Crate glsl_lang_quote

glsl-lang-quote offers proc-macros to quote GLSL syntax in Rust, using the glsl_lang crate.

Usage

use glsl_lang_quote::glsl;

// Parse a translation unit at compile time
let ast = glsl! {
    void main() {
        gl_FragColor = vec4(1., 0., 0., 1.);
    }
};

// There is exactly one external declaration
assert_eq!(ast.0.len(), 1);

Parsing expressions

This crate offers a set of features quote-expr, quote-preprocessor, and quote-statement. Enabling those features enable the respective parser-expr, parser-preprocessor and parser-statement in glsl_lang, which creates dedicated parsers for those types of GLSL fragments of the language grammar.

This is the most efficient option for parsing lots of expressions and statements at compile-time, however this will slow down the initial compilation of glsl-lang-quote since the generated parser file in glsl_lang will be much larger.

This is why by default, this crate enables the quote-parsable feature, which uses glsl_lang’s glsl_lang::parse::Parsable trait, whose limitations apply. Whichever method you chose, the following code will work:

use glsl_lang_quote::glsl_expr;

// Parse an expression
let ast = glsl_expr! {
    a = vec4(1., 0., 0., 1.)
};

Quoting and stateful lexers

Since glsl_lang’s parser has a stateful lexer (to handle the fact that GLSL’s grammar is not context-free), declaring a type (a struct for example) and using it must happen in the same macro invocation, otherwise the parser will forget about the previously declared types. The best is to only parse whole translation units (glsl! macro), or parse unambiguous fragments (such as expressions, but not statements).

use glsl_lang_quote::{glsl, glsl_statement};

// This is ok:
let ast = glsl! {
    struct PointLight {
        vec3 pos;
        vec3 color;
    }

    PointLight p;
};

// This will not compile, PointLight can't be parsed as a type name without extra state
let statement = glsl_expr! {
    PointLight p;
};

Macros

glsl	Parse a translation unit at compile time
glsl_expr	Parse an expression at compile time
glsl_statement	Parse a statement at compile time