<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 Bylokhov Sergey.Bylokhov at oracle.com
Thu Sep 29 19:18:59 UTC 2016

On 29.09.16 22:08, Sergey Malenkov wrote:
>> 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.

It depends from the application, just checked on the list of emails in 
the Thunderbird which have small "deadzone". I think we should not do 
any magic in this files. only get native event and post it to upper 
level(the int value should be accumulated) And this is responsibility of 
upper level to do some work depending from the MouseWheelEvent.

>>> 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)

This how these component implemented and I think we can change or tweak 
this. If you run SwingSet2 demo on "Scroll Pane Demo" you will see that 
it is possible to scroll per units(every pixel on non-retina/every two 
pixels on the retina).

Best regards, Sergey.

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