Display fringe only if not one-window-p?

[Drew Adams]

I generally use one window per frame, and I automatically resize the frame
to fit the window (using
http://www.emacswiki.org/elisp/auto-resize-frames.el).

In Emacs 21 (.3.50), I would like to remove the fringe area for such
windows, but I don't necessarily want to remove the fringe area when a frame
has more than one window. Anyone know how to do this easily?

Better: Is there a way (an easy way) to associate a _predicate_ with display
of things like fringe area - to display the fringe area for a window, for
instance, only if a line wraps or is truncated?   I can of course modify
display-buffer, but I'm wondering if there is a clean and easier way.

Also, I don't see what fringes-outside-margins does. I've changed it to t or
nil and done set-window-buffer, but I don't seen any visible change.