Path: utzoo!mnetor!uunet!husc6!ut-sally!tut.cis.ohio-state.edu!osu-cis!att-cb!clyde!watmath!watmsg!achowe
From: achowe@watmsg.waterloo.edu (CrackerJack)
Newsgroups: comp.sys.atari.st
Subject: Re: accessory and RAM resident stuff
Message-ID: <17681@watmath.waterloo.edu>
Date: 21 Mar 88 16:19:06 GMT
References: <8803190107.AA03238@ucbvax.Berkeley.EDU>
Sender: daemon@watmath.waterloo.edu
Reply-To: achowe@watmsg.waterloo.edu (CrackerJack)
Organization: U. of Waterloo, Ontario
Lines: 55

>Is there any definitive book on what you can or can't do when writing
>desk accessories?  There is a little bit in the MWC Version 2.00 docs,
>and they have an example, along with acskel.c from the developer's kit.
>But I would like to know how far you can deviate from those basic
>skelatins.  For instance, I would like to be able to use string writting
>functions in which you can do a newline and the text will scroll up without
>having to rewrite each line.   That pretty much precludes the use of windows,
>which seems to be the structural backbone of desk accessories.

Well, as an on going exercise, I've writing my own shell program that
comes in two forms - as a .PRG and a .ACC. I had the idea to do the
ACC version too because it was the only why at the time I could think
to autoload a GEM program. I soon found out the following problems
with ACC programs...

o You can NOT execute a GEM program using Pexec from an ACC.
  It seems that windows, desktop and menu resources just go NUTS.
  Maybe there is a way but it won't be standard.

o You can NOT hide the menu bar from a ACC because you can't find
  the root of the object tree with all the resources. This means if
  you use a text screen and just try and do a form_dail () to redraw
  the desktop on exit you'll find that the menu bar is missing BUT
  active. Of course if when you exit from a PRG the whole desktop
  is restored - no problem. Grrrr!

+ To solve this problem I took the example of the VT52 emulator which
  is an ACC that handled text mode and screen rewrite just fine. 
  How could Atari get away with it and not tell anyone? Well I spent
  about 7 hrs one night using SID to trace through the emulator ACC
  to find the method (this was before DISTOMWC.PRG). I've had plenty
  of practice using ZSID and DDT from my CP/M days doing this sort of
  learn without source. It was a pain (especially at 03.00 in the morn)
  but I found out that the emulator cheated. It saved the contents of
  video RAM that held the menu bar some where else to be later restored.
  Grrr Woof!