Question about tab effect

Can any one please explain how to properly use the tab effect? From the view documents. tab Generate tab buttons with rounded corners. The optional arguments are: a PAIR that specifies the edge to round, a TUPLE that is used as an edge color, an INTEGER that indicates the radius of the curves, and an INTEGER that controls the thickness of the edge. I only get a new window with no faces on it when I try this: view layout [box effect [tab]] view layout [box effect [tab 1x1 255.0.0 3 3]] To check my I also tried with the arrow and grid effect, they do behave as expected. view layout [box effect [arrow]] view layout [box effect [grid]] Thanks for the help, Jaime -- The best way to predict the future is to invent it -- Steve Jobs