Unicode characters in javax.swing only display when using the default font-size

Question

I'm trying to display a few Unicode characters inside of a jLabel. Take for example, the "degrees Fahrenheit" character (℉ or "\u2109"). This character is only being displayed when I use the default font-size, which happens to be 11. When I change the font-size, the character is replaced with an empty square. I've tried several different sizes and several different fonts that supposedly support a wide range of unicode characters. Can anyone tell me why Swing only displays this unicode character under a specific font-size?

Proof:

Proof

All the code related to the UI is auto-generated by NetBeans using the designer, but here is how I'm supplying the text to the jLabel:

private void btnConvertActionPerformed(java.awt.event.ActionEvent evt) {                                           
    if(optToFarenheit.isSelected())
    {
        int tempFahr = (int)((Double.parseDouble(txtInput.getText()))
                * 1.8 + 32);
        lblResult.setText(tempFahr + " ℉");
        //lblResult.setText(tempFahr + " \u2109"); <-- Tried this too
    }
}

Without seeing your code it will likely be impossible for anyone to help you. — Jim Garrison
@JimGarrison updated my question. I see how it may clarify things, but the code is pretty trivial. — Mr Jones
You have omitted the important part, which is where you "change the font size". — Jim Garrison
Font support to U+2109 is relatively limited and does not include e.g. Tahoma, which you mention in a comment. — Jukka K. Korpela
Note that the DEGREES FAHRENHEIT character is not recommended. It has been included in Unicode only for compatibility with old character codes. A combination of DEGREE SIGN and a normal capital letter (°F) should be used instead. Ref.: Unicode standard, ch. 15, p. 481. — Jukka K. Korpela

MadProgrammer MadProgrammer · Accepted Answer · 2013-09-12T00:11:44

Instead of "changing" the font, which might lead you to a font that is incompatible, try simply changing the label's "default" font's size

enter image description here

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestUnicodeFont {

    public static void main(String[] args) {
        new TestUnicodeFont();
    }

    public TestUnicodeFont() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            JLabel normal = new JLabel("Normal - ?");
            JLabel byCode = new JLabel("Normal code - \u2109");

            JLabel normalLarger = new JLabel("Large - ?");
            normalLarger.setFont(normalLarger.getFont().deriveFont(48f));
            JLabel byCodeLatger = new JLabel("Large code - \u2109");
            byCodeLatger.setFont(byCodeLatger.getFont().deriveFont(48f));

            add(normal, gbc);
            add(byCode, gbc);
            add(normalLarger, gbc);
            add(byCodeLatger, gbc);
        }
    }

}

Unicode characters in javax.swing only display when using the default font-size

3 Answers