React Native Skia Gesture 🤌🏽

A detection system for React Native Skia components.

Motivation

React Native Skia, provides many declarative APIs for building screens using React Components. However, Skia components are not real components, but abstract representations of a part of a drawing. Therefore direct interactions with individual Skia components can only be achieved indirectly from the Canvas (trying to figure out if the point on the screen that was clicked is within the element we want to interact with).

This package, simply provides a set of APIs to be able to interact directly with individual components.

Installation

You need to have already installed @shopify/react-native-skia (>= 0.1.157)

Open a Terminal in your project’s folder and install the library using yarn:

yarn add react-native-skia-gesture

or with npm:

npm install react-native-skia-gesture

Usage

import {
  Circle,
  useValue,
} from '@shopify/react-native-skia';

import {
  withTouchableHandler,
  Canvas,
  useGestureHandler,
} from 'react-native-skia-gesture';

const TouchableCircle = withTouchableHandler(Circle);

export default function App() {
  const cx = useValue(100);
  const cy = useValue(100);

  const circleGesture = useGestureHandler<{ x: number; y: number }>({
    onStart: (_, context) => {
      context.x = cx.current;
      context.y = cy.current;
    },
    onActive: ({ translationX, translationY }, context) => {
      cx.current = context.x + translationX;
      cy.current = context.y + translationY;
    },
  });

  return (
    <Canvas style={styles.fill}>
      <TouchableCircle cx={cx} cy={cy} r={50} color="red" {...circleGesture} />
    </Canvas>
  );
}

If the element is a Circle, Rect or RoundedRect, the package will automatically derive its touchablePath. Alternatively it will have to be passed as a parameter to the TouchableComponent.

...
const touchablePath = useComputedValue(() => {
  const path = new Path();
  path.addCircle(cx.current, cy.current, 50);
  return path;
}, [cx, cy]);

return (
  <Canvas style={styles.fill}>
    <TouchableCircle cx={cx} cy={cy} r={50} color="red" touchablePath={touchablePath} {...circleGesture} />
  </Canvas>
);
...

Ingredients

Canvas

It’s simply a Wrapper of Skia’s Canvas.


withTouchableHandler

It’s a HOC with which to wrap all Skia components with which you want to interact directly.


useGestureHandler

It’s a hook from which onStart, onActive, onEnd interactions can be managed. The hook provides as the second parameter of each callback a context that can be optionally used (strongly inspired by the useAnimatedGestureHandler hook).


Contributing

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

License

MIT


GitHub

View Github