Name: jl125535 Date: 12/18/2001


java version "1.4.0-beta3"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta3-b84)
Java HotSpot(TM) Client VM (build 1.4.0-beta3-b84, mixed mode)

JSplitPane component with a left and right component has its current divider
position incorrectly set to -1 once it is fully realized. For JDK 1.3.1, its
value is set to 0. The current position of the divider should be the current
position of the divider once layout management is complete. If the divider is
moved one pixel, the current divider position is updated to the correct value
but the last divider position is then set to -1 (i.e. the last value of the
current divider position). If the divider is moved again, everything is OK.

Below is an example of the problem... bring up the example and click the
trigger button. It will show that the current divider position is incorrect
(says that it is -1 but it should not be). Slide the divide one pixel and
click the trigger button again. It will show that the current divider position
is now current but the last divider position is set to 0.


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

public class SplitPaneTest
{
    public static void main(String[] args)
    {
        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        
        JFrame frame = new JFrame("Split Pane Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.getContentPane().setLayout(new BorderLayout());

        JButton leftButton = new JButton("Left Button");
        JButton rightButton = new JButton("Right Button");
        
        final JSplitPane splitPane =
            new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,
                           true,
                           leftButton,
                           rightButton);
        frame.getContentPane().add(splitPane, BorderLayout.CENTER);
        
        JToggleButton triggerButton = new JToggleButton("Trigger");
        triggerButton.setPreferredSize(
            new Dimension(800, triggerButton.getPreferredSize().height));
        triggerButton.setMinimumSize(
            new Dimension(800, triggerButton.getPreferredSize().height));
        triggerButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event)
            {
                System.out.println("Current=" + splitPane.getDividerLocation()
                                   + ",Last="
                                   + splitPane.getLastDividerLocation());
            }
        });
        frame.getContentPane().add(triggerButton, BorderLayout.SOUTH);
        
        frame.pack();
        frame.setVisible(true);
    }
}

ADDITIONAL COMMENTS FROM ANALYZER

Windows 2000 with JDK 1.3.1 or JDK 1.4 beta 3 produces output that
looks like the following (Solaris 8 with JDK 1.3.1 behaves similarly):

Current=-1,Last=0
Current=92,Last=91
Current=90,Last=91
Current=90,Last=91
Current=92,Last=91
Current=116,Last=115

Notice that
  getLastDividerLocation() = getDividerLocation() + delta,
  where delta is a number whose absolute value is <= 2

regardless of where the user moves the splitter.


Solaris 8 with JDK 1.4 beta 3 produces output that looks like
the following:

Current=-1,Last=0
Current=-1,Last=0
Current=87,Last=-1
Current=87,Last=-1
Current=92,Last=87
Current=83,Last=92
Current=83,Last=92
Current=83,Last=120

The mismatch between last values and preceding current values
is unexpected

In both cases, having a divider location of -1 seems odd.
(Review ID: 136972)
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