RFR: 8349188: LineBorder does not scale correctly [v3]

[Alexey Ivanov]

On Mon, 30 Jun 2025 14:57:34 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

>> And this https://mail.openjdk.org/pipermail/2d-dev/2016-October/007772.html (it has a looong discissuin thread)
>
> @mrserb Putting the discussions aside, does the suggested fix look good to you?
> 
> As I said, border painting uses `clipRound` consistently: both in coordinate calculation and in thickness calculation. This approach resolves the problem reported.
> 
> Looking at descriptions of `clipScale` and `clipRound`, it seems the former suits better… Yet it makes the rendering less consistent with other borders: using `clipScale` switches to 2-pixel and 3-pixel border at 1.50 and 2.50 correspondingly (from 1 and 2 with `clipRound`). In other cases, the border thickness also increases, which may be undesirable.
> 
> Overall, there are 6 failures of the `ScaledLineBorderTest.java` test when the code in JDK uses `clipScale` instead of `clipRound`.

I looked at another test case Rajat and I discussed, and using `clipScale` doesn't help there either. I prefer rendering with `clipRound`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26025#discussion_r2175305371