render: add theme.minimum_contrast #231

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natsukium merged 1 commit from render/minimum-contrast into main 2026-10-23 11:25:45 +09:00

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natsukium commented 2026-10-22 08:41:41 +09:00

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Adds theme.minimum_contrast, a WCAG contrast ratio (1–21, default 1 = off) that every cell's text color is raised to against its resolved background, so a palette or a program's color choice cannot leave text unreadable.

• felis-render-core: a contrast module (WCAG luminance and ratio; the text color moves along the Oklab line toward white or black, keeping its hue, by the smallest step that meets the ratio). It runs last in resolve_cell, after reverse video, cursor, selection and faint. Text drawn in its own background color is left hidden; the bidi warning cell is untouched. No glyph-class exemption.
• The ratio is judged against the straight (not premultiplied) background, so a translucent window does not change the result.
• Config: clamped to [1, 21] with a validation warning, NaN falls back to off; hot-reloads like the other theme keys. Schema regenerated.
• Tests: unit tests and proptests on the math, resolve_cell cases, config clamp, and a golden paint fixture at 4.5.
• Docs: config reference, rendering pipeline; CHANGELOG.

Closes #218

Adds `theme.minimum_contrast`, a WCAG contrast ratio (1–21, default 1 = off) that every cell's text color is raised to against its resolved background, so a palette or a program's color choice cannot leave text unreadable. - `felis-render-core`: a `contrast` module (WCAG luminance and ratio; the text color moves along the Oklab line toward white or black, keeping its hue, by the smallest step that meets the ratio). It runs last in `resolve_cell`, after reverse video, cursor, selection and faint. Text drawn in its own background color is left hidden; the bidi warning cell is untouched. No glyph-class exemption. - The ratio is judged against the straight (not premultiplied) background, so a translucent window does not change the result. - Config: clamped to [1, 21] with a validation warning, NaN falls back to off; hot-reloads like the other theme keys. Schema regenerated. - Tests: unit tests and proptests on the math, `resolve_cell` cases, config clamp, and a golden paint fixture at 4.5. - Docs: config reference, rendering pipeline; CHANGELOG. Closes #218

natsukium added 1 commit 2026-10-22 08:41:41 +09:00

render: add theme.minimum_contrast ... bbf7e3cc40

A program that hard-codes SGR colors can print text the user's theme
makes unreadable, such as blue on a dark background. Neither side can
fix it: the program does not know the theme, and the theme does not
know the program. kitty, Ghostty and WezTerm offer a minimum-contrast
setting for this; felis had none.

The adjustment runs last in resolve_cell, so it judges the colors a
cell is painted with after reverse video, cursor, selection and faint.
It moves the fg along the OKLab line toward white or black, which keeps
the hue, unlike Ghostty's snap to black or white. A translucent window
is judged by the configured background, not the premultiplied one the
surface draws, which goes black at zero opacity. The default of 1
leaves output unchanged.

Assisted-by: Claude Code

natsukium force-pushed render/minimum-contrast from bbf7e3cc40 to b29c54ee80 2026-10-23 11:07:10 +09:00 Compare

natsukium force-pushed render/minimum-contrast from b29c54ee80 to 8042d07544 2026-10-23 11:07:24 +09:00 Compare

natsukium merged commit 9b5ee28d27 into main 2026-10-23 11:25:45 +09:00

natsukium deleted branch render/minimum-contrast 2026-10-23 11:25:45 +09:00

natsukium referenced this pull request from a commit 2026-10-23 11:25:45 +09:00

Merge pull request 'render: add theme.minimum_contrast' (#231) from render/minimum-contrast into main

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