[webkit-dev] Mouse wheel event precision

Peter Kasting pkasting at google.com
Thu Jun 10 18:22:04 PDT 2010

On Thu, Jun 10, 2010 at 12:26 PM, David Hyatt <hyatt at apple.com> wrote:

> Having investigated the original bug and its fix that caused this
> regression,  Safari 4's behavior was correct.  The new behavior is broken.
>  A tiny continuous event in Safari 4 correctly reported values that are
> smaller than one line delta, because that's exactly what was supposed to
> happen in terms of scrolling.

I spent a while today digging into this more deeply.  I believe both
behaviors are wrong, chiefly because both allow the "wheelDelta" amount to
be affected by acceleration, when it shouldn't be.  If we ignore
acceleration, then trunk's behavior (before this was backed out) was to
report a wheelDelta of 120 for one scroll wheel tick, which is correct,
while Safari 4 reported a delta of 3, which is wrong.  Of course,
acceleration results in "120" rapidly blowing up into the 7000 range during
more rapid scrolling, which is also wrong.

I've commented in slightly more detail on
https://bugs.webkit.org/show_bug.cgi?id=29601 .

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