static Component componentAtMouse() {
  ret (Component) swing(func {
    Point p = MouseInfo.getPointerInfo().getLocation();
    Window window = locationToWindow(p);
    if (window == null) null;
    SwingUtilities.convertPointFromScreen(p, window);
    ret SwingUtilities.getDeepestComponentAt(window, p.x, p.y);
  });
}