// Interactive X = X*X + C Iterations,  Evgeny Demidov, 30 June 2006
  import java.awt.*;
  import java.awt.event.*;
  import java.util.StringTokenizer;
  
  public class applet-math-fractal-iterateL extends java.applet.Applet
         implements MouseMotionListener, KeyListener {
  Image buffImage;          Graphics buffGraphics;
  int maxIt = 10, numIt,  w,h,h2,  iXo,iYo,  lbSize = 30,
      xFun[],yFun[],  xGist[],yGist[], xIt[],yIt[];
  double C = -.5, maxIYI = 2., Xo = 0., Step;
  Label     lbIt, lbL, lbC, lbXo;
  TextField tfIt, tfL, tfC, tfXo;
  
  public void init() {
    h = Integer.parseInt(getParameter("height")) - lbSize;    h2 = h / 2;
    w = Integer.parseInt(getParameter("width"));
    String s=getParameter("Xo");
    if (s != null) Xo = Double.valueOf(s).doubleValue();
    s=getParameter("MaxIt"); if (s != null) maxIt=Integer.parseInt(s);
    s = getParameter("C");  if (s != null) C = Double.valueOf(s).doubleValue();
    xFun = new int[h];    for (int i = h-1; i >= 0; i--) xFun[i] = i;
    yFun = new int[h];
    buffImage = createImage(w, h);
    buffGraphics = buffImage.getGraphics();
    lbC = new Label("C", Label.RIGHT);   add(lbC);
    tfC = new TextField( "" + C, 6);     add(tfC);
    lbXo = new Label("Xo", Label.RIGHT); add(lbXo);
    tfXo = new TextField( ""+Xo, 4);     add(tfXo);
    lbIt = new Label("It", Label.RIGHT); add(lbIt);
    tfIt = new TextField( "" + maxIt, 2); add(tfIt);
    lbL = new Label("L", Label.RIGHT);   add(lbL);
    tfL = new TextField( "" + 0, 4);     add(tfL);
    tfC.addKeyListener(this);
    tfIt.addKeyListener(this);  tfXo.addKeyListener(this);
    addMouseMotionListener(this);
    Step = 4./h;
    iXo = iYo = h2;
    draw();
  }
  
  public void destroy() {  removeMouseMotionListener(this); }
  public void keyTyped(KeyEvent e) {}
  public void keyPressed(KeyEvent e) {}
  public void keyReleased(KeyEvent e) {
    final int keyEnter = 10;
    if (e.getKeyCode() == keyEnter) {
      try{
        maxIt = Integer.parseInt( tfIt.getText() );
        C = Double.valueOf(tfC.getText()).doubleValue();
        Xo = Double.valueOf(tfXo.getText()).doubleValue();
      }catch ( NumberFormatException ne) {}
      draw();    repaint();
    }
    e.consume();
  }
  
  public void mouseMoved(MouseEvent e) {}
  public void mouseDragged(MouseEvent e) {
    if ( e.isShiftDown() ){
     Xo = Step*(e.getX() - h2);
     tfXo.setText( Float.toString((float)Xo) );}
    else{
     C = Step*(h2 - (e.getY() - lbSize));
     tfC.setText( Float.toString((float)C) );}
    draw();    repaint();
    e.consume();
  }
  
  public void draw() {
    xGist = new int[maxIt<<1 + 1];    yGist = new int[maxIt<<1 + 1];
    xIt = new int[maxIt+1];    yIt = new int[maxIt+1];
    for (int i = 0; i <= maxIt; i++)
      xIt[i] = h + (int)((w-h-1)*(double)i/(maxIt));
    generateFun();        iterations();
    buffGraphics.setColor(Color.white);
    buffGraphics.fillRect(0, 0, w  - 1, h - 1);
    buffGraphics.setColor(Color.black);
    buffGraphics.drawRect(0, 0, w  - 1, h - 1);
    buffGraphics.drawLine(h, 0, h, h - 1);
    buffGraphics.drawLine(0, iYo, w  - 1, iYo);
    buffGraphics.drawLine(iXo, 0, iXo, h - 1);
    buffGraphics.setColor(Color.green);
    buffGraphics.drawLine(0, h, h, 0);
    buffGraphics.setColor(Color.blue);
    buffGraphics.drawPolyline( xFun, yFun, h );
    buffGraphics.setColor(Color.red);
    buffGraphics.drawPolyline( xGist, yGist, numIt<<1 );
    buffGraphics.drawPolyline( xIt, yIt, numIt+1 );
    buffGraphics.fillRect(xGist[0]-1, yGist[0]-1, 3, 3);
  }
  
  public void paint(Graphics g) {
    g.drawImage(buffImage, 0, lbSize, this);
  //  showStatus( "It=" + numIt);
  }
  
  public void iterations() {
    double X = Xo, Y, PX = 1, L;         int bakX, bakY;
    xGist[0] = bakX = h2 + (int)(Xo/Step);
    yGist[0] = h2;  yIt[0] = h - bakX;
    for (int i = 1; i <= maxIt; i++) {
      Y = X*X + C;   PX *= X;
      int i2 = i<<1;
      xGist[i2 - 1] = bakX;
      yGist[i2 - 1] = ( bakY = h2 - (int)(Y/Step) );
      xGist[i2] = ( bakX = h2 + (int)(Y/Step) );
      yGist[i2] = yIt[i] = bakY;
      X = Y;    numIt = i;
      if (Math.abs(Y) > maxIYI) break;
    }
    L = Math.log(2.) + Math.log(Math.abs(PX))/maxIt;
    tfL.setText( Float.toString((float)L) );
  }
  
  public void generateFun() {
    for (int i = h - 1; i >= 0; i--) {
      double X = (i-h2)*Step;
      X = X*X + C;
      yFun[i] = h2 - (int)(X/Step);
    }
  }
  
  public void update(Graphics g)   {  paint(g);  }
  
  }