Lars von Trier, maker of calculating horror comedies, is a shrewd showman -- if not exactly in the classic Hollywood tradition then at least in the Barnum & Bailey one. He pleases his audiences by teasing, taunting and testing them, keeping his tongue in his cheek. I picture him as a dancing, grinning little prankster on the fringes of world cinema, alternately flaunting a streak of astringent sadism and hiding for safety behind a shield of facetiousness.