chrome/browser/resources/uber/uber_utils.js

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 /**
   6  * @fileoverview A collection of utility methods for UberPage and its contained
   7  *     pages.
   8  */
   9
  10 cr.define('uber', function() {
  11
  12   /**
  13    * Fixed position header elements on the page to be shifted by handleScroll.
  14    * @type {NodeList}
  15    */
  16   var headerElements;
  17
  18   /**
  19    * This should be called by uber content pages when DOM content has loaded.
  20    */
  21   function onContentFrameLoaded() {
  22     headerElements = document.getElementsByTagName('header');
  23     document.addEventListener('scroll', handleScroll);
  24
  25     // Prevent the navigation from being stuck in a disabled state when a
  26     // content page is reloaded while an overlay is visible (crbug.com/246939).
  27     invokeMethodOnParent('stopInterceptingEvents');
  28
  29     // Trigger the scroll handler to tell the navigation if our page started
  30     // with some scroll (happens when you use tab restore).
  31     handleScroll();
  32
  33     window.addEventListener('message', handleWindowMessage);
  34   }
  35
  36   /**
  37    * Handles scroll events on the document. This adjusts the position of all
  38    * headers and updates the parent frame when the page is scrolled.
  39    * @private
  40    */
  41   function handleScroll() {
  42     var scrollLeft = scrollLeftForDocument(document);
  43     var offset = scrollLeft * -1;
  44     for (var i = 0; i < headerElements.length; i++) {
  45       // As a workaround for http://crbug.com/231830, set the transform to
  46       // 'none' rather than 0px.
  47       headerElements[i].style.webkitTransform = offset ?
  48           'translateX(' + offset + 'px)' : 'none';
  49     }
  50
  51     invokeMethodOnParent('adjustToScroll', scrollLeft);
  52   };
  53
  54   /**
  55    * Handles 'message' events on window.
  56    * @param {Event} e The message event.
  57    */
  58   function handleWindowMessage(e) {
  59     if (e.data.method === 'frameSelected')
  60       handleFrameSelected();
  61     else if (e.data.method === 'mouseWheel')
  62       handleMouseWheel(e.data.params);
  63   }
  64
  65   /**
  66    * This is called when a user selects this frame via the navigation bar
  67    * frame (and is triggered via postMessage() from the uber page).
  68    * @private
  69    */
  70   function handleFrameSelected() {
  71     setScrollTopForDocument(document, 0);
  72   }
  73
  74   /**
  75    * Called when a user mouse wheels (or trackpad scrolls) over the nav frame.
  76    * The wheel event is forwarded here and we scroll the body.
  77    * There's no way to figure out the actual scroll amount for a given delta.
  78    * It differs for every platform and even initWebKitWheelEvent takes a
  79    * pixel amount instead of a wheel delta. So we just choose something
  80    * reasonable and hope no one notices the difference.
  81    * @param {Object} params A structure that holds wheel deltas in X and Y.
  82    */
  83   function handleMouseWheel(params) {
  84     window.scrollBy(-params.deltaX * 49 / 120, -params.deltaY * 49 / 120);
  85   }
  86
  87   /**
  88    * Invokes a method on the parent window (UberPage). This is a convenience
  89    * method for API calls into the uber page.
  90    * @param {string} method The name of the method to invoke.
  91    * @param {Object=} opt_params Optional property bag of parameters to pass to
  92    *     the invoked method.
  93    * @private
  94    */
  95   function invokeMethodOnParent(method, opt_params) {
  96     if (window.location == window.parent.location)
  97       return;
  98
  99     invokeMethodOnWindow(window.parent, method, opt_params, 'chrome://chrome');
 100   }
 101
 102   /**
 103    * Invokes a method on the target window.
 104    * @param {string} method The name of the method to invoke.
 105    * @param {Object=} opt_params Optional property bag of parameters to pass to
 106    *     the invoked method.
 107    * @param {string=} opt_url The origin of the target window.
 108    * @private
 109    */
 110   function invokeMethodOnWindow(targetWindow, method, opt_params, opt_url) {
 111     var data = {method: method, params: opt_params};
 112     targetWindow.postMessage(data, opt_url ? opt_url : '*');
 113   }
 114
 115   return {
 116     invokeMethodOnParent: invokeMethodOnParent,
 117     invokeMethodOnWindow: invokeMethodOnWindow,
 118     onContentFrameLoaded: onContentFrameLoaded,
 119   };
 120 });