/* Copyright 1998, John C. Lahr */
import java.awt.*;
import java.applet.*;

public class spiral extends Applet implements Runnable{
    Dimension size;               // Screen dimensions of applet
    boolean please_stop;
    Image buffer;
    protected Image john;
    protected MediaTracker tracker;
    Graphics bufferGraphics;
    Thread runner;
    double ncycles = 12.;
    double ncircles = 6.;
    double diameter = 200.;
    double bgdelt = diameter/ncircles;
    double smdelt = bgdelt/ncycles;
    double diamst;
    double a = Math.pow(diameter, 1./(double)(ncircles-1));
    double b = 1.0/Math.pow(a, (1./ncycles));
    double t, lastt = 1.0;
    double diam = 1.;
    int j = 0;
    int section = 1;
    int frame_delay = 10;
    int duration = 1500;
    int nloops = duration/frame_delay;
    Button repeat_button;
    Button speedup_button;
    double xcenter;
    double ycenter;

    public void init() {
    repeat_button = new Button("Repeat at same speed");
    this.add(repeat_button);
    speedup_button = new Button("Speed up");
    this.add(speedup_button);
    tracker = new MediaTracker(this);
    String file = "john.gif";
    john = this.getImage(this.getDocumentBase(), file);
    tracker.addImage(john, 1);
    size = this.size();
    buffer = this.createImage(size.width, size.height);
    bufferGraphics = buffer.getGraphics();
    xcenter = size().width*0.5;
    ycenter = size().height*0.5;
    }

    public void start() {
        if (runner == null) {
            please_stop = false;
            runner = new Thread(this);
            runner.start();
        }
    }

    public void stop() {
        please_stop = true;
    }

    public void paint(Graphics g) {
/*
        System.out.println("begin paint"); 
*/
        if (section == 1) {
/*
           System.out.println("section 1"); 
*/         
           bufferGraphics.setColor(Color.black);  // fill with black
           bufferGraphics.fillRect(0, 0, size().width, size().height);

           bufferGraphics.setColor(Color.white); 
           bufferGraphics.drawString("Focus your view on the center of the circles", 185,
              450);
           bufferGraphics.drawString("Speed = " + nloops, 185,465);
           g.drawImage(buffer, 0, 0, this);
         }


         if (section == 2) {
/*
               System.out.print("section 2:  nloops = "); 
               System.out.println(nloops); 
*/
               bufferGraphics.setColor(Color.white); // white circle  
               bufferGraphics.fillOval((int)(xcenter-diameter*0.5), 
                 (int)(ycenter-diameter*0.5), 
                 (int)diameter, (int)diameter);
               bufferGraphics.setColor(Color.black);
               diam = diamst;
               for (j = 0; j < ncircles; j++) {
                   bufferGraphics.drawOval((int)(xcenter-diam*0.5), 
                       (int)(ycenter-diam*0.5), 
                      (int)diam, (int)diam);
                   diam = diam - bgdelt;
               }
               g.drawImage(buffer, 0, 0, this);
          }
  
           if (section == 3) {
/*
               System.out.println("section 3"); 
*/
               bufferGraphics.setColor(Color.black);  // fill with black
               bufferGraphics.fillRect(0, 0, size().width, size().height);
               bufferGraphics.drawImage(john, 140, 145, this);
               g.drawImage(buffer, 0, 0, this);
           }
    }

    public void run() {
/*
        System.out.println("begin run"); 
*/
        section = 1;
        System.out.println("Begin run routine"); 
        repaint(0, 0, size().width, size().height);
        try {Thread.sleep(20);}  // Pause xx ms
        catch (InterruptedException e) {;}

        section = 2;
        for (int i = 0; i < nloops; i++) {
            diamst = diameter;
            for (int kk = 0; kk < ncycles; kk++) {
                repaint( (int) (xcenter-0.5*diameter),
                    (int) (ycenter-0.5*diameter),
                    (int) diameter, (int) diameter);

                try {Thread.sleep(frame_delay);}  // Pause xx ms
                catch (InterruptedException e) {;}

                diamst = diamst - smdelt;
            }
        }

        section = 3;
        repaint();
        runner = null;
    }

    public void update(Graphics g) { paint(g); }
	    

  /** Repeat at same speed **/
  public boolean action(Event e, Object arg) {
    if (e.target == repeat_button) {
/*
      System.out.println("pressed repeat button");
*/
      start();
      return true;
    }
    if (e.target == speedup_button) {
/*
      System.out.println("pressed speedup button");
*/
      frame_delay = frame_delay - 2;
      if (frame_delay <= 2) frame_delay = 10;
      nloops = duration/frame_delay;
      start();
      return true;
    }
    return false;
  }
}