build.rs

#![cfg_attr(any(not(target_os = "macos"), feature = "macos-blade"), allow(unused))]

//TODO: consider generating shader code for WGSL
//TODO: deprecate "runtime-shaders" and "macos-blade"

fn main() {
    #[cfg(target_os = "macos")]
    macos::build();
}

#[cfg(target_os = "macos")]
mod macos {
    use std::{
        env,
        path::{Path, PathBuf},
    };

    use cbindgen::Config;

    pub(super) fn build() {
        generate_dispatch_bindings();
        #[cfg(not(feature = "macos-blade"))]
        {
            let header_path = generate_shader_bindings();

            #[cfg(feature = "runtime_shaders")]
            emit_stitched_shaders(&header_path);
            #[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(),
            "TransformationMatrix".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");
            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);
        }
    }
}