phaser/src/math/RotateAround.js

/**
 * @author       Richard Davey <rich@photonstorm.com>
 * @copyright    2020 Photon Storm Ltd.
 * @license      {@link https://opensource.org/licenses/MIT|MIT License}
 */

/**
 * Rotate a `point` around `x` and `y` to the given `angle`, at the same distance.
 *
 * In polar notation, this maps a point from (r, t) to (r, angle), vs. the origin (x, y).
 *
 * @function Phaser.Math.RotateAround
 * @since 3.0.0
 *
 * @param {(Phaser.Geom.Point|object)} point - The point to be rotated.
 * @param {number} x - The horizontal coordinate to rotate around.
 * @param {number} y - The vertical coordinate to rotate around.
 * @param {number} angle - The angle of rotation in radians.
 *
 * @return {Phaser.Geom.Point} The given point, rotated by the given angle around the given coordinates.
 */
var RotateAround = function (point, x, y, angle)
{
    var c = Math.cos(angle);
    var s = Math.sin(angle);

    var tx = point.x - x;
    var ty = point.y - y;

    point.x = tx * c - ty * s + x;
    point.y = tx * s + ty * c + y;

    return point;
};

module.exports = RotateAround;