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Program reacts slowly to ESCAPE key

© December 2004 Tony Lawrence

As explained below, the ESCape key can be a bit of a problem for terminal apps that are not reading keycodes directly - because many other valid sequences may begin with ESC, they don't know how long to wait before deciding this is just ESCAPE.

The opposite problem can exist also - the following character coming too slowly, so the app thinks it got ESCape alone. SCO's "recon" command can buffer these.

Another possible reason for slowness and confusion is padding - these are null bytes added to account for the fact that the terminal divice is busy performing the escape sequence function. Misinterpretation causes this to briefly ignore keystrokes or to miss sequences intended.

From: Roberto Zini <fred@strhold.it>
Newsgroups: comp.unix.sco.misc
Subject: Re: Please help with Response Time and Screen Views
Date: Tue, 14 Dec 1999 17:29:26 +0100
Message-ID: <38567066.D5D8FBD@strhold.it> 

Tony Lawrence wrote:
> Kyu Rhee wrote:
> >
> > Hi there
> >
> > We have a SCO UNIX application in which we use the [Esc] key to view the
> > previous screen.  For some reason, it takes consistently up to half a second
> > before the previous screen shows up.  Server connection is via a 57800
> > serial line.
> You've given very little informmation here, and that's
> foolish, because it's quite possible that you could get an
> immediate fix if we knew what this mysterious application
> is.
> For example, there are several common applications that use
> "ESC", but will also work (and will work instantly) with
> another key: sometimes TAB or F12.  Sometimes the app can be
> specifically told to recognize another key- but how would we
> know, since you just say it's a "SCO Unix application".
> I'm sorry, maybe I'm just extra grumpy this morning, but I'd
> really suggest that you identify the app- I bet it's
> RealWorld or Mas90?
> The reason for the ESC problem is that most terminals use
> ESC as the "lead in" sequence for other keys.  For example,
> F1 actually sends ESC-[-M on an ansi terminal.  Because of
> this, when an application sees ESC, it has to wait to see
> what follows to determine whether or not this is just RSC or
> a function key.  Many, many apps handle that wait poorly,
> and no doubt that's the source of your problem.

This could be noticed while using cursor keys while in a vi(C)
session 'trhu a telnet connection to another machine; in fact,
while some commands get recognized, very often you could hear
a "beep" tone which is the way used by vi(C) to inform you that
it's been unable to process the command (for the reasons given
above). In vi(C) there's a simple solution; hit the ESC key,
press ":" and type "set noto" (no double quotes) + ENTER.

I'm not sure about your problem; I seem to remember that a long 
time ago I was being told by a cobol programmer you could do
the same trick accordingly to the cobol you were using but
presently I'm unable to provide you with additional info :-(

Roberto Zini                                  email : fred@strhold.it
Technical Support Manager -- Strhold Sistemi EDP Reggio Emilia(ITALY)
"Has anybody around here seen an aircraft carrier?"                
        (Pete "Maverick" Mitchell - Top Gun)

Got something to add? Send me email.

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-> Program reacts slowly to ESCAPE key ––>Re: Please helpwith Response Time and Screen Views

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