Keg Components

• Base UI Components for the Keg Core and Tap extensions

Add to your project

  yarn add @keg-hub/keg-components
  npm install @keg-hub/keg-components

Developer setup

• git clone https://github.com/simpleviewinc/keg-hub.git ~/keg-hub
• cd ~/keg-hub/repos/keg-components
• yarn install
• yarn sb - local storybook
• yarn sb:native - native local storybook
• yarn sb:web - web local storybook
• yarn format - formats your code based on the config set in configs/eslint.config.js && configs/prettier.config.js
• yarn eslint:watch - watches any code change for any lint errors

Theming

Keg Components leverages re-theme for dynamic theming across platforms and viewport sizes

Theme objects

• For new components, create and export your theme objects in src/theme/components

Using themes in components

• Use the useThemePath hook:

  import { useThemePath } from '../../hooks'
  
  const FooBar = (props) => {
    // theme from `src/theme/components/fooBar.js`
    const fooBarTheme = useThemePath('fooBar')
    return (
      <View style={fooBarTheme.main}>
        ...
      </View>
    )
  }

Conventions

Folder structure:

• if you are creating a function that has a different implementation for native
  • DO
    • place them in a folder with the same name as the export
    • add an alias for them in the /configs/aliases.json file
    • add a index.js exporting the alias

       /src/components
          /linearGradient
             linearGradient.js
             linearGradient.native.js
             index.js   
                    
        // /configs/aliases.json
        {
          ...other aliases,
          "KegLinearGradient": "src/components/linearGradient/linearGradient${platform}.js",
        }
    
        // /src/components/linearGradient/index.js
        export * from 'KegLinearGradient'
    

Every component implemented in keg-components that has a theme should define main and content styles:

/* src/theme/components/sampleButton.js */
export const sampleButton = {
  main: { ... },
  content: { ... }
}

• main: the root styles of the component
• content: the styles for content in the component
• Example: a simple Button component's main style would theme its root View component, whereas the content style themes its inner Text component:

  /* src/components/button/sampleButton.js */
  export const SampleButton = (props) => {
    const buttonTheme = useThemePath('sampleButton', props.style)
    return (
      <View style={buttonTheme.main}>
        <Text style={buttonTheme.content}>
          { props.text }
        </Text>
      </View>
    )
  }

Components sometimes import/consume other keg-components and then need to style those imported components within their styling context. These styles should be defined in the consumer's theme object

• Example: a button with an icon

/* src/theme/components/iconButton.js */
export const iconButton= {
  main: { ... },
  content: { ... },
  icon: {
    main: { ... },
    content: { ... }
  }
}

Use size keys (e.g. $small, $medium, etc.) and platform keys (e.g. $native, $web, $all, etc.) to wrap style properties only. This ensures that the shape of the theme object remains constant across all platforms and viewport sizes.

• DON'T do this:

export const button = {
  $web: { 
    main: {
      backgroundColor: 'coral'
    },
  },
  $native: {
    main: { 
      backgroundColor: 'green' 
    },
    content: { 
      margin: 15 
    }
  }
}

• DO this:

export const button = {
  main: {
    $native: { 
      backgroundColor: 'green'
    },
    $web: { 
      backgroundColor: 'coral'
    }
  },
  content: {
    $native:  { 
      margin: 15
    }
  }
}

• In the first case, the theme object would not have the content styles on the $web platform, making it inconsistent with $native

Icons

• TODO - add info on adding SVG's

Accessibility

• Mapping of accessibilityRole prop value to Web Element
• Example => <Link accessibilityRole='link'> => <a role='link'>

  article: 'article',
  banner: 'header',
  complementary: 'aside',
  contentinfo: 'footer',
  form: 'form',
  link: 'a',
  list: 'ul',
  listitem: 'li',
  main: 'main',
  navigation: 'nav',
  region: 'section',
  adjustable: 'slider',
  button: 'button',
  // Heading mapping leverages the `aria-level` prop to determine the heading element
  // Example <Text accessibilityRole='header' aria-level='1' > => <h1>
  header: 'heading',
  image: 'img',
  link: 'link',
  none: 'presentation',
  search: 'search',
  summary: 'region',

Create Element

• This library exports a createElement method
• This method allows create custom native elements per platform, for needs such as:
  • Defining className when on a web platform
  • Overwriting the Text component, but still taking advantage of the accessability props
  • TODO: Give more examples