// version 1b = version 1a + program does double-buffering

import java.awt.image.* ; 
import java.awt.* ; 
import java.awt.event.* ; 
import javax.swing.* ; 

/**
  *  The draw application.
  */
public class Draw extends JFrame {
   /**
     * The easel for this application.
     */
   private DrawPanel panel ;

   public Draw() { 
      super("Draw") ; 
      // create menubar
      // create toolbar      
      panel = new DrawPanel() ; 
      panel.setBackground(Color.white) ;  
      // add components to toolbar
      this.setLayout(new BorderLayout()) ; 
      this.getContentPane().add("Center", panel) ; 
      this.setVisible(true) ; 
      this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE) ; // exitExam()
   }
      
   public static void main(String[] args) { 
      Draw draw = new Draw() ; 
      draw.setSize(300,375) ; 
      draw.setLocation(500,500) ; 
      draw.setVisible(true) ; 
   }

}

//////////////////////////////////////////////////
/**
  *  The  drawing panel.
  */
class DrawPanel extends JPanel 
               implements MouseListener,
               MouseMotionListener { 

   private Point pivot ; // mark mouse down
   private int lastx, lasty ; // for dragging
   private BufferedImage buffer ; // off-screen drawing buffer
   BasicStroke stroke ; 

   public DrawPanel() { 
      this.addMouseListener(this) ; 
      this.addMouseMotionListener(this) ; 
      pivot = new Point() ; 
      buffer = new BufferedImage(1000,1000,BufferedImage.TYPE_INT_RGB) ; 
      Graphics g = buffer.getGraphics() ; 
      g.setColor(Color.WHITE) ; 
      g.fillRect(0,0,1000,1000) ; // set background for buffer to white
      // test stroke
      stroke = new BasicStroke(3) ; 
   }

   // MouseListener
   public void mouseClicked(MouseEvent e) {}
   public void mouseEntered(MouseEvent e) {}
   public void mouseExited(MouseEvent e) {}
   public void mousePressed(MouseEvent e) {
      // mark mouse down  
      pivot.x = e.getX() ;
      pivot.y = e.getY() ; 
      lastx = pivot.x ; 
      lasty = pivot.y ; 
   }
   public void mouseReleased(MouseEvent e) {}

   // MouseMotionListener
   public void mouseMoved(MouseEvent e) {}
   public void mouseDragged(MouseEvent e) { 
      Graphics2D g = (Graphics2D)buffer.getGraphics() ; // off-screen 
      g.setStroke(stroke) ; 
      if (e.isShiftDown()) { // straight line 
         //erase last rubber banding
         g.setColor(this.getBackground()) ; 
         g.drawLine(pivot.x,pivot.y,lastx,lasty) ; 
         // draw new rubber banding
         g.setColor(Color.black) ; 
         g.drawLine(pivot.x,pivot.y,e.getX(),e.getY()) ; 
         lastx = e.getX() ;
         lasty = e.getY() ; 
      }
      else { // "demonstrate scattering"
         // draw new rubber banding
         g.setColor(Color.black) ; 
         g.drawRect(e.getX(),e.getY(),2,2) ; 
      }
      // on-screen 
      Graphics ong = this.getGraphics() ; 
      ong.drawImage(buffer,0,0,this) ; 
   }

   public void paintComponent(Graphics g) { 
      g.drawImage(buffer,0,0,this) ; 
   }

}