import java.applet.Applet;
import java.util.Random;
import java.awt.*;


public class RANDunif2d extends Applet implements Runnable
{
  Canvas canvas = new Canvas();
  Button stopButton = new Button("Stop");
  Button goButton = new Button("Go");
  Button clearButton = new Button("Clear");
  Label nbLabel = new Label("Nb of pts (x100):");
  GridBagLayout layout = new GridBagLayout();
  GridBagConstraints c = new GridBagConstraints();

  long nbpoints = 0;

  // Double buffering
  Graphics offGraphics;
  Image offImage;
  Dimension offDimension;

  // Threads
  boolean frozen = true;
  Thread drawThread = null;

  //Random generator
  Random rand = new Random(45682);

  public void init() 
  {
    //Graphic Interface
    setLayout(layout);
    setFont(new Font("Helvetica",Font.PLAIN,10));
    canvas.resize(150,150);
    c.fill = GridBagConstraints.VERTICAL;
    c.gridheight = 10;
    c.gridwidth = 10;
    c.gridx = 0;
    c.gridy = 0;
    c.insets = new Insets(0,2,0,0);
    layout.setConstraints(canvas,c);
    add(canvas);
    c.gridheight = 1;
    c.gridwidth = 5;
    c.gridx = 11;
    c.gridy = 0;
    c.fill = GridBagConstraints.BOTH;
    layout.setConstraints(clearButton,c);
    add(clearButton);
    c.gridy = 1;
    layout.setConstraints(goButton,c);
    add(goButton);
    c.gridy = 2;
    layout.setConstraints(stopButton,c);
    add(stopButton);
    nbLabel = new Label("Nb of pts :");
    nbLabel.setBackground(Color.white);
    c.gridy = 3;
    c.insets = new Insets(4,4,0,4);
    layout.setConstraints(nbLabel,c);
    add(nbLabel);
    nbLabel = new Label("0",Label.CENTER);
    nbLabel.setBackground(Color.white);
    c.gridy = 4;
    c.insets = new Insets(0,4,4,4);
    layout.setConstraints(nbLabel,c);
    add(nbLabel);
    
    show(); validate();
  }

  public void paint(Graphics g)
  {
    update(g);
    super.repaint();
  }

  public void update(Graphics g)
  {
    Dimension d = canvas.size();

    //Create the offscreen graphics context, if no good one exists.
    if ( (offGraphics == null)
	 || (d.width != offDimension.width)
	 || (d.height != offDimension.height) ) 
      {
	offDimension = d;
	offImage = createImage(d.width, d.height);
	offGraphics = offImage.getGraphics();
	offGraphics.setColor(Color.blue);
	offGraphics.fillRect(0,0,d.width-1,d.height-1);
	offGraphics.setColor(Color.black);
	offGraphics.drawRect(0,0,d.width-1,d.height-1);
	offGraphics.setColor(Color.red);
      }

    canvas.getGraphics().drawImage(offImage,0,0,canvas);
  }
    
    
  public void run()
  {
    int x,y,i;
    Dimension dim = canvas.size();

    Thread.currentThread().setPriority(Thread.MIN_PRIORITY);

    while (Thread.currentThread() == drawThread)
      {
	for(i=0;i<100;i++)
	  {
	    x = 1+(int)(rand.nextFloat()*(dim.width-2));
	    y = 1+(int)(rand.nextFloat()*(dim.height-2));
	    offGraphics.drawLine(x,y,x,y);
	  }
	nbpoints+=100;
	nbLabel.setText(Long.toString(nbpoints));
	repaint();

	try
	  {
	    drawThread.sleep(10);
	  }
	catch(InterruptedException e)
	  {
	  }
      }
  }


  public void stop()
  {
    drawThread = null;
  }

  public void start()
  {
    if(frozen)
      {} // Do nothing
    else
      { // Start new thread
	if(drawThread==null) drawThread = new Thread(this,"Draw");
	drawThread.start();
      }
  }

  public boolean action(Event e, Object arg) 
  {
    Object target = e.target;
    String str;
    Dimension d = canvas.size();

    if(target==this)
      {
	repaint();
	return true;
      }

    if(target==goButton)
      {
	stop();
	frozen = false;
	start();
	return true;
      }

    if(target==stopButton)
      {
	frozen = true;
	stop();
	return true;
      }

    if(target==clearButton)
      {
	stop();
	offGraphics.setColor(Color.blue);
	offGraphics.fillRect(0,0,d.width-1,d.height-1);
	offGraphics.setColor(Color.black);
	offGraphics.drawRect(0,0,d.width-1,d.height-1);
	offGraphics.setColor(Color.red);
	nbpoints = 0;
	nbLabel.setText(Long.toString(nbpoints));
	repaint();
	start();
	return true;
      }

    return false;
  }
  
}