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From: csbrod@immd4.informatik.uni-erlangen.de (Claus Brod)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: requirements to use VDI
Keywords: VDI ttp appl_init
Message-ID: <1991Jun19.161901.1808@informatik.uni-erlangen.de>
Date: 19 Jun 91 16:19:01 GMT
References: <1991Jun19.112606.20682@convex.com>
Organization: CSD., University of Erlangen, Germany
Lines: 50

rosenkra@convex.com (William Rosencranz) writes:

>is it possible to call VDI routines without writing a full blown GEM
>application? ideally, i would like to just use something like v_fillarea
>or somesuch. i realize that i need a device handle, so maybe i need
>all the other stuff (baggage) too. it would be great to be able to
>use VDI in .ttp programs. can u open a device without appl_init?

There are good reasons why TTP programs are meant as non-GEM programs.
You shouldn't use VDI or AES calls in a TTP program.

>if it is not possible to write a .ttp with VDI (i suppose it is not
>since the extension tells the OS to either prepare for GEM or don't)
>then is it possible to read command line args with a GEM program (.prg)?
>i.e. one doing appl_init, open workstation, etc. if so, how? i use
>alcyon. my shell is gulam. is it possible with gcc/gemfast/etc?

No problem at all. A full-blown GEM program can read a command line
just like any other program can. You should, however, use shel_read()
to look for a command line passed to your program from its ancestor
via shel_write(). If there's no command line in the shel_read buffer,
check for a GEMDOS command line in the basepage using the standard
argc/argv mechanism.

>i'd hate to have to do the fill with line A or directly to the screen.
>i only need white fills. this makes drawing 3-d xyz datasets (like
>FFT maps) easy if u draw from back to front. the fill eliminates hidden
>features of the plot (desirable). i have used this in full GEM progs,
>but want to use it in .ttp progs where i draw points and lines (with
>line A). don't beat me up about line A, either. if/when i get a TT,
>i will switch. as far as i know, line A is the ONLY way to draw lines
>(other than fixing pixels in Physbase) in a .ttp.

Strictly speaking, it isn't even appropiate to use line A in a TTP.
The line A routines were meant as low-level subroutines for the built
in VDI screen driver. As such, they are part of the VDI, and if you
want to avoid VDI calls, the consequence is not to use line A either
in a TTP.

As long as you don't want to publish your program in some way, you can,
however, stick to the line A method. I think you can even use VDI calls
in TTPs without major problems, but as you said before, this isn't the
kind of thing you're meant to do.

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Claus Brod, Am Felsenkeller 2,			Things. Take. Time.
D-8772 Marktheidenfeld, Germany		 	(Piet Hein)
csbrod@medusa.informatik.uni-erlangen.de
Claus_Brod@wue.maus.de
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