fix(@typegpu/gl): Better support for texture arrays in GLSL

[iwoplaza]

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Bundle size comparison (import * as ... in PR vs import * as ... in target):

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0	325	0	0

import { ... } in PR vs import * as ... in PR (is the library tree-Shakeable?):

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tgpu_mutableAccessor.ts	57.04 kB ($${\color{green}-79.1\%}$$)
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tgpu_lazy.ts	54.95 kB ($${\color{green}-79.8\%}$$)
tgpu_fragmentFn.ts	39.68 kB ($${\color{green}-85.4\%}$$)
tgpu_fn.ts	39.62 kB ($${\color{green}-85.5\%}$$)
tgpu_vertexFn.ts	39.50 kB ($${\color{green}-85.5\%}$$)
tgpu_computeFn.ts	39.20 kB ($${\color{green}-85.6\%}$$)
tgpu_vertexLayout.ts	28.33 kB ($${\color{green}-89.6\%}$$)
tgpu_comptime.ts	15.93 kB ($${\color{green}-94.2\%}$$)
tgpu_unroll.ts	1.75 kB ($${\color{green}-99.4\%}$$)
tgpu_slot.ts	1.70 kB ($${\color{green}-99.4\%}$$)

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[Copilot]

Pull request overview

Improves the GLSL generator’s handling of texture_2d_array sampling by normalizing arguments so the array index is combined with UV coordinates into a single vec3(...), matching GLSL’s sampler2DArray sampling signatures.

Changes:

• Add GLSL argument normalization to combine (vec2 coords, array_index) into vec3(coords, array_index) for textureSample* calls on 2D-array textures.
• Update textureSample, textureSampleBias, and textureSampleLevel emission to use the normalized argument list consistently.
• Add test coverage asserting correct GLSL output for 2D-array sampling with offsets, bias, and explicit LOD.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
packages/typegpu-gl/src/glslGenerator.ts	Normalizes 2D-array texture sampling arguments and updates GLSL emission for textureSample*.
packages/typegpu-gl/tests/glslGenerator.test.ts	Adds regression tests for 2D-array sampling codegen (coords+layer merging; bias/level with offsets).

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[pullfrog]

✅ No new issues found.

Reviewed changes

• #normalizeTextureArrayArguments helper — For 2d-array textures, finds the uv vector arg and merges it with the trailing array_index into a single vec3/uvec3/ivec3 constructor (dispatch on the coord primitive type), applying the existing flip-Y conditional to the coords first. For plain textures it splices the oriented coords back in place.
• emitCall restructure — textureSample/textureSampleBias/textureSampleLevel now normalize args up front, destructure [texture, sampler, coords, ...rest], and re-derive level/bias/offset from rest.
• Three new snapshot tests for 2d-array sampling (plain/offset, bias+offset, level+offset).

I traced the new argument-shuffling against the WGSL std signatures (e.g. textureSample(texture2dArray, coords: v2f, arrayIndex, offset?)) and confirmed the merged-vec3 forms are correct, and the refactor preserves non-array output. The new tests are exact snapshots (not loose assertions) and all 28 tests pass.

ℹ️ Array-texture support is scoped to the sample trio and the 2d-array dimension

Since this PR positions itself as "better support for texture arrays," one follow-up to keep on the radar (not blocking): textureLoad → texelFetch on a 2d-array texture also takes coords, arrayIndex, level, but that path destructures const [texture, coords, level] = args and is not normalized here, so it would read arrayIndex as level. The same is true of cube-array textures, which fall through the isTextureArray 2d-array check entirely.

Also a low-priority robustness nit: the coord-primitive dispatch in #normalizeTextureArrayArguments (f32/u32/i32) silently falls back to leaving the uv and array_index as separate args for any unhandled coord vector type, which would emit an incorrect sampling call rather than throwing. It is unreachable through the typed std API (2d-array coords are pinned to v2f), so a defensive guard is optional.

Technical details

# Array-texture emission scope

## Affected sites
- packages/typegpu-gl/src/glslGenerator.ts:647 (`textureLoad` → `texelFetch`, args destructured as `[texture, coords, level]`, no array-index normalization).
- packages/typegpu-gl/src/glslGenerator.ts:555 — `isTextureArray` only matches `dimension === '2d-array'`.

## Required outcome
- (Optional, author discretion) Normalize 2d-array `textureLoad` coords+index and/or fold `cube-array` into the same merge, or explicitly document them as out of scope.
- Add a defensive guard so an unhandled coordinate vector type throws rather than emitting malformed GLSL.

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