<AWT Dev> [9] Review request for 8166591 [macos 10.12] Trackpad scrolling of text on OS X 10.12 Sierra is very fast (Trackpad, Retina only)

[Sergey Malenkov]

>> Look at the following scenario:
>> - Perform slow and short scroll gesture
>> - Accumulator is less than threshold
>> - All wheel events during this gesture has wheelRotation=0
>> - Nothing is scrolled actually.
>> - Repeat several such gestures - nothing is scrolled
>
> Just to clarify, if you perform slow scroll gesture and the accumulator will
> be less than threshold means that you should not scroll, no? Because the sum
> of overall scroll events are less than one line. The fact that you need to
> "move a certain minimum distance before the scroll takes effect" is OSX bug,
> I wonder how the native app works, do they have the same "deadzone"?

Native apps support per-pixel scrolling, so their "deadzone" is 10 times less.

>> So I suggest to process the phase end to align accumulated value.
>> It adds an ability to scroll with short scroll gesture.
>> If you align accumulated value to bigger integer,
>> it also aligns scrolled lines automatically
>> when we support per-pixel scrolling.
>
> Per pixel scrolling should depend from the preciseWheelRotation, otherwise
> on the retina display you will be able to scroll only by the units(2
> pixels).

In Java lists and trees a unit is a line (~12 or ~24 pixels)

-- 
Best regards,
Sergey A. Malenkov