RFR: JDK-8313628: Column drag header, overlay and line are not correctly aligned

[Marius Hanl]

On Mon, 14 Aug 2023 18:36:57 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> It probably won't hurt. But since the mismatch is visible even at a normal scale, I didn't bothered to do so.
>
> ... as a safeguard for any possible regressions?

Well, the question is: Is there really something to test? E.g. a lot of `Pane` classes do have quite complext logic to layout their children. 
For `Controls` and their skins, it is a bit easier. `layoutChildren()` does already have the correct snapped coordinates. And as we just use `x` and `y` from it, there is not sooo much benefit of testing scales here. Not sure if we have already, but to test `layoutChildren` with a generic `Control` and with different `Insets` and scales might be better here.
Maybe worth exploring, if there is no test yet.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1193#discussion_r1294946601