FIX: Color.setStyle has parser gaps and silent failures for valid CSS color forms

[MITHRAN-BALACHANDER]

Summary

Color.setStyle() silently left colors unchanged for several valid CSS inputs.
This PR fixes the parser gaps, adds case-insensitive model name matching, and adds explicit warnings instead of silent no-ops.

Closes #33195

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Problem

Input	Before	After
rgb(255 0 0)	123456 (no-op)	ff0000 ✓
rgb(255 0 0 / 0.5)	123456 (no-op)	ff0000 + alpha warning ✓
hsl(120deg 100% 50%)	123456 (no-op)	00ff00 ✓
rgb(100%,50%,10%,50%)	123456 (no-op)	ff801a + alpha warning ✓
RGB(255,0,0)	"Unknown color model" warning, no-op	ff0000 ✓
HSL(120,100%,50%)	"Unknown color model" warning, no-op	00ff00 ✓
rgb(255,0,oops)	silent no-op	explicit invalid-components warning ✓

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Root causes

1. Separate rigid regexes per token format.
The original parser used two distinct hardcoded regexes for rgb (integer form, percent form) and one for hsl. Any input that did not match both patterns fell through the switch without warning, returning this silently.

2. Case-sensitive switch on the model name.
RGB, RGBA, HSL, HSLA fell into the default branch and emitted "Unknown color model", leaving the color unchanged.

3. No CSS Color 4 space/slash syntax support.
rgb(255 0 0) and rgb(255 0 0 / 0.5) / hsl(120deg 50% 50%) are valid CSS Color 4 forms. The parser had no path for space-separated values or slash-delimited alpha.

4. Percentage alpha was rejected.
rgb(100%,50%,10%,50%) — the alpha 50% failed the original \d*\.?\d+ numeric-only regex.

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Changes

src/math/Color.js

• handleAlpha — refactored to accept a pre-parsed number instead of a raw string, removing redundant parseFloat.
• parseAlpha (new) — parses an optional alpha token that may be a decimal (0.5) or percentage (50%); returns undefined for absent, null for malformed, and a clamped [0,1] value otherwise.
• parseFunctionComponents (new) — single entry point for tokenizing the argument list of any CSS color function. Handles:
  • Comma-separated form: 255, 0, 0 / 255, 0, 0, 0.5
  • Space-separated form: 255 0 0
  • Space/slash alpha form: 255 0 0 / 0.5
• parseRGBValue (new) — converts a single RGB channel token (integer 0–255 or percentage 0–100%) to a [0,1] float.
• parseHue (new) — parses a hue token that may be a bare number or include the optional deg unit suffix.
• parsePercent (new) — parses a n% token and returns n/100.
• Model matching — m[1].toLowerCase() is applied before the switch, making RGB, Rgb, etc. all resolve correctly.
• Outer regex tightened — changed from /^(\w+)\(([^\)]*)\)/ to /^\s*([A-Za-z]+)\(([^\)]*)\)\s*$/ to anchor the full string and avoid partial matches.
• Explicit warnings — both rgb/rgba and hsl/hsla branches now emit Color: Invalid color components <style> when the model was recognised but components could not be parsed, eliminating the silent no-op path.

test/unit/src/math/Color.tests.js

Seven new test cases added after the existing setStyle* block:

Test name	Input
setStyleRGBSpaceSeparated	rgb(255 0 0)
setStyleRGBSpaceSeparatedWithAlpha	rgb(255 0 0 / 0.5)
setStyleRGBPercentAlphaPercent	rgb(100%,50%,10%,50%)
setStyleHSLSpaceSeparatedWithDegrees	hsl(120deg 100% 50%)
setStyleUpperCaseRGBModel	RGB(255,0,0)
setStyleUpperCaseHSLModel	HSL(120,100%,50%)
setStyleInvalidKnownModelDoesNotApply	rgb(255,0,oops) — asserts color is not mutated

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Test results

npm run test-unit -- --filter "Color"

TAP version 13
...
ok 48 Maths > Color > setStyleRGBSpaceSeparated
ok 49 Maths > Color > setStyleRGBSpaceSeparatedWithAlpha
ok 50 Maths > Color > setStyleRGBPercentAlphaPercent
ok 57 Maths > Color > setStyleHSLSpaceSeparatedWithDegrees
ok 58 Maths > Color > setStyleUpperCaseRGBModel
ok 59 Maths > Color > setStyleUpperCaseHSLModel
ok 60 Maths > Color > setStyleInvalidKnownModelDoesNotApply
...
1..67
# pass 67
# skip 0
# todo 0
# fail 0

All 67 Color tests pass. No regressions.

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Scope / non-goals

• This PR does not change hsl to accept rad, turn, or grad angle units — only deg (the CSS Color 4 default) is added. Additional unit support can follow in a separate PR.
• none keyword values (CSS Color 4 missing-component syntax) are not handled — out of scope.
• Alpha is still ignored at render time; handleAlpha continues to emit the existing warning when alpha < 1.

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Files changed

• src/math/Color.js
• test/unit/src/math/Color.tests.js

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	359.97 85.54	359.97 85.54	+0 B +0 B
WebGPU	631.34 175.16	631.34 175.16	+0 B +0 B
WebGPU Nodes	629.46 174.87	629.46 174.87	+0 B +0 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	492.17 120.12	492.83 120.38	+662 B +264 B
WebGPU	703.77 190	704.43 190.24	+662 B +233 B
WebGPU Nodes	653 177.4	653.66 177.63	+662 B +236 B

[mrdoob]

Nice!

Did you use any AI for this?

[MITHRAN-BALACHANDER]

Yes, I used AI only to help refine the documentation and wording.

The issue identification, debugging, refactoring, and implementation were done by me, and I added the unit tests to ensure correctness and avoid regressions.