Hello Jonathan!

Wednesday December 27 1995, Jonathan de Boyne Pollard writes to John Poltorak:

 >> There are no equivalent ASCII characters which I can use. I have a DOS
 >> program (but no source), which displays the screens
 >> properly in full screen, and I would like to be able to do
 >> the same thing in OS/2, but I have no idea how to code it.

 JdBP>   Before I start, I'll restate my opinion that going for a text-mode
 JdBP>   program will probably end up being harder in the long run than going
 JdBP>   for a PM program.

I don't think so. I know very little about PM and it seems to include a
huge number of API calls. VIO only has around 40, and most of those are
extremely straightforward so I should be able to pick it up more quickly.
Besides, I already have a DOS model to base my program on.

 JdBP>   With a PM program displaying teletext characters would simply be a
 JdBP>   matter of whipping up a custom font using the font editor, and writing
 JdBP>   the display logic (which will at most devolve into a succession of
 JdBP>   GpiCharStrAt calls).

 JdBP>   With a text-mode program you'll have to set up a custom VGA text-mode
 JdBP>   character set

The graphic characters consist simply of six blocks

 JdBP> (VioSetFont is not the most heavily documented call in the VIO
 JdBP> subsystem),

You're not kidding.. I just dug out a few old books, Ray Duncan's original
classic which documents them all, but only shows examples of the simpler
ones. The other by Schildt mentions VioGetFont and VioSetFont only in so
far as they are beyond the scope of his book!

 JdBP> and *require* full-screen, since custom
 JdBP> character
 JdBP>   sets (obviously) will not operate in a window (i.e. when the display
 JdBP>   is in graphics mode).

That's not a problem. I have to run my DOS program in full-screen for it to
display properly anyway.

 >> I don't expect that I can use the Vio commands since I
 >> think it will have to be full screen.

 JdBP>   Wrong way around.  All of the VIO calls are available to a full-screen
 JdBP>   text-mode program.  Only a subset are available to windowable
 JdBP>   text-mode programs.  The reason being (of course) that the calls to
 JdBP>   access the physical text-mode video buffer directly are prohibited to
 JdBP>   windowable text-mode programs.

I see. I didn't realise this before. Do you know any good sources on VIO? I
have  PRCP.INF but could do with a few examples...

John
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