path: root/js/lib/heart_renderer.js

'use strict';

((window) => {

  const kColorIteratorLimit = 256;

  /**
   * Renders a Heart, has its own canvas, which will be placed in the element
   * set by calling #render.
   *
   * @class HeartRenderer
   * @param {object} config configuration, extends any member of the renderer
   */
  const HeartRenderer = class HeartRenderer {

    constructor(config) {

      /**
       * The instance of the heart renderer being used
       *
       * @memberof HeartRenderer
       * @instance
       * @name canvas
       * @type HTMLCanvasElement
       * @default A brand new canvas
       */
      this.canvas = window.document.createElement('canvas');

      /**
       * The maximum fps that will be used
       *
       * @memberof HeartRenderer
       * @instance
       * @name fps
       * @type Number
       * @default 60
       */
      this.fps = 60;

      /**
       * The size of the heart as a percentage of the canvas smallest dimension
       *
       * @memberof HeartRenderer
       * @instance
       * @name heartSize
       * @type Number
       * @default 40
       */
      this.heartSize = 40;

      /**
       * The max size of the heart as a percentage of the canvas smallest dimension
       *
       * @memberof HeartRenderer
       * @instance
       * @name maxHeartSize
       * @type Number
       * @default 75
       */
      this.maxHeartSize = 75;

      /**
       * The min size of the heart as a percentage of the canvas smallest dimension
       *
       * @memberof HeartRenderer
       * @instance
       * @name minHeartSize
       * @type Number
       * @default 10
       */
      this.minHeartSize = 10;

      this._ticking = false; // Lock for wheel event.
      this._resizeMagnitude = 0.1; // Multiplies the wheel delta to resize the heart
      this._resizeSpeed = 1; // How many percent points per frame we'll resize to match target
      this._trackingSpeed = 10; // How many pixels per frame will we move to match target
      this._following = null; // The status of mouse follow.
      this._center = null; // The actual center
      this._targetHeartSize = this.heartSize;
      this._targetCenter = {
        x: 0,
        y: 0
      }; // the target coordinates
      this._animating = false; // The status of the animation.
      this._previousFrameTime = Date.now(); // The timestamp of the last frame for fps control
      this._cursorTimeout = 500; // Timeout to hide the cursor in milliseconds
      this._currentColor = { // The current color that will be painted
        red: 100,
        blue: 0,
        green: 50
      };
      this._colorSpeed = {
        red: 0.1,
        blue: 0.2,
        green: 0.15
      };
      this._colorDirection = {
        red: 1,
        blue: 1,
        green: 1
      };

      this._detectWheel();
      this.startFollowingMouse();

      Object.assign(this, config);
    }

    /**
     * Attaches the canvas to an HTML element
     *
     * @memberof HeartRenderer
     * @function render
     * @instance
     * @param {HTMLElement} element the element where we will attach our canvas
     */
    render(element) {

      element.appendChild(this.canvas);

      this._targetCenter = {
        x: Math.round(this.canvas.width / 2),
        y: Math.round(this.canvas.height / 2)
      }; // the target coordinates
      this.resize();
    }

    /**
     * Resizes the canvas
     *
     * @memberof HeartRenderer
     * @function render
     * @instance
     */
    resize() {

      if (this.canvas.parentElement) {
        this.canvas.width = this.canvas.parentElement.offsetWidth;
        this.canvas.height = this.canvas.parentElement.offsetHeight;
      }
    }

    /**
     * Follows the mouse
     *
     * @memberof HeartRenderer
     * @function startFollowingMouse
     * @instance
     */
    startFollowingMouse() {

      if (!this._following) {
        this._following = this._setCenterFromMouse.bind(this);
        this.canvas.addEventListener('mousemove', this._following);
      }
    }

    /**
     * Stop following the mouse
     *
     * @memberof HeartRenderer
     * @function stopFollowingMouse
     * @instance
     */
    stopFollowingMouse() {

      if (this._following) {
        this.canvas.removeEventListener('mouseover', this._following);
        this._following = null;
        this._targetCenter = {
          x: Math.round(this.canvas.width / 2),
          y: Math.round(this.canvas.height / 2)
        }; // the target coordinates
      }
    }

    /**
     * Gets the context from the current canvas and starts the animation process
     *
     * @memberof HeartRenderer
     * @function activate
     * @instance
     */
    activate() {

      const context = this.canvas.getContext('2d');
      this._startAnimating(context);
    }

