Shaders: rust-gpu integration to compile shader nodes to WGSL (#3097)

* shaders: shader compilation setup

* nix: use rustc_codegen_spirv.so from nix

* shaders: codegen for per_pixel_adjust shader nodes

* shaders: disable nodes needing bool

* shaders: `#[repr(u32)]` some enums

* shaders: add lint ignores from rust-gpu

* shaders: fix node-macro tests

* gcore-shaders: toml cleanup

* shader-nodes feature: put rust-gpu to wgsl compile behind feature gate

* shaders: fix use TokenStream2

* shaders: allow providing shader externally

* Update iai runner in workflow

---------

Co-authored-by: Timon Schelling <me@timon.zip>
Co-authored-by: Dennis Kobert <dennis@kobert.dev>

node-graph/graster-nodes/shaders/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "graphene-raster-nodes-shaders"
+version = "0.1.0"
+edition = "2024"
+description = "graphene raster data format"
+authors = ["Graphite Authors <contact@graphite.rs>"]
+license = "MIT OR Apache-2.0"
+
+[dependencies]
+
+[build-dependencies]
+cargo-gpu = { workspace = true }
+env_logger = { workspace = true }

node-graph/graster-nodes/shaders/build.rs

@@ -0,0 +1,55 @@
+use cargo_gpu::InstalledBackend;
+use cargo_gpu::spirv_builder::{MetadataPrintout, SpirvMetadata};
+use std::path::PathBuf;
+
+pub fn main() -> Result<(), Box<dyn std::error::Error>> {
+	env_logger::builder().init();
+
+	// Skip building the shader if they are provided externally
+	println!("cargo:rerun-if-env-changed=GRAPHENE_RASTER_NODES_SHADER_PATH");
+	if !std::env::var("GRAPHENE_RASTER_NODES_SHADER_PATH").unwrap_or_default().is_empty() {
+		return Ok(());
+	}
+
+	// Allows overriding the PATH to inject the rust-gpu rust toolchain when building the rest of the project with stable rustc.
+	// Used in nix shell. Do not remove without checking with developers using nix.
+	println!("cargo:rerun-if-env-changed=RUST_GPU_PATH_OVERRIDE");
+	if let Ok(path_override) = std::env::var("RUST_GPU_PATH_OVERRIDE") {
+		let current_path = std::env::var("PATH").unwrap_or_default();
+		let new_path = format!("{path_override}:{current_path}");
+		// SAFETY: Build script is single-threaded therefore this cannot lead to undefined behavior.
+		unsafe {
+			std::env::set_var("PATH", &new_path);
+		}
+	}
+
+	let shader_crate = PathBuf::from(concat!(env!("CARGO_MANIFEST_DIR"), "/.."));
+
+	println!("cargo:rerun-if-env-changed=RUSTC_CODEGEN_SPIRV_PATH");
+	let rustc_codegen_spirv_path = std::env::var("RUSTC_CODEGEN_SPIRV_PATH").unwrap_or_default();
+	let backend = if rustc_codegen_spirv_path.is_empty() {
+		// install the toolchain and build the `rustc_codegen_spirv` codegen backend with it
+		cargo_gpu::Install::from_shader_crate(shader_crate.clone()).run()?
+	} else {
+		// use the `RUSTC_CODEGEN_SPIRV` environment variable to find the codegen backend
+		let mut backend = InstalledBackend::default();
+		backend.rustc_codegen_spirv_location = PathBuf::from(rustc_codegen_spirv_path);
+		backend.toolchain_channel = "nightly".to_string();
+		backend.target_spec_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+		backend
+	};
+
+	// build the shader crate
+	let mut builder = backend.to_spirv_builder(shader_crate, "spirv-unknown-naga-wgsl");
+	builder.print_metadata = MetadataPrintout::DependencyOnly;
+	builder.spirv_metadata = SpirvMetadata::Full;
+	builder.shader_crate_features.default_features = false;
+	let wgsl_result = builder.build()?;
+	let path_to_spv = wgsl_result.module.unwrap_single();
+
+	// needs to be fixed upstream
+	let path_to_wgsl = path_to_spv.with_extension("wgsl");
+
+	println!("cargo::rustc-env=GRAPHENE_RASTER_NODES_SHADER_PATH={}", path_to_wgsl.display());
+	Ok(())
+}

node-graph/graster-nodes/shaders/spirv-unknown-naga-wgsl.json

@@ -0,0 +1,26 @@
+{
+	"allows-weak-linkage": false,
+	"arch": "spirv",
+	"crt-objects-fallback": "false",
+	"crt-static-allows-dylibs": true,
+	"crt-static-respected": true,
+	"data-layout": "e-m:e-p:32:32:32-i64:64-n8:16:32:64",
+	"dll-prefix": "",
+	"dll-suffix": ".spv.json",
+	"dynamic-linking": true,
+	"emit-debug-gdb-scripts": false,
+	"env": "naga-wgsl",
+	"linker-flavor": "unix",
+	"linker-is-gnu": false,
+	"llvm-target": "spirv-unknown-naga-wgsl",
+	"main-needs-argc-argv": false,
+	"metadata": {
+		"description": null,
+		"host_tools": null,
+		"std": null,
+		"tier": null
+	},
+	"panic-strategy": "abort",
+	"simd-types-indirect": false,
+	"target-pointer-width": "32"
+}

node-graph/graster-nodes/shaders/src/lib.rs

@@ -0,0 +1 @@
+pub const WGSL_SHADER: &str = include_str!(env!("GRAPHENE_RASTER_NODES_SHADER_PATH"));