// Conservative Henon map with Orbits,   Evgeny Demidov,  11 July 07
  import java.awt.*;
  import java.awt.event.*;
  import java.awt.image.*;
  import java.util.StringTokenizer;
  public class applet-math-fractal-quadmap extends java.applet.Applet implements MouseListener,
    KeyListener, ActionListener {
    int w,h,w2,h2, it=3000, rand=50;
    double Xo=3, Yo=-4, a=.3,  Pi2 = Math.PI*2,
      Xc=Math.PI, Yc=0, dX=Pi2, Mx, My;
    Image buffImage; Graphics buffGraphics;
    boolean   bClear = true;
    Label     lbA, lbIt;
    TextField tfA, tfXY, tfIt, tfRand;
    Button    btClear, btRand;
  
  public void init() {
    double  dx = Pi2,  dy = 4.;
    w = getSize().width;   h = getSize().height;
    w2 = w/2;  h2 = h/2;
    buffImage = createImage(w, h);
    buffGraphics = buffImage.getGraphics();
  //  buffGraphics.setFont(
  //    new Font( buffGraphics.getFont().getName(), Font.BOLD, 15 ) );
    String s=getParameter("A");
    if (s != null) a = Double.valueOf(s).doubleValue();
    s=getParameter("it");  if (s != null) it = Integer.parseInt(s);
    s=getParameter("rand"); if (s != null) rand = Integer.parseInt(s);
    s=getParameter("coord");  if (s != null){
      StringTokenizer st = new StringTokenizer(s);
      Xc = Double.valueOf(st.nextToken()).doubleValue();
      Yc = Double.valueOf(st.nextToken()).doubleValue();
      dx = Double.valueOf(st.nextToken()).doubleValue();
      dy = Double.valueOf(st.nextToken()).doubleValue();}
    Mx = dx/w;  My = dy/h;
    this.setLayout( new FlowLayout(FlowLayout.LEFT, 0, 0) );
    tfXY = new TextField( ""+(float)Xc+" "+(float)Yc+"; "+(float)dx+
      " "+(float)dy, 30);   add(tfXY);
    lbA = new Label("a", Label.RIGHT); add(lbA);
    tfA = new TextField( "" + a, 3);   add(tfA);
    tfA.addKeyListener(this);
    lbIt = new Label("it", Label.RIGHT); add(lbIt);
    tfIt = new TextField( "" + it, 3);   add(tfIt);
    tfIt.addKeyListener(this);
    btClear = new Button("Clear"); btClear.addActionListener(this); add(btClear);
    btRand = new Button("Rand");   btRand.addActionListener(this);  add(btRand);
    tfRand = new TextField( "" + rand, 2);   add(tfRand);
    tfRand.addKeyListener(this);
    addMouseListener(this);
    clear();
    random();
  }
  public void destroy() {
    removeMouseListener(this);
  }
  
  public void random(){
    buffGraphics.setColor(Color.blue);
    for(int i = 0; i < rand; i++){
      Xo = Xc + Mx*w*(Math.random() - .5);
      Yo = Yc + My*h*(Math.random() - .5);
      iterate();}
  }
  
  public void iterate() {
    double X=Xo, Y;
    for(int i = 0; i < it; i++){
      Y = X;
      X = a + X*X + Yo;
      int ix  = w2 + (int)((X-Xc)/Mx), iy  = h2 - (int)((Y-Yc)/My);
      buffGraphics.drawLine( ix,iy, ix,iy);
      Yo = Y;}
    repaint();
  }
  
  public void Orbits(int kit) {
      buffGraphics.setColor(Color.red);
      double X=Xo, Y;
      int ix, iy,  ix0  = w2 + (int)((Xo-Xc)/Mx), iy0 = h2 - (int)((Yo-Yc)/My);
      for(int i = 0; i < kit; i++){
        Y = X;
        X = a + X*X + Yo;
        ix  = w2 + (int)((X-Xc)/Mx); iy  = h2 - (int)((Y-Yc)/My);
        buffGraphics.drawLine( ix0,iy0, ix,iy);
        buffGraphics.fillRect( ix0, iy0, 3, 3);
        ix0 = ix;  iy0 = iy;
        Yo = Y;}
  //  repaint();
  }
  
  public void mouseClicked(MouseEvent e){}       // event handling
  public void mousePressed(MouseEvent e) {
    int mx0 = e.getX() - w2,  my0 = h2 - e.getY();
    Xo = mx0*Mx + Xc;  Yo = my0*My + Yc;
    if ( e.isAltDown() ){
      Xc = Xo;  Yc = Yo;
      My /= 2.;  if ( !e.isShiftDown() ) Mx /= 2.;
      tfXY.setText(""+(float)Xc+" "+(float)Yc+"; "+(float)(w*Mx)+
        " "+(float)(h*My) );
      clear(); random();
      return;}
    if ( e.isControlDown() ){
      Xc = Xo;  Yc = Yo;
      My *= 2.;  if ( !e.isShiftDown() ) Mx *= 2.;
      tfXY.setText(""+(float)Xc+" "+(float)Yc+"; "+(float)(w*Mx)+
        " "+(float)(h*My) );
      clear(); random();
      return;}
    if ( e.isShiftDown() ){ Orbits(1); repaint();}
    else{
      showStatus("X=" + (float)Xo + "  Y=" + (float)Yo );
      buffGraphics.setColor(Color.black);
      iterate();}
  }
  public void mouseReleased(MouseEvent e){}
  public void mouseEntered(MouseEvent e) {}
  public void mouseExited(MouseEvent e)  {}
  public void actionPerformed(ActionEvent e){
    if ( e.getActionCommand().equals("Clear") ){
      clear(); repaint();}
    else random();
  }
  public void keyTyped(KeyEvent e) {}
  public void keyPressed(KeyEvent e) {}
  public void keyReleased(KeyEvent e) {
    final int keyEnter = 10;
    if (e.getKeyCode() == keyEnter) {
      try{
        double Ao = a;
        a = Double.valueOf(tfA.getText()).doubleValue();
        it = Integer.parseInt(tfIt.getText());
        rand = Integer.parseInt(tfRand.getText());
        if (Ao != a){ clear(); random();}
      }catch ( NumberFormatException ne) {}
    }
    e.consume();
  }
  
  public void clear(){
    buffGraphics.setColor(Color.white);
    buffGraphics.fillRect(0, 0, w, h);
  }
  
  public void paint(Graphics g) {
    drawLabel();
    g.drawImage(buffImage, 0, 0, this);
  }
  
  public void drawLabel() {
   int max=0;
   double dw2 = w2, dh2 = h2;
   while (true) {
     String s = getParameter("or"+max);
     if (s == null) break;
     StringTokenizer st = new StringTokenizer(s);
     Xo = Double.valueOf(st.nextToken()).doubleValue();
     Yo = Double.valueOf(st.nextToken()).doubleValue();
     Orbits( Integer.parseInt(st.nextToken()) );
     max++; }
   max = 0;
   buffGraphics.setColor(Color.black);
   while (true) {
     String s=getParameter("lb"+max);
     if (s == null) break;
     StringTokenizer st = new StringTokenizer(s);
     double x=w2+(Double.valueOf(st.nextToken()).doubleValue()-Xc)/Mx,
     y=h2-(Double.valueOf(st.nextToken()).doubleValue()-Yc)/My;
     if ( (x<w)&&(x>0)&&(y<h)&&(y>0) )
       buffGraphics.drawString(st.nextToken(), (int)x, (int)y);
     max++; }
  }
  
  public void update(Graphics g){ paint(g); }
  
  }