g-oscillator.html

<link rel="import" href="./bower_components/polymer/polymer.html">
<link href='http://fonts.googleapis.com/css?family=Inconsolata' rel='stylesheet' type='text/css'>

<polymer-element name="g-oscillator" attributes="log speed">
  <template>
  <style>
    canvas {
      position: absolute;
      width: 100%;
      height: 100%;
    }
  </style>
  <canvas id="freq" 
      on-mousedown={{onMouseDown}}
      on-mouseup={{onMouseUp}}
      on-mousemove={{onMouseMove}}
      on-mouseout={{onMouseOut}}
      on-touchstart={{onTouchStart}}
      on-touchend={{onTouchEnd}}
      on-touchmove={{onTouchMove}}></canvas>
  </template>
  <script>
Polymer('g-oscillator', {
  gainAmount: 0.2,
  history: [],
  log: false,
  speed: 2,

  fadeTime: 0.01,

  attachedCallback: function() {
    this.audioContext = new AudioContext();
    this.loop();
  },

  loop: function() {
    this.width = window.innerWidth;
    this.height = window.innerHeight;

    this.addHistory(this.lastY);
    var canvas = this.$.freq;
    var ctx = canvas.getContext('2d');
    canvas.width = this.width;
    canvas.height = this.height;

    var size = 6;
    var nyquist = this.audioContext.sampleRate/2;

    for (var i = 0; i < this.history.length; i++) {
      var y = this.history[i];
      if (y === null) {
        continue;
      }
      var x = this.width - (this.history.length - i - 1) * this.speed;
      // TODO(smus): Elimiate fudge factor.
      ctx.fillStyle = 'red';
      ctx.fillRect(x - size/2, y - size/2, size, size);
    }

    if (this.osc_) {
      // Label the point.
      var label = this.formatFrequency_(this.lastFreq);
      ctx.font = '20px Inconsolata'
      ctx.fillText(label, this.lastX, this.lastY);
    }
    requestAnimationFrame(this.loop.bind(this));
  },

  formatFrequency_: function(freq) {
    return Math.round(freq) + ' Hz';
  },

  onMouseDown: function(event) {
    if (this.osc_) {
      // There can be only one oscillator.
      return;
    }
    this.updatePointer(event);
    // Create an oscillator.
    this.osc_ = this.createOscillator_();
    this.lastFreq = this.getLastFrequency();
    this.osc_.frequency.value = this.lastFreq;
  },

  onMouseUp: function() {
    this.deleteOscillator_();
    this.updatePointer(null);
    this.lastFreq = null;
  },

  onMouseMove: function(event) {
    if (this.osc_) {
      this.updatePointer(event);
      this.lastFreq = this.getLastFrequency();
      this.osc_.frequency.value = this.lastFreq;
    }
  },

  onMouseOut: function(event) {
    this.deleteOscillator_();
    this.updatePointer(null);
    this.lastFreq = null;
  },

  onTouchStart: function(event) {
    event.preventDefault();
    if (this.osc_) {
      return;
    }
    this.updatePointer(event);
    // Create an oscillator.
    this.osc_ = this.createOscillator_();
    this.lastFreq = this.getLastFrequency();
    this.osc_.frequency.value = this.lastFreq;
  },

  onTouchMove: function(event) {
    event.preventDefault();
    if (this.osc_) {
      this.updatePointer(event);
      this.lastFreq = this.getLastFrequency();
      this.osc_.frequency.value = this.lastFreq;
    }
  },

  onTouchEnd: function(event) {
    event.preventDefault();
    this.updatePointer(null);
    this.deleteOscillator_();
    this.lastFreq = null;
  },

  updatePointer: function(event) {
    event = event || {};
    var type = event.type || '';
    if (type.indexOf('mouse') == 0) {
      this.lastX = event.pageX;
      this.lastY = event.pageY;
    } else if (type.indexOf('touch') == 0) {
      this.lastX = event.touches[0].pageX;
      this.lastY = event.touches[0].pageY;
    } else {
      this.lastX = null;
      this.lastY = null;
    }
  },

  addHistory: function(freq) {
    if (this.history.length > 100) {
      this.history.splice(0, 1);
    }
    this.history.push(freq);
  },

  getLastFrequency: function() {
    var x = this.lastX;
    var y = this.lastY;

    // Linearly divide the Y axis and assign frequency.
    var percent = 1 - (y / this.height);
    var nyquist = this.audioContext.sampleRate/2;
    if (this.log) {
      percent = this.logScale_(percent * 1000, 1000) / 1000;
    }
    return percent * nyquist;
  },

  createOscillator_: function() {
    // Create a gain node.
    var gain = this.audioContext.createGain();
    gain.gain.value = 0;
    gain.connect(this.audioContext.destination);
    // TODO(smus): Clean this up!
    this.gain_ = gain;

    // Create an oscillator and connect it through the gain.
    var osc = this.audioContext.createOscillator();
    osc.connect(gain);

    // Start it with a fade-in.
    gain.gain.linearRampToValueAtTime(this.gainAmount,
        this.audioContext.currentTime + this.fadeTime);
    osc.start(0);
    return osc;
  },

  deleteOscillator_: function() {
    if (this.osc_) {
      var endTime = this.audioContext.currentTime + this.fadeTime;
      this.gain_.gain.linearRampToValueAtTime(0, endTime);
      this.osc_.stop(endTime);
      this.osc_ = null;
    }
  },

  /**
   * Given an index and the total number of entries, return the
   * log-scaled value.
   */
  logScale_: function(index, total, opt_base) {
    var base = opt_base || 2;
    var logmax = this.logBase(total + 1, base);
    var exp = logmax * index / total;
    return Math.pow(base, exp) - 1;
  },

  logBase: function(val, base) {
    return Math.log(val) / Math.log(base);
  },
});
  </script>
</polymer-element>