mixins/Hittable.js

  1. 'use strict';
  3. const { Point2D } = require('../shared.js');
  4. const Interactable = require('./Interactable.js');
  6. /**
  7.  * The Hitbox interface is used by the Hittable mixin. If a Hitbox is attached
  8.  * to a Hittable instance object, hit detection will be performed on the object
  9.  * when the user's first input in an interaction sequence touches down.
  10.  *
  11.  * Note that a class implementing the Hitbox interface should not worry about
  12.  * applying transformations to the points it receives. That will be taken care
  13.  * of by the Hittable mixin. To produce accurate results, a Hitbox should behave
  14.  * as if the object it is associated with is positioned at x = 0, y = 0, with
  15.  * scale = 1 and rotation = 0. That is, with the identity transformation.
  16.  *
  17.  * @interface Hitbox
  18.  * @memberof module:shared
  19.  */
  21. /**
  22.  * Report whether the given (x,y) point is contained within the shape.
  23.  *
  24.  * @function
  25.  * @name module:shared.Hitbox#contains
  26.  * @param {module:shared.Point2D} point - The point to test.
  27.  * @return {boolean} True if the given point is inside the shape, false
  28.  * otherwise.
  29.  */
  31. /**
  32.  * This mixin extends the Interactable mixin by allow hit detection. A Hittable
  33.  * will not automatically be able to respond to hit detection. To make a
  34.  * Hittable item responsive, add a 'hitbox' property to the class or
  35.  * instantiated object, which is itself an instance of a class which implements
  36.  * the 'Hitbox' interface.
  37.  *
  38.  * The purpose of the Hittable mixin is simply to provide functionality for
  39.  * interacting with the 'hitbox' property.
  40.  *
  41.  * @private
  42.  * @memberof module:mixins
  43.  *
  44.  * @mixin
  45.  * @mixes module:mixins.Interactable
  46.  */
  47. const Hittable = (sclass) =>
  48.   class Hittable extends Interactable(sclass) {
  49.     /**
  50.      * The hitbox for this Hittable instance. If it is null, hit detection will
  51.      * always return a falsy value.
  52.      *
  53.      * @name hitbox
  54.      * @type {?module:shared.Hitbox}
  55.      * @default undefined
  56.      * @memberof module:mixins.Hittable
  57.      */
  59.     /**
  60.      * Checks whether a point with the given x,y coordinates is contained by
  61.      * this item.
  62.      *
  63.      * @memberof module:mixins.Hittable
  64.      *
  65.      * @param {number} px - x coordinate of the point to check.
  66.      * @param {number} py - y coordinate of the point to check.
  67.      *
  68.      * @return {boolean} True if the (x,y) point is located inside this Item.
  69.      * False otherwise.
  70.      */
  71.     containsPoint(px, py) {
  72.       const point = new Point2D(px, py).minus(this).divideBy(this.scale).rotate(this.rotation);
  73.       return this.hitbox && this.hitbox.contains(point);
  74.     }
  75.   };
  77. module.exports = Hittable;