phaser/src/geom/polygon/Contains.js

A fast, free and fun HTML5 Game Framework for Desktop and Mobile web browsers from the team at Phaser Studio Inc.

/**
 * @author       Richard Davey <rich@phaser.io>
 * @copyright    2013-2025 Phaser Studio Inc.
 * @license      {@link https://opensource.org/licenses/MIT|MIT License}
 */

// Checks whether the x and y coordinates are contained within this polygon.
//  Adapted from http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html by Jonas Raoni Soares Silva

/**
 * Checks if a point is within the bounds of a Polygon.
 *
 * @function Phaser.Geom.Polygon.Contains
 * @since 3.0.0
 *
 * @param {Phaser.Geom.Polygon} polygon - The Polygon to check against.
 * @param {number} x - The X coordinate of the point to check.
 * @param {number} y - The Y coordinate of the point to check.
 *
 * @return {boolean} `true` if the point is within the bounds of the Polygon, otherwise `false`.
 */
var Contains = function (polygon, x, y)
{
    var inside = false;

    for (var i = -1, j = polygon.points.length - 1; ++i < polygon.points.length; j = i)
    {
        var ix = polygon.points[i].x;
        var iy = polygon.points[i].y;

        var jx = polygon.points[j].x;
        var jy = polygon.points[j].y;

        if (((iy <= y && y < jy) || (jy <= y && y < iy)) && (x < (jx - ix) * (y - iy) / (jy - iy) + ix))
        {
            inside = !inside;
        }
    }

    return inside;
};

module.exports = Contains;