Name: rk38400 Date: 05/12/98


I'm using WinNT v4.0, SP3 and JDK v1.1.6, Swing v1.0.2.

I've attached a minimal sample program to illustrate the behavior.

A couple weeks ago I sent in a bug report which described a problem
where the glasspane of a JFrame would not trap keyboard events (although
it would correctly trap mouse events). You replied to my report by
saying that I could set the focus to the glasspane and that would
accomplish the effect I was after.

Here's a quote from the "setGlassPane()" method of the
"RootPaneContainer" interface. This quote indicates I should simply be
able to add a key listener to the glasspane and then make the glasspane
visible:

    "The glassPane is always the first child of the
     rootPane and the rootPanes layout manager ensures
     that it's always as big as the rootPane. By default
     it's transparent and not visible. It can be used to
     temporarily grab all keyboard and mouse input by
     adding listeners and then making it visible.
     By default it's not visible."


Furthermore, explicitly setting the focus to the glasspane (as you
suggested) has two undesirable effects:

1. If an underlying control (for example, a JButton on the content pane)
has the focus, then setting the focus to the glasspane results in the
focus rectangle being removed from the control.

2. If a JTextField on the content pane has the focus when the glass pane
is made visible, then the caret is removed from the JTextField when the
glasspane receives the focus.

I believe the glasspane should be able to trap all mouse/keyboard input
without the underlying content pane changing its appearance (i.e.,
carets and focus rectangles being removed).

I was hoping you could re-evaluate this behavior and classify it as a
bug -- it still seems to be a bug to me.


import com.sun.java.swing.*;
import java.awt.*;
import java.awt.event.*;


public class Tester
{
   public static void main(String[] args)
   {
      final JFrame f = new JFrame();
        
      f.addWindowListener(new WindowAdapter()
      {
         public void windowClosing(WindowEvent evt)
         {
            ((Window)evt.getSource()).dispose();
            System.exit(0);
         }
      });
      
      
      JPanel p = new JPanel(false);
      
      JButton glassPaneButton = new JButton("Make Glass Pane Visible");
      p.add(glassPaneButton);
      
      JTextField tf = new JTextField(15);
      p.add(tf);
      
      f.getContentPane().add(p, BorderLayout.CENTER);
      
      glassPaneButton.addActionListener(new ActionListener()
      {
         public void actionPerformed(ActionEvent evt)
         {
            f.getGlassPane().setVisible(true);
            // If you uncomment the line below, the glass pane will pick up
            // all key presses. Unfortunately, any focus rectangle present
            // on the underlying controls will also be removed.
            //f.getGlassPane().requestFocus();
         }
      });
      
      f.getGlassPane().addMouseListener(new MouseAdapter()
      {
         public void mousePressed(MouseEvent evt)
         {
            System.out.println(" ----- A mouse button was pressed...");
         }
      });
      
      f.getGlassPane().addKeyListener(new KeyAdapter()
      {
         public void keyPressed(KeyEvent evt)
         {
            System.out.println(" ----- A key was pressed...");
         }
      });
      
      

      // The rest of this code simply changes the LaF...
      final JButton windowsButton = new JButton("Windows"),
                     motifButton = new JButton("Motif"),
                     metalButton = new JButton("Metal");
               
      ActionListener LaFListener = new ActionListener()
      {
         public void actionPerformed(ActionEvent evt)
         {
            JButton b = (JButton)evt.getSource();

            try
            {
               if(b == windowsButton)
       UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
               else if (b == motifButton)
       UIManager.setLookAndFeel("com.sun.java.swing.plaf.motif.MotifLookAndFeel");
               else
       UIManager.setLookAndFeel("com.sun.java.swing.plaf.metal.MetalLookAndFeel");

       SwingUtilities.updateComponentTreeUI(b.getRootPane());
    }
    catch(Exception e)
    {
    System.err.println("*** ERROR: " + e);
    System.exit(2);
    }
         }
      };
      
      windowsButton.addActionListener(LaFListener);
      motifButton.addActionListener(LaFListener);
      metalButton.addActionListener(LaFListener);
      
      JPanel LaFButtonsPanel = new JPanel(false);
      LaFButtonsPanel.add(windowsButton);
      LaFButtonsPanel.add(motifButton);
      LaFButtonsPanel.add(metalButton);
      
      f.getContentPane().add(LaFButtonsPanel, BorderLayout.SOUTH);

      f.setBounds(65, 65, 450, 190);
      f.setVisible(true);
   }
}
(Review ID: 30202)
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