build.rs

#![cfg_attr(not(target_os = "macos"), allow(unused))]

use std::{
    env,
    path::{Path, PathBuf},
};

use cbindgen::Config;

fn main() {
    #[cfg(target_os = "macos")]
    generate_dispatch_bindings();
    #[cfg(target_os = "macos")]
    let header_path = generate_shader_bindings();
    #[cfg(target_os = "macos")]
    #[cfg(feature = "runtime_shaders")]
    emit_stitched_shaders(&header_path);
    #[cfg(target_os = "macos")]
    #[cfg(not(feature = "runtime_shaders"))]
    compile_metal_shaders(&header_path);
}

fn generate_dispatch_bindings() {
    println!("cargo:rustc-link-lib=framework=System");
    println!("cargo:rerun-if-changed=src/platform/mac/dispatch.h");

    let bindings = bindgen::Builder::default()
        .header("src/platform/mac/dispatch.h")
        .allowlist_var("_dispatch_main_q")
        .allowlist_var("_dispatch_source_type_data_add")
        .allowlist_var("DISPATCH_QUEUE_PRIORITY_DEFAULT")
        .allowlist_var("DISPATCH_QUEUE_PRIORITY_HIGH")
        .allowlist_var("DISPATCH_TIME_NOW")
        .allowlist_function("dispatch_get_global_queue")
        .allowlist_function("dispatch_async_f")
        .allowlist_function("dispatch_after_f")
        .allowlist_function("dispatch_time")
        .allowlist_function("dispatch_source_merge_data")
        .allowlist_function("dispatch_source_create")
        .allowlist_function("dispatch_source_set_event_handler_f")
        .allowlist_function("dispatch_resume")
        .allowlist_function("dispatch_suspend")
        .allowlist_function("dispatch_source_cancel")
        .allowlist_function("dispatch_set_context")
        .parse_callbacks(Box::new(bindgen::CargoCallbacks))
        .layout_tests(false)
        .generate()
        .expect("unable to generate bindings");

    let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
    bindings
        .write_to_file(out_path.join("dispatch_sys.rs"))
        .expect("couldn't write dispatch bindings");
}

fn generate_shader_bindings() -> PathBuf {
    let output_path = PathBuf::from(env::var("OUT_DIR").unwrap()).join("scene.h");
    let crate_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
    let mut config = Config::default();
    config.include_guard = Some("SCENE_H".into());
    config.language = cbindgen::Language::C;
    config.export.include.extend([
        "Bounds".into(),
        "Corners".into(),
        "Edges".into(),
        "Size".into(),
        "Pixels".into(),
        "PointF".into(),
        "Hsla".into(),
        "ContentMask".into(),
        "Uniforms".into(),
        "AtlasTile".into(),
        "PathRasterizationInputIndex".into(),
        "PathVertex_ScaledPixels".into(),
        "ShadowInputIndex".into(),
        "Shadow".into(),
        "QuadInputIndex".into(),
        "Underline".into(),
        "UnderlineInputIndex".into(),
        "Quad".into(),
        "SpriteInputIndex".into(),
        "MonochromeSprite".into(),
        "PolychromeSprite".into(),
        "PathSprite".into(),
        "SurfaceInputIndex".into(),
        "SurfaceBounds".into(),
    ]);
    config.no_includes = true;
    config.enumeration.prefix_with_name = true;

    let mut builder = cbindgen::Builder::new();

    let src_paths = [
        crate_dir.join("src/scene.rs"),
        crate_dir.join("src/geometry.rs"),
        crate_dir.join("src/color.rs"),
        crate_dir.join("src/window.rs"),
        crate_dir.join("src/platform.rs"),
        crate_dir.join("src/platform/mac/metal_renderer.rs"),
    ];
    for src_path in src_paths {
        println!("cargo:rerun-if-changed={}", src_path.display());
        builder = builder.with_src(src_path);
    }

    builder
        .with_config(config)
        .generate()
        .expect("Unable to generate bindings")
        .write_to_file(&output_path);

    output_path
}

/// To enable runtime compilation, we need to "stitch" the shaders file with the generated header
/// so that it is self-contained.
#[cfg(feature = "runtime_shaders")]
fn emit_stitched_shaders(header_path: &Path) {
    use std::str::FromStr;
    fn stitch_header(header: &Path, shader_path: &Path) -> std::io::Result<PathBuf> {
        let header_contents = std::fs::read_to_string(header)?;
        let shader_contents = std::fs::read_to_string(shader_path)?;
        let stitched_contents = format!("{header_contents}\n{shader_contents}");
        let out_path = PathBuf::from(env::var("OUT_DIR").unwrap()).join("stitched_shaders.metal");
        let _ = std::fs::write(&out_path, stitched_contents)?;
        Ok(out_path)
    }
    let shader_source_path = "./src/platform/mac/shaders.metal";
    let shader_path = PathBuf::from_str(shader_source_path).unwrap();
    stitch_header(header_path, &shader_path).unwrap();
    println!("cargo:rerun-if-changed={}", &shader_source_path);
}
#[cfg(not(feature = "runtime_shaders"))]
fn compile_metal_shaders(header_path: &Path) {
    use std::process::{self, Command};
    let shader_path = "./src/platform/mac/shaders.metal";
    let air_output_path = PathBuf::from(env::var("OUT_DIR").unwrap()).join("shaders.air");
    let metallib_output_path = PathBuf::from(env::var("OUT_DIR").unwrap()).join("shaders.metallib");
    println!("cargo:rerun-if-changed={}", shader_path);

    let output = Command::new("xcrun")
        .args([
            "-sdk",
            "macosx",
            "metal",
            "-gline-tables-only",
            "-mmacosx-version-min=10.15.7",
            "-MO",
            "-c",
            shader_path,
            "-include",
            &header_path.to_str().unwrap(),
            "-o",
        ])
        .arg(&air_output_path)
        .output()
        .unwrap();

    if !output.status.success() {
        eprintln!(
            "metal shader compilation failed:\n{}",
            String::from_utf8_lossy(&output.stderr)
        );
        process::exit(1);
    }

    let output = Command::new("xcrun")
        .args(["-sdk", "macosx", "metallib"])
        .arg(air_output_path)
        .arg("-o")
        .arg(metallib_output_path)
        .output()
        .unwrap();

    if !output.status.success() {
        eprintln!(
            "metallib compilation failed:\n{}",
            String::from_utf8_lossy(&output.stderr)
        );
        process::exit(1);
    }
}