def _set_topleft(el, pos):
    """Set element <el>'s topleft using its storer_rect as reference."""
    left, top = pos
    x_shift = 0
    y_shift = 0
    if left is not None:
        x_shift = left - el.get_storer_rect().left
    if top is not None:
        y_shift = top - el.get_storer_rect().top
    el.move((x_shift, y_shift))
