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

/** 
 * An applet that displays a simple animation using double-buffering 
 * and clipping
 **/
public class niag extends Applet implements Runnable {
  Dimension size;                  // The size of the applet
  Image buffer;                    // The off-screen image for double-buffering
  protected Image niag;            // Picture of  Niagara Falls
  protected MediaTracker tracker;
  Graphics bufferGraphics;         // A Graphics object for the buffer
  Thread animator;                 // Thread that performs the animation
  boolean please_stop;             // A flag asking animation thread to stop
  int x1 = 160;
  int x2 = 230;
  int ymin = 80;
  int linespace = 15;
  int nincrements = 5;
  int increment = linespace/nincrements;
  int number_of_lines = 10;
  int ict;
  int ymax = ymin+linespace*number_of_lines;
  int section = 1;
  int frame_delay = 25;
  int duration = 2000;
  int nloops = duration/frame_delay;
  Button repeat_button;
  Button speedup_button;

  /** Set up an off-screen Image for double-buffering */
  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 = "niag.jpg";
    niag = this.getImage(this.getDocumentBase(), file);
    tracker.addImage(niag, 1);
    size = this.size();
    buffer = this.createImage(size.width, size.height);
    bufferGraphics = buffer.getGraphics();
  }

  /** Draw frame, lines, or image depending on the value of section **/
  public void paint(Graphics g) {
  // Draw into the off-screen buffer.
  // Note, we could do even better clipping by setting the clip rectangle
  // of bufferGraphics to be the same as that of g.
  // In Java 1.1:  bufferGraphics.setClip(g.getClip());
         if (section == 1) {
           bufferGraphics.setColor(Color.white);
           bufferGraphics.fillRect(0, 0, size().width, size().height);

           bufferGraphics.setColor(Color.red);
           bufferGraphics.drawRect(x1-1, ymin-1, x2-x1+2, ymax-ymin+2);
          
           bufferGraphics.setColor(Color.black);
           bufferGraphics.drawString(
             "Focus your view on the center of the rectangle", 70, 60);
           bufferGraphics.drawString("Speed = " + nloops, 70, 75);
           // Now copy the off-screen buffer onto the screen
           g.drawImage(buffer, 0, 0, this);
         }


         if (section == 2) {
           bufferGraphics.setColor(Color.white);
           bufferGraphics.fillRect(x1, ymin, x2-x1, ymax-ymin);
           bufferGraphics.setColor(Color.black);
           int y = ymax - ict*increment;
           for (int j = 0; j < number_of_lines; j++) {
               bufferGraphics.drawLine(x1, y, x2, y);
               y -= linespace;
           }
           // Now copy the off-screen buffer onto the screen
           g.drawImage(buffer, 0, 0, this);
         }
  
         if (section == 3) {
           bufferGraphics.drawImage(niag, 70, 50, this); 
             
           g.drawImage(buffer, 0, 0, this); 
         }
    }

  /** Don't clear the screen; just call paint() immediately
  *   It is important to override this method like this for double-buffering */
  public void update(Graphics g) { paint(g); }

  /** The body of the animation thread */
  public void run() {

        section = 1;
        repaint(0, 0, size().width, size().height); 
        try {Thread.sleep(250);}  // Pause xx ms 
        catch (InterruptedException e) {;}

        section = 2;
        for (int k = 1; k < nloops; k++) {  
            for (ict = 0; ict < nincrements; ict++) {  
                repaint(x1+1, ymin+1, x2-x1-2, ymax-ymin-2); 
          
                try {Thread.sleep(frame_delay);}  // Pause xx ms
                catch (InterruptedException e) {;}
            }
        }

        section = 3;
        repaint();

    animator = null;
  }

  /** Start the animation thread */
  public void start() {
    if (animator == null) {
      please_stop = false;
      animator = new Thread(this);
      animator.start();
    }
  }

  /** Stop the animation thread */
  public void stop() { please_stop = true; }


  /** 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 - 5;
      if (frame_delay == 0) frame_delay = 25;
      nloops = duration/frame_delay;
      start();
      return true;
    }
    return false;
  }
}