Clearing the screen and other such things.

[Tim McNerney <TIM@MIT-MC.ARPA>]

    Date: Sun, 28 Jul 1985  17:31 EDT
    From: Rob MacLachlan <RAM at CMU-CS-C.ARPA>

        It may or may not be a good idea to have a Common Lisp virtual
    terminal, as is being suggested, but in any case, I think it is
    important that this idea not be confused with the default stream
    terminal I/O.  I think it would be a bad idea to force the default
    stream interaction into a fixed-width character-oriented model.
    Whatever interface is chosen should be willing to admit the
    possibility of virtual terminal emulation being done in a totally
    different fashion that default terminal I/O.

Perhaps this "virtual terminal" package would be best put into the yellow
pages.  Given a sufficiently efficient implementation of the basic terminal
I/O stream or at least a binary stream to the terminal, it could be written
entirely in Lisp.

A useful bit of white pages support for a virtual terminal package would be
a way for the Lisp to find out whether the operating system has trashed the
screen (by sending out a system notice, or something) thus randomizing the
cursor position, etc.  This could be in the form of an "environment query"
function.  There should probably be another function which returns T or NIL
depending on whether the implementation supports this feature.