How to get rid of the space around buttons in Nimbus LAF?

Question

I need to put some JButtons in a very small place, and the problem is that the Nimbus LAF automatically puts some space around them, and as a result the buttons look smaller than they really are.

In the following example program I use a FlowLayout with 0 horizontal and vertical gaps, and I expected the buttons to sit tightly without any space between them. If I comment out the setting of the Nimbus LAF, they behave as expected.

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

public class NimbusSpace {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                buildGUI();
            }
        });
    }

    private static void buildGUI() {
        try {
            UIManager.setLookAndFeel("javax.swing.plaf.nimbus.NimbusLookAndFeel");
        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException e) {
            e.printStackTrace();
        }

        JFrame f = new JFrame("Test");
        f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        JPanel p = new JPanel(new FlowLayout(FlowLayout.LEFT, 0, 0));
        p.add(createButton("aa"));
        p.add(createButton("bb"));
        p.add(createButton("cc"));

        f.add(p);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    private static JButton createButton(String text) {
        JButton b = new JButton(text);

//        b.setBorder(null);
//        b.setBorderPainted(false);
//        b.setMargin(new Insets(0,0,0,0));
//        b.putClientProperty("JComponent.sizeVariant", "large");
//        b.putClientProperty("JComponent.sizeVariant", "mini");

//        UIDefaults def = new UIDefaults();
//        def.put("Button.contentMargins", new Insets(0,0,0,0));
//        b.putClientProperty("Nimbus.Overrides", def);

        return b;
    }
}

As you can see in the commented out code in createButton, I tried quite a few things, but they didn't remove the space around the buttons.

EDIT: Based on the discussions in the comments, it seems that it is not possible to remove the space between the rectangular edges of the button and the drawn rounded-rectangle outline. Nimbus reserves these two pixels for the "focus highlight", and probably this cannot be changed without re-implementing a lot of Nimbus functionality.

So I accepted guleryuz's trick: if the buttons are positioned at overlapping and negative positions, they can look bigger. In practice this idea seems to work, but it is not a very clean solution, so if you know a better (and reasonably easily implemented) solution, don't hesitate to answer...

Answer 1

Note that if you set the background color and then call setOpaque(true), you can see that the buttons ARE right up against each other. That's just how Nimbus draws a button; I don't think you can change the space between the rectangular edges of the button and the drawn rounded-rectangle outline.

If space is a premium, you can shrink the size a bit by uncommenting your UIDefaults lines and modifying the contentMargins property (but don't use 0,0,0,0, use something like 2,8,2,8).

Answer 2

approach 1:

JPanel p = new JPanel(new FlowLayout(FlowLayout.LEFT, -4, 0));

approach 2:

    JPanel p = new JPanel(new FlowLayout(FlowLayout.LEFT, 0, 0));
    p.add(createButton("aa", 1));
    p.add(createButton("bb", 2));
    p.add(createButton("cc", 3));

with some modifications in createButton method

private static JButton createButton(String text, final int s) {
    JButton b = new JButton(text){
        @Override
        public void setLocation(int x, int y) {
            super.setLocation(x-(s*4), y);
        }
    };
    return b;
}

approach 3

JPanel p = new JPanel(new MigLayout("ins 0, gap -5","[][][]"));