[webkit-dev] Mouse wheel event precision

[Nathan Vander Wilt]

> On Jun 9, 2010, at 3:51 PM, David Hyatt wrote:
>> On Jun 9, 2010, at 2:25 AM, Andy Estes wrote:
>> 
>>> 
>>> On Jun 8, 2010, at 8:34 PM, Nathan Vander Wilt wrote:
>>> 
>>>> What Safari 4 seemed to do was simply provide much greater precision, where scrolling half a line simply yielded about 20 units instead of being ignored. So the above code would yield integral deltas in browsers that only fired events in 3-line increments, but nice fractional deltas in WebKit.
>>> 
>>> Some sites choose to completely ignore wheel deltas less than 120.  On devices like trackpads where a slow but continuous scrolling gesture tends to result in a series of small, non-cumulative mousewheel events, the old behavior caused these gestures to be completely ignored.  Yahoo! Mail was one such site where the small fractional values caused compatibility issues.
>>> 
>>>> What Safari 5's WebKit does is turn one "line" into 4800 (!) units instead of 40.
>>> 
>>> This could be plausible on a trackpad that scales the wheelDelta based on gesture velocity, although I'd expect a value of 120 for each tick of a conventional wheel mouse.  As Peter said, if you have a test case where Safari disagrees with IE on Windows or Chrome on either platform, please file a bug and we'll investigate.
>> 
>> Just a guess, but we might have a regression when dealing with the continuous events generated by a MacBook trackpad.


For those following along at home, looks like this issue is being tracked (and discussed) via https://bugs.webkit.org/show_bug.cgi?id=29601
-nvw