Integrated: 8089589: [ListView] ScrollBar content moves toward-backward during scrolling.

[Johan Vos]

On Tue, 9 Feb 2021 12:21:28 GMT, Johan Vos <jvos at openjdk.org> wrote:

> This PR introduces a refactory for VirtualFlow, fixing a number of issues reported about inconsistent scrolling speed (see https://bugs.openjdk.java.net/browse/JDK-8089589)
> The problem mentioned in the JBS issue (and in related issues) is that the VirtualFlow implementation depends on cell index and cell count, instead of on pixel count. The latter is unknown when the VirtualFlow is created, and pre-calculating the size of a large set of items would be very expensive.
> Therefore, this PR uses a combination of a gradual calculation of the total size in pixels (estimatedSize) and a smoothing part that prevents the scrollback to scroll in the reverse direction as the requested change.
> This PR currently breaks a number of tests that hard-coded depend on a number of evaluations. This is inherit to the approach of this PR: if we want to estimate the total size, we need to do some additional calculations. In this PR, I try to balance between consistent behavior and performance.

This pull request has now been integrated.

Changeset: 8e547571
Author:    Johan Vos <jvos at openjdk.org>
URL:       https://git.openjdk.java.net/jfx/commit/8e547571
Stats:     570 lines in 6 files changed: 427 ins; 92 del; 51 mod

8089589: [ListView] ScrollBar content moves toward-backward during scrolling.

Reviewed-by: kcr, aghaisas

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PR: https://git.openjdk.java.net/jfx/pull/398