// This class is a very simple implementation of AudioListener. By implementing this interface, 
  // you can add instances of this class to any class in Minim that implements Recordable and receive
  // buffers of samples in a callback fashion. In other words, every time that a Recordable object has 
  // a new buffer of samples, it will send a copy to all of its AudioListeners. You can add an instance of 
  // an AudioListener to a Recordable by using the addListener method of the Recordable. If you want to 
  // remove a listener that you previously added, you call the removeListener method of Recordable, passing 
  // the listener you want to remove.
  //
  // Although possible, it is not advised that you add the same listener to more than one Recordable. 
  // Your listener will be called any time any of the Recordables you've added it have new samples. This 
  // means that the stream of samples the listener sees will likely be interleaved buffers of samples from 
  // all of the Recordables it is listening to, which is probably not what you want.
  //
  // You'll notice that the three methods of this class are synchronized. This is because the samples methods 
  // will be called from a different thread than the one instances of this class will be created in. That thread 
  // might try to send samples to an instance of this class while the instance is in the middle of drawing the 
  // waveform, which would result in a waveform made up of samples from two different buffers. Synchronizing 
  // all the methods means that while the main thread of execution is inside draw, the thread that calls 
  // samples will block until draw is complete. Likewise, a call to draw will block if the sample thread is inside 
  // one of the samples methods. Hope that's not too confusing!
  
  class WaveformRenderer implements AudioListener
  {
    private float[] left;
    private float[] right;
    
    WaveformRenderer()
    {
      left = null; 
      right = null;
    }
    
    synchronized void samples(float[] samp)
    {
      left = samp;
    }
    
    synchronized void samples(float[] sampL, float[] sampR)
    {
      left = sampL;
      right = sampR;
    }
    
    synchronized void draw()
    {
      // we've got a stereo signal if right is not null
      if ( left != null && right != null )
      {
        noFill();
        stroke(255);
        beginShape();
        for ( int i = 0; i < left.length; i++ )
        {
          vertex(i, height/4 + left[i]*50);
        }
        endShape();
        beginShape();
        for ( int i = 0; i < right.length; i++ )
        {
          vertex(i, 3*(height/4) + right[i]*50);
        }
        endShape();
      }
      else if ( left != null )
      {
        noFill();
        stroke(255);
        beginShape();
        for ( int i = 0; i < left.length; i++ )
        {
          vertex(i, height/2 + left[i]*50);
        }
        endShape();
      }
    }
  }