fix: make topic colors legible across dark, night, and light themes #2050
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,5 +1,30 @@ | ||
| import { expect } from 'chai' | ||
| import { defineColors, getRandomColor, readableColor } from '@/utils/colors' | ||
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| const hexToRgb = (hex: string): [number, number, number] => { | ||
| const h = hex.replace('#', '') | ||
| return [parseInt(h.slice(0, 2), 16), parseInt(h.slice(2, 4), 16), parseInt(h.slice(4, 6), 16)] | ||
| } | ||
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| const lightness = (hex: string): number => { | ||
| const [r, g, b] = hexToRgb(hex).map((v) => v / 255) | ||
| const max = Math.max(r, g, b) | ||
| const min = Math.min(r, g, b) | ||
| return (max + min) / 2 | ||
| } | ||
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| const hue = (hex: string): number => { | ||
| const [r, g, b] = hexToRgb(hex).map((v) => v / 255) | ||
| const max = Math.max(r, g, b) | ||
| const min = Math.min(r, g, b) | ||
| if (max === min) return 0 | ||
| const d = max - min | ||
| let h = 0 | ||
| if (max === r) h = (g - b) / d + (g < b ? 6 : 0) | ||
| else if (max === g) h = (b - r) / d + 2 | ||
| else h = (r - g) / d + 4 | ||
| return h / 6 | ||
| } | ||
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| describe('colors utility functions', () => { | ||
| it('defineColors should have 5 predefined colors', () => { | ||
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@@ -14,4 +39,56 @@ describe('colors utility functions', () => { | |
| const randomColor = getRandomColor() | ||
| expect(randomColor).to.match(/^#[0-9A-F]{6}$/) | ||
| }) | ||
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| describe('readableColor', () => { | ||
| describe('on dark or night theme', () => { | ||
| it('lightens a very dark color to L >= 0.6', () => { | ||
| // The reported failing case: dark indigo on the Night theme | ||
| const out = readableColor('#0F003A', 'dark' as Theme) | ||
| expect(lightness(out)).to.be.at.least(0.6 - 1e-6) | ||
| }) | ||
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| it('applies the same clamp on night as on dark', () => { | ||
| const out = readableColor('#0F003A', 'night' as Theme) | ||
| expect(lightness(out)).to.be.at.least(0.6 - 1e-6) | ||
| }) | ||
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| it('preserves hue when lightening', () => { | ||
| const out = readableColor('#0F003A', 'dark' as Theme) | ||
| expect(Math.abs(hue(out) - hue('#0F003A'))).to.be.lessThan(0.01) | ||
| }) | ||
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| it('returns colors already in the readable band unchanged', () => { | ||
| // Light cyan from the predefined palette — already legible on dark bg | ||
| expect(readableColor('#6ECBEE', 'dark' as Theme)).to.equal('#6ECBEE') | ||
| }) | ||
| }) | ||
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| describe('on light theme', () => { | ||
| it('darkens a near-white color to L <= 0.55', () => { | ||
| const out = readableColor('#F5F5F5', 'light' as Theme) | ||
| expect(lightness(out)).to.be.at.most(0.55 + 1e-6) | ||
| }) | ||
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| it('returns dark colors unchanged', () => { | ||
| expect(readableColor('#0F003A', 'light' as Theme)).to.equal('#0F003A') | ||
| }) | ||
| }) | ||
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| describe('input handling', () => { | ||
| it('returns empty input unchanged', () => { | ||
| expect(readableColor('', 'dark' as Theme)).to.equal('') | ||
| }) | ||
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| it('returns non-hex input unchanged', () => { | ||
| expect(readableColor('not-a-color', 'dark' as Theme)).to.equal('not-a-color') | ||
| }) | ||
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| it('accepts 3-character shorthand hex', () => { | ||
| // #003 expands to #000033 — very dark, should be lightened on dark theme | ||
| const out = readableColor('#003', 'dark' as Theme) | ||
| expect(lightness(out)).to.be.at.least(0.6 - 1e-6) | ||
