[webkit-dev] Mouse wheel event precision
aestes at apple.com
Wed Jun 9 00:25:54 PDT 2010
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.
More information about the webkit-dev