feat: support hex colors with alpha #4090
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edemaine
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Thanks for working on this! I have a few comments.
src/Parser.js
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| return null; | ||
| } | ||
| const match = (/^(#[a-f0-9]{3}|#?[a-f0-9]{6}|[a-z]+)$/i).exec(res.text); | ||
| const match = (/^(#[a-f0-9]{3}|#?[a-f0-9]{6}|#?[a-f0-9]{8}|[a-z]+)$/i).exec(res.text); |
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There's also 4-digit hex codes. See https://developer.mozilla.org/en-US/docs/Web/CSS/hex-color
Is there some way to avoid the repetition here? I'm not sure.
- Add 4-digit hex color support (#RGBA) - Remove 8-digit color support without # prefix - Optimize regex pattern for better readability - Remove redundant parsing tests - Inline invalid color test cases
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Hi @edemaine, Thanks for the feedback! I’ve made the requested changes: 1.Added support for 4-digit hex colors. I’ve pushed the updates and opened a new pull request with these fixes. Please take a look when you get a chance. |
Pull Request is not mergeable
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Tests are failing; could you take a look?
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- Split regex across lines to meet 84-character limit - Update badCustomColorExpression2 from #fA6f to #fA6f1 (5-digit invalid) - Ensure all tests pass and linting requirements are met
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fix: resolve linting and test issues
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Hi @edemaine, Thanks for approving the changes! I can see that all the screenshotter tests are passing and the deploy preview looks good. Could you please approve the 2 pending workflows so that the |
## [0.16.24](v0.16.23...v0.16.24) (2025-10-12) ### Features * support hex colors with alpha ([#4090](#4090)) ([8c9b306](8c9b306)), closes [#4067](#4067) [#fA6](https://github.com/KaTeX/KaTeX/issues/fA6) [#fA6f1](https://github.com/KaTeX/KaTeX/issues/fA6f1)
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🎉 This PR is included in version 0.16.24 🎉 The release is available on: Your semantic-release bot 📦🚀 |
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Hi @edemaine, Thanks for merging the PR! 😊 |
What is the previous behavior before this PR?
KaTeX only supported 3-digit (#RGB), 6-digit (#RRGGBB), and named colors (red, blue, etc.). 8-digit hex colors with alpha transparency (#RRGGBBAA) were rejected by the parser with "Invalid color" errors.
Example that failed before:
What is the new behavior after this PR?
KaTeX now accepts and processes 8-digit hex colors with alpha transparency in both #RRGGBBAA and RRGGBBAA formats. The alpha channel is preserved and passed through to CSS for browser rendering.
Examples that work after:
\textcolor{#FF000080}{F=ma} % 50% transparent red
\textcolor{#228B2280}{F=ma} % 50% transparent green
\textcolor{00FF0040}{F=ma} % 25% opaque green (no # prefix)
The parser now:
Validates 8-digit hex color format
Automatically adds # prefix when missing for 8-digit colors
Maintains full backward compatibility with existing color formats
Outputs standard CSS #RRGGBBAA format for modern browser alpha support
Fixes #4067