RFR: 8323511: Scrollbar Click jumps inconsistent amount of pixels [v3]

[eduardsdv]

On Mon, 6 May 2024 08:49:27 GMT, Florian Kirmaier <fkirmaier at openjdk.org> wrote:

>> As seen in the unit test of the PR, when we click on the area above/below the scrollbar the position jumps - but the jump is now not always consistent.
>> In the current version on the last cell - the UI always jumps to the top. In the other cases, the assumed default cell height is used.
>> 
>> With this PR, always the default cell height is used, to determine how much is scrolled.
>> This makes the behavior more consistent.
>> 
>> Especially from the unit-test, it's clear that with this PR the behavior is much more consistent.
>> 
>> This is also related to the following PR: https://github.com/openjdk/jfx/pull/1194
>
> Florian Kirmaier has updated the pull request incrementally with one additional commit since the last revision:
> 
>   JDK-8323511: Fix scrolling when clicking the scrollbar track when only one cell is visible

I added a new method ``VirtualFlow.getBlockIncrement()``, which returns the amount of pixels by which the position of the VirtualFlow should be adjusted when clicking on the scrollbar track.

Now, if only one cell is visible, the ``VirtualScrollBar`` changes the position of the ``VirtualFlow`` simply by calling the VirtualFlow.scrollPixels(double)``.

-------------

PR Comment: https://git.openjdk.org/jfx/pull/1326#issuecomment-2095542279