,

   get enabled() {

     return this._enabled;

   },

   init: function() {

     this._enabled = Services.prefs.getBoolPref(kAsyncPanZoomEnabled);

     if (!this._enabled) {

       return;

     }

     let os = Services.obs;

     os.addObserver(this, "apzc-transform-begin", false);

     Elements.tabList.addEventListener("TabSelect", this, true);

     Elements.browsers.addEventListener("pageshow", this, true);

     messageManager.addMessageListener("Content:ZoomToRect", this);

   },

   shutdown: function shutdown() {

     if (!this._enabled) {

       return;

     }

     let os = Services.obs;

     os.removeObserver(this, "apzc-transform-begin");

     Elements.tabList.removeEventListener("TabSelect", this, true);

     Elements.browsers.removeEventListener("pageshow", this, true);

     messageManager.removeMessageListener("Content:ZoomToRect", this);

   },

   handleEvent: function APZC_handleEvent(aEvent) {

     switch (aEvent.type) {

       case 'TabSelect':

         this._resetDisplayPort();

         break;

       case 'pageshow':

         if (aEvent.target != Browser.selectedBrowser.contentDocument) {

           break;

         }

         this._resetDisplayPort();

         break;

     }

   },

   observe: function ao_observe(aSubject, aTopic, aData) {

     if (aTopic == "apzc-transform-begin") {

       // When we're panning, hide the main scrollbars by setting imprecise

       // input (which sets a property on the browser which hides the scrollbar

       // via CSS).  This reduces jittering from left to right. We may be able

       // to get rid of this once we implement axis locking in /gfx APZC.

       if (InputSourceHelper.isPrecise) {

         InputSourceHelper._imprecise();

       }

     }

   },

   receiveMessage: function(aMessage) {

     let json = aMessage.json;

     let browser = aMessage.target;

     switch (aMessage.name) {

       case "Content:ZoomToRect": {

         let { presShellId, viewId } = json;

         let rect = Rect.fromRect(json.rect);

         if (this.isRectZoomedIn(rect, browser.contentViewportBounds)) {

           // If we're already zoomed in, zoom out instead.

           rect = new Rect(0,0,0,0);

         }

         let data = [rect.x, rect.y, rect.width, rect.height, presShellId, viewId].join(",");

         Services.obs.notifyObservers(null, "apzc-zoom-to-rect", data);

       }

     }

   },

   /**

    * Check to see if the area of the rect visible in the viewport is

    * approximately the max area of the rect we can show.

    * Based on code from BrowserElementPanning.js

    */

   isRectZoomedIn: function (aRect, aViewport) {

     let overlap = aViewport.intersect(aRect);

     let overlapArea = overlap.width * overlap.height;

     let availHeight = Math.min(aRect.width * aViewport.height / aViewport.width, aRect.height);

     let showing = overlapArea / (aRect.width * availHeight);

     let ratioW = (aRect.width / aViewport.width);

     let ratioH = (aRect.height / aViewport.height);

     return (showing > 0.9 && (ratioW > 0.9 || ratioH > 0.9));

   },

   _resetDisplayPort: function () {

     // Start off with something reasonable. The apzc will handle these

     // calculations once scrolling starts.

     let doc = Browser.selectedBrowser.contentDocument.documentElement;

     // While running tests, sometimes this can be null. If we don't have a

     // root document, there's no point in setting a scrollable display port.

     if (!doc) {

       return;

     }

     let win = Browser.selectedBrowser.contentWindow;

     let factor = 0.2;

     let portX = 0;

     let portY = 0;

     let portWidth = ContentAreaObserver.width;

     let portHeight = ContentAreaObserver.height;

     if (portWidth < doc.scrollWidth) {

       portWidth += ContentAreaObserver.width * factor;

       if (portWidth > doc.scrollWidth) {

         portWidth = doc.scrollWidth;

       }

     }

     if (portHeight < doc.scrollHeight) {

       portHeight += ContentAreaObserver.height * factor;

       if (portHeight > doc.scrollHeight) {

         portHeight = doc.scrollHeight;

       }

     }

     if (win.scrollX > 0) {

       portX -= ContentAreaObserver.width * factor;

     }

     if (win.scrollY > 0) {

       portY -= ContentAreaObserver.height * factor;

     }

     let cwu = Browser.selectedBrowser.contentWindow

                       .QueryInterface(Ci.nsIInterfaceRequestor)

                       .getInterface(Ci.nsIDOMWindowUtils);

     cwu.setDisplayPortForElement(portX, portY,

                                  portWidth, portHeight,

                                  Browser.selectedBrowser.contentDocument.documentElement,

                                  0);

   }

 };