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From: barmar@mit-eddie.UUCP (Barry Margolin)
Newsgroups: net.emacs
Subject: Re: 79-character screen
Message-ID: <39@mit-eddie.UUCP>
Date: Wed, 9-Oct-85 03:03:48 EDT
Article-I.D.: mit-eddi.39
Posted: Wed Oct  9 03:03:48 1985
Date-Received: Fri, 11-Oct-85 07:46:09 EDT
References: <70@druhi.UUCP> <336@uwvax.UUCP> <17@mit-eddie.UUCP> <1776@umcp-cs.UUCP>
Reply-To: barmar@mit-eddie.UUCP (Barry Margolin)
Organization: MIT, Cambridge, MA
Lines: 29

In article <1776@umcp-cs.UUCP> chris@umcp-cs.UUCP (Chris Torek) writes:
>... I have thought
>about `fixing' the problem in our local Emacs; it would be relatively
>trivial---simply set the number of characters to
>
>	width - (autowrap && line == length ? 1 : 0)

Well, I am not familiar with the internals of Gosling Emacs, only
Multics Emacs.  Its redisplay-line routine is independent of the actual
screen line, so it only has the global line length variable to deal
width.  I am not defending this (I didn't write it), just explaining my
reason for assuming that Gosling Emacs assumes a rectangular screen.

>---but there is no real incentive since most of our local terminals
>are automatically set to non-wrap mode while running Emacs.

How do you deal with the different ways that terminals handle the
no-wrap case, with respect to relative cursor motion after entering a
character in the 80th column?  On the VT100, if you enter a character
into column 70 then send a BS or CUL (CUrsor Left escape sequence) you
end up in column 70, but if you do the same thing in column 80 you end
up in column 79.  On other terminals (e.g. Honeywell VIP7800 series),
there is a "phantom" column 81, which can contain the cursor but not a
real character, and that is where the cursor goes after a character is
entered into column 80, so that relative motion works properly.
-- 
    Barry Margolin
    ARPA: barmar@MIT-Multics
    UUCP: ..!genrad!mit-eddie!barmar