Re: tn3270, mset and map3270

[David Holland <dholland-tech%netbsd.org@localhost>]

On Sun, Mar 07, 2010 at 03:37:58AM -0500, der Mouse wrote:
 >> Nothing prevents a serial-attached terminal from sending key-up and
 >> key-down codes of whatever kind it prefers.  Nothing except of course
 >> legacy Unix-derived system software that can't cope with the concept.
 > 
 > Not so much Unix-derived; other OSes also tend to expect serial lines
 > to carry characters rather than keystrokes (and, like Unices, could
 > probably be hacked on to take keystrokes, given reason enough).

Well, yes. But only Unix has this enshrined in the tty subsystem.
Elsewhere (e.g. in DOS, AmigaOS, etc.) a serial port is something that
sends octets, and you can run anything you want over it without
getting in (much) trouble. In Unix owing to some poor early design
decisions you need a special-case kernel hack to support each new such
application. We already have those hacks in place for SLIP and PPP and
a few other things, but otherwise it's a pretty painful mess.

 > >> [...]
 > > [...]
 > 
 > Shrug.  You asked for examples, I offered mine.  Whether you consider
 > it worth paying attention to is up to you.

Well, you'd need to make your examples/argument quite a bit stronger
to persuade me that what you want can't or shouldn't be done some
other way. Especially when I have my system architect hat on and I'm
thinking about other concerns as well, like vt bombs.

 > As for your doubt "whether either of [the functionalities that would be
 > casualties of a switch to curses] really matters" - at least some of
 > the application-specific optimizations very much do matter; they take
 > performance from unusable to usable in some of my use cases.

If you say so, but I must say that it sounds like you have cases where
$20 of hardware (probably faster terminals / better cables) would
solve the problem better.

 > >> Furthermore, it's pretty pointless.  If I as a code author were
 > >> subjected to such a system, honestly, I would most likely simply
 > >> ship a copy of libtermcap and/or libterminfo with my application.
 > > ...which would accomplish no more than redboxing on a tcpip network.
 > > :-)
 > 
 > > (red? I think I mean red...)
 > 
 > Wikipedia leads me to think redboxing is a form of coin-phone fraud
 > based on forging in-band signals.  If that's what you mean, I don't see
 > the similarity.

Emitting in-band terminal control signals to a screen device that
doesn't support in-band signalling is fairly useless.

-- 
David A. Holland
dholland%netbsd.org@localhost