presets

Presets

A preset teaches glslint about one shader ecosystem — as data, not code. Every preset in this directory is compiled into the binary and applied automatically when its [detect] rules match. The linter core carries no ecosystem-specific knowledge; it all lives here.

The files in this directory (maplibre.toml, shadertoy.toml, deck.toml, …) use the exact same schema a project can drop at its own root as glslint.toml. So shipping a preset here and configuring a private project are the same act — the bundled presets are just examples you can copy. The schema is published at schema/glslint.schema.json; point your editor at it (via SchemaStore, keyed on the glslint.toml filename) for validation and autocomplete.

deck.toml is the smallest full example of the deck = true builtin path: its prelude is the stub fallback, while the real deck signatures are resolved dynamically from node_modules (in src/deck.rs) when available.

Why a preset, when discovery is automatic

glslint already works on an unfamiliar project with no preset: it discovers the shared library (any sibling .glsl file with no main) and resolves it, so shared functions type-check with zero config. A preset adds the things discovery can't do or can't do fast:

• A #pragma DSL. maplibre's #pragma maplibre: define lowp float opacity is a maplibre invention with no GLSL standard behind it — glslint can only expand it if a preset says how. This is the main reason a preset exists.
• Speed and precision. Listing the shared-library files ([library]) and injected macros (defines) lets glslint skip the discovery scan and pin exactly the right files (e.g. mercator over globe).

Fields

See schema/glslint.schema.json for the full contract. In brief:

Field	Purpose
name	Preset identifier (required).
[detect] source_contains / sibling_files	When the preset activates: a substring in the shader, or a file next to it. Any hit wins.
[library] vertex / fragment	Shared-library files spliced ahead of every shader, in order. Omit to let glslint discover no-main siblings.
defines	Names of build-injected macros to default (#ifndef-guarded).
discover_defines	Also scan the project's JS/TS for injected #define NAME ${…} macros. Off by default (it walks the repo).
prelude / prelude_vertex / prelude_fragment	GLSL prepended as implicit globals.
epilogue	GLSL appended when the source has no main (e.g. ShaderToy's driver main).
[[expand]]	Directive-expansion rules — the #pragma DSL.

[[expand]] rules

Each rule rewrites one #pragma <ns>: <verb> <args…> line, in place, into GLSL. Tokens after the verb bind positionally to args, and {name} placeholders are substituted (so u_{name} becomes u_opacity):

[[expand]]
pragma = ["maplibre", "mapbox"]   # one namespace, or a list to share the rule
verb   = "define"                 # omit to match the namespace alone
args   = ["prec", "type", "name"]
vertex   = "in {prec} {type} a_{name};\nout {prec} {type} {name};"
fragment = "in {prec} {type} {name};"
# `emit = "..."` sets a template for any stage without a stage-specific one

The load-bearing rule of thumb: an expansion only has to make symbols resolve with the right type — glslint isn't replicating the ecosystem's runtime. Keep a rule's define and initialize templates consistent (the attribute a define declares is the one an initialize reads) and the expansion can never be the source of a type error.

TOML gotcha

Top-level keys (name, defines, prelude*, epilogue, discover_defines) must appear before any [table] header — TOML assigns a bare key to the most recent table otherwise. The schema uses deny_unknown_fields, so a misplaced key fails loudly with a clear message rather than being silently ignored.

Contributing a preset

1. Copy shadertoy.toml (prelude-only) or maplibre.toml (the full works) and adapt it.
2. Add its include_str! line to bundled() in src/preset.rs.
3. Validate against real shaders: glslint check 'path/to/shaders/**/*.glsl' should come back clean, and a deliberately broken shader should still error (a preset must not become a blanket suppressor).
4. Add a parse assertion to src/preset.rs's tests.