smooth rounded corners in swing

Question

I want to make smooth rounded corners for my swing application, but I can\'t get my desired result...

here\'s the screenshots:

1.setShape() for JFra

Answer 1

Sorry, not an answer, but hopefully at least one step towards an acceptable answer: From my analysis so far, it might be that this is simply a bug somewhere deep (deeeep!) inside the rendering pipeline.

The following MVCE shows two (undecorated) frames, each containing a button. They are equal, except for the background of the frames. For one frame, the color is transparent, and for the other one, it is opaque.

import java.awt.Color;
import java.awt.Font;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;

public class TextRenderBug extends JFrame {

    public static void main(String[] args)
    {
        setLookAndFeel();
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                createAndShowGUI(new Color(0,0,0  ), 400);
                createAndShowGUI(new Color(0,0,0,0), 600);
            }
        });
    }

    private static void setLookAndFeel()
    {
        try
        {
            for (UIManager.LookAndFeelInfo info : 
                    UIManager.getInstalledLookAndFeels())
            {
                if ("Nimbus".equals(info.getName()))
                {
                    UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    private static void createAndShowGUI(Color background, int x)
    {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setUndecorated(true);
        f.setBackground(background);
        JButton b = new JButton("Text");
        b.setFont(new Font("Tahoma", 0, 15));
        f.getContentPane().add(b);
        f.setBounds(x, 400, 200, 50);
        f.setVisible(true);
    }
}

It clearly shows that the text is rendered differently, solely depending on the background being transparent - and of course, this should not be the case.

(This is not Nimbus-specific, by the way: It also applies to other LookAndFeels. Just remove the line where the LaF is set).

What I found out so far:

• The behavior is somehow caused by the drawString method of the sun.swing.SwingUtilities2 class
• It does not appear in all components. It can be observed on JButton and JLabel, but not on a normal JComponent
• Update: It also does not depend on the font (although with other fonts, the effect is not so noticable). When rendered correctly, the font looks a little bit more bold, but of course, it is not simply the same font as a Font.BOLD.
• The painting process is rather complicated.

(OK, some of you might already have known the latter).

Here is an example that shows the last observations, maybe it can serve as a starting point for further research of others:

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.lang.reflect.Method;

import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class TextRenderBugTest
{
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                createAndShowGUI(new Color(0,0,0  ), 400);
                createAndShowGUI(new Color(0,0,0,0), 600);
            }
        });
    }

    private static void createAndShowGUI(Color background, int x)
    {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setUndecorated(true);
        f.setBackground(background);

        JButton b = new JButton("Text");
        b.setFont(new Font("Tahoma", 0, 15));

        JComponent c = new ExampleComponent();
        c.setFont(new Font("Tahoma", 0, 15));

        f.getContentPane().setLayout(new GridLayout(0,1));
        f.getContentPane().add(b);
        f.getContentPane().add(c);

        f.setBounds(x, 400, 200, 100);
        f.setVisible(true);
    }

    static class ExampleComponent 
        //extends JComponent
        extends JButton
    {
        @Override
        protected void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            g.setColor(getBackground());
            g.fillRect(0, 0, getWidth(), getHeight());
            g.setColor(getForeground());
            g.drawString("Text", 10, 20);
            drawStringWithSwingUtilities(g, 60, 20);
        }

        private void drawStringWithSwingUtilities(Graphics g, int x, int y)
        {
            try
            {
                Class c = Class.forName("sun.swing.SwingUtilities2");
                Method m = c.getMethod("drawString", JComponent.class,
                    Graphics.class, String.class, int.class, int.class);
                m.invoke(null, this, g, "Text", x, y);
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }

        }

    }

}

I already tried to analyze this further, and played around with RenderingHints like KEY_TEXT_ANTIALIASING and KEY_TEXT_LCD_CONTRAST and other settings that are changed in the painting pipeline while it is heading towards the pixels that are finally placed on the screen, but no further insights until now.

(If you want to, you can add this information to your original question, then I'll delete this (not-)answer)