static void onMouseDown(Component c, O r) {
  if (c != null && r != null) swing {
    c.addMouseListener(new MouseAdapter {
      public void mousePressed(MouseEvent e) {
        if (e.getButton() == MouseEvent.BUTTON1)
          pcallF(r);
      }
    });
  }
}

static MouseAdapter onMouseDown(Component c, IVF1<MouseEvent> f) {
  ret c == null || f == null ?: swing(-> {
    MouseAdapter ma = new {
      public void mousePressed(MouseEvent e) {
        if (e.getButton() == MouseEvent.BUTTON1)
          f.get(e);
      }
    };
    c.addMouseListener(ma);
    ret ma;
  });
}