Mac: Prevent NTP mousewheel events from being suppressed on Lion.

chrome/browser/resources/ntp4/page_list_view.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview PageListView implementation.
  * PageListView manages page list, dot list, switcher buttons and handles apps
  * pages callbacks from backend.
  *
  * Note that you need to have AppLauncherHandler in your WebUI to use this code.
@@ skipping 163 matching lines @@
         e.preventDefault();
       }, true);
 
       this.tilePages = this.pageList.getElementsByClassName('tile-page');
       this.appsPages = this.pageList.getElementsByClassName('apps-page');
 
       // Initialize the cardSlider without any cards at the moment
       this.sliderFrame = cardSliderFrame;
       this.cardSlider = new cr.ui.CardSlider(this.sliderFrame, this.pageList,
           this.sliderFrame.offsetWidth);
-      this.cardSlider.initialize();
+
+      // Attaching *any* listener for mousewheel will prevent two-finger swipe

[Nico, 2012/04/17 23:22:35]

Only if the listener does event.preventDefault(), right?

[Patrick Dubroy, 2012/04/18 14:43:06]

Hmmm, you're right. I had a test that I thought showed that having any attached
handler would do it, but you're right -- only if it calls
event.preventDefault().

+      // gestures on Mac OS from working, so don't add the listeners if that
+      // feature is enabled.
+      var ignoreMouseWheelEvents =
+          templateData.isSwipeTrackingFromScrollEventsEnabled;
+      this.cardSlider.initialize(ignoreMouseWheelEvents);
+
+      // Handle mousewheel events anywhere in the card slider, so that wheel
+      // events on the page switchers will still scroll the page.
+      if (!ignoreMouseWheelEvents) {
+        var cardSlider = this.cardSlider;
+        cardSliderFrame.addEventListener('mousewheel', function(e) {
+          cardSlider.currentCardValue.handleMouseWheel(e);
+        });
+      }
 
       // Handle events from the card slider.
       this.pageList.addEventListener('cardSlider:card_changed',
                                      this.onCardChanged_.bind(this));
       this.pageList.addEventListener('cardSlider:card_added',
                                      this.onCardAdded_.bind(this));
       this.pageList.addEventListener('cardSlider:card_removed',
                                      this.onCardRemoved_.bind(this));
 
       // Ensure the slider is resized appropriately with the window
@@ skipping 526 matching lines @@
       if (page.navigationDot)
         page.navigationDot.remove(opt_animate);
       this.cardSlider.removeCard(page);
     },
   };
 
   return {
     PageListView: PageListView
   };
 });