Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!rutgers!sri-spam!sri-unix!hplabs!decwrl!pyramid!prls!philabs!micomvax!musocs!mcgill-vision!iros1!burj
From: burj@iros1.UUCP
Newsgroups: comp.terminals
Subject: Re: A Question About the Infamous VT100 Line Wrap Bug
Message-ID: <103@Mannix.iros1.UUCP>
Date: Sun, 1-Feb-87 03:39:03 EST
Article-I.D.: Mannix.103
Posted: Sun Feb  1 03:39:03 1987
Date-Received: Tue, 3-Feb-87 06:51:47 EST
References: <1504@blia.BLI.COM> <121@lmi-angel.UUCP> <581@vu-vlsi.UUCP> <5559@brl-smoke.ARPA>
Reply-To: burj@iros1.UUCP (Justin Bur)
Distribution: na
Organization: Universite de Montreal
Lines: 37
Summary: In defense of the vt100

From reading the termcap(5) manual entry and the comments in the
/etc/termcap file (on 4.2BSD systems), I gather that the "xn"
capability was originally intended for terminals like the Concept
which eat a newline immediately after wrapping:  i.e. after 80th
character, cursor wraps to col. 1 of next line but doesn't move
down again if a newline comes next.  With much gnashing of teeth
("all versions of vi before 3.7 don't handle xn right on vt100",
says the comment in /etc/termcap) the "xn" capability was modified
to work with vt100s.

But this is unnecessary maligning of the poor vt100.  The vt100,
with wrap turned on or off in SET-UP, behaves just like a terminal
with no wrap at all, *as long as the program does not purposely
hammer against the right margin*.  In particular, with wrap turned
on, vi works fine whether the termcap has "am" and "xn" set or not.
(Just don't set "am" without also setting "xn".)

The way I see it, the vt100 lets programs that do screen management
pretend that the terminal never wraps, leaving the choice of whether
to wrap or not while typing plain text entirely up to the user.

(I was rather surprised to see that the Ultrix termcap file lets
all the criticism stand.  No one at DEC came to the defense of
their own terminal!)

In article <5559@brl-smoke.ARPA> gwyn@brl-smoke.ARPA (Doug Gwyn) writes:

> A related problem is that many VT100 termcap descriptions I have
> seen specify "am" for the VT100.  This is absolutely wrong and
> should be removed

It's no problem if "xn" is there as well.  But why bother with two
separate termcaps (vt100-am and vt100-nam)?  Why not, as Doug Gwyn
suggests, just drop "am" (and "xn") and put a comment in termcap
saying "vt100s work fine no matter how you set the wrap in SET-UP!"

justin