On 2017-11-27 7:00 AM, Seymour J Metz wrote:
> What is "GDDM graphics", APA or PSS?
"All Points Addressable" and "Programmable Symbol Sets" are what I take
these acronyms (initializations?) to mean.
You could say that "GDDM graphics" is graphics performed by employing
calls to GDDM. If displaying the graphics on a TSO 3270 terminal, then
GDDM will employ one of PSS (really raster graphics - the original 3270
graphics) or what I call "native 3270 vector graphics" (no programmed
symbols here - first supported by the 3179G I believe) or the even newer
"enhanced PC handshaking vector graphics" implemented in the data stream
after PCs pretending to be 3270 terminals became widespread.
(The "PC handshaking" as I call it, was known as DOSLINK, then later on
as OS2LINK, then as PCLK, and was not used with any real 3270 hardware,
Typically, the TSO terminal will only fully support one of these. The
support for these can be determined by an application from the response
to a Read Partition (Query). PCOMM3270 allows you to enable any one or
none of these 3 3270 graphics options.
In a sense, PSS does provide APA, it could be argued.
Once you have the ability to specify the illumination of each pixel in
any of the supported colors (ok, I want to say colours) independently
from the illumination of any other pixel, you effectively have APA.
(The 3179G which supported vector graphics did also support single-plane
programmed symbols - meaning monochrome - whereas only triple-plane
programmed symbols can provide multiple colours in a single character.)
But really, with each symbol, you are specifying how a character display
location is used whenever that symbol is displayed. This is very
efficient (I think) if you have symbols that you are going to reuse
because you can specify (load) them once and then reuse them many times
with relatively small overhead.
In practice, what were they used for? Diagrams? Text with custom
symbols? I think mainly for graphs and charts - probably mainly from
MVS performance data. There may well have been many other uses by
applications, but I think it was MVS performance folks who were the
majority of users.
So how do you make a graph or chart? Well, I would make a big rectangle
of pixels into which I would project the chart, and then I would map
each 9x16 (or 8x10 or 10x8 or whatever the terminal - screen or printer
- used) cell and load each symbol into consecutive codes points and then
after the symbols were loaded then I would switch to that character set
and display those points: x'4142434445446...FCFDFEFF' and then switch to
the next character set and display those and so on until the whole chart
was on display.
Or for vector graphics, you could effectively display a bitmap by
sending rows of pixels - again the single plane (monochrome - meaning
you choose the 1 3270 colour to use) or triple-plane (RGB - really GRB
for 3270) concepts apply.
Anyway, enough of my waffle. Most of what I know about 3270 graphics is
I am hardly a world authority on the topic, so if you spot anything
which needs to be corrected then please let me know - preferably with
the correction to be made.
Recently I optimized the REVIEW display of pictures using programmed
symbols where LPS recycle did not occur, and so I may have broken the
display where LPS recycle did occur (ie. larger pictures) so if there is
a bug in that which you would like fixed, give the relevant test
conditions and I'll try to have a look at it.
REVIEW employs 3270 graphics to
- display PCX files
- display BMP files
- display GIF files
- don't do JPEGs because I don't understand how to decode them -
assembler code donations welcome.
<insert cheesy grin here>
Programmed symbol and native vector graphics terminals are supported by
assembler invocations of TPUT. "PC handshaking" graphics is supported
by calling GDDM.
In RFE (REVIEW Front End - poor man's PDF for use when ISPF is broken or
not present) when a specific volume is selected in option 3.4 at the
bottom of the data set list when geometry suits and programmed symbols
are supported, a row of graphics is displayed depicting the space usage
of the volume, where each vertical slice of pixels represents 1
cylinder. That is, the scale is 1 pixel per track. Tracks addressed by
the same head are in the same horizontal line of pixels. Colour code
indicates use. (eg. white=VTOC, green=DSCB1/DSCB8 descriptors,
yellow=DSCB3 descriptors, red=tracks in more than 1 extent (error) etc.)
For completeness I'll mention that the RFE main menu uses programmed
symbols under MVS/370 to display:
- virtual storage page assignment
- UIC frame population bar graph
- real storage frame assignment.
The colour codes are documented in the TSO HELP member for the RFE command.
If you want to look at REVIEW, go ahead, but do not install releases
47.5 to 47.7 into production just now - wait for 47.8 which should be
out in a few days because it will fix a few things. But if you want to
browse a tape data set made using LBI, or browse jar files in z/OS UNIX,
then REVIEW could be for you.
The REVIEW source is available so you can vet it. The only value of APF
(only use an alias for this) is to allow browsing of BCS and VVDS -
perhaps of use to sysprogs. No MODESET macros are present.
In contrast, IMON (my 1980s z/OS monitor) - which uses 3270 graphics to
show a small logo on the main menu - is free but OCO.
Then there's TERMTEST which I used to design the chess pieces for the
3270 graphics add-on to Duchess, the chess program from Duke University
written to run in a TSO session under MVT.
Ok, way too much of my waffle...
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