I was so very happy today, because I had my UI looking just really blody
flash. Then I tried moving a JInternalFrame, and the whole house of
cards tumbled down.

My whole L&F depends on having a JPanel in the background of an MDI
form. That background panel has a tiled image of a cute little
watermark. Buttons on the left, JDesktop taking up the rest of the
space, with JInternal frames popping up as required.

As I said in my opening paragraph, the problem is that moving the
JInternalFrames about leaves a mess behind on the JDesktopPane.

I've put together a simple class that shows my problem exactly. It'll
wrap, but it's also available for download at...

http://www.webber.com.au/pub/TransparentMDI.java

I'd greatly appreciate any thought on this. The sample code is below.

TIA,
Luke

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package test;

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

/*
 * A sample of problems encountered with transparent JDesktopPanes
 *
 * If pnlLeft isn't added, the red background from pnlMain doesn't
 * even show though, but that's not the biggest problem.
 * Moving the JInternalFrame around (WinXP, JDK1.5.0_07), makes one
 * hell of a mess. OTOH, resizing the internal frame works just fine,
 * even removing the artifacts left by previous moves.
 */
public class TransparentMDI extends JFrame implements WindowListener
{
  JDesktopPane desktop = new JDesktopPane();

  public static void main(String[] args)
  {
    new TransparentMDI().setVisible(true);
  }

  public TransparentMDI()
  {
    super("Transparent Desktop Test");
    Container cp = getContentPane();
    JPanel pnlMain = new JPanel(new BorderLayout());
    pnlMain.setBackground(Color.RED);
    JPanel pnlLeft = new JPanel(new BorderLayout());
    pnlLeft.setOpaque(false);
    pnlLeft.add(new JLabel("JDK "+System.getProperty("java.version")),
BorderLayout.NORTH);
    pnlMain.add(pnlLeft, BorderLayout.WEST);
    // Make the desktop semi-transparent
    Color db = new Color(0,0,0, 32);
    desktop.setBackground(db);
    desktop.setOpaque(false);
    pnlMain.add(desktop, BorderLayout.CENTER);
    JInternalFrame jif = new JInternalFrame("Internal Frame", true, true);
    jif.setBounds(0, 0, 300, 300);
    Container jifcp = jif.getContentPane();
    jifcp.setLayout(new BorderLayout());
    jifcp.add(new JLabel("Move me", JLabel.CENTER), BorderLayout.CENTER);
    jif.setVisible(true);
    desktop.add(jif);
    cp.setLayout(new BorderLayout());
    cp.add(pnlMain, BorderLayout.CENTER);
    addWindowListener(this);
    pack();
    setExtendedState(MAXIMIZED_BOTH);
  }

  public void windowClosing(WindowEvent we)
  {
    System.exit(0);
  }

  public void windowActivated(WindowEvent e) {}
  public void windowClosed(WindowEvent e) {}
  public void windowDeactivated(WindowEvent e) {}
  public void windowDeiconified(WindowEvent e) {}
  public void windowIconified(WindowEvent e) {}
  public void windowOpened(WindowEvent e) {}
}
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