Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!ukma!uflorida!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn )
Newsgroups: comp.unix.questions
Subject: Re: linewrap
Keywords: linewrap VT100 termcap terminfo
Message-ID: <9159@smoke.BRL.MIL>
Date: 12 Dec 88 22:29:02 GMT
References: <658@nvuxl.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 32

In article <658@nvuxl.UUCP> myron@nvuxl.UUCP (Myron Seto) writes:
>I have to set Line Wrap=On. If not, whenever I do a 'cat' command,
>for example, the text runs off at the end of the line.
>The problem is that whenever I use vi, many strange things
>happen-lines appear twice(!), deleting lines is a hassle,
>etc.  Basically, the CRT does not show what it supposes to
>show in vi with line wrap on.
>Can anyone tell me how I can have both Line wrap, and not
>have vi going berserk?
>Procomm is emulating the vt100 by the way, if that is part
>of my problem.

The primary principle is that your actual terminal (or terminal
emulator) behavior and the UNIX terminal handler modes must
agree with  the terminal description contained in the termcap
(or terminfo) database in order for screen-oriented utilities
to work properly.

Another important thing to know is that the termcap (or terminfo)
"am" Boolean capability does NOT describe the behavior of a
genuine VT100.  Further, a real VT100 is so bizarre in this that
most emulations of it don't attempt to get it exactly the same.

Termcap/terminfo-using software should never assume that the
absence of "am" implies that lines are necessarily trimmed at
the right margin; they might wrap anyway (e.g. with VT100-like
behavior).

It sound to me as though either your termcap/terminfo VT100
description erroneously includes "am" and your VT100 emulator
in line-wrap mode doesn't implement termcap-style "am", or
your "vi" doesn't correctly interpret the absence of "am".