FULL PRODUCT VERSION :
java version "1.4.2_01"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_01-b06)
Java HotSpot(TM) Client VM (build 1.4.2_01-b06, mixed mode)

FULL OS VERSION :
Microsoft Windows 2000
Version 5.0 (Build 2195: Service Pack 3)

A DESCRIPTION OF THE PROBLEM :
GridBagLayout 'collapses' in version 1.4 when there is not space enough
to draw the components. Components are drawn on top of each other. The
outcome is so strange that the poor user might think his program has
crasched.

In previous versions, a centered view of the otherwise correctly laid out
components was shown. The user could immediately realise what had happened.

A situation where a panel is too small to accommodate its components is
not uncommon in applications with resizable windows and/or split panes.
I belive that effort should be taken to rescue such a situation in as
graceful a way as possible. Collapsing the layout is not very graceful.

A good solution would be to add a new constructor parameter to
GridBagLayout, describing the action when the panel is too small. Possible
values could be:
COLLAPSE (like in 1.4)
CENTERED_VIEW (like in 1.3)
WEST_VIEW
NORTH_WEST_VIEW
and so on...


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile the supplied test program.
Run it under 1.3 and 1.4 and compare the behaivour.
Resize the frame, drag the splitter back and forth, change 'cards'.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
When a panel is too small to accomodate its components, I expect it
to be laid out in a way that makes it obvious to see that it is too
small.
ACTUAL -
GridBagLayout in Java 1.4 lays out too small panels in a way that confuses the user.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

/**********************************************************************
**********************************************************************/
public class GBLBug extends JFrame {

  // Try different settings of this parameter
  boolean CONTINOUS_SPLIT_LAYOUT = false;

  JSplitPane panSplit = new JSplitPane (JSplitPane.HORIZONTAL_SPLIT,
                                        CONTINOUS_SPLIT_LAYOUT);
  JList lstLeft = new JList ();
  JPanel panRight = new JPanel ();
  JPanel panCards = new JPanel ();
  JLabel lblRight = new JLabel ();
  CardLayout lmCards = new CardLayout ();
  DefaultListModel listModel = new DefaultListModel ();

  /********************************************************************
  ********************************************************************/
  public GBLBug () {
    super ("GBL Bug - Java version " + System.getProperty ("java.version"));

    panRight.setLayout (new BorderLayout (5, 5));
    panCards.setLayout (lmCards);

    lblRight.setBackground (UIManager.getColor ("activeCaption"));
    lblRight.setForeground (UIManager.getColor ("activeCaptionText"));
    lblRight.setHorizontalAlignment (SwingConstants.CENTER);
    lblRight.setOpaque (true);

    // Allow the splitter to slide
    panRight.setMinimumSize (new Dimension (20, 200));

    panRight.add (lblRight, BorderLayout.NORTH);
    panRight.add (panCards, BorderLayout.CENTER);
    panSplit.setLeftComponent (lstLeft);
    panSplit.setRightComponent (panRight);
    getContentPane().add (panSplit);

    for (int i = 1; i <= 3; i++) {
      createCard (i);
    }//end for

    lstLeft.setSelectionMode (ListSelectionModel.SINGLE_SELECTION);
    lstLeft.setModel (listModel);

    addWindowListener (new WindowAdapter () {
      public void windowClosing (WindowEvent evt) {
        System.exit (0);
      }//end windowClosing
    });

    lstLeft.addListSelectionListener (new ListSelectionListener () {
      public void valueChanged (ListSelectionEvent evt) {
        String cardTitle = (String)(lstLeft.getSelectedValue ());
        selectCard (cardTitle);
      }//end valueChanged
    });

    lstLeft.setSelectedIndex (0);
  }//end constructor

  /********************************************************************
  ********************************************************************/
  void selectCard (String cardTitle) {
    lblRight.setText (cardTitle);
    lmCards.show (panCards, cardTitle);
  }//end selectCard

  /********************************************************************
  ********************************************************************/
  void createCard (int cardIndex) {
    String title = "Card #" + cardIndex;
    JPanel card = new JPanel ();
    card.setLayout (new GridBagLayout ());

    JLabel lblCard = new JLabel ("Label on " + title);
    JTextField txtCard = new JTextField (5 + 10*cardIndex) {
      public Dimension getMinimumSize () {
        return getPreferredSize (); // Prevent collapse
      }//end getMinimumSize
    };
    txtCard.setText ("TextField on " + title);
    JCheckBox chkCard = new JCheckBox ("Checkbox on " + title);
    JButton btnCard = new JButton ("Button on " + title);

    card.add (lblCard, new GridBagConstraints (0, 0, 1, 1, 0.0, 0.0,
                                               GridBagConstraints.WEST,
                                               GridBagConstraints.NONE,
                                               new Insets (0, 0, 0, 0),
                                               0, 0));
    card.add (txtCard, new GridBagConstraints (1, 0, 1, 1, 0.0, 0.0,
                                               GridBagConstraints.WEST,
                                               GridBagConstraints.NONE,
                                               new Insets (0, 0, 0, 0),
                                               0, 0));
    card.add (chkCard, new GridBagConstraints (0, 1, 1, 1, 0.0, 0.0,
                                               GridBagConstraints.WEST,
                                               GridBagConstraints.NONE,
                                               new Insets (0, 0, 0, 0),
                                               0, 0));
    card.add (btnCard, new GridBagConstraints (1, 1, 1, 1, 0.0, 0.0,
                                               GridBagConstraints.WEST,
                                               GridBagConstraints.NONE,
                                               new Insets (0, 0, 0, 0),
                                               0, 0));
    panCards.add (card, title);
    listModel.addElement (title);
  }//end createCard

  /********************************************************************
  ********************************************************************/
  public static void main (String[] args) {
    JFrame f = new GBLBug ();
    f.pack ();
    f.setVisible (true);
  }//end main

}//end class GBLBug

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
You might be able to rescue the situation by placing the GBL panel inside
a scroll pane, but it doesn't work well when you have components with fill
and weight in your GBL.

Release Regression From : 1.3.1
The above release value was the last known release where this
bug was known to work. Since then there has been a regression.
###@###.### 2005-03-08 05:29:22 GMT