Thread: translucent windows support — is this really supported in majority of OS?

Hi.

After a lot of struggling I have finally code of per pixel transparency which works: JFrame with translucent gradient background + 1 opaque button. BUT! I works only (among other tested OS/JDK) in JDK7 and windows 7. Alpha channel is totally missing with windows 10, XFCE, both using JDK8.

So the question is:
is this feature actually working and I'm just missing some magical switches in windows / xfce? Or it's rather considered as unstable feature?

Note: code in question is just a prototype, what I'm really after is ability "to see through some glass" and being able to paint on it, regardless what applications (not just mine, therefore no glasspane) are running below. If there is nice solution I can use instead you can recommend, please do! (note2: screenshotting using robot could be considered as plan-b, but really insufficient one, as it disallows to see changes below "glass").

Thanks!

EDIT, the code(I stole it somewhere and did some minor fixing changes. But again on windows7 JDK7 it works perfectly.):

 
import static java.awt.GraphicsDevice.WindowTranslucency.PERPIXEL_TRANSLUCENT;
 
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
 
import javax.swing.*;
 
public class Trans3 extends JFrame {
    public Trans3() {
        super("GradientTranslucentWindow");
        setUndecorated(true);
        setBackground(new Color(0, 0, 0, 0));
        setSize(new Dimension(300, 200));
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        JPanel panel = new JPanel() {
            @Override
            protected void paintComponent(Graphics g) {
                if (g instanceof Graphics2D) {
                    final int R = 240;
                    final int G = 240;
                    final int B = 240;
                    Paint p =
                            new GradientPaint(0.0f, 0.0f, new Color(R, G, B, 0),
                                    0.0f, getHeight(), new Color(R, G, B, 255), true);
                    Graphics2D g2d = (Graphics2D) g;
                    g2d.setPaint(p);
                    g2d.fillRect(0, 0, getWidth(), getHeight());
                }
            }
        };
        setContentPane(panel);
        setLayout(new GridBagLayout());
        JButton button = new JButton("exit");
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                setVisible(false);
                dispose();
            }
        });
        add(button);
    }
 
    public static void main(String[] args) {
        // Determine what the GraphicsDevice can support.
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice gd = ge.getDefaultScreenDevice();
        boolean isPerPixelTranslucencySupported = gd.isWindowTranslucencySupported(PERPIXEL_TRANSLUCENT);
        //If translucent windows aren't supported, exit.
        if (!isPerPixelTranslucencySupported) {
            System.out.println("Per-pixel translucency is not supported");
            System.exit(0);
        }
        JFrame.setDefaultLookAndFeelDecorated(false);
        // Create the GUI on the event-dispatching thread
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                Trans3 gtw = new Trans3();
                // Display the window.
                gtw.setVisible(true);
            }
        });
    }
}

resolved for both windows 10 and xfce.

1. windows: I found this question on on stackoverflow:
https://stackoverflow.com/questions/...-in-windows-10
which I built in idea and it worked! So this example is proper example for windows 10. Next, I retried some examples which did not work previously on win 10 and found they are working now as well! That came to me as a shock, since one cannot mistake black background with transparent one. Maybe I did some minor changes after testing on win 10, which made it working now, I don't know. Nevertheless it works now.

2. linux&xfce. Even code in link above did not work. So I tried to look for potential problems in system setting and one of tested setting was "turned off compositor" (compositors are sometimes turned of because they'are known to cause some graphical issues in xfce). With compositor turned back on, java transparency work OK.

so this resolves this topic. Thanks to all readers trying to help me.
M.