For reliable setting of WINDOW start position, make sure point is
at a position that will be visible when that start is in effect,
otherwise there's a chance POS will be disregarded, e.g., if point
-winds up in a partially-visible line. */)
+winds up in a partially-visible line.
+
+The setting of the WINDOW's start position takes effect during the
+next redisplay cycle, not immediately. If NOFORCE is nil or
+omitted, forcing the display of WINDOW to start at POS cancels
+any setting of WINDOW's vertical scroll (\"vscroll\") amount
+set by `set-window-vscroll' and by scrolling functions. */)
(Lisp_Object window, Lisp_Object pos, Lisp_Object noforce)
{
register struct window *w = decode_live_window (window);