index.js

import React, { Component } from 'react';
import PropTypes from 'prop-types';
import { ART } from 'react-native';
const { Shape, Path } = ART;

/**
 * Wedge is a React component for drawing circles, wedges and arcs.	Like other
 * ReactART components, it must be used in a <Surface>.
 */
export default class Wedge extends Component<void, any, any> {

  static propTypes = {
    outerRadius: PropTypes.number.isRequired,
    startAngle: PropTypes.number.isRequired,
    endAngle: PropTypes.number.isRequired,
    originX: PropTypes.number.isRequired,
    originY: PropTypes.number.isRequired,
    innerRadius: PropTypes.number,
  };


  constructor(props : any) {
    super(props);
    (this:any).circleRadians = Math.PI * 2;
    (this:any).radiansPerDegree = Math.PI / 180;
    (this:any)._degreesToRadians = this._degreesToRadians.bind(this);
  }

  /**
   * _degreesToRadians(degrees)
   *
   * Helper function to convert degrees to radians
   *
   * @param {number} degrees
   * @return {number}
   */
  _degreesToRadians(degrees : number) : number {
    if (degrees !== 0 && degrees % 360 === 0) { // 360, 720, etc.
      return (this:any).circleRadians;
    }
    return degrees * (this:any).radiansPerDegree % (this:any).circleRadians;
  }

  /**
   * _createCirclePath(or, ir)
   *
   * Creates the ReactART Path for a complete circle.
   *
   * @param {number} or The outer radius of the circle
   * @param {number} ir The inner radius, greater than zero for a ring
   * @return {object}
   */
  static _createCirclePath(or : number, ir : number) : Path {
    const path = new Path();

    path.move(0, or)
      .arc(or * 2, 0, or)
      .arc(-or * 2, 0, or);

    if (ir) {
      path.move(or - ir, 0)
        .counterArc(ir * 2, 0, ir)
        .counterArc(-ir * 2, 0, ir);
    }

    path.close();

    return path;
  }

  /**
   * _createArcPath(sa, ea, ca, or, ir)
   *
   * Creates the ReactART Path for an arc or wedge.
   *
   * @param originX
   * @param originY
   * @param {number} startAngle The starting degrees relative to 12 o'clock
   * @param {number} endAngle The ending degrees relative to 12 o'clock
   * @param {number} or The outer radius in pixels
   * @param {number} ir The inner radius in pixels, greater than zero for an arc
   * @return {object}
   */
  _createArcPath(originX : number, originY : number, startAngle : number, endAngle : number, or : number, ir : number) : Path {
    const path = new Path();

    // angles in radians
    const sa = this._degreesToRadians(startAngle);
    const ea = this._degreesToRadians(endAngle);

    // central arc angle in radians
    const ca = sa > ea ? (this:any).circleRadians - sa + ea : ea - sa;

    // cached sine and cosine values
    const ss = Math.sin(sa);
    const es = Math.sin(ea);
    const sc = Math.cos(sa);
    const ec = Math.cos(ea);

    // cached differences
    const ds = es - ss;
    const dc = ec - sc;
    const dr = ir - or;

    // if the angle is over pi radians (180 degrees)
    // we will need to let the drawing method know.
    const large = ca > Math.PI;

    // TODO (sema) Please improve theses comments to make the math
    // more understandable.
    //
    // Formula for a point on a circle at a specific angle with a center
    // at (0, 0):
    // x = radius * Math.sin(radians)
    // y = radius * Math.cos(radians)
    //
    // For our starting point, we offset the formula using the outer
    // radius because our origin is at (top, left).
    // In typical web layout fashion, we are drawing in quadrant IV
    // (a.k.a. Southeast) where x is positive and y is negative.
    //
    // The arguments for path.arc and path.counterArc used below are:
    // (endX, endY, radiusX, radiusY, largeAngle)

    path.move(or + or * ss, or - or * sc) // move to starting point
      .arc(or * ds, or * -dc, or, or, large) // outer arc
      .line(dr * es, dr * -ec);	// width of arc or wedge

    if (ir) {
      path.counterArc(ir * -ds, ir * dc, ir, ir, large); // inner arc
    }

    return path;
  }

  render() : any {
    // angles are provided in degrees
    const startAngle = this.props.startAngle;
    const endAngle = this.props.endAngle;
    // if (startAngle - endAngle === 0) {
    // 	return null;
    // }

    // radii are provided in pixels
    const innerRadius = this.props.innerRadius || 0;
    const outerRadius = this.props.outerRadius;

    const { originX, originY } = this.props;

    // sorted radii
    const ir = Math.min(innerRadius, outerRadius);
    const or = Math.max(innerRadius, outerRadius);

    let path;
    if (endAngle >= startAngle + 360) {
      path = Wedge._createCirclePath(or, ir);
    } else {
      path = this._createArcPath(originX, originY, startAngle, endAngle, or, ir);
    }

    return <Shape {...this.props} d={path} />;
  }
}