gleam-raylib-sample

Created for learning purposes, just copy what you need!

Tested on:

• Windows 10
• Erlang 26
• Raylib 5
• Gleam 1.0.0
• GCC 10.2.1 (MinGW-W64 x86_64-posix-seh).

GCC 13.x.x did not work for me, throws function not defined inside Erlang's headers.

How to run

1. Clone this repository

2. cd gleam-raylib-sample

3. Compile src/raylib_ffi.cpp to a shared library. Example on Windows:

   g++ -fPIC -shared -o raylib_ffi.dll src\raylib_ffi.cpp -I"C:\Program Files\Erlang OTP\usr\include" -lraylib -lgdi32 -lwinmm
   

4. Run sample code:

   gleam run
   

5. Run asteroids example:

   gleam run -m asteroids
   

How to generate bindings from raylib.h

*Note: In progress. Saves ignored functions in generate_bindings.log.

1. To generate .erl, .gleam and .cpp files:

   gleam run -m generate_bindings
   

   Note: this will overwrite src/raylib.gleam, src/raylib_ffi.erl and src/raylib_ffi.cpp.

2. Compile src/raylib_ffi.cpp to a shared library. Example on Windows:

   g++ -fPIC -shared -o raylib_ffi.dll src\raylib_ffi.cpp -I"C:\Program Files\Erlang OTP\usr\include" -lraylib -lgdi32 -lwinmm
   

3. Run:

   gleam run
   

How it works

To call raylib functions, we need:

• Bindings from C/C++ to raylib: src/raylib_ffi.cpp
• Bindings from Erlang to C: src/raylib_ffi.erl
• Bindings from Gleam to Erlang: src/raylib.gleam

C/C++ to Raylib

See src/raylib_ffi.cpp.

Documentation for Erlang NIF: https://www.erlang.org/doc/man/erl_nif.html

The function definitions follow this convention:

static ERL_NIF_TERM set_target_fps(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
  ...
}

Every function must be exported at the end:

static ErlNifFunc nif_funcs[] =
{
  {"set_target_fps", 1, set_target_fps},
  ...
}

ERL_NIF_INIT(raylib_ffi, nif_funcs, NULL, NULL, NULL, NULL)

raylib_ffi refers to raylib_ffi.erl module's name, I believe.

1 is the arity of the function.

Erlang to C

See src/raylib_ffi.erl.

Erlang NIF works by creating an Erlang module with an init() function. This function is called when Erlang loads the module.

erlang:load_nif replaces the definitions of all functions mentioned in -nifs([ ... ]). with code to call the C functions.

-export([
  init/0
  ...
]).
-on_load(init/0).

init() ->
  erlang:load_nif("raylib_ffi", 0).

raylib_ffi refers to the name of the shared library, in my case raylib_ffi.dll.

To add new functions, change the -export([ ... ])., -nifs([ ... ])., and define the function as:

get_mouse_y() ->
	erlang:nif_error("NIF library not loaded").

Gleam to Erlang

See src/raylib.gleam.

Example:

@external(erlang, "raylib_ffi", "set_target_fps")
pub fn set_target_fps(fps: Int) -> Nil

raylib_ffi refers to the raylib_ffi.erl module name.

Tips

• This breaks easily... if there are exported functions in raylib_ffi.cpp not defined in raylib_ffi.erl, etc.
• You can use erlang interactive shell to debug some problems: c("src/raylib_ffi.erl").
• For String arguments, I had to use Charlist in Gleam.
• For Vector2 arguments, the C++ code used Erlang's Tuples.