zrender/src/contain/polygon.ts

A lightweight graphic library providing 2d draw for Apache ECharts

import windingLine from './windingLine';
import { VectorArray } from '../core/vector';

const EPSILON = 1e-8;

function isAroundEqual(a: number, b: number): boolean {
    return Math.abs(a - b) < EPSILON;
}

export function contain(points: VectorArray[], x: number, y: number) {
    let w = 0;
    let p = points[0];

    if (!p) {
        return false;
    }

    for (let i = 1; i < points.length; i++) {
        const p2 = points[i];
        w += windingLine(p[0], p[1], p2[0], p2[1], x, y);
        p = p2;
    }

    // Close polygon
    const p0 = points[0];
    if (!isAroundEqual(p[0], p0[0]) || !isAroundEqual(p[1], p0[1])) {
        w += windingLine(p[0], p[1], p0[0], p0[1], x, y);
    }

    return w !== 0;
}