Baseline Kit

Baseline Kit is a lightweight development tool for visualizing and debugging grid systems and spacing in React 19 applications. It provides configurable overlays for both column-based and baseline grids, flexible layout components, and theme-aware configuration—all optimized for performance and built with TypeScript.

Features

• 📏 Baseline Grid: Core system for maintaining vertical rhythm and consistent spacing across your layouts
• 🎯 Column Grid Guide: Customizable overlay system for visualizing column-based layouts and alignment
• 📦 Box Component: Basic container with configurable spacing that snaps to the baseline grid
• 🧩 Layout Component: CSS Grid-based container with automatic column calculations and baseline alignment
• 📐 Stack Component: Flex-based container that maintains consistent spacing and baseline alignment
• 🎨 Theme System: Customizable colors and debug visuals through a centralized configuration

Requirements

• React 19: Baseline Kit is built for React 19 and uses the latest React features like the use hook
• Modern Browsers: Supporting the latest CSS features

Installation

# Using npm
npm install baseline-kit

# Using yarn
yarn add baseline-kit

# Using pnpm
pnpm add baseline-kit

After installation, import both the styles and theme in your application:

// Import in your main entry file (e.g., index.js, App.js)
import 'baseline-kit/styles';  // Required core styles
import 'baseline-kit/theme';   // Recommended theme (or use your own)

Baseline Kit is written in TypeScript and includes built-in type definitions—no additional packages required.

Quick Start

import React from 'react'
import { Config, Guide, Baseline, Box } from 'baseline-kit'

function App() {
  const isDev = process.env.NODE_ENV === 'development'
  const debugging = isDev ? 'visible' : 'hidden'

  return (
    <Config
      base={8}
      baseline={{ debugging }}
      box={{ debugging }}
      guide={{ debugging }}
      spacer={{ debugging }}
    >
      {/* Baseline Grid for typography alignment */}
      <Baseline
        height="100vh"
        debugging="visible"
      />

      {/* Column Grid Guide */}
      <Guide
        variant="pattern"
        columns={['100px', '200px', '100px']}
        gap={16}
        align="center"
        width="1200px"
      />

      {/* Box with baseline alignment */}
      <Box
        block={[2, 5]}
        debugging="visible"
      >
        <h1>Content Aligned to the Grid</h1>
      </Box>

      <main>Your main content goes here...</main>
    </Config>
  )
}

Core Concepts

Base Unit

The base unit is the foundation of Baseline Kit's spacing system. All measurements are calculated as multiples of this unit:

<Config base={8}> // Sets 8px as the base unit
  <Layout
    block={17}        // Will be rounded to 16px (2 * base)
    inline={22}       // Will be rounded to 24px (3 * base)
  >
    {/* Content automatically aligned to the 8px grid */}
  </Layout>
</Config>

Spacing Values

Spacing props (block, inline, gap) accept values in three formats:

// Single number (applies to both sides)
block={16}                  // 16px top and bottom

// Array [start, end]
block={[2, 3]}                // 2px top, 3px bottom

// Object with explicit values
block={{ start: 2, end: 3 }}  // Same as above

Grid Snapping

Components automatically adjust their spacing to maintain baseline grid alignment:

• Box: Adjusts bottom padding to ensure total height aligns with base unit
• Stack: Maintains baseline alignment in flex layouts
• Layout: Ensures grid cells align with baseline

Debugging Modes

Three modes are available for development and testing:

debugging = "visible"        // Shows all grid lines and measurements
debugging = "hidden"         // Elements exist but are invisible
debugging = "none"           // Removes debug elements entirely

Components

Component Hierarchy

1. Core Components

• Box Basic container for text alignment
• Stack Flex-based layouts (one-dimensional)
• Layout Grid-based layouts (two-dimensional)

2. Development Tools

• Baseline Horizontal grid overlay
• Guide Vertical grid overlay
• Spacer Precise spacing measurement

