PostCSS Sign Functions [][PostCSS]

npm install @csstools/postcss-sign-functions --save-dev

[PostCSS Sign Functions] lets you use the sign and abs functions, following the [CSS Values 4] specification.

``css
.sign {
z-index: sign(-10px);
}

.sign {
z-index: sign(0);
}

.sign {
z-index: sign(10px);
}

.abs {
z-index: abs(-10px);
}

.abs {
z-index: abs(0);
}

.abs {
z-index: abs(10px);
}

.abs {
z-index: abs(10%);
}

/ becomes /

.sign {
z-index: -1;
}

.sign {
z-index: 0;
}

.sign {
z-index: 1;
}

.abs {
z-index: 10px;
}

.abs {
z-index: 0;
}

.abs {
z-index: 10px;
}

.abs {
z-index: max((10%), -1 * (10%));
}
`

> [!NOTE]
> The utility of static fallbacks for sign and abs is limited.
> The most interesting values are variables and dynamic values (e.g. those containing %).
> It is impossible to generate static fallbacks in a build process for values that are dynamic on the client.

Usage

Add [PostCSS Sign Functions] to your project:

`bash
npm install postcss @csstools/postcss-sign-functions --save-dev
`

Use it as a [PostCSS] plugin:

`js
const postcss = require('postcss');
const postcssSignFunctions = require('@csstools/postcss-sign-functions');

postcss([
postcssSignFunctions(/ pluginOptions /)
]).process(YOUR_CSS /, processOptions /);
`

⚠️ About custom properties

Given the dynamic nature of custom properties it's impossible to know what the variable value is, which means the plugin can't compute a final value for the stylesheet.

Because of that, any usage that contains a var is skipped.

Options

$3

The preserve option determines whether the original notation
is preserved. By default, it is not preserved.

`js
postcssSignFunctions({ preserve: true })
`

`css
.sign {
z-index: sign(-10px);
}

.sign {
z-index: sign(0);
}

.sign {
z-index: sign(10px);
}

.abs {
z-index: abs(-10px);
}

.abs {
z-index: abs(0);
}

.abs {
z-index: abs(10px);
}

.abs {
z-index: abs(10%);
}

/ becomes /

.sign {
z-index: -1;
z-index: sign(-10px);
}

.sign {
z-index: 0;
z-index: sign(0);
}

.sign {
z-index: 1;
z-index: sign(10px);
}

.abs {
z-index: 10px;
z-index: abs(-10px);
}

.abs {
z-index: 0;
z-index: abs(0);
}

.abs {
z-index: 10px;
z-index: abs(10px);
}

.abs {
z-index: max((10%), -1 * (10%));
z-index: abs(10%);
}
``

[cli-url]: https://github.com/csstools/postcss-plugins/actions/workflows/test.yml?query=workflow/test
[css-url]: https://cssdb.org/#sign-functions
[discord]: https://discord.gg/bUadyRwkJS
[npm-url]: https://www.npmjs.com/package/@csstools/postcss-sign-functions

[PostCSS]: https://github.com/postcss/postcss
[PostCSS Sign Functions]: https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-sign-functions
[CSS Values 4]: https://drafts.csswg.org/css-values-4/#sign-funcs