// Lissagous figures, Evgeny Demidov, 16 Jan 2003
  import java.awt.*;
  
  public class applet-math-lissa extends java.applet.Applet implements Runnable {
  final int Max=10*360, M1=Max-1, lbSize=50;
  int[] arrSin=new int[Max+1];
  int height, width, iYo=0, parM=1, parN=2, delay=10;
  Thread ScopeTrace;
  Choice chDelay, chM, chN;
  Label  lbDelay, lbM, lbN;
  Image buffImage;
  Graphics buffGraphics;
  
  public void init() {
    height= Integer.parseInt(getParameter("height"));
    width = Integer.parseInt(getParameter("width"));
    int radius = width / 2;  int m2 = Max/2;
    double SiF=Math.sin(3.14159265/m2), CoF=Math.cos(3.14159265/m2);
    double Si=-SiF, Co=CoF;
    for (int i=0; i<=m2; i++) {
      Si=Si*CoF+Co*SiF; Co=Co*CoF-Si*SiF;
      int s= (int) (radius*Si);
      arrSin[i]=radius+s; arrSin[i+m2]=radius-s;
    }
    chM = new Choice();  chN = new Choice();
    for (int i=1; i<10; i++) {
      chM.addItem(Integer.toString(i));
      chN.addItem(Integer.toString(i));
    }
    chN.select(parN-1);
    lbM = new Label("M", Label.RIGHT);  add(lbM);  add(chM);
    lbN = new Label("N", Label.RIGHT);  add(lbN);  add(chN);
    lbDelay = new Label("Delay(ms)", Label.RIGHT); add(lbDelay);
    chDelay = new Choice();
    chDelay.addItem("0");    chDelay.addItem("10");
    chDelay.addItem("20");   chDelay.addItem("50");
    chDelay.addItem("100");  chDelay.addItem("200");
    chDelay.addItem("500");  chDelay.addItem("999");
    chDelay.select("10");     add(chDelay);
    buffImage = createImage(width, width);
    buffGraphics = buffImage.getGraphics();
  }               
  
  public void paint(Graphics g) {
    long cntTime = System.currentTimeMillis();
    int iX,iY, iXo=0, aX,aY, aXo=arrSin[0],aYo=arrSin[iYo];
    buffGraphics.clearRect(0, 0, width, width);
    for (int j=Max; j>0; j--) {
      iX=(iXo+parM) % Max;    iY=(iYo+parN) % M1;
      aX=arrSin[iX];  aY=arrSin[iY];
      buffGraphics.drawLine( aXo,aYo, aX,aY);
      iXo=iX; iYo=iY; aXo=aX; aYo=aY;
    }
    g.drawImage(buffImage, 0, lbSize, this);
  //  showStatus( "time=" + (System.currentTimeMillis()-cntTime) );
  }
  
  public boolean action(Event evt, Object obj)  {
    if(evt.target instanceof Choice) {
      if(evt.target.equals(chDelay))
        delay=Integer.parseInt( chDelay.getSelectedItem() );
      else if(evt.target.equals(chM)) parM=chM.getSelectedIndex()+1;
      else if(evt.target.equals(chN)) parN=chN.getSelectedIndex()+1;
      else return false;
      return true;
    }
    return false;
  }
  
  public void update(Graphics g)   {  paint(g);  }
  
  public void run() {
    while(true) {
      repaint();
      try {  Thread.sleep( delay );
      } catch (InterruptedException e) { }
    }
  }
  
  public void start() {
    ScopeTrace = new Thread(this);
    ScopeTrace.start();
  }
  
  public void stop() {  ScopeTrace.stop(); }
  
  }