//SimpleCanvas.java
package util;

import java.awt.*;
import java.awt.event.*;


public class SimpleCanvas extends Canvas
{
   // default size of Canvas
   public static final int DEFAULT_WIDTH  = 400;
   public static final int DEFAULT_HEIGHT = 400;

   public SimpleCanvas (int width, int height)
   {
      super();
      setSize(width, height);

      // set up for interaction
      addMouseMotionListener(
         new MouseMotionListener()
         {
	    public void mouseMoved(MouseEvent e)
            {
	       SimpleCanvas.this.mouseMoved(e.getPoint());
	    }
	    public void mouseDragged(MouseEvent e)
            {
	       SimpleCanvas.this.mouseDragged(e.getPoint());
	    }
	 });

      addMouseListener(
	 new MouseListener()
         {
	    public void mousePressed(MouseEvent e)
            {
	       SimpleCanvas.this.mousePressed(e.getPoint());
	    }
	    public void mouseReleased(MouseEvent e)
            {
	       SimpleCanvas.this.mouseReleased(e.getPoint());
	    }
	    public void mouseClicked(MouseEvent e)
            {
	       SimpleCanvas.this.mouseClicked(e.getPoint());
	    }
	    public void mouseEntered(MouseEvent e)
            {
	       SimpleCanvas.this.mouseEntered(e.getPoint());
	    }
	    public void mouseExited(MouseEvent e)
            {
	       SimpleCanvas.this.mouseExited(e.getPoint());
	    }
	 });
      
      addKeyListener(
         new KeyListener()
         {
	    public void keyPressed(KeyEvent e)
            {
	       SimpleCanvas.this.keyPressed(KeyEvent.getKeyText(e.getKeyCode()));
	    }
	    public void keyReleased(KeyEvent e)
            {
	       SimpleCanvas.this.keyTyped(KeyEvent.getKeyText(e.getKeyCode()));
	    }
	    public void keyTyped(KeyEvent e)
            {
	       SimpleCanvas.this.keyTyped("" + e.getKeyChar());
	    }
	 });
   }

   // provide a reasonable alternative
   public SimpleCanvas (Dimension d)
   {
      this(d.width, d.height);
   }

   // provide a reasonable default
   public SimpleCanvas ()
   {
      this(SimpleCanvas.DEFAULT_WIDTH, SimpleCanvas.DEFAULT_HEIGHT);
   }

   // Do not clear the screen
   //   instead call paint() method with buffergraphics
   //   and paint the image
   public void update (Graphics g)
   {
      Dimension size = getSize();

      // set up for animation
      if ((myBuffer == null) || 
	  (size.width != myBuffer.getWidth(this)) || (size.height != myBuffer.getHeight(this)))
      {
         myBuffer = createImage(size.width, size.height);
         myBufferGraphics = myBuffer.getGraphics();
      }

      // clear image in preparation for next frame
      myBufferGraphics.clearRect(0, 0, size.width, size.height);

      // give subclasses a chance to paint
      paint(myBufferGraphics);
      // then copy off-screen buffer onto the screen
      g.drawImage(myBuffer, 0, 0, this);
   }


   // override the following to provide meaningful reactions
   // by default they do nothing
   public void mouseMoved(Point pt)
   {}
   public void mouseDragged(Point pt)
   {}
   public void mousePressed(Point pt)
   {}
   public void mouseReleased(Point pt)
   {}
   public void mouseClicked(Point pt)
   {}
   public void mouseEntered(Point pt)
   {}
   public void mouseExited(Point pt)
   {}
   public void keyPressed(String key)
   {}
   public void keyReleased(String key)
   {}
   public void keyTyped(String key)
   {}


   // do double-buffering automagically
   private Image    myBuffer;
   private Graphics myBufferGraphics;
}