> That's a good idea, but unfortunately there's no way to predict more 
> scrolling will happen after several lines scrolled up. 

Look at how xterm does jump scroll -- if a single "chunk" of output
(probably from a single write() call) contains multiple newlines, it
scrolls the screen by that many lines in one chunk and then draws in
the four new lines of text.  On an N line screen, this allows
scrolling by K lines all at once take (N-K) units of work rather than
K*(N-1).

Last time I looked at this (some months ago), I came to the conclusion
that some of the wscons internals need to be tweaked to allow for
lookahead in the output stream..

					- Bill