[Enhancement]: Single jar for both java 21 and java 8

[SmearyThrower]

Description

Making the mod use a single JAR that works on both Java 8 and Java 21 would really help, since players wouldn’t need separate downloads or switch Java versions, and it would also be great for modpack integration because pack creators could rely on one unified file that works smoothly across different setups and launchers.

This is not a bug report

• I confirm that this is not a bug report, and that this issue can be deleted without notice if this is a bug report.

[basdxz]

There are no plans to do this.

The Java 21 version is if you use LWJGL 3, and the Java 8 version is if you don't.
Can you provide concrete examples of where it would be inconvenient to ship either the J8 or J21 jar?

As for the technical reasoning:

As it stands, the Java 8 jar builds against LWJGL 2 while the Java 21 jar builds against LWJGL 3 (with LWJGLify).

Currently the Java 21 version potentially offers better performance as it were compiled against modern Java, and can make use of some more efficient APIs provided by LWJGL 3.

Beddium is based on the Celeritas Core API which itself is built against Java 21 + LWJGL 3 (Since it was based on Embeddium, which targets modern MC that already uses both LWJGL 3 and Java 17+)

We end up having to maintain both a soft-fork of Celeritas that can work with LWJGL2, plus a separate branch to make this work. Our simplest solution would be to ditch the J8 version and only ship J21 with a hard dependency on LWJGL3ify.

As for potential solutions:

We haven't really measured the performance impact, but it may be negligible enough to simply have one release with the Java 8 build. This would be the simplest, albeit 'slowest' option.

Another would be to ship a jar which provides both like you are suggesting, with some sort of magic to load the correct class versions. Or to perform the downgrading patching on the fly. This is more involved but may also allow us to have an automatic downgrader for Celeritas.

[SmearyThrower]

Thanks for the detailed explanation, it definitely helps clarify why the two separate builds exist.