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From: dsp@ptsfa.UUCP (Dave St.Pierre )
Newsgroups: net.info-terms
Subject: Re: vt100, :am:, :xn:, :in:
Message-ID: <301@ptsfa.UUCP>
Date: Thu, 18-Oct-84 13:48:37 EDT
Article-I.D.: ptsfa.301
Posted: Thu Oct 18 13:48:37 1984
Date-Received: Sun, 21-Oct-84 15:17:35 EDT
References: <459@uwvax.UUCP> <5084@brl-tgr.ARPA> <194@bragvax.UUCP> <297@ptsfa.UUCP> <5339@brl-tgr.ARPA> <368@umcp-cs.UUCP>
Organization: Pacific Bell, San Francisco
Lines: 42

> *	From: gwyn@brl-tgr.ARPA (Doug Gwyn )
> 	There is a common misconception about the VT100 and the xn/xenl
> 	capability; ... The wrapping upon character insert is
> 	independent of auto-margin and is supposed to be described by
> 	the "in" capability.

Hmmm ... Then I guess the documentation in terminfo(4) is in error
(see Glitches and Braindamage, SV_R2). Also, termcap comes with a
rather lengthy discussion on pros and cons.

I COULD turn off am/xn; I have to for an emacs I have which doesn't
know about the vagaries of vt100's on column 80. I leave it turned
on when possible since our default initialization sequence turns
on autowrap mode - it gets difficult reading long lines of text when
it's all beating on the last column.

Televideo 970's appear to be the same as vt100's, TTY 5420's do wrap
"correctly", even though they're otherwise vt100 clones. I don't
remember what my vt400 did, think it needed xenl.

:in: doesn't really seem to be applicable to this problem or this
terminal class at all. I've tried various combinations of am/mi/xn
and run 

vi xxx > xxx.out;od -c xxx.out

to see what's happening. All terminals issue cursor movement sequences
when a line "wraps" in vi in standout mode to get to the next line.
If "mi" is off it turns on insert mode and places the character at the
beginning of the line; otherwise it just emits the character.
Crosstalk just refuses to push ANY characters over to the right on the
second line.

There's supposed to be a new version of XTALK XVI out soon. Maybe this
will be fixed. Or maybe I'll find out it's a feature. Nothing I was
able to change in termcap/terminfo seemed to fix the problem. What I
thought was more interresting was that the software really does support
insert/delete modes. It makes windowing applications bearable.

Thanks for all the discussion so far. I should note that I'm on
vi 3.9, SV_R2. If anyone really comes up with a fix to termcap,
please post it.