3. Configuration

• Config Theme and settings provider

Key Components

Config

<Config
  base={8}                         // Base unit for calculations
  baseline={{ debugging }}         // Baseline grid visibility
  guide={{ debugging }}            // Guide customization
>
  {children}
</Config>

Baseline

<Baseline
  height="100vh"          // Overlay height
  variant="line"          // "line" or "flat"
  debugging="visible"     // Show the grid overlay
/>

Guide

<Guide
  variant="pattern"                     // "line", "pattern", "fixed", or "auto"
  columns={['100px', '1fr', '100px']}   // Column definition
  gap={8}                               // Gap value
  width="1200px"                        // Container width
/>

Box

<Box
  block={[2, 5]}         // Vertical padding in base units
  span={2}               // Grid column span when used in Layout
  snapping="height"      // "none", "height", or "clamp"
>
  <p>Content aligned to baseline grid</p>
</Box>

Theme System

Baseline Kit comes with two CSS files:

1. styles.css - Contains the core component styles required for functionality
2. theme.css - Contains color variables and theming (optional but recommended)

Theme Options

You have three options for using the theme system:

1. Use the Built-in Theme

import 'baseline-kit/theme';  // Default theme with light/dark mode support

2. Create a Custom Theme

Create your own theme.css file:

/* yourCustomTheme.css */
:root {
  /* Component-specific colors */
  --bk-baseline-color-line-theme: hsla(210, 100%, 50%, 0.15);
  --bk-baseline-color-flat-theme: hsla(270, 100%, 60%, 0.2);
  /* Add other component colors as needed */
}

/* Optional dark mode support */
@media (prefers-color-scheme: dark) {
  :root {
    --bk-baseline-color-line-theme: hsla(210, 100%, 50%, 0.2);
  }
}

Then import your custom theme:

import 'baseline-kit/styles';  // Required core styles
import './path/to/yourCustomTheme.css';  // Your custom theme

3. Override via Config

For minor adjustments, use the Config component:

<Config
  baseline={{
    colors: {
      line: 'rgba(255,0,0,0.1)',   // Custom red baseline lines
      flat: 'rgba(255,0,0,0.05)',  // Custom red baseline backgrounds
    }
  }}
>
  {/* Your components here */}
</Config>

Theme Variables Reference

See the default theme file for a complete example.

Browser Support

• Modern browsers (Chrome, Firefox, Safari, Edge)
• Requires CSS Grid Layout support and CSS Custom Properties
• Falls back gracefully in unsupported browsers

React 19 Features

Baseline Kit leverages React 19's latest features:

• use Hook: Replaces useContext for better performance and cleaner code
• Streamlined Context API: Uses the simplified Context Provider syntax
• JSX Transform: Takes advantage of the mandatory JSX transform in React 19

These modern features allow for cleaner code and better performance, but require React 19.

Server-Side Rendering (SSR)

Baseline Kit is fully compatible with React's Server-Side Rendering in frameworks like Next.js, Remix, and other React Router-based applications.

SSR-Friendly Design

Components are designed to:

• Provide consistent rendering between server and client
• Avoid hydration mismatches by using deterministic initial values
• Progressively enhance with client-side measurements after hydration
• Work with frameworks that use streaming SSR

SSR Mode Prop

Components accept an ssrMode prop to explicitly optimize for server rendering:

<Baseline
  height="100vh"
  ssrMode={true}
  debugging="visible"
/>

With ssrMode enabled, components use simplified rendering during SSR and initial hydration, then enhance with full features after client-side hydration completes.

Development

# Clone the repository
git clone https://github.com/dnvt/baseline-kit.git

# Install dependencies
bun install

# Start development server
bun run dev

# Run tests
bun run test

Performance Features

• Virtualizes large grid overlays
• Optimizes re-renders using React.memo
• Supports tree-shaking for minimal bundle size

Contributing

Please see CONTRIBUTING.md for detailed guidelines.

License

MIT © François Denavaut