export WGSL shader source code directly from vello_sparse_shaders (#1016)

# Context

Addresses comment
#1011 (comment)
from @DJMcNab . Replaces `include_str!` with a direct import from
`vello_sparse_shaders` to get access to the wgsl source code.

### Changes

- Adds a `wgsl` module to the build-time module generated by
`vello_sparse_shaders`.

This allows `render_strips.wgsl` to be accessed via:
`vello_sparse_shaders::wgsl::RENDER_STRIPS` instead of a cross-package
`include_str!`.

- Adds a `glsl` feature flag to `vello_sparse_shaders` so the default
compiled module does not include `glsl` unless the `glsl` feature is
used. This makes builds much leaner for wgsl without glsl.

### Test plan

Reviewed generated code, and tested both examples manually:
 - `cargo run_wasm -p wgpu_webgl --release --port 8001`
 - `cargo run_wasm -p native_webgl --release --port 8000`

Finally, CI is very thorough.

Author: ajakubowicz-canva

sparse_strips/vello_hybrid/Cargo.toml

@@ -49,5 +49,5 @@ roxmltree = "0.20.0"
 
 [features]
 default = ["wgpu"]
-wgpu = ["dep:wgpu"]
-webgl = ["dep:js-sys", "dep:web-sys", "dep:vello_sparse_shaders"]
+wgpu = ["dep:wgpu", "dep:vello_sparse_shaders"]
+webgl = ["dep:js-sys", "dep:web-sys", "dep:vello_sparse_shaders", "vello_sparse_shaders/glsl"]

sparse_strips/vello_hybrid/src/render/wgpu.rs

@@ -227,16 +227,12 @@ impl Programs {
 
         let strip_shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
             label: Some("Strip Shader"),
-            source: wgpu::ShaderSource::Wgsl(
-                include_str!("../../../vello_sparse_shaders/shaders/render_strips.wgsl").into(),
-            ),
+            source: wgpu::ShaderSource::Wgsl(vello_sparse_shaders::wgsl::RENDER_STRIPS.into()),
         });
 
         let clear_shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
             label: Some("Clear Slots Shader"),
-            source: wgpu::ShaderSource::Wgsl(
-                include_str!("../../../vello_sparse_shaders/shaders/clear_slots.wgsl").into(),
-            ),
+            source: wgpu::ShaderSource::Wgsl(vello_sparse_shaders::wgsl::CLEAR_SLOTS.into()),
         });
 
         let strip_pipeline_layout =

sparse_strips/vello_sparse_shaders/Cargo.toml

@@ -17,10 +17,13 @@ default-target = "x86_64-unknown-linux-gnu"
 targets = []
 
 [dependencies]
-naga = { version = "24.0.0", features = ["wgsl-in", "glsl-out"] }
+naga = { version = "24.0.0", features = ["wgsl-in", "glsl-out"], optional = true }
 
 [build-dependencies]
-naga = { version = "24.0.0", features = ["wgsl-in", "glsl-out"] }
+naga = { version = "24.0.0", features = ["wgsl-in", "glsl-out"], optional = true }
+
+[features]
+glsl = ["dep:naga"]
 
 [lints]
 workspace = true

sparse_strips/vello_sparse_shaders/build.rs

@@ -9,20 +9,22 @@ use std::fs;
 use std::path::{Path, PathBuf};
 
 #[allow(warnings)]
+#[cfg(feature = "glsl")]
 #[path = "src/compile.rs"]
 mod compile;
 #[allow(warnings)]
+#[cfg(feature = "glsl")]
 #[path = "src/types.rs"]
 mod types;
 
+#[cfg(feature = "glsl")]
 use compile::compile_wgsl_shader;
 
 // TODO: Format the generated code via `rustfmt`.
 // TODO: Use `quote` instead of string concatenation to generate code.
 fn main() {
     // Rerun build if the shaders directory changes
     println!("cargo:rerun-if-changed=shaders");
-
     let out_dir = env::var_os("OUT_DIR").unwrap();
     // Build outputs a `compiled_shaders.rs` module containing the GLSL source and reflection
     // metadata.
@@ -63,18 +65,45 @@ fn generate_compiled_shaders_module(buf: &mut String, shader_infos: &[(String, S
         "// Generated code by `vello_sparse_shaders` - DO NOT EDIT"
     )
     .unwrap();
-    writeln!(
-        buf,
-        "/// Build time GLSL shaders derived from wgsl shaders."
-    )
-    .unwrap();
+
+    writeln!(buf, "/// Re-exporting wgsl shader source code.").unwrap();
+
+    writeln!(buf, "pub mod wgsl {{").unwrap();
+    for (shader_name, shader_source) in shader_infos {
+        generate_wgsl_shader_module(buf, shader_name, shader_source).unwrap();
+    }
+    writeln!(buf, "}}").unwrap();
 
     // Implementation for creating a CompiledGlsl struct per shader assuming the standard entry
     // names of `vs_main` and `fs_main`.
-    for (shader_name, shader_source) in shader_infos {
-        let compiled = compile_wgsl_shader(shader_source, "vs_main", "fs_main");
+    #[cfg(feature = "glsl")]
+    {
+        writeln!(
+            buf,
+            "/// Build time GLSL shaders derived from wgsl shaders."
+        )
+        .unwrap();
 
-        let generated_code = compiled.to_generated_code(shader_name);
-        writeln!(buf, "{generated_code}").unwrap();
+        for (shader_name, shader_source) in shader_infos {
+            let compiled = compile_wgsl_shader(shader_source, "vs_main", "fs_main");
+
+            let generated_code = compiled.to_generated_code(shader_name);
+            writeln!(buf, "{generated_code}").unwrap();
+        }
     }
 }
+
+fn generate_wgsl_shader_module<T: Write>(
+    buf: &mut T,
+    shader_name: &str,
+    shader_source: &str,
+) -> std::fmt::Result {
+    let const_name = shader_name.to_uppercase();
+    writeln!(buf, "    /// Source for `{shader_name}.wgsl`")?;
+    writeln!(
+        buf,
+        "    pub const {const_name}: &str = r###\"{shader_source}\"###;"
+    )?;
+
+    Ok(())
+}

sparse_strips/vello_sparse_shaders/src/lib.rs

@@ -3,7 +3,9 @@
 
 //! This is a utility library to help integrate `vello_hybrid` WebGPU wgsl shaders into glsl.
 
+#[cfg(feature = "glsl")]
 mod compile;
+#[cfg(feature = "glsl")]
 mod types;
 
 include!(concat!(env!("OUT_DIR"), "/compiled_shaders.rs"));

sparse_strips/vello_sparse_shaders/src/types.rs

@@ -79,7 +79,7 @@ impl CompiledGlsl {
     pub(crate) fn to_generated_code(&self, shader_name: &str) -> String {
         let mut code = format!("/// Compiled glsl for `{shader_name}.wgsl`\n");
         code.push_str(&format!("pub mod {shader_name} {{\n"));
-        code.push_str(r#"    #![allow(missing_docs, reason="No metadata to generate precise documentation forgenerated code.")]"#);
+        code.push_str(r#"    #![allow(missing_docs, reason="No metadata to generate precise documentation for generated code.")]"#);
         code.push_str("\n\n");
 
         code.push_str("    pub const VERTEX_SOURCE: &str = r###\"");