FULL PRODUCT VERSION :
java version "1.6.0-beta2"
Java(TM) SE Runtime Environment (build 1.6.0-beta2-b76)
Java HotSpot(TM) Client VM (build 1.6.0-beta2-b76, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Linux io 2.6.11.4-21.11-smp #1 SMP Thu Feb 2 20:54:26 UTC 2006 i686 i686 i386 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
Baseline alignment does not work correctly for GridBagLayout. When the baseline alignment is used in a JPanel with a GridBagLayout manager the components added to the JPanel are not rendered correctly. JLabels for example are truncated in the y direction.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile the example attached to this report:
jdk1.6.0-beta2-b76/bin/javac GridBagBaselinePanel.java
Run the example:
java/jdk1.6.0-beta2-b76/bin/java GridBagBaselinePanel

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
In order to see the expected result:
- Change the private member useBaseline of the class GridBagBaselinePanel to false
- Recompile the program
- Run the program

The JLabels and JSpinners are now fully visible (but the texts are not baseline aligned).

For the baseline alignment working correctly I would expect the JLabels and JSpinners to be fully visible with the texts aligned at the baseline.
ACTUAL -
When baseline alignment is switched on the JLabels and JSpinners in the example are truncated in the y direction.

REPRODUCIBILITY :
This bug can be reproduced always.

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

public class GridBagBaselinePanel extends JPanel {
    private GridBagLayout gridbag;
    private GridBagConstraints c;
    private int row;
    private boolean useBaseline;

    public GridBagBaselinePanel() {
        useBaseline = true;
        gridbag = new GridBagLayout();
        c = new GridBagConstraints();
        setLayout(gridbag);
        row = 0;
        addRow("Speed", "m/s");
        addRow("Distance", "m");
        addRow("Time", "s");
    }

    private void addRow(String desc, String unit) {
        JLabel descLabel = new JLabel(desc);
        descLabel.setHorizontalAlignment(SwingConstants.TRAILING);
        c.gridx = 0;
        c.gridy = row;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.fill = GridBagConstraints.BOTH;
        c.ipadx = 0;
        c.ipady = 0;
        if (row == 0) {
            c.insets = new Insets(0, 0, 0, 12);
        } else {
            c.insets = new Insets(5, 0, 0, 12);
        }
        if (useBaseline) {
            c.anchor = GridBagConstraints.BASELINE_LEADING;
        } else {
            c.anchor = GridBagConstraints.LINE_START;
        }
        c.weightx = 0.0;
        c.weighty = 0.0;
        gridbag.setConstraints(descLabel, c);
        add(descLabel, c);

        JSpinner valueSpinner = new JSpinner();
        c.gridx = 1;
        if (row == 0) {
            c.insets = new Insets(0, 0, 0, 6);
        } else {
            c.insets = new Insets(5, 0, 0, 6);
        }
        c.weightx = 1.0;
        gridbag.setConstraints(valueSpinner, c);
        add(valueSpinner, c);

        JLabel unitLabel = new JLabel(unit);
        c.gridx = 2;
        if (row == 0) {
            c.insets = new Insets(0, 0, 0, 0);
        } else {
            c.insets = new Insets(5, 0, 0, 0);
        }
        c.weightx = 0.0;
        gridbag.setConstraints(unitLabel, c);
        add(unitLabel, c);

        row++;
    }

    private static void createAndShowGUI() {
        JPanel panel = new GridBagBaselinePanel();
        panel.setBorder(BorderFactory.createEmptyBorder(12, 12, 11, 11));

        JFrame frame = new JFrame("GridBagBaselineBug");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

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

CUSTOMER SUBMITTED WORKAROUND :
Don't use baseline alignment.