fix(import): apply the sRGB transfer function to srgb-linear colours and keep alpha

[rubenvdlinde]

Importing a W3C design tokens file gave the wrong colour for an srgb-linear colour and for any colour with alpha.

The defect

DesignTokensMapper::serializeColorObject() sent srgb and srgb-linear components to the same converter, which scaled each component by 255 without the sRGB transfer function and wrote three channels only. A linear 0.5 grey became #808080 instead of about #bcbcbc, and alpha was never read, so a translucent colour imported opaque. Nothing was reported.

The tests that were red

In tests/Unit/Service/DesignTokensMapperTest.php: testSrgbLinearAppliesTransferFunction, testSrgbLinearNearBlackUsesTheLinearSegment, testAlphaKeptAsEightDigitHex, testSrgbLinearWithAlpha and testAlphaIsAddedToTheHexFallback. testOpaqueColourStaysSixDigitHex guards existing sets.

The fix

• srgb-linear components go through the CSS Color 4 sRGB transfer function before scaling, including its linear segment near black.
• An alpha below 1 is kept as the fourth pair of an 8-digit hex, on the components path and on the 6-digit hex fallback. An opaque colour stays a 6-digit hex, so existing imports do not change.

The other colour spaces and the out-of-gamut reasons in authoring-dtcg-export task 2.2 are not part of this change. The contrast audit and the dark palette do not read 8-digit hex yet; that is #696.

Verified

• composer check:strict: exit 0 (its test:all skips in a bare clone, so PHPUnit ran separately).
• PHPUnit with the server's lib/private on the autoloader: 861 tests, the same 11 errors and 7 failures as on development (missing Symfony and server classes outside a Nextcloud tree).
• npm run lint, format, test:l10n, check:l10n-js, check:manifest, test:unit: all exit 0.
• Hydra gates --scope-to-diff: exit 0.

Fixes #695

[github-actions]

Quality Report — ConductionNL/thematiq @ d087570

Check	PHP	Vue	Security	License	Tests
lint	✅
phpcs	✅
phpmd	✅
psalm	✅
phpstan	✅
phpmetrics	✅
eslint		✅
stylelint		✅
build		✅
check-manifest		✅
test-l10n		✅
format		✅
composer			✅	✅ 107/107
npm			✅	✅ 2/2
app:check-code	⏭️
info.xml	✅
REUSE	✅
lockfile sync		✅
PHPUnit					✅
Newman					✅
Playwright					⏭️ deferred: E2E runs locally and on the promotion path only. This pull request targets development, so the suite is asked once per promotion into beta and main rather than once per push per open pull request. Run it on any branch from the Actions tab, or locally with npx playwright test.
Hydra gates					✅

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Quality workflow — 2026-09-28 15:18 UTC

Download the full PDF report from the workflow artifacts.