Visually indicate buffer boundaries and scrolling.
If non-nil, the first and last line of the buffer are marked in the fringe
of a window on window-systems with angle bitmaps, or if the window can be
scrolled, the top and bottom line of the window are marked with up and down
If value is a symbol `left' or `right', both angle and arrow bitmaps
are displayed in the left or right fringe, resp. Any other value
that doesn't look like an alist means display the angle bitmaps in
the left fringe but no arrows.
You can exercise more precise control by using an alist as the
value. Each alist element (INDICATOR . POSITION) specifies
where to show one of the indicators. INDICATOR is one of `top',
`bottom', `up', `down', or t, which specifies the default position,
and POSITION is one of `left', `right', or nil, meaning do not show
For example, ((top . left) (t . right)) places the top angle bitmap in
left fringe, the bottom angle bitmap in right fringe, and both arrow
bitmaps in right fringe. To show just the angle bitmaps in the left fringe, but no arrow bitmaps, use ((top . left) (bottom . left)).