Java SE (Java Platform, Standard Edition)

I'm using JInternalFrame as a modal frame( we couldn't use JDialog).
For that I used an example that i found on net, which in this way the JInternalFrame is added to GlassPane of JFrame .

On JInternalFrame there is a JComboBox.
When I drag its scrollpad and move it up and down (to see items in Combo box), content moves ok, but scrollpad stays fixed on one place (instead of going up and down too).
Also, when mouse points an item, it's not highlighted.

After browsing the web and this forum i found 2 threads about this but no answer.

Does anyone have a solution for that?

Sample code:

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

public class ModalInternalFrame extends JInternalFrame {

  private static final JDesktopPane glass = new JDesktopPane();
  
  public ModalInternalFrame(String title, JRootPane 
      rootPane, Component desktop) {
    super(title);

    // create opaque glass pane    
    glass.setOpaque(false);
    glass.setDragMode(JDesktopPane.OUTLINE_DRAG_MODE);

    // Attach mouse listeners
    MouseInputAdapter adapter = new MouseInputAdapter(){};
    glass.addMouseListener(adapter);
    glass.addMouseMotionListener(adapter);
   
    desktop.validate(); 
    try {
      setSelected(true);
    } catch (PropertyVetoException ignored) {
    }

    // Add modal internal frame to glass pane
    glass.add(this);

    // Change glass pane to our panel
    rootPane.setGlassPane(glass);

  }
  
    @Override
  public void setVisible(boolean value) {
    super.setVisible(value);
    // Show glass pane, then modal dialog
    if(glass != null)
        glass.setVisible(value);    
    if (value) {
      startModal();
    } else {
      stopModal();
    }
  }

  private synchronized void startModal() {
        
    try {
      if (SwingUtilities.isEventDispatchThread()) {
        EventQueue theQueue = 
          getToolkit().getSystemEventQueue();
        while (isVisible()) {
          AWTEvent event = theQueue.getNextEvent();
          Object source = event.getSource();
          if (event instanceof ActiveEvent) {              
            ((ActiveEvent)event).dispatch();
          } else if (source instanceof Component) {
              ((Component)source).dispatchEvent(event);                            
          } else if (source instanceof MenuComponent) {              
            ((MenuComponent)source).dispatchEvent(
              event);
          } else {
            System.out.println(
              "Unable to dispatch: " + event);
          }
        }
      } else {
        while (isVisible()) {
          wait();
        }
      }
    } catch (InterruptedException ignored) {
    }
  }
  
  private synchronized void stopModal() {
    notifyAll();
  }

  public static void main(String args[]) {
  
      final JFrame frame = new JFrame(
      "Modal Internal Frame");
    frame.setDefaultCloseOperation(
      JFrame.EXIT_ON_CLOSE);

    final JDesktopPane desktop = new JDesktopPane();
    
    ActionListener showModal = 
        new ActionListener() {
      Integer ZERO = new Integer(0);
      Integer ONE = new Integer(1);
      public void actionPerformed(ActionEvent e) {

        // Construct a message internal frame popup
        final JInternalFrame modal = 
          new ModalInternalFrame("Really Modal", 
          frame.getRootPane(), desktop);
          
        JTextField text = new JTextField("hello");
        JButton btn = new JButton("close");
        JComboBox cbo = new JComboBox(new String[]{"-01-", "-02-", "-03-", "-04-", "-05-", "-06-", "-07-", "-08-", "-09-", "-10-", "-11-", "-12-"});
        
        btn.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                        modal.setVisible(false);
                    }
                });
                
        cbo.setLightWeightPopupEnabled(false);
        Container iContent = modal.getContentPane();
        iContent.add(text, BorderLayout.NORTH);
        iContent.add(cbo, BorderLayout.CENTER);        
        iContent.add(btn, BorderLayout.SOUTH);
        //modal.setBounds(25, 25, 200, 100);
        modal.pack();
        modal.setVisible(true);     
        
      }
    };
    
    JInternalFrame jif = new JInternalFrame();
    jif.setSize(200, 200);
    desktop.add(jif);
    jif.setVisible(true);
    JButton button = new JButton("Open");
    button.addActionListener(showModal);

    Container iContent = jif.getContentPane();
    iContent.add(button, BorderLayout.CENTER);
    jif.setBounds(25, 25, 200, 100);
    jif.setVisible(true);
    
    Container content = frame.getContentPane();
    content.add(desktop, BorderLayout.CENTER);
    frame.setSize(500, 300);
    frame.setVisible(true);
  }
  
}