Class SafeScaleManager

src/scale-manager/SafeScaleManager.js:23–198

 * Handles scaling the game
 */
export class SafeScaleManager {
  /**
   * Creates an instance of SafeScaleManager.
   * @param  {object} param
   * @param  {Number} param.width width of game
   * @param  {Number} param.height height of game
   * @param  {Number} param.safeWidth width of safe area for the game
   * @param  {Number} param.safeHeight height of safe area for the game
   * @param  {ScaleCallback} param.callback function called to scale game and canvas
   * @memberof SafeScaleManager
   */
  constructor({
    width,
    height,
    safeWidth = Infinity,
    safeHeight = Infinity,
    callback = () => {}
  }) {
    this.gameWidth = width;
    this.gameHeight = height;
    this.safeWidth = safeWidth <= width ? safeWidth : width;
    this.safeHeight = safeHeight <= height ? safeHeight : height;
    this.callback = callback;
    this.scaleRatio = 1;

    // Rectangle containing the total viewable game content.
    this.viewArea = { 
      x: 0, 
      y: 0, 
      width: 0, 
      height: 0, 
      left: 0, 
      right: 0, 
      top: 0, 
      bottom: 0 
    };

    /** @type {ScaledEntity[]} */
    this.entities = [];

    /** @private */
    this.resizer = new ResizeHelper(this.onResize.bind(this));

    if (callback instanceof Function) {
      this.enable(callback);
    }
  }

  /**
   * onResize maps and passes the relevant data to the user provided callback function.
   * @param {object} param
   * @param {number} param.width - Current window width
   * @param {number} param.height - Current window height
   * @private
   */
  onResize({ width, height }) {
    // Calculate the scaling ratio.
    this.scaleRatio = Math.min(width / this.safeWidth, height / this.safeHeight);