154 lines
3 KiB
Markdown
154 lines
3 KiB
Markdown
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# PostCSS Calc [<img src="https://postcss.github.io/postcss/logo.svg" alt="PostCSS" width="90" height="90" align="right">][PostCSS]
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[![NPM Version][npm-img]][npm-url]
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[![Support Chat][git-img]][git-url]
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[PostCSS Calc] lets you reduce `calc()` references whenever it's possible.
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When multiple units are mixed together in the same expression, the `calc()`
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statement is left as is, to fallback to the [W3C calc() implementation].
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## Installation
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```bash
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npm install postcss-calc
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```
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## Usage
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```js
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// dependencies
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var fs = require("fs")
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var postcss = require("postcss")
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var calc = require("postcss-calc")
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// css to be processed
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var css = fs.readFileSync("input.css", "utf8")
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// process css
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var output = postcss()
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.use(calc())
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.process(css)
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.css
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```
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Using this `input.css`:
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```css
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h1 {
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font-size: calc(16px * 2);
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height: calc(100px - 2em);
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width: calc(2*var(--base-width));
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margin-bottom: calc(16px * 1.5);
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}
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```
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you will get:
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```css
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h1 {
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font-size: 32px;
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height: calc(100px - 2em);
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width: calc(2*var(--base-width));
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margin-bottom: 24px
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}
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```
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Checkout [tests] for more examples.
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### Options
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#### `precision` (default: `5`)
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Allow you to define the precision for decimal numbers.
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```js
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var out = postcss()
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.use(calc({precision: 10}))
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.process(css)
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.css
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```
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#### `preserve` (default: `false`)
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Allow you to preserve calc() usage in output so browsers will handle decimal
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precision themselves.
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```js
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var out = postcss()
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.use(calc({preserve: true}))
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.process(css)
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.css
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```
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#### `warnWhenCannotResolve` (default: `false`)
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Adds warnings when calc() are not reduced to a single value.
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```js
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var out = postcss()
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.use(calc({warnWhenCannotResolve: true}))
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.process(css)
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.css
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```
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#### `mediaQueries` (default: `false`)
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Allows calc() usage as part of media query declarations.
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```js
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var out = postcss()
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.use(calc({mediaQueries: true}))
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.process(css)
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.css
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```
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#### `selectors` (default: `false`)
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Allows calc() usage as part of selectors.
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```js
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var out = postcss()
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.use(calc({selectors: true}))
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.process(css)
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.css
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```
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Example:
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```css
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div[data-size="calc(3*3)"] {
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width: 100px;
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}
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```
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---
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## Related PostCSS plugins
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To replace the value of CSS custom properties at build time, try [PostCSS Custom Properties].
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## Contributing
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Work on a branch, install dev-dependencies, respect coding style & run tests
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before submitting a bug fix or a feature.
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```bash
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git clone git@github.com:postcss/postcss-calc.git
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git checkout -b patch-1
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npm install
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npm test
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```
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## [Changelog](CHANGELOG.md)
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## [License](LICENSE)
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[git-img]: https://img.shields.io/badge/support-chat-blue.svg
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[git-url]: https://gitter.im/postcss/postcss
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[npm-img]: https://img.shields.io/npm/v/postcss-calc.svg
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[npm-url]: https://www.npmjs.com/package/postcss-calc
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[PostCSS]: https://github.com/postcss
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[PostCSS Calc]: https://github.com/postcss/postcss-calc
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[PostCSS Custom Properties]: https://github.com/postcss/postcss-custom-properties
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[tests]: src/__tests__/index.js
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[W3C calc() implementation]: https://www.w3.org/TR/css3-values/#calc-notation
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