    /**
     * Stops the animation process
     *
     * @memberof HeartRenderer
     * @function deactivate
     * @instance
     */
    deactivate() {

      this._stopAnimating();
    }

    // Starts the animation loop
    _startAnimating(context) {

      this._frameDuration = 1000 / this.fps;
      this._animating = true;

      this._animate(context);
    }

    // Stops the animation on the next frame.
    _stopAnimating() {

      this._animating = false;
    }

    // Runs the animation step controlling the FPS
    _animate(context) {

      if (!this._animating) {
        return;
      }

      window.requestAnimationFrame(this._animate.bind(this, context));

      const currentFrameTime = Date.now();
      const delta = currentFrameTime - this._previousFrameTime;

      if (delta > this._frameDuration) {
        this._previousFrameTime = Date.now();
        this._animateStep(context, delta);
      }
    }

    // The actual animation processing function.
    _animateStep(context, delta) {

      this._updateColor(delta);
      this._drawHeart(context, delta);
    }

    // Updates the current color
    _updateColor(delta) {

      const red = this._updateColorComponent('red', delta);
      const green = this._updateColorComponent('green', delta);
      const blue = this._updateColorComponent('blue', delta);

      this._currentColor.red = red;
      this._currentColor.green = green;
      this._currentColor.blue = blue;
    }

    // Updates a single color component.
    _updateColorComponent(component, delta) {

      let color = Math.round(this._currentColor[component] + (delta * this._colorSpeed[component] * this._colorDirection[component]));
      if (color >= kColorIteratorLimit) {
        this._colorDirection[component] = -1;
        color = kColorIteratorLimit;
      }

      if (color <= 0) {
        this._colorDirection[component] = 1;
        color = 0;
      }

      return color;
    }

    // Draws a heart
    _drawHeart(context, delta) {

      const canvasHeight = this.canvas.height;
      const canvasWidth = this.canvas.width;

      const referenceDimension = canvasWidth < canvasHeight ? canvasWidth : canvasHeight;

      this.heartSize += Math.sign(this._targetHeartSize - this.heartSize) * this._resizeSpeed;

      const heartSize = Math.round(referenceDimension * this.heartSize * .01);
      const radius = heartSize / 2;

      if (!this._center) {
        this._center = {};
        this._center.x = Math.round(canvasWidth / 2);
        this._center.y = Math.round(canvasHeight / 2);
      }

      const deltaY = this._targetCenter.y - this._center.y;
      const deltaX = this._targetCenter.x - this._center.x;
      const angle = Math.atan2(deltaY, deltaX);

      // Move towards the target
      this._center.x += Math.cos(angle) * this._trackingSpeed;
      this._center.y += Math.sin(angle) * this._trackingSpeed;

      const canvasCenterX = this._center.x;
      const canvasCenterY = this._center.y;
      const centerX = -radius;
      const centerY = -radius;


      // translate and rotate, adjusting for weight of the heart.
      context.translate(canvasCenterX, canvasCenterY + radius / 4);
      context.rotate(-45 * Math.PI / 180);

      // Fill the ventricles of the heart
      context.fillStyle = `rgb(${this._currentColor.red}, ${this._currentColor.green}, ${this._currentColor.blue})`;
      context.fillRect(centerX, centerY, heartSize, heartSize);

      // Left atrium
      context.beginPath();
      context.arc(centerX + radius, centerY, radius, 0, 2 * Math.PI, false);
      context.fill();
      context.closePath();

      // Right atrium
      context.beginPath();
      context.arc(centerX + heartSize, centerY + radius, radius, 0, 2 * Math.PI, false);
      context.fill();
      context.closePath();

      context.setTransform(1, 0, 0, 1, 0, 0);
    }

    // Sets the center from mouse
    _setCenterFromMouse(event) {

      this._showCursor();
      this._targetCenter.x = event.offsetX;
      this._targetCenter.y = event.offsetY;
      setTimeout(this._hideCursor.bind(this), this._cursorTimeout);
    }

    // Binds the wheel event to resize the heart
    _detectWheel() {

      this.canvas.addEventListener('wheel', this._onWheel.bind(this));
    }

    // Handle the mouse wheel movement
    _onWheel(event) {

      if (!this._ticking) {
        this._ticking = true;
        window.requestAnimationFrame(this._resizeHeartFromDelta.bind(this, event.deltaY));
      }
    }

    // Use delta to resize the heart
    _resizeHeartFromDelta(delta) {

      let heartSize = this.heartSize + (this._resizeMagnitude * delta);

      if (heartSize > this.maxHeartSize) {
        heartSize = this.maxHeartSize;
      }

      if (heartSize < this.minHeartSize) {
        heartSize = this.minHeartSize;
      }

      this._targetHeartSize = heartSize;
      this._ticking = false;
    }

    // Apply a class to show the cursor.
    _showCursor() {

      this.canvas.classList.add('mouse-moving');
    }

    // Remove class to hide the cursor.
    _hideCursor() {

      this.canvas.classList.remove('mouse-moving');
    }
  };


  window.HeartRenderer = HeartRenderer;
})(window);