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List:       openjdk-openjfx-dev
Subject:    Re: RFR: 8323511 Scrollbar Click jumps inconsistent amount of pixels
From:       Marius Hanl <mhanl () openjdk ! org>
Date:       2024-03-31 14:27:37
Message-ID: PcJoJJIef_8Y2x9YCe9DK11BBNcpz7UF-gs2G53IssQ=.fecba87a-14c0-44fe-b3a1-798f3997587c () github ! com
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On Thu, 11 Jan 2024 12:17:11 GMT, Marius Hanl <mhanl@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
> 
> Agree, with all the tests added, especially in this area in \
> https://github.com/openjdk/jfx/pull/1194 and in \
> https://github.com/openjdk/jfx/pull/1246, it is much easier for us to catch \
> regression. I will also have a look in the next days. I also noted that I got weird \
> scrolling behaviour once before, but could never reproduce it.

> The suggested patch changes the conceptual idea of `VirtualFlow.scrollTo(int \
> index)` where a negative index is not specified (this is probably what @Maran23 \
> asked at [#1326 (comment)](https://github.com/openjdk/jfx/pull/1326#discussion_r1530233902) \
> .

Yes, this is exactly what I mean and where I do not know if this is the right \
approach.

> The way the scrollTo(int index) is modified doesn't sound right to me

Agree, it sounds somewhat weird to me that when `scrollTo` is called with index = -1, \
that means we just scroll up more gradually (not to the top of the cell).

> If the latter is the preferred case, this looks to a behavior that is more similar \
> to the Event that is received when the mousewheel is used (and which invokes \
> VirtualFlow.scrollPixels(double delta))

I completely agree. This sounds like we may should call `scrollPixels`  directly \
instead. As @johanvos mentioned, we also need to change the "specification" in the \
comment at least.

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

PR Comment: https://git.openjdk.org/jfx/pull/1326#issuecomment-2028769290


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