Unselectable overlay in java

Question

My question is essentially is if there was a way, in Java, to have some type of un-selectable overlay on the screen. By 'un-selectable' I mean, if I overlayed the JWindow/JFrame over a window from another process for example, I can still interact with the window as normal, but I can render content in the JWindow/JFrame that appears on top of the window at the same time.

Simply creating a component and setting the following flags AutoRequestFocus/Focusable/Enabled to false does not achieve my goal as the overlay blocks the mouse from clicking on anything behind it.

This would be on a windows system but preferably isn't restricted to OS.

Answer 1

Only option i can see of achieving this is to use JNA, and this works. You have to refer JNA libraries

public class Main
{
    public static void main(String[] args)
    {
        TestFrame frame = new TestFrame();
        frame.setVisible(true);
        WinDef.HWND hwnd = User32.INSTANCE.FindWindow("SunAwtFrame", "Transparent Window");

        int wl =  User32.INSTANCE.GetWindowLong(hwnd, WinUser.GWL_EXSTYLE);
        wl = wl | 0x80000 | 0x20;
        User32.INSTANCE.SetWindowLong(hwnd, WinUser.GWL_EXSTYLE, wl);
    }

    public static long getHWnd(Frame f) {
        return f.getPeer() != null ? ((WComponentPeer) f.getPeer()).getHWnd() : 0;
    }

    static class TestFrame extends JFrame
    {
        public TestFrame()
        {
            super("Transparent Window");
            setUndecorated(true);
            setBackground(new Color(0, 0, 0, 0));
            setAlwaysOnTop(true);
            setSize(800, 600);
            // Without this, the window is draggable from any non transparent
            // point, including points  inside textboxes.
            getRootPane().putClientProperty("apple.awt.draggableWindowBackground", false);

            getContentPane().setLayout(new java.awt.BorderLayout());
            getContentPane().add(new JTextField("text field north"), java.awt.BorderLayout.NORTH);
            getContentPane().add(new JTextField("text field south"), java.awt.BorderLayout.SOUTH);
        }

        @Override
        public void paint(Graphics g)
        {
            super.paint(g);
            g.setColor(Color.BLUE);
            g.fill3DRect(0,0,100,100,false);
        }
    }
}

Answer 2

I think it is possible, because I used to create the opposite thing. A window, that is transparent, but receives Events.

You will need to write an application, which creates a completely transparent Window (I used SWT). Every part, that is complete transparent, will not receive any events. Parts, which are not complete transparent, will get events.

Your application will need to interact with the operatingsystem, to find the correct process and get the windows position and size.

Within your paintloop, you will need to set your windows position and size.

This part was easier in my application, because it was the same process.

Answer 3

Have a look at this demo, it shows how to pass click events from the glass pane (where you paint your extra content) to the underlying "real" pane (where you want the clicks/events to happen). See the method redispatchMouseEvent. Some relevant parts of the code are below:

glass = new FixedGlassPane(jFrame.getContentPane());
jFrame.setGlassPane(glass);

public class FixedGlassPane extends JPanel
    ...
    addMouseListener(this);
    addMouseMotionListener(this);
    addFocusListener(this);
    ...
  }

  public void mouseDragged(MouseEvent e) {
    if (needToRedispatch)
      redispatchMouseEvent(e);
  }

  public void mouseMoved(MouseEvent e) {
    if (needToRedispatch)
      redispatchMouseEvent(e);
  }

  ... other mouse event methods ...

 private void redispatchMouseEvent(MouseEvent e) {
    boolean inButton = false;
    boolean inMenuBar = false;
    Point glassPanePoint = e.getPoint();
    Component component = null;
    Container container = contentPane;
    Point containerPoint = SwingUtilities.convertPoint(this,
        glassPanePoint, contentPane);
    int eventID = e.getID();

    if (containerPoint.y < 0) {
      inMenuBar = true;
      container = menuBar;
      containerPoint = SwingUtilities.convertPoint(this, glassPanePoint,
          menuBar);
      testForDrag(eventID);
    }

    //XXX: If the event is from a component in a popped-up menu,
    //XXX: then the container should probably be the menu's
    //XXX: JPopupMenu, and containerPoint should be adjusted
    //XXX: accordingly.
    component = SwingUtilities.getDeepestComponentAt(container,
        containerPoint.x, containerPoint.y);

    if (component == null) {
      return;
    } else {
      inButton = true;
      testForDrag(eventID);
    }

    if (inMenuBar || inButton || inDrag) {
      Point componentPoint = SwingUtilities.convertPoint(this,
          glassPanePoint, component);
      component.dispatchEvent(new MouseEvent(component, eventID, e
          .getWhen(), e.getModifiers(), componentPoint.x,
          componentPoint.y, e.getClickCount(), e.isPopupTrigger()));
    }
  }

  private void testForDrag(int eventID) {
    if (eventID == MouseEvent.MOUSE_PRESSED) {
      inDrag = true;
    }
  }
}