postcss-fluid-sizing-function

PostCSS plugin to transform fluid() to an expression using clamp(), known as fluid typography.

h1 {
  font-size: fluid(640px 2rem, 1440px 4rem);
}

.container {
  padding: fluid(640px 24px, 1440px 48px) fluid(640px 32px, 1440px 64px);
}

will be processed to:

h1 {
  font-size: clamp(2rem, 4vw + 0.4rem, 4rem);
}

.container {
  padding: clamp(24px, 3vw + 4.8px, 48px) clamp(32px, 4vw + 6.4px, 64px);
}

Checkout tests for more examples.

The fluid(from-viewport-width from-size, to-viewport-width to-size) function accepts four dimensions as two comma-separated pairs as its parameters.

• from-viewport-width: The starting viewport-width.
• from-size: The starting size. For narrower viewport-widths than from-viewport-width, the starting size is used.
• to-viewport-width: The ending viewport-width.
• to-size: The ending size. For wider viewport-widths than to-viewport-width, the ending size is used.

It supports px units and rem units, but from-viewport-width and to-viewport-width or from-size and to-size must each have the same units.

Usage

Step 1: Install plugin:

npm install --save-dev postcss postcss-fluid-sizing-function

Step 2: Check you project for existed PostCSS config: postcss.config.js in the project root, "postcss" section in package.json or postcss in bundle config.

If you do not use PostCSS, add it according to official docs and set this plugin in settings.

Step 3: Add the plugin to plugins list:

module.exports = {
  plugins: [
+   require('postcss-fluid-sizing-function'),
    require('autoprefixer'),
  ],
}

Options

viewportWidths

Type: { [key: string]: string }
Default: {}

Defines the viewport-widths that can be referenced from from-viewport-width and to-viewport-width via those keys.

require('postcss-fluid-sizing-function')({
  viewportWidths: {
    sm: '640px',
    lg: '1440px',
  },
});

Example:

h1 {
  font-size: fluid(sm 2rem, lg 4rem);
  /* same as fluid(640px 2rem, 1440px 4rem) */
}

You can also define default values if viewport-widths is omitted by using DEFAULT_FROM or DEFAULT_TO as keys.

require('postcss-fluid-sizing-function')({
  viewportWidths: {
    DEFAULT_FROM: '640px',
    DEFAULT_TO: '1440px',
  },
});

Example:

h1 {
  font-size: fluid(2rem, 4rem);
  /* same as fluid(640px 2rem, 1440px 4rem) */
}

useLogicalUnits

Type: Boolean
Default: false

Allows you to use vi units instead of vw units for the output.

Example:

h1 {
  font-size: fluid(640px 2rem, 1440px 4rem);
}

will be processed to:

h1 {
  font-size: clamp(2rem, 4vi + 0.4rem, 4rem);
}

rootFontSize

Type: Number
Default: 16

Allows you to set the font-size of the root used in the calculations for rem units.

precision

Type: Number
Default: 5

Allows you to control the number of decimal places in the output numbers.