This is an offshoot of bugid 4411089. The crash that bug report
described was fixed in Ladybird, but does not exist in Merlin.
Unfortunately, other problems do exist in Merlin: the application doesn't
draw correctly, the buttons are non-responsive, and it hangs.

I tested with Merlin build 53. Please compare with the way it works in 1.3


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

public class JPopupCoreDemo extends JWindow
{
  private JButton btn1;
  private JButton btn2;
  private JButton btn3;

  private JPopupMenu popup;
  private JMenu menu;
  private JMenuItem[] mainMenuItems;
  private JMenuItem[] subMenuItems;

  public JPopupCoreDemo()
  {
    super();
    
    menu = new JMenu("Menu 1");
    
    for(int i=0; i<5; i++)
    {
      menu.add( "Sub MenuItem " + Integer.toString(i) );
      if( (0 != i) && (0 == i%2) )
        menu.addSeparator();
    }

    popup = new JPopupMenu("Demo JPopupMenu");
    popup.setLightWeightPopupEnabled(true);
    popup.add( menu );
    popup.addSeparator();

    ActionListener listener = new ActionListener()
      {
        public void actionPerformed (ActionEvent evt)
        {
          System.out.println("Doing something");
        }
      };
    
    for(int j=0; j<10; j++)
    {
      JMenuItem mi = popup.add( "Main MenuItem " + Integer.toString(j) );
      mi.addActionListener( listener );
      
      if( (0 != j) && (0 == j%2) )
        popup.addSeparator();
    }

    btn1 = new JButton("Button1");
    btn1.setToolTipText("Show JPopupMenu");
    btn1.addActionListener( new ActionListener()
      {
        public void actionPerformed (ActionEvent evt)
        {
           popup.show( btn1, 0, btn1.getSize().height );
        }
      });

    btn2 = new JButton("Button2");
    btn2.setToolTipText("Show JPopupMenu");
    btn2.addActionListener( new ActionListener()
      {
        public void actionPerformed (ActionEvent evt)
        {
           popup.show( btn2, 0, btn2.getSize().height );
        }
      });

    btn3 = new JButton("Button3");
    btn3.setToolTipText("Show JPopupMenu");
    btn3.addActionListener( new ActionListener()
      {
        public void actionPerformed (ActionEvent evt)
        {
           popup.show( btn3, 0, btn3.getSize().height );
        }
      });

    Box bx = Box.createHorizontalBox();
    bx.add(btn1);
    bx.add(Box.createHorizontalGlue());
    bx.add(btn2);
    bx.add(Box.createHorizontalGlue());
    bx.add(btn3);

    super.setContentPane( bx );

    MouseAdapter mouseAdp = new MouseAdapter()
      {
        public void mouseClicked(MouseEvent e)
        {
          if( (( e.getModifiers() & e.BUTTON3_MASK ) != 0 ) ||
              e.isPopupTrigger() )
          {
            popup.show( e.getComponent(), e.getX(), e.getY() );
          }
        }
      };

    super.addMouseListener(mouseAdp);

    pack();

    super.setSize( super.getToolkit().getScreenSize().width,
                   super.getSize().height );

    super.setVisible(true);
  }

  public static void main(String[] arg)
  {
    new JPopupCoreDemo();
  }
  
}