Playing with CRUNCH, literally

Hi all,

I have been experimenting with CRUNCH, and it is exciting! It has
great potential for game dev, because of its performance and easy
deployment. PC, mobile devices, game consoles... even web browsers!

I have written an SDL3 demo that can run natively and in a browser,
using CRUNCH and emscripten to compile Scheme to C to WASM. I could
never get that working with CHICKEN, but it was trivial with CRUNCH.
This makes it super easy to deploy games for game jams, etc.

You can see the demo running in your browser:

   https://croisant.net/projects/crunch-sdl3-demo/demo.html

And get the annotated source code, with build instructions:

   https://croisant.net/projects/crunch-sdl3-demo/demo.scm

I plan to develop CRUNCH bindings to SDL3 and several other game
libraries. I have already been working on CHICKEN bindings to those
libraries, which I still plan to finish, because CHICKEN offers some
advantages like interactive coding and debugging. The goal would be
for the APIs to be compatible as much as possible, so people can
develop using CHICKEN then deploy using CRUNCH, with minimal porting.

I do have a small-ish feature request for CRUNCH, which would enable
me to share code across CHICKEN and CRUNCH, instead of needing to
maintain separate codebases. That is the ability to define type
aliases, as with CHICKEN's define-type or define-foreign-type.

In CHICKEN, I wrap struct pointers in records, for type checking and
safety. In CRUNCH, I just use bare struct pointers, because CRUNCH and
the C compiler both do type checking already. So I could conditionally
define corresponding type aliases like this:

   (cond-expand
    (crunched
     (define-type SDL_Window* (pointer (typename SDL_Window))))
    (else
     (define-type SDL_Window* (struct window))
     (define-foreign-type SDL_Window*
                          (c-pointer "SDL_Window")
                          unwrap-window
                          wrap-window)))

After that it's just a matter of adjusting my helper macros to
conditionally expand to c-external instead of foreign-lambda, c-value
instead of foreign-value, etc. And voila, 80% of my existing code
suddenly works in CRUNCH, verbatim or with only minor tweaks.

I have a wishlist of other small CRUNCH features that would make FFI
easier in CRUNCH, but type aliases would be... a game changer. B-)

If there is anything I can do to help make this a reality, I'm happy
to lend a hand!

- John Croisant