RFR: 8370729: Precision errors in Marlin 0.9.4.6 can cause rendering errors [v2]

Fri Jan 16 18:55:06 UTC 2026

On Thu, 15 Jan 2026 11:18:37 GMT, Laurent Bourgès <lbourges at openjdk.org> wrote:

>> merged changes with Java2D bug JDK-8341381 (trivial port on src only)
>> 
>> See https://github.com/openjdk/jdk/commit/46c23bb1a252916096876c2ae3a72f4a525dd6f9
>
> Laurent Bourgès has updated the pull request incrementally with one additional commit since the last revision:
> 
>   made Helpers.ulp public to fix compilation

The tricky part in this test consists in falling in magic cubic values depending on scale & viewport... that should be reproduced as in the gif case.
I will try capturing a failing cubic value in marlin2d to draw it exactly with javafx (same exact coefficients) ...
It will take me spare time so this PR can be back to draft.

> I came up with what I think is an equivalent of the Main.java in https://bugs.openjdk.org/browse/JDK-8341381
> 
> I noticed that the shapes do not correspond to the GIF in the ticket - the curves in the bug form a text outline, whereas the GIF shows something else. Not sure if important.
> 
> What's important is that I cannot reproduce the issue with the latest master branch.
> 
> Please use the latest monkey tester from https://github.com/andy-goryachev-oracle/MonkeyTest
> 
> select the Shape page and set the properties according to the screenshot: <img alt="Screenshot 2026-01-16 at 09 27 59" width="1145" height="866" src="https://private-user-images.githubusercontent.com/107069028/536927849-2a177f43-a1ca-4c11-8a8d-57fe7dfcb4a5.png?jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJnaXRodWIuY29tIiwiYXVkIjoicmF3LmdpdGh1YnVzZXJjb250ZW50LmNvbSIsImtleSI6ImtleTUiLCJleHAiOjE3Njg1ODk0ODgsIm5iZiI6MTc2ODU4OTE4OCwicGF0aCI6Ii8xMDcwNjkwMjgvNTM2OTI3ODQ5LTJhMTc3ZjQzLWExY2EtNGMxMS04YThkLTU3ZmU3ZGZjYjRhNS5wbmc_WC1BbXotQWxnb3JpdGhtPUFXUzQtSE1BQy1TSEEyNTYmWC1BbXotQ3JlZGVudGlhbD1BS0lBVkNPRFlMU0E1M1BRSzRaQSUyRjIwMjYwMTE2JTJGdXMtZWFzdC0xJTJGczMlMkZhd3M0X3JlcXVlc3QmWC1BbXotRGF0ZT0yMDI2MDExNlQxODQ2MjhaJlgtQW16LUV4cGlyZXM9MzAwJlgtQW16LVNpZ25hdHVyZT0zNzYzYzcxNTdjNmFhZWJlYmE5MGU0MWVjYTA0MWM5MmM4NDkxZmY0NDdkZGVmYjMzOTQ5OTUxNTI1MGYwNGQ5JlgtQW16LVNpZ25lZEhlYWRlcnM9aG9zdCJ9.gXJg8ARqE1-rcBqXTYakaLpm41v6ZtxpByfqXQQfKYA">
> 
> Here is the reproducer part of the code: https://github.com/andy-goryachev-oracle/MonkeyTest/blob/b19d640533b89068644426dcf6aa7f137b4d4334/src/com/oracle/tools/fx/monkey/pages/ShapePage.java#L213
> 
> What am I doing wrong, @bourgesl ?

I will try reproducing this weird scale or extract transformed values to make bad cubics

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PR Comment: https://git.openjdk.org/jfx/pull/2039#issuecomment-3761352904
PR Comment: https://git.openjdk.org/jfx/pull/2039#issuecomment-3761359615