On 2017-11-27 7:42 AM, Tom Brennan wrote:
Years ago I was getting help from Greg Price
Probably circa turn of the century (before Vista was also a release of
Windows) I thought it might be nice if one the the
not-prohibitively-expensive TN3270 clients supported a form of 3270
graphics, and so I sent an email or two to Tom with a view to convincing
him that (a) programmed symbol graphics is fully documented in the 3270
Data Stream Programmer's Guide and (b) it is a "simple matter of
programming" to implement it.
Looking after a few data structure arrays must be bread-and-butter to
anyone who can code up a reliable and function-rich TN3270 client, was
my considered opinion, not that I really know about such things, of course.
Basically, the TN3270 client has to
- flag in the response to a Read Partition (Query) that it supports such
functionality
- understand and digest the LPS (Load Programmed Symbols) data stream
- render loaded symbols into the screen buffer when SA or SFE orders
request a switch to that character set.
A point to remember is that the TN3270 client cannot simply have a
storage array for each RWS (read/write storage) being emulated.
An IBM 3279G will show the "green lightning" while an LPS data stream is
being processed, but all of the RWSes added up cannot supply enough
characters to paint an entire 32x80 screen. So at least some of them
are used more than once, in the usual case, before input-inhibit is
reset (or the keyboard is unlocked, if you prefer) to allow a user response.
BUT - the symbols rendered when the "first lot" of symbols were in the
RWSes must still be rendered that way, even though the relevant RWSes
have been overlaid with a new set of symbol data, which is quite often
used to render the bit-less-than-second-half of the screen.
So, symbol data must be remembered by the TN3270 client until BOTH of
- the symbols are no longer in any current RWS
- the symbols are no longer displayed on the screen
are true.
At the time, Vista 1.24 was the current release.
Once Tom took up the challenge, in fairly short order (no comment from
me on how much work it did or did not take to do it) there was a quite
impressive (to me) Vista 1.25 which did a very good job of displaying
the graphics that I could produce.
But Tom has serious paying customers who don't really care for what I
may or may not want in a TN3270 client and so I gather that these code
changes were more of a prototype quality rather than production quality
code and so were not copied into the product's code base used going forward.
(Tom can correct me here if I have any of this wrong, of course.)
I think it was Win7 that introduced the Program Data directory, yes?
Anyway, Tom had to make a change to Vista so it was a happy Win7 citizen
(IIRC). The net result of the new directory paradigm was that it was a
pain to use the 1.25 version under Win7 and later so I gave it away in
the end.
Hmmm, probably time to cast the net more widely...
I still refer anyone who asks me about Vista 1.25 to Tom.
I asked Paul Mattes about x3270 graphics support, and he said that it
was a to-be-done thing and had been for years. I gave him a TSO
graphics program in my brief dialogue with him, and he said that he now
had his sample application, the lack of which had been one of the
stumbling blocks up till that time. He seemed confident that rendering
symbols constructed at run-time would not be a problem. I can't see
that much has been done in this area in the years since, though. Still,
he does work on it without pay (I believe) so that's understandable.
It's probably better to keep it running satisfactorily for the existing
customer base that to appease a former MVS sysprog.
My next port-of-call was Hans Erik at Nexus Terminal.
I went through my shtick and he also took up the challenge. Further, it
is now part of the base product, and therefore officially supported, I
believe.
So, for regular 3270 work, I have the choice of two great TN3270
clients, both with expert support, and for my graphics work, there's
Nexus Terminal.
(Bonus points for spotting that the map on the http://www.nexit.com/ web
page is from one of my sample pictures available from the REVIEW (TSO
command) home page and from CBT file 134.)
Cheers,
Greg
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
