[Info-vax] VTxxx/VMS term driver: bug or feature?
Johnny Billquist
bqt at softjar.se
Tue Jul 5 12:58:32 EDT 2011
On 2011-07-05 18.45, Jan-Erik Soderholm wrote:
> VAXman- @SendSpamHere.ORG wrote 2011-07-05 16:26:
>> In article<W75R8kxItmfA at eisner.encompasserve.org>,
>> koehler at eisner.nospam.encompasserve.org (Bob Koehler) writes:
>>> In article<00AB1B94.1FA197E0 at SendSpamHere.ORG>, VAXman-
>>> @SendSpamHere.ORG writes:
>>>>
>>>> Initially, I would have thought that the local nowrap, terminal driver
>>>> /WRAP combination should have appears the same. Strangely enough, the
>>>> terminal emulator I was checking didn't show this. While testing it,
>>>> I was performing the same tests on 2 VT terminals (VT220 and VT525, as
>>>> well as, a DECterm). I was simple taken aback when I saw differences
>>>> that were shown on the VTs and DECterm but not this terminal emulator.
>>>> I am, of course, convinced now that the terminal emulator got it flat
>>>> out wrong.
>>>
>>> After further investigation, I decided to try the other two
>>> combinations: local nowrap and driver /NOWRAP, local wrap
>>> and driver /WRAP. In doing so, I reduced the line separation to try
>>> to fit everything on one screen.
>>>
>>> The results are much different, in comaring DEC VTSTAR to PuTTY's
>>> emulation. I haven't tried it on anything else yet.
>>
>> Right.
>>
>> When using real VT terminals, the result with the /WRAP and no local wrap
>> shows that the terminal driver doesn't have knowledge of where the string
>> of digits begins. The terminal driver could, however, know if it issued
>> a CPR but that's _NOT_ what's at issue here. The issue is whether or not
>> these real VT results should be expected on the VT terminal emulators. I
>> am going to say that they should reproduce these results IF they were
>> true
>> VT emulations. I'd conclude from my testing of several emulators is that
>> they've all got it wrong.
>>
>
> Now, emulators have been there for, say, 20+ years.
> I have a hard time thinking this is a *real* problem
> if the emululators still works as they do ("wrong" in
> your opinion). If this was a real problem, I would have
> expected this to be "fixed" long ago.
>
> What is the real-life example where this is an issue ?
Yes, the bugs have been around for a long time in the emulators. And as
I mentioned before, talking to the persons writing putty, they have been
notified of some problems, but they choose to continue to be buggy.
And, as a real life example, I can mention my Z-machine emulator, which
works correct on a real DEC terminal, but which produces weird output
under putty. But many programs do not do enough odd stuff to expose
these bugs, so they get away with it.
And also, most screen aware programs on Unix systems (which means
exposure to lots of people) use termcap, which explicitly works around
these potential problems.
Johnny
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