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

chrome/browser/resources/ntp4/page_list_view.js

Index: chrome/browser/resources/ntp4/page_list_view.js
diff --git a/chrome/browser/resources/ntp4/page_list_view.js b/chrome/browser/resources/ntp4/page_list_view.js
index abe3e826560524b9caf20477d9d7d250cedb14ae..8040a9e43a8c7ffc23e560c8ef3569a287e5cba7 100644
--- a/chrome/browser/resources/ntp4/page_list_view.js
+++ b/chrome/browser/resources/ntp4/page_list_view.js
@@ -181,7 +181,22 @@ cr.define('ntp', function() {
       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',