Re: ISO VT320 emulator with key-bindings for Oracle Forms

In article <7jjshc$ere$1_at_newsmaster.cc.columbia.edu>, Frank da Cruz <fdc_at_watsun.cc.columbia.edu> wrote:
>Yes, we know this, but the situation is far, FAR more complex than that. Try
>writing a communication program for UNIX that is:
>
> a. Portable to many UNIX varieties;
> b. Portable to assorted communication methods;

This can be handled by writing it as a wrapper around cu, kermit, tip, or whatever. That way it'll even work for dumb programs that don't use termcap.

> c. Works on the console, in remote sessions, and in xterm windows.

The latter case is not difficult. I wrote a termcap library back in '82, and a vt100 and televideo emulator a few years later. If the system's termcap is broken, you can fall back to that one, and at least one of the freeware "vi" clones uses my termcap for that very purpose.

> a. Buggy;
> b. Inconsistent among different UNIX platforms and versions (e.g. the
> APIs differ -- even a simple function like tputs() has practically
> infinite combinations of return type and argument types, thus preventing
> any program that uses it from being portable without including hundreds
> of #ifdefs);

I haven't run into this problem, and I've written and ported an awful lot of curses-based code between UNIX systems. Some code did a good job of encapsulating the slight differences between implemetations of the termlib API, and other code made no attempt to hide system dependencies and just scattered ifdefs all over the place. Even otherwise well-written code like early versions of Kermit had that problem.

> c. Dependent on buggy and/or incomplete databases;

That's something the end-user can fix.

> d. Offer only an incomplete and sketchy model of any real terminal,
> not even close to sufficient for defining an accurate emulation;

My vt100 emulator, which used raw termlib, did a better job of vt100 emulation than most commercial packages. It didn't try and provide perfect visuals: double-wide and double-high letters, for example, were simply not addressed. But it passed the vt100 torture test.

> e. Notorious for refusing to work due to library version mismatches;
> f. Sometimes not available at all.

That's an easy fix. Same solution as B.

>And that in any case, this does not solve the original problem:
>
> How do I map Shift-Alt-F7 to such-and-such a function?
>
>The answer will still be: "you can't, because the software has no way of
>knowing that you pressed Shift-Alt-F7".

With a keyboard mapping file that maps escape sequences to symbols that the user's interested in.

>Furthermore, even when we give up on discovering what key the user actually
>pressed and follow the termcap/terminfo escape-sequence model, we still have
>the age-old problem of distinguishing the case where the user types the Esc
>key and then some other keys (as s/he might do when using EMACS) from the case
>where an escape sequence is generated by curses.

Oh yes, that's definitely a problem, but there's nothing any terminal emulator can resolve, UNIX-based or not, because once it's mapped "UP" into "ESC O A" or "ESC [ A" the bits on the wire are the same.

>If it was easy (or even possible) to write terminal emulators for UNIX, we'd
>have as many of them already floating around as we do for DOS and Windows.

Well, most modern UNIX systems come with an X-based VT100 emulator and there's an X-based 3270 emulator from the same source available. There's not much demand for curses-based emulators, because almost all UNIX software uses termlib... the last time I had to configure a UNIX program for a terminal was for the text editor in Intel's PL/M development kit back around 1984.

But there's at least a dozen commercial terminal emulators for UNIX... back when I wrote my own (so we could run VMS software on our mix of Televideo and Unisys tubes) I must have looked at six or eight of them just for Xenix-286 (which was admittedly the #1 selling UNIX at the time). None of them allowed you to wrap an arbitrary program, alas, and that was a hard requirement.

Since then xterm and x3270 have become what Eric Raymond calls "category killers". There's little demand for third-party free software alternates, though that didn't stop rxvt from showing up. And I still get ads in the mail for things like FacetTerm.

--
In hoc signo hack, Peter da Silva <peter_at_baileynm.com>  `-_-' Ar rug tú barróg ar do mhactíre inniu?   'U` "Be vewy vewy quiet...I'm hunting Jedi." -- Darth Fudd Received on Wed Jun 09 1999 - 05:42:49 CDT