/*
 *  File:  MovingPolygons2.java
 *
 *  Moving polygons with boundary checking and double buffering
 *
 *  Copyright:  Northeast Parallel Architectures Center
 *
 */

import java.applet.Applet;
import java.awt.*;

public class MovingPolygons2 extends Applet implements Runnable {

  // Instance variables:
  private final int numPoly = 3;      // number of drawable polygons
  private MovablePolygon polygon[];   // array of drawable polygons
  private Thread thread;              // a thread
  private Image buffer;               // image object for double buffering
  private Graphics gOffScreen;        // graphics object for double buffering
    
  // Override java.applet.Applet.init:
  public void init () {

    setBackground( Color.black );
    setForeground( Color.white );
    
    // Instantiate the polygon array:
    polygon = new MovablePolygon[ numPoly ];

    // Instantiate a square:
    polygon[0] = new Square( 75, 75, 70 );
    polygon[0].setDelta( 2, 3 );
    polygon[0].setColor( Color.red );

    // Instantiate a regular hexagon:
    polygon[1] = new MovablePolygon( 125, 60, 50, 6 );
    polygon[1].setDelta( -3, 2 );
    polygon[1].setColor( Color.blue );

    // Instantiate an equilateral triangle:
    polygon[2] = new MovablePolygon( 60, 125, 50, 3 );
    polygon[2].setDelta( -2, 2 );
    polygon[2].setColor( Color.green );
    
    // Create an off-screen image for double buffering:
    buffer = createImage( getSize().width, getSize().height );
    // Get off-screen graphics context:
    gOffScreen = buffer.getGraphics(); 

  }

  // Override java.applet.Applet.start:
  public void start() {
    if ( thread == null ) {
      thread = new Thread( this );
      thread.start();
    }
  }
  
  // Override java.applet.Applet.stop:
  public void stop() {
    if ( thread != null ) {
      thread.stop();
      thread = null;
    }
  }
  
  // Implement java.lang.Runnable.run:
  public void run() {
    while ( thread != null ) {
      try {
        Thread.sleep( 20 );
      } catch ( InterruptedException e ) {
        // do nothing   
      }
      repaint();
    }
  }

  // Override java.awt.Component.update:
  public void update( Graphics g ) {

    // Clear the buffer:
    gOffScreen.setColor( getBackground() );
    gOffScreen.fillRect( 0, 0, getSize().width, getSize().height );
    
    // Paint the polygons off screen, that is, in the buffer:
    paint( gOffScreen );
    
    // Draw the buffer in the applet window:
    g.drawImage( buffer, 0, 0, this );

  }
  
  // Override java.awt.Component.paint:
  public void paint( Graphics g ) {
  
    // Check, move, and fill each polygon:
    for ( int i = 0; i < numPoly; i++ ) {
      polygon[i].checkBounds( this.getBounds() );
      polygon[i].move();
      polygon[i].fill( g );
    }
    
  }
  
}