| }) | ||
| }) | ||
|
Comment on lines
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Contributor
Author
There was a problem hiding this comment. Added a regression test in 124eee2 — |
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| }) | ||
| }) | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
|
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@@ -9,4 +9,83 @@ export const getRandomColor = (): string => { | |
| return color | ||
| } | ||
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| const hexToRgb = (hex: string): [number, number, number] | null => { | ||
| const m = hex.replace('#', '').match(/^([0-9a-f]{6}|[0-9a-f]{3})$/i) | ||
| if (!m) return null | ||
| let h = m[1] | ||
| if (h.length === 3) | ||
| h = h | ||
| .split('') | ||
| .map((c) => c + c) | ||
| .join('') | ||
| return [parseInt(h.slice(0, 2), 16), parseInt(h.slice(2, 4), 16), parseInt(h.slice(4, 6), 16)] | ||
| } | ||
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| const rgbToHex = (r: number, g: number, b: number): string => { | ||
| const clamp = (n: number) => Math.max(0, Math.min(255, Math.round(n))) | ||
| return '#' + [r, g, b].map((n) => clamp(n).toString(16).padStart(2, '0')).join('') | ||
| } | ||
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| const rgbToHsl = ([r, g, b]: [number, number, number]): [number, number, number] => { | ||
| r /= 255 | ||
| g /= 255 | ||
| b /= 255 | ||
| const max = Math.max(r, g, b) | ||
| const min = Math.min(r, g, b) | ||
| const l = (max + min) / 2 | ||
| let h = 0 | ||
| let s = 0 | ||
| if (max !== min) { | ||
| const d = max - min | ||
| s = l > 0.5 ? d / (2 - max - min) : d / (max + min) | ||
| switch (max) { | ||
| case r: | ||
| h = (g - b) / d + (g < b ? 6 : 0) | ||
| break | ||
| case g: | ||
| h = (b - r) / d + 2 | ||
| break | ||
| case b: | ||
| h = (r - g) / d + 4 | ||
| break | ||
| } | ||
| h /= 6 | ||
| } | ||
| return [h, s, l] | ||
| } | ||
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| const hslToRgb = ([h, s, l]: [number, number, number]): [number, number, number] => { | ||
| if (s === 0) { | ||
| const v = l * 255 | ||
| return [v, v, v] | ||
| } | ||
| const hue2rgb = (p: number, q: number, t: number) => { | ||
| if (t < 0) t += 1 | ||
| if (t > 1) t -= 1 | ||
| if (t < 1 / 6) return p + (q - p) * 6 * t | ||
| if (t < 1 / 2) return q | ||
| if (t < 2 / 3) return p + (q - p) * (2 / 3 - t) * 6 | ||
| return p | ||
| } | ||
| const q = l < 0.5 ? l * (1 + s) : l + s - l * s | ||
| const p = 2 * l - q | ||
| return [hue2rgb(p, q, h + 1 / 3) * 255, hue2rgb(p, q, h) * 255, hue2rgb(p, q, h - 1 / 3) * 255] | ||
| } | ||
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| // Clamp HSL lightness so a topic color stays legible against the current | ||
| // theme's background. Hue and saturation are preserved, so a "blue" topic | ||
| // stays blue — only the lightness shifts into a readable band. | ||
| export const readableColor = (hex: string, theme: Theme): string => { | ||
| if (!hex) return hex | ||
| const rgb = hexToRgb(hex) | ||
| if (!rgb) return hex | ||
| const [h, s, l] = rgbToHsl(rgb) | ||
| const minL = theme === 'light' ? 0 : 0.6 | ||
| const maxL = theme === 'light' ? 0.55 : 1 | ||
| const newL = Math.max(minL, Math.min(maxL, l)) | ||
| if (newL === l) return hex | ||
| const [r, g, b] = hslToRgb([h, s, newL]) | ||
| return rgbToHex(r, g, b) | ||
|
Comment on lines
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Contributor
Author
There was a problem hiding this comment. Same fix applied to the web copy in 124eee2 — symmetric with the desktop change. |
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| } | ||
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| export default {} | ||
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Good catch — thanks. Fixed in 124eee2: when the early-return path is hit, the helper now normalizes 3-char shorthand to 6-char so the
${color}1Aalpha-suffix idiom always yields valid CSS. 6-char input still passes through unchanged to preserve casing.