Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!lll-tis!daitc!jkrueger
From: jkrueger@daitc.daitc.mil (Jonathan Krueger)
Newsgroups: comp.databases
Subject: Re: Informix problem with escape sequences
Message-ID: <191@daitc.daitc.mil>
Date: 3 Oct 88 07:50:21 GMT
References: <483@pan.UUCP> <860@vsi.UUCP> <262@fsc2086.UUCP> <12648@ncoast.UUCP>
Reply-To: jkrueger@daitc.daitc.mil.UUCP (Jonathan Krueger)
Organization: Defense Applied Information Technology Center, Alexandria VA
Lines: 34

In article <12648@ncoast.UUCP> allbery@ncoast.UUCP (Brandon S. Allbery) writes:

>The problem is handling ESC-prefixed keys while also using a bare ESC
>as a command

I agree with your assessment of the problem; formally, it's an
ambiguous input stream.  But timing isn't a safe disambiguating
method.  Terminal interfaces make no guarantees about maintaining the
timing characteristics of user typing.  Characters that were bunched
together when typed won't necessarily be bunched together when they
arrive at the host.  If they're meaningful either way, but mean
different things, users will get unreliable and unpredictable
responses to same inputs.  I've seen Unify lose pretty badly when
connected via networks such as TYMNET or DDN.

A better solution is to remove the ambiguity.  In general, function
keys generate a sequence that begins with an escape.  So, don't
support function keys and also escape by itself as a command.  But you
can assign a function key to perform whatever escape used to do.  Or
you can support an interface that doesn't depend on function keys, and
retain escape by itself as a command, useful for terminals without
lots of function keys.  INGRES supports both approaches.  Or you can
remove escape by itself as a command, use function keys where
available, and support user-typed sequences that begin with escape,
including longer commands that echo on a command line.  GNU Emacs does
this.  All three methods work correctly across all communications
equipment and paths, and with all UNIX (and other) terminal drivers.

-- Jon

-- 
Jonathan Krueger  uunet!daitc!jkrueger  jkrueger@daitc.arpa  (703) 998-4777

Inspected by: No. 15