Why does my JMenuBar leave a blank space on the Mac OS X screen menu bar?

Issue with JMenuBar Shifting on Mac OS X

When attempting to move a JMenuBar to the screen menu bar in a Mac OS X environment, a blank space is often left behind where the menu would reside within the window. This issue can be resolved by establishing the property "apple.laf.useScreenMenuBar" at the appropriate time.

Solution

To address this problem, set the property "apple.laf.useScreenMenuBar" at program launch using one of the following methods:

1. Launch Command: Include the property setting in the launch command:

java -Dapple.laf.useScreenMenuBar=true -jar MyApplication.jar

2. Info.plist Modification: Add the property to the application bundle's Info.plist file:

<key>Properties</key>
<dict>
    <key>apple.laf.useScreenMenuBar</key>
    <string>true</string>
    ...
</dict>

Additional Considerations

It's important to note that setting the property after the application has launched may not be effective. The following code demonstrates a correct implementation where no blank space is present:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JPanel;

/** @see http://stackoverflow.com/questions/8955638 */
public class NewMain {

    public static void main(String[] args) {
        System.setProperty("apple.laf.useScreenMenuBar", "true");
        System.setProperty(
            "com.apple.mrj.application.apple.menu.about.name", "Name");
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {

                JFrame frame = new JFrame("Gabby");
                final JPanel dm = new JPanel() {

                    @Override
                    public Dimension getPreferredSize() {
                        return new Dimension(320, 240);
                    }
                };
                dm.setBorder(BorderFactory.createLineBorder(Color.blue, 10));

                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(dm);
                frame.pack();
                frame.setLocationByPlatform(true);

                JMenuBar menuBar = new JMenuBar();
                JMenu fileMenu = new JMenu("File");
                menuBar.add(fileMenu);
                frame.setJMenuBar(menuBar);
                frame.setVisible(true);
            }
        });
    }
}

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