/*
 *  File:  mObjApplet.java
 *
 *  Double-buffered version of mRectApplet.java
 *  with boundary checking
 */

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

public class mObjApplet extends Applet implements Runnable 
{
  // Instance variables:
  private int numObj = 3;       // number of movable objects
  private mPoint object[];      // array of movable objects
  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 object array:
    object = new mPoint[ numObj ];
    // Instantiate a rectangle:
    object[0] = new mRectangle( 10, 10, 100, 100 );
    object[0].setDelta( 2, 3 );
    object[0].setColor( Color.red );
    // Instantiate a circle:
    object[1] = new mOval( 200, 10, 100, 100 );
    object[1].setDelta( -3, 2 );
    object[1].setColor( Color.blue );
    // Instantiate a triangle:
    object[2] = new mTriangle( 10, 200, 100, 100 );
    object[2].setDelta( -2, 2 );
    object[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() 
  {
       thread = null;
  }
  
  // Implement java.lang.Runnable.run:
  public void run() 
  {
    while ( thread != null ) 
    {
      repaint();
      try 
      { Thread.sleep(20);
      } catch ( InterruptedException e ) {   };    // Do nothing  
    }
  }

  // Override java.awt.Component.update
  public void update (Graphics g)
  { paint (g);
  }
    
  // Override java.awt.Component.paint
  public void paint( Graphics g ) 
  {
    // Fill background:
    gOffScreen.setColor( getBackground() );
    gOffScreen.fillRect( 1, 1, getSize().width - 2, getSize().height - 2 );

    //  move each object after checking the boundary:
       for ( int i = 0; i < numObj; i++ ) 
        {
        object[i].checkBoundary( getBounds() );
        object[i].move();
        object[i].paint(gOffScreen);
        }
    
    // Draw the buffer in the applet window:
    g.drawImage( buffer, 0, 0, this );
  }
}