On Mon, 7 Sep 2020 17:54:31 GMT, Jose Pereda <jper...@openjdk.org> wrote:

> This PR fixes an issue that happens when adding new items to a `TableView` or 
> any other control that uses
> `VirtualFlow`, if the scroll position is not 0: the virtual flow is slightly 
> shifted down.
> For instance, let's say that a cell has a layoutY of -10.0. After adding a 
> new item to the table, during the layout
> pass the new value is initially modified to -9.999999999999996 
> (`VirtualFlow::adjustByPixelAmount`) , and then, after
> calling `VirtualFlow::positionCell` (that uses `snapSizeY(position)`) the 
> layoutY is modified to -9.5, causing an
> undesired positive shift of 0.5 pixels.  `Region` has different snap methods: 
>  `snapSizeX/Y` are used to snap node
> dimension values, like width or height, by ceiling to the nearest pixel 
> (which explains the -9.5 value), while
> `snapSpaceX/Y` are used to snap position values like insets, by rounding to 
> the nearest pixel (this will give the
> expected -10.0).   Therefore, this PR modifies `VirtualFlow::positionCell` to 
> use the `snapSpaceX/Y` methods, since
> these are being used to set the layout of the cell and not its size.  Test: A 
> unity test has been included. It
> simulates the case of adding new items to the virtual flow after an initial 
> scroll. It currently fails after adding a
> few items, and it passes with the changes of this PR.

This pull request has now been integrated.

Changeset: 205e4b95
Author:    Jose Pereda <jper...@openjdk.org>
URL:       https://git.openjdk.java.net/jfx/commit/205e4b95
Stats:     24 lines in 2 files changed: 22 ins; 0 del; 2 mod

8178297: TableView scrolls slightly when adding new elements

Reviewed-by: kcr, aghaisas

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PR: https://git.openjdk.java.net/jfx/pull/297

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