react-native-layout-primitives

react-native-layout-primitives

A collection of layout components based on View designed to supercharge your UI development process.

• Motivation
• Installation
• Usage
• API
  • Stack
  • Row
  • AbsoluteStack
  • Size
• Example
• Contributing
• License

Motivation

Layout is one of the most overlooked aspects of design systems. React Native provides the View component as the foundational building block for user interfaces. This low-level primitive offers significant flexibility, including over 50 style properties. However, when you have that many options it's a breeze to end up with messy code, characterized by:

• Mixing inline styles with styles defined in StyleSheet
• Utilizing arbitrary values, or "magic numbers."
• An over reliance on margins, the devil of layout
• Disrupting the natural top-to-bottom flow due to styles being placed at the bottom of the file
• A lack of separation of concerns, with the Text component also handling layout responsibilities
• Non-adherence to design system conventions

This library aims to introduce the right abstractions on top of View to address these issues, establishing clear rules and guidelines supported by industry-leading experts:

• Components should be free of surrounding white space
• Layout components are responsible for managing whitespace
• The use of margins is generally prohibited, except for negative margins

These principles let you approach layout with the precision of a designer.

For those interested in exploring these concepts further, the article Rethinking Layout Practices provides an in-depth analysis.

Installation

npm install react-native-layout-primitives

Usage

import {
  Stack,
  Row,
  AbsoluteStack,
  Size,
} from 'react-native-layout-primitives';

const App = () => (
  <Stack flex={1}>
    <Row background="lightblue" padding={[Size.M, Size.L]} spacing={Size.M}>
      <Row align="center" padding={Size.S}>
        <Text>Foo</Text>
      </Row>
      <Stack justify="center" padding={Size.S} spacing={Size.Xs}>
        <Text>Hello</Text>
        <Text>World</Text>
      </Stack>
      <Stack width="100%" height={100} background="red" borderRadius={Size.S} />
    </Row>
    <Row flex={1} background="gray" padding={Size.Xl} spacing={Size.L}>
      <Stack grow={1}>
        <Button />
      </Stack>
      <Stack basis={120}>
        <Button />
      </Stack>
    </Row>
    <AbsoluteStack
      width={100}
      height={100}
      bottom={Size.M}
      right={Size.M}
      background="black"
    />
  </Stack>
);

API

This library provides three layout components and a valuable enum for grid-based spacing.

Stack

The Stack component is essential for layout tasks, stacking children vertically by default, akin to the View component. It extends the ViewProps interface, allowing it to accept all the properties available to View. Additionally, it introduces the following properties to control layout:

// See the `Size` enum for possible values
type GridValue = Size | 0

interface StackProps extends ViewProps {
  flex?: number;
  direction?: FlexStyle['flexDirection'];
  padding?:
    | GridValue
    | [GridValue]
    | [GridValue, GridValue]
    | [GridValue, GridValue, GridValue, GridValue];
  spacing?: GridValue;
  justify?: FlexStyle['justifyContent'];
  align?: FlexStyle['alignItems'];
  wrap?: FlexStyle['flexWrap'];
  borderRadius?: number;
  background?: string;
  grow?: number;
  shrink?: number;
  basis?: number;
  width?: number | DimensionValue;
  height?: number | DimensionValue;
  children?: React.ReactNode;
}

As a last resort, you can always use the style prop to pass custom styles.

Row

A container that stacks children horizontally. It serves as syntactic sugar for a Stack with direction="row". By default, it wraps them into multiple lines and offers the same properties as the Stack component.

AbsoluteStack

A container with absolute positioning. It serves as syntactic sugar for Stack with position="absolute". In addition to all Stack properties, it introduces four new ones: top, right, bottom, and left.

Size

Size is a practical numerical enum that adopts the t-shirt sizing convention. This approach is preferred over using strings, like m or s, because it enables mathematical operations in specific scenarios, such as:

• Creating multiples of a size, indicated by values like XXl or XXXl.
• Adding or subtracting sizes to devise custom spacing, exemplified by Size.M + Size.Xs.

enum Size {
  None = 0,
  Xs = 4,
  S = 8,
  M = 16,
  L = 24,
  Xl = 32,
}

Example

You can play with the Expo example app in the example folder. To run it, follow these steps:

cd example
npm install
npm start

Alternatively, you can run the example app in the browser by visiting this snack link.

Contributing

See the contributing guide to learn how to contribute to the repository and the development workflow.

License

MIT

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