static JWindow makeAlwaysOnTopTranslucentWindow() {
  ret makeAlwaysOnTopTranslucentWindow(screenRect(), withAlpha(.2, Color.BLUE));
}

// component can be a custom-painted JComponent
static JWindow makeAlwaysOnTopTranslucentWindow(Rect bounds, Color backgroundWithAlpha, JComponent component default null) {
  ret swing(() -> {
    new JWindow f;
    f.setAlwaysOnTop(true);
    f.setBackground(backgroundWithAlpha);
    f.setBounds(toRectangle(bounds));
    JComponent c = component;
    if (c == null)
      c = onClickDisposeWindow(
        //jtransparent_recursive(jpanel())
        dynamicallyPaintedComponent2((w, h, g) -> {})
      );
    add(f, c);
    vmBus_send willShowNewAlwaysOnTopWindow(f);
    ret f;
  });
}

Began life as a copy of #1032087