GameMaker / Rust Demos

Sending and recieving numbers, strings, and window handles.

Tested with GameMaker Runtime Version 2.2.2.326.

In some examples, some dependencies may be omitted to brevity, but they can be seen in src/lib.rs.

In Cargo.toml:

[lib]
crate-type = ["cdylib"]

Sending number (ty_real):

// src/lib.rs
#[no_mangle]
pub extern "cdecl" fn foo(bar: f64) -> () {
    println!("{:?}", bar);
}

Compile as 32bit DLL for compatibility with the 32bit YoYoGames runner:

$ cargo +stable-i686-pc-windows-gnu build --release

GameMaker script:

var foo = external_define("gamemaker_rust_dll_example.dll", "foo", dll_cdecl, ty_real, 1, ty_real);
external_call(foo, 123);

Sending string (ty_string):

In Cargo.toml:

[dependencies]
libc ="*"

extern crate libc;
use libc::c_char;
use std::ffi::CStr;

#[no_mangle]
pub extern "cdecl" fn bar(baz: *const c_char) -> () {
    let c_str: &CStr = unsafe { CStr::from_ptr(baz) };
    let str_slice: &str = c_str.to_str().unwrap();
    println!("baz: {}", str_slice);
}   

var bar = external_define("gamemaker_rust_dll_example.dll", "bar", dll_cdecl, ty_real, 1, ty_string);
external_call(bar, "baz");

Sending window_handle()

In GameMaker, the result of window_handle() must be cast into a (hex) ty_string with string().

var print_window_handle = external_define("gamemaker_rust_dll_example.dll", "print_window_handle", dll_cdecl, ty_real, 1, ty_string);
external_call(print_window_handle, string(window_handle()));

In Rust, the hex string must be interpreted as a HWND, which is basically an i64. Although there is some nuance here that you can google for, such as the value will never exceed the maximum value of an i32, or something along those lines.

use std::i64;

// ...

#[no_mangle]
pub extern "cdecl" fn print_window_handle(handle: *const c_char) -> () {
    let c_str: &CStr = unsafe { CStr::from_ptr(handle) };
    let hex_string: &str = c_str.to_str().unwrap();
    let handle = i64::from_str_radix(hex_string, 16);
    println!("HWND -  HEX: {}, DEC: {:?}", hex_string, handle);
}

Recieving string

var foo_bar_baz = external_define(
    "gamemaker_rust_dll_example.dll", 
    "foo_bar_baz", 
    dll_cdecl, 
    ty_string, 
    0
);
show_debug_message(external_call(foo_bar_baz)); // => foo bar baz

#[no_mangle]
pub extern "cdecl" fn foo_bar_baz() -> *const c_char {
    let c_string = CString::new("foo bar baz").unwrap();
    let pointer = c_string.into_raw();
    pointer
}

Recieving number

var elite_number = external_define("gamemaker_rust_dll_example.dll", "elite_number", dll_cdecl, ty_real, 0);
show_debug_message(external_call(elite_number)); // => 1337

#[no_mangle]
pub extern "cdecl" fn elite_number() -> f64 {
    1337.0f64
}