p5Drawer/Ray.functions.js

'use strict';


const Rac = require('../Rac');
const utils = require('../util/utils');


module.exports = function attachRayFunctions(rac) {

  /**
  * Returns a new `Point` located where the ray touches the canvas edge.
  *
  * When the ray is outside the canvas and pointing away, `null` is
  * returned.
  *
  * Added  to `Rac.Ray.prototype` when `{@link Rac.P5Drawer}` is setup as
  * `[rac.drawer]{@link Rac#drawer}`.
  * @returns {?Rac.Point}
  */
  Rac.Ray.prototype.pointAtCanvasEdge = function(margin = 0) {
    let edgeRay = this.rayAtCanvasEdge(margin);
    if (edgeRay == null) {
      return null;
    }

    return edgeRay.start;
  };


  /**
  * Returns a new `Ray` that starts at the point where the `this` touches
  * the canvas edge and pointed towards the inside of the canvas.
  *
  * When the ray is outside the canvas and pointing away, `null` is
  * returned.
  *
  * Added  to `Rac.Ray.prototype` when `{@link Rac.P5Drawer}` is setup as
  * `[rac.drawer]{@link Rac#drawer}`.
  *
  * @returns {?Rac.Ray}
  */
  Rac.Ray.prototype.rayAtCanvasEdge = function(margin = 0) {
    const turn = this.angle.turn;
    const p5 = this.rac.drawer.p5;

    const downEdge  = p5.height - margin;
    const leftEdge  = margin;
    const upEdge    = margin;
    const rightEdge = p5.width - margin;

    // pointing down
    if (turn >= 1/8 && turn < 3/8) {
      let edgeRay = null;
      if (this.start.y < downEdge) {
        edgeRay = this.pointAtY(downEdge).ray(this.rac.Angle.up);
        if (edgeRay.start.x > rightEdge) {
          edgeRay = this.pointAtX(rightEdge).ray(this.rac.Angle.left);
        } else if (edgeRay.start.x < leftEdge) {
          edgeRay = this.pointAtX(leftEdge).ray(this.rac.Angle.right);
        }
      }
      return edgeRay;
    }

    // pointing left
    if (turn >= 3/8 && turn < 5/8) {
      let edgeRay = null;
      if (this.start.x >= leftEdge) {
        edgeRay = this.pointAtX(leftEdge).ray(this.rac.Angle.right);
        if (edgeRay.start.y > downEdge) {
          edgeRay = this.pointAtY(downEdge).ray(this.rac.Angle.up);
        } else if (edgeRay.start.y < upEdge) {
          edgeRay = this.pointAtY(upEdge).ray(this.rac.Angle.down);
        }
      }
      return edgeRay;
    }

    // pointing up
    if (turn >= 5/8 && turn < 7/8) {
      let edgeRay = null;
      if (this.start.y >= upEdge) {
        edgeRay = this.pointAtY(upEdge).ray(this.rac.Angle.down);
        if (edgeRay.start.x > rightEdge) {
          edgeRay = this.pointAtX(rightEdge).ray(this.rac.Angle.left);
        } else if (edgeRay.start.x < leftEdge) {
          edgeRay = this.pointAtX(leftEdge).ray(this.rac.Angle.right);
        }
      }
      return edgeRay;
    }

    // pointing right
    let edgeRay = null;
    if (this.start.x < rightEdge) {
      edgeRay = this.pointAtX(rightEdge).ray(this.rac.Angle.left);
      if (edgeRay.start.y > downEdge) {
          edgeRay = this.pointAtY(downEdge).ray(this.rac.Angle.up);
        } else if (edgeRay.start.y < upEdge) {
          edgeRay = this.pointAtY(upEdge).ray(this.rac.Angle.down);
        }
    }
    return edgeRay;
  };

} // attachRayFunctions
Source: p5Drawer/Ray.functions.js
