def _align_center(widget, top_pad=0, bottom_pad=0, left_pad=0, right_pad=0):
    """Align center (horizontally) and pad."""
    alignment = Alignment(0.5, 0, 0, 1)
    alignment.set_padding(top_pad, bottom_pad, left_pad, right_pad)
    alignment.add(widget)
    return alignment

def _align_middle(widget, top_pad=0, bottom_pad=0, left_pad=0, right_pad=0):
    """Align center (vertically) and pad."""
    alignment = Alignment(0, 0.5, 0, 0)
    alignment.set_padding(top_pad, bottom_pad, left_pad, right_pad)
    alignment.add(widget)
    return alignment

def _align_right(widget, top_pad=0, bottom_pad=0, left_pad=0, right_pad=0):
    """Align right and pad."""
    alignment = Alignment(1, 0, 0, 1)
    alignment.set_padding(top_pad, bottom_pad, left_pad, right_pad)
    alignment.add(widget)
    return alignment