arcade-physics/lib/geom/line/BresenhamPoints.js

Use Arcade Physics without Phaser.

"use strict";
/**
 * @author       Richard Davey <rich@photonstorm.com>
 * @copyright    2020 Photon Storm Ltd.
 * @license      {@link https://opensource.org/licenses/MIT|MIT License}
 */
Object.defineProperty(exports, "__esModule", { value: true });
/**
 * Using Bresenham's line algorithm this will return an array of all coordinates on this line.
 *
 * The `start` and `end` points are rounded before this runs as the algorithm works on integers.
 *
 * @function Phaser.Geom.Line.BresenhamPoints
 * @since 3.0.0
 *
 * @param {Phaser.Geom.Line} line - The line.
 * @param {number} [stepRate=1] - The optional step rate for the points on the line.
 * @param {Phaser.Types.Math.Vector2Like[]} [results] - An optional array to push the resulting coordinates into.
 *
 * @return {Phaser.Types.Math.Vector2Like[]} The array of coordinates on the line.
 */
const BresenhamPoints = (line, stepRate, results) => {
    if (stepRate === undefined) {
        stepRate = 1;
    }
    if (results === undefined) {
        results = [];
    }
    let x1 = Math.round(line.x1);
    let y1 = Math.round(line.y1);
    const x2 = Math.round(line.x2);
    const y2 = Math.round(line.y2);
    const dx = Math.abs(x2 - x1);
    const dy = Math.abs(y2 - y1);
    const sx = x1 < x2 ? 1 : -1;
    const sy = y1 < y2 ? 1 : -1;
    let err = dx - dy;
    results.push({ x: x1, y: y1 });
    let i = 1;
    while (!(x1 === x2 && y1 === y2)) {
        const e2 = err << 1;
        if (e2 > -dy) {
            err -= dy;
            x1 += sx;
        }
        if (e2 < dx) {
            err += dx;
            y1 += sy;
        }
        if (i % stepRate === 0) {
            results.push({ x: x1, y: y1 });
        }
        i++;
    }
    return results;
};
exports.default = BresenhamPoints;
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