RFR: 8264999: GeneralPath.lineTo() to itself produces jagged lines [v4]

[Laurent Bourgès]

On Fri, 10 Jun 2022 01:24:48 GMT, Jeremy <duke at openjdk.java.net> wrote:

>> Previously when you drew a line that moved exactly (+0, +0) with a miter stroke the Stroker class acted like a horizontal miter was appropriate. Now we abort instead, so no miter is applied.
>> 
>> The new unit test tests the original steps plus several variations.
>> 
>> I'm a little nervous about this change because it looks like someone previously considered this exact condition and implemented a different behavior. I don't think I understand the original rationale.
>
> Jeremy has updated the pull request incrementally with one additional commit since the last revision:
> 
>   JDK-8264999: GeneralPath.lineTo() to itself produces jagged lines
>   
>   Revising failing (commented out) scenarios.

Concerning the test cases where the expected output is unknown, we could test java2d pipeline without antialiasing (not marlin renderer) or compare with other svg renderers like browsers or image magick (linux). 
Reference images could be generated by other tools and loaded as png images ?

Finally it is possible to compare with former Ductus AA renderer if tests are run on oracle jdk8.

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PR: https://git.openjdk.org/jdk/pull/8943