Tailwind Baseline

This package provides a Tailwind CSS plugin that allows you to align text to baseline.

Installation

npm install tailwind-baseline

Configuration

This plugin uses the baseline key in your Tailwind config’s theme object to generate aspect baseline utilities. Here is an example:

// tailwind.config.js
const defaultTheme = require("tailwindcss/defaultTheme");

module.exports = {
  theme: {
    extend: {
      fontFamily: {
        sans: ["Inter var", ...defaultTheme.fontFamily.sans],
        serif: ["Merriweather", ...defaultTheme.fontFamily.serif],
        mono: ["Roboto Mono", ...defaultTheme.fontFamily.mono],
      },
      baseline: {
        fonts: {
          sans: {
            descenderHeightScale: 0.136,
            capHeight: 0.723,
          },
          serif: {
            descenderHeightScale: 0.144,
            capHeight: 0.7462,
          },
          mono: {
            descenderHeightScale: 0.111,
            capHeight: 0.7077,
          },
        },
      },
    },
  },
  variants: {},
  plugins: [require("tailwind-baseline")],
};

The fonts theme object is a dictionary where the key is the fontFamily, and the value is a dictionary. The value dictionary has two keys, descenderHeightScale and capHeight, that take decimal numbers as values.

Defining descenderHeightScale

Descender height is the space between the baseline of your font and the bounding box when the line height is 1. You can measure descenderHeightScale by setting line-height to 1 and measuring how much space there is between the bottom of the letter "x" and the bottom of the bounding box.

For example, the descenderHeightScale for the Inter font is 0.136, which means that when font-size is 1000px and line-height is 1 there is 136px between the bottom of the letter x and the bounding box.

Defining capHeight

Cap height is the height of capital letters in comparison to the bounding box when the line-height is 1. The easiest way to measure a cap height of a Google Font is by using this Codepen.

For example, the capHeight for the Inter font is 0.723, which means that when font-size is 1000px and line-height is 1 the height of the letter "H" is 723px.

Usage

You can align the text of an element to baseline by adding the class baseline to the same element, where you define the line-height (e.g. leading-2). You can define the font-family (e.g. font-sans) and font-size (e.g. text-sm) anywhere.

 <div class="font-sans text-sm">
    <p class="leading-2 baseline">
      Hello! This text is aligned on the baseline.
    </p>
</div>

Debugging Vertical Rhythm

This package includes two classes for debugging whether your design follows a consistent vertical rhythm.

• .baseline-debug-stripe adds green/light-green stripes to background of the element.
• .baseline-debug-line adds red lines to background of the element.

License

MIT © Ari-Pekka Koponen