RFR: 8323511: Scrollbar Click jumps inconsistent amount of pixels [v8]

[Kevin Rushforth]

On Fri, 17 May 2024 07:28:44 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: Adjust javadoc of VirtualFlow.getViewportLength()

modules/javafx.controls/src/main/java/javafx/scene/control/skin/VirtualFlow.java line 1918:

> 1916:      * Returns the length of the viewport portion of the {@code VirtualFlow} as computed during the layout pass.
> 1917:      * For a vertical flow, this corresponds to the height and for a horizontal flow to the width of the clip view,
> 1918:      * but it does not necessarily have to be the same value.

@johanvos added a question in the CSR about this last  part:

> I understand and agree with the goal behind this.
> 
> I'm a bit confused though about the following: "...but it does not necessarily have to be the same value." -> can you elaborate a bit about this?

I share this concern. I think that removing that last clause and putting a period after "clip view" is probably the best.

Johan: what do you think?

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PR Review Comment: https://git.openjdk.org/jfx/pull/1326#discussion_r1608994568