# postcss-font-family-system-ui [<img src="https://postcss.github.io/postcss/logo.svg" alt="PostCSS Logo" width="90" height="90" align="right">][postcss]

[![CSS Standard][css-img]][css-url]
[![NPM Version][npm-img]][npm-url]
[![Linux Build Status][cli-img]][cli-url]
[![Windows Build Status][win-img]][win-url]
[![Greenkeeper][gkp-img]][gkp-url]
[![Gitter Chat][git-img]][git-url]

[postcss-font-family-system-ui] lets you use `system-ui` in CSS, following the
[CSS Fonts Module Level 4] specification.

```css
body {
  font: 100%/1.5 system-ui;
}

/* becomes */

body {
  font: 100%/1.5 system-ui, -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Oxygen, Ubuntu, Cantarell, Fira Sans, Droid Sans, Helvetica Neue;
}
```

## Usage

Add [postcss-font-family-system-ui] to your build tool:

```bash
npm install postcss-font-family-system-ui --save-dev
```

#### Node

Use [postcss-font-family-system-ui] to process your CSS:

```js
import postcssSystemUiFont from 'postcss-font-family-system-ui';

postcssSystemUiFont.process(YOUR_CSS);
```

#### PostCSS

Add [PostCSS] to your build tool:

```bash
npm install postcss --save-dev
```

Use [postcss-font-family-system-ui] as a plugin:

```js
import postcss from 'gulp-postcss';
import postcssSystemUiFont from 'postcss-font-family-system-ui';

postcss([
  postcssSystemUiFont(/* options */)
]).process(YOUR_CSS);
```

#### Gulp

Add [Gulp PostCSS] to your build tool:

```bash
npm install gulp-postcss --save-dev
```

Use [postcss-font-family-system-ui] in your Gulpfile:

```js
import postcss from 'gulp-postcss';
import postcssSystemUiFont from 'postcss-font-family-system-ui';

gulp.task('css', () => gulp.src('./src/*.css').pipe(
  postcss([
    postcssSystemUiFont(/* options */)
  ])
).pipe(
  gulp.dest('.')
));
```

#### Grunt

Add [Grunt PostCSS] to your build tool:

```bash
npm install grunt-postcss --save-dev
```

Use [postcss-font-family-system-ui] in your Gruntfile:

```js
import postcssSystemUiFont from 'postcss-font-family-system-ui';

grunt.loadNpmTasks('grunt-postcss');

grunt.initConfig({
  postcss: {
    options: {
      use: [
       postcssSystemUiFont(/* options */)
      ]
    },
    dist: {
      src: '*.css'
    }
  }
});
```

## Options

### family

The `family` option defines the fallback families used to polyfill `system-ui`.
It accepts an array or a comma-separated string.

```js
import postcssSystemUiFont from 'postcss-font-family-system-ui';

postcssSystemUiFont({
  family: 'system-ui, Segoe UI, Roboto, Helvetica Neue' // use less fallbacks
});
```

[css-url]: https://jonathantneal.github.io/css-db/#css-fonts-system-ui-def
[css-img]: https://jonathantneal.github.io/css-db/badge/css-fonts-system-ui-def.svg
[npm-url]: https://www.npmjs.com/package/postcss-font-family-system-ui
[npm-img]: https://img.shields.io/npm/v/postcss-font-family-system-ui.svg
[cli-url]: https://travis-ci.org/JLHwung/postcss-font-family-system-ui
[cli-img]: https://img.shields.io/travis/JLHwung/postcss-font-family-system-ui.svg
[win-url]: https://ci.appveyor.com/project/JLHwung/postcss-font-family-system-ui
[win-img]: https://img.shields.io/appveyor/ci/JLHwung/postcss-font-family-system-ui.svg
[gkp-url]: https://greenkeeper.io/
[gkp-img]: https://badges.greenkeeper.io/JLHwung/postcss-font-family-system-ui.svg
[git-url]: https://gitter.im/postcss/postcss
[git-img]: https://img.shields.io/badge/chat-gitter-blue.svg

[CSS Fonts Module Level 4]: https://drafts.csswg.org/css-fonts-4/#system-ui-def
[Gulp PostCSS]: https://github.com/postcss/gulp-postcss
[Grunt PostCSS]: https://github.com/nDmitry/grunt-postcss
[postcss-font-family-system-ui]: https://github.com/JLHwung/postcss-font-family-system-ui
[PostCSS]: https://github.com/postcss/postcss