[Webkit-unassigned] [Bug 228009] Add key-driven smooth scrolling to macOS

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Wed Jul 21 23:06:12 PDT 2021


--- Comment #9 from Tim Horton <thorton at apple.com> ---
Comment on attachment 433969
  --> https://bugs.webkit.org/attachment.cgi?id=433969

View in context: https://bugs.webkit.org/attachment.cgi?id=433969&action=review

>> Source/WebCore/page/EventHandler.cpp:4323
>> +    return view->scrollAnimator().beginKeyboardScrollAnimation(scroll, event);
> Are we always beginning here, or might the animation already be running from a previous event?

It's the beginning /of a scroll/ (or a scroll gesture, or whatever you want to call it), but you're right, the animation might already be running.

>> Source/WebCore/platform/ScrollAnimator.cpp:316
>> +            axesToApplySpring = perpendicularAbsoluteUnitVector(direction);
> Why is anything happening on the perpendicular axis? Wouldn't a keyboard scroll just be on one axis?

(It took me a while to re-figure this out: while the key is down, the spring is not engaged in the axis of scrolling motion (instead, the force comes from the key), but we still want to let previous animations that might have stretched the string perpendicular to the current animation keep running to completion.)

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