Effective rendering?

Hello!

I try to build a simple fictive transperant window. I got som help with a example from the Internet but I was not happy with the calculating of X and Y cordinates for the position. So I tried to calculate it my self but the result was that my calulate was raelly not effective since the window flicker alot when draging it around.

But I can't tell why.

To see the window now you will se a red circle.

So if any one could help me and explaine whay and a better whay to drag the window around I would be most thankfull.

The code below is when the rendering is effective, to try when the cordinates for the loction is better you have to uncomment the code inside mousePressed and mouseDraged and block the code that is open now.

Best regards
Fredrik Andersson

import java.util.*;
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.applet.*;
import java.awt.event.*;
import javax.swing.event.*;
import javax.swing.border.*;
import java.awt.image.*;

public class GlassWindowTest extends JWindow implements MouseListener, MouseMotionListener
{
    private Image screen;
    private Image backBuffer;
    private Graphics backGraphics;

    private Dimension preferredSize = new Dimension(250,200);
    private Dimension screenSize;
    private Rectangle screenRectangle;
    private int xdiff = 0;
    private int ydiff = 0;
    private static Robot robot;

    private int mousePressedX;
    private int mousePressedY;
    private int mouseDraggedX;
    private int mouseDraggedY;

    private Dimension windowSize;

    private int newX;
    private int newY;

    public GlassWindowTest()
    {
        super();

        JPanel content = (JPanel) getContentPane();
        content.setOpaque(false);
        setSize( getPreferredSize() );

        windowSize = getSize();
        screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        screenRectangle = new Rectangle();
        screenRectangle.setSize( screenSize );
        Rectangle bounds = getBounds();
        newX = (screenSize.width - bounds.width) / 2;
        newY = (screenSize.height - bounds.height) / 2;

        try
        {
            robot = new Robot();
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }

        addMouseListener( this );
        addMouseMotionListener( this );

        copyScreen();

        setSize(250, 200);
        centerFrameOnScreen();
        show();
    }



    public void update(Graphics g)
    {
        paint(g);
    }

    public void paint(Graphics g)
    {
        if(backBuffer == null)
        {
            createBackGraphics();
        }

        if( screen != null )
        {
            backGraphics.drawImage( screen, 0, 0, windowSize.width, windowSize.height, newX, newY, newX+windowSize.width, newY+windowSize.height, null);
        }

        backGraphics.setColor(Color.red);
        backGraphics.fillOval(50, 50, 50,50);

        g.drawImage(backBuffer, 0, 0, null);
    }

    private void createBackGraphics()
      {
        backBuffer = createImage(250, 200);
        backGraphics = backBuffer.getGraphics();
    }

    public void centerFrameOnScreen()
    {
        setBounds( newX, newY, 250, 200);
      }

      public void copyScreen()
      {
        screen = robot.createScreenCapture( screenRectangle );
    }

      public Dimension getMinimumSize()
      {
        return this.preferredSize;
    }

    public Dimension getPreferredSize()
    {
        return this.preferredSize;
    }

      public void mouseClicked(MouseEvent e)
      {
    }

      public void mouseReleased(MouseEvent e)
      {
    }

      public void mouseEntered(MouseEvent e)
      {
    }

      public void mouseExited(MouseEvent e)
      {
    }

      public void mousePressed(MouseEvent e)
      {
        xdiff = e.getX() - newX;
        ydiff = e.getY() - newY;

        if( xdiff < 0 )
        {
            xdiff = -xdiff;
        }
        if( ydiff < 0 )
        {
              ydiff = -ydiff;
        }
        /*
        mousePressedX = e.getX();
        mousePressedY = e.getY();
        */
    }

      public void mouseDragged(MouseEvent e)
      {
        newX = newX + (e.getX() - xdiff);
        newY = newY + (e.getY() - ydiff);
        setLocation( newX, newY );
        repaint();

        /*
        mouseDraggedX = e.getX();
        mouseDraggedY = e.getY();

        xdiff = mouseDraggedX - mousePressedX;
        ydiff = mouseDraggedY - mousePressedY;

        mousePressedX = mouseDraggedX;
        mousePressedY = mouseDraggedY;

        newX = newX + (xdiff);
        newY = newY + (ydiff);

        setLocation( newX , newY );
        repaint();
        */
    }

    public void mouseMoved(MouseEvent e)
    {
    }

    public static void main(String[] args)
    {
        GlassWindowTest glassWindow = new GlassWindowTest();
    }


}