Hi, the reason for using C99 is that it is fully compatible with other languages. If you write a library in Rust you might be tempted to use Rust only feature which will then make it hard to wrap the library for other languages. And if you don't use those features from Rust in your library people will comment that your library isn't Rust enough. Same thing applies to C++. To that extent my advice is to write C in C rather than C in Rust or C++.

Also if people don't have a Rust toolchain setup, compiling the library and using it from source would be hard. In some cases integrating Rust in their toolchain could be hard.

Regarding metal and vulkan I will edit the article to mention Vulkan there too alongside metal. Thanks for your feedback.

I suppose wrapping it for other languages can be harder, but should be doable I think. The benefit of Rust though is using a much better language with rich standard library.

As for toolchain, Rust can be set up basically anywhere llvm can, which is quite a lot. There are rare cases where llvm wasn't ported yet to, but I don't think they are enough to make C a compelling option in general, and I don't think any of them are gaming related.

If you are in such case - then sure, but otherwise, I'd still prefer Rust.

I think the Rust standard library is actually a liability in this case, not an advantage. The rust stdlib will essentially be an extra dependency and also the rust standard library doesn't have allocators, so unless you are very careful you might violate the principle of not doing allocations for the user. Also, even if it did have allocators, passing allocators from to Rust via a C interface would probably be awkward.

So if you do choose to make the implementation in another language, there are extra considerations that you have to take into account.