agb/template/src/main.rs

// Games made using `agb` are no_std which means you don't have access to the standard
// rust library. This is because the game boy advance doesn't really have an operating
// system, so most of the content of the standard library doesn't apply.
//
// Provided you haven't disabled it, agb does provide an allocator, so it is possible
// to use both the `core` and the `alloc` built in crates.
#![no_std]
// `agb` defines its own `main` function, so you must declare your game's main function
// using the #[agb::entry] proc macro. Failing to do so will cause failure in linking
// which won't be a particularly clear error message.
#![no_main]
// This is required to allow writing tests
#![cfg_attr(test, feature(custom_test_frameworks))]
#![cfg_attr(test, reexport_test_harness_main = "test_main")]
#![cfg_attr(test, test_runner(agb::test_runner::test_runner))]

use agb::{display, syscall};

// The main function must take 1 arguments and never return. The agb::entry decorator
// ensures that everything is in order. `agb` will call this after setting up the stack
// and interrupt handlers correctly. It will also handle creating the `Gba` struct for you.
#[agb::entry]
fn main(mut gba: agb::Gba) -> ! {
    let mut bitmap = gba.display.video.bitmap3();

    for x in 0..display::WIDTH {
        let y = syscall::sqrt(x << 6);
        let y = (display::HEIGHT - y).clamp(0, display::HEIGHT - 1);
        bitmap.draw_point(x, y, 0x001F);
    }

    loop {
        syscall::halt();
    }
}