def add_symbolic_contents_constraints(namespace):
    """ Add constraints to a namespace that are LinearExpressions of basic
    constraints.

    """
    left = namespace.contents_left
    right = namespace.contents_right
    top = namespace.contents_top
    bottom = namespace.contents_bottom
    namespace.contents_width = right - left
    namespace.contents_height = top - bottom
    namespace.contents_v_center = bottom + namespace.contents_height / 2.0
    namespace.contents_h_center = left + namespace.contents_width / 2.0
