prettier-plugin-glsl

This is a plugin for Prettier (version 3.x), the opinionated code
formatter, for GLSL, the shading language used in WebGL and other places. It
uses a custom parser based on Chevrotain and does not
require any external dependencies.

**NB: this is still in active development, breaking/formatting changes may be
included in any version.**

Formatting

This plugin tries to match the formatting rules for JavaScript as closely as
possible. Issues or PRs which make the formatting closer to JavaScript are
welcome.

$3

This plugin will attempt to parse #define macros as top-level declarations,
statements or expressions. If successful, these will be formatted as usual.

For example,
#define MAX3(genType) genType max3(genType a, genType b, genType c) { / comment / return max(max(a, b), c); }
will be formatted as:

``glsl
#define MAX3(genType) \
genType max3(genType a, genType b, genType c) { \
/ comment / \
return max(max(a, b), c); \
}
`

$3

Comments which start with /** will be passed to the markdown formatter.

For an example, see ./builtins.glsl.

Installation

`sh
npm install --save-dev prettier-plugin-glsl
`

Prettier will automatically pick up the plugin. The following extensions will be
recognized as GLSL files by default.

.fp .frag .frg .fs .fsh .fshader .geo .geom .glsl .glslf
.glslv .gs .gshader .rchit .rmiss .shader .tesc .tese .vert
.vrx .vsh .vshader

Note that .frag files are recognized as JavaScript files by default. Add the
following to your Prettier configuration to format them as GLSL.

`json
"overrides": [{"files": ["*.frag"], "options": {"parser": "glsl-parser"}}]
`

Limitations due to preprocessor

As GLSL includes a C++-style preprocessor, this presents some difficulties when
formatting. For example, the plugin does not attempt to be able to format crazy
(but technically valid) constructs such as:

`glsl
#define LBRACE {
void main() LBRACE
}
`

Instead, the plugin effectively treats preprocessor directives such as #define
as their own statements. This covers most cases, for example, the following
works fine:

`glsl
#define AA 2
#define ZERO (min(iFrame, 0))
void main() {
// ...
#if AA > 1
for (int m = ZERO; m < AA; m++)
for (int n = ZERO; n < AA; n++) {
// pixel coordinates
vec2 o = vec2(float(m), float(n)) / float(AA) - 0.5;
vec2 p = (2.0 * (fragCoord + o) - iResolution.xy) / iResolution.y;
#else
vec2 p = (2.0 * fragCoord - iResolution.xy) / iResolution.y;
#endif

// use p

#if AA > 1
}
tot /= float(AA * AA);
#endif
}
`

However, the following does not, as the #else and #endif are treated as the
bodies of the if-statement, which leads to the else following a {} block
instead of an if block, which is invalid.

`glsl
#if FOO
if (a())
#else
if (b())
#endif
{ }
else
{ }
`

In general this approach works well. Of the top 100
Shadertoy shaders, 145/152 compilation units (95%)
can be formatted without any changes.

- 1 has actually invalid code. (It doesn't cause compilation errors as it is
excluded via #if/#endif.)
- 1 uses a not self-contained function macro. (It requires a specific token
before its call.)
- 4 mix #if/#else/#endif and if/else` which leads to issues as above.
- 1 uses complicated macro constructions to compose music.