// Interactive X = X*X + C Iterations,  Evgeny Demidov, 30 June 2006
import java.awt.*;
import java.awt.event.*;
import java.util.StringTokenizer;

public class @file 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);  }

}