White spots appear with text in JFrame

Question

It looks like:

As seen in the image there are white spots with the text.

My code is:

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

public class SubsFrame extends JFrame {
    private String text;
    private JLabel label;
    private byte mode;

    private static SubsFrame instance;

    public static void build(long mode) throws Exception{
        if(instance == null) {
            instance = new SubsFrame(mode);
        }else{
            throw new Exception("Another instance already exists!");
        }
    }

    public static void buildSilent(long mode) throws Exception{
        if(instance == null)
            instance = new SubsFrame(mode);
    }

    public static void showFrame(){
        instance.setVisible(true);
    }

    public static void hideFrame(){
        instance.setVisible(false);
    }

    public static void destroy() {
        instance.dispose();
        instance = null;
    }

    public static void setOpacity(double opacity){
        instance.setBackground(new Color(1.0f,1.0f,1.0f,(float)opacity));
    }

    private SubsFrame(long mode) throws Exception{
        if(JSubsConstants.isValidMode(mode))
            this.mode = (byte)mode;
        else
            throw new Exception("Invalid Mode Selected!");
        if(!this.isAlwaysOnTopSupported()){
            throw new Exception("Always on top is not supported!");
        }
        label = new JLabel("Hello World!          Welcome to this app!");
        label.setFont(new Font("Consolas", Font.PLAIN, 25));
        this.setLayout(new FlowLayout());
        this.add(label);
        this.setDefaultCloseOperation(HIDE_ON_CLOSE);
        this.setAlwaysOnTop(true);
        this.setUndecorated(true);
        if(this.mode == JSubsConstants.AUTO_SIZED_FRAME_AUTO_POSITIONED){
            handleFrameSize();
            handleFrameLocation();
        }
        else if(this.mode == JSubsConstants.AUTO_SIZED_FRAME_MANUAL_POSITIONED){
            handleFrameSize();
        }
    }

    private void handleFrameLocation() {
        this.setLocation(250, 350);
    }

    private void handleFrameSize() {
        this.pack();
        this.setSize(this.getWidth() + 20, this.getHeight() + 10);
    }
}

Why are these coming and how can I remove them?

I guess these are to do with the font itself and not Java but I am not sure of that. I tried with some other fonts as well same results.

If you need more information please ask me.

Answer 1

My "suspicion" is the algorithm trying to figure out how the composition should work is having trouble with the anti aliasing of the text.

Generally when I want to do these things, I make the window completely transparent and move the logic to another container instead, this seems to do a better job, generally and eliminates the "oddities" created by the platform and how it handles transparent windows - but that's me.

import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JWindow;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.border.EmptyBorder;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class TranscluentWindow {

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

    public TranscluentWindow() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (Exception ex) {
                }

                JWindow frame = new JWindow();
                frame.setAlwaysOnTop(true);
                frame.addMouseListener(new MouseAdapter() {
                    @Override
                    public void mouseClicked(MouseEvent e) {
                        if (e.getClickCount() == 2) {
                            SwingUtilities.getWindowAncestor(e.getComponent()).dispose();
                        }
                    }
                });
                frame.setBackground(new Color(0, 0, 0, 0));
                frame.add(new TranslucentPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TranslucentPane extends JPanel {

        private float opacity = 1;

        public TranslucentPane() {
            setOpaque(false);
            setLayout(new BorderLayout());
            JLabel label = new JLabel("Hello World!          Welcome to this app!");
            label.setForeground(Color.RED);
            label.setBorder(new EmptyBorder(8, 8, 8, 8));
            add(label);

            JSlider slider = new JSlider();
            slider.setMinimum(0);
            slider.setMaximum(100);
            slider.setValue(100);
            slider.addChangeListener(new ChangeListener() {
                @Override
                public void stateChanged(ChangeEvent e) {
                    setOpacity(slider.getValue() / 100f);
                }
            });

            add(slider, BorderLayout.SOUTH);
        }

        public void setOpacity(float opacity) {
            this.opacity = opacity;
            repaint();
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setComposite(AlphaComposite.SrcOver.derive(opacity));
            g2d.setColor(getBackground());
            g2d.fillRect(0, 0, getWidth(), getHeight());
            g2d.dispose();
        }

    }

}