README.md

@dcl/react-ecs

React bindings for Decentraland's Entity Component System (ECS), providing a declarative way to build UIs in Decentraland scenes using React's component model and JSX syntax.

Features

• Flexbox-based Layout: Implements a subset of CSS Flexbox for powerful and intuitive UI layouts
• React Components: Familiar React-like component API for building UIs
• Type Safety: Full TypeScript support with proper type definitions
• Event Handling: Support for mouse events and user interactions
• Performance: Optimized reconciliation for minimal runtime overhead
• Theme Support: Built-in light and dark theme system with context-based switching

Component Guidelines

All components in @dcl/react-ecs must:

• Return JSX.Elements for consistency and composability
• Support theme integration through context
• Be reusable and composable with other components

Installation

npm install @dcl/react-ecs

Basic Usage

import { ReactEcs, UiEntity, Label, Button } from '@dcl/react-ecs'

export function MyUI() {
  return (
    <UiEntity
      uiTransform={{
        width: 300,
        height: 100,
        display: 'flex',
        justifyContent: 'center',
        alignItems: 'center'
      }}
    >
      <Label value="Hello Decentraland!" />
      <Button value="Click Me!" onMouseDown={() => console.log('clicked!')} />
    </UiEntity>
  )
}

Theme System

The package includes a theme system for consistent UI styling:

import { ReactEcs, ThemeProvider, Button } from '@dcl/react-ecs'

// Wrap your UI with ThemeProvider
export function MyUI() {
  return (
    <ThemeProvider>
      <Button value="Theme-Aware Button" />
    </ThemeProvider>
  )
}

// Use themes in custom components
function CustomComponent() {
  const { theme, toggleTheme } = React.useContext(ThemeContext)

  return (
    <UiEntity
      uiBackground={{
        color: theme === 'light' ? '#FFFFFF' : '#000000'
      }}
      onMouseDown={toggleTheme}
    />
  )
}

Components

Core Components

• UiEntity: Base component for UI elements
• Label: Text display component
• Button: Interactive button component
• Input: Text input field
• Dropdown: Selection dropdown menu

Layout System

The layout system is based on Flexbox and supports the following properties:

• display: 'flex'
• flexDirection: 'row' | 'column'
• justifyContent: 'flex-start' | 'center' | 'flex-end' | 'space-between' | 'space-around'
• alignItems: 'flex-start' | 'center' | 'flex-end' | 'stretch'
• width, height
• margin, padding
• positionType: 'absolute' | 'relative'

Event Handling

Components support the following mouse events:

<Button onMouseDown={() => {}} onMouseUp={() => {}} onMouseEnter={() => {}} onMouseLeave={() => {}} />

Technical Details

The package implements a custom React reconciler that bridges React's component model with Decentraland's ECS. It:

1. Translates JSX into ECS entities and components
2. Manages component lifecycle and updates
3. Handles event delegation and bubbling
4. Provides a performant update mechanism

Related Documentation

For more details about the UI system architecture and design decisions:

• ADR-124: Implementing Flexbox-based UI
• ADR-125: User Interface Components
• ADR-237: SDK 7 Custom UI Components

License

Apache 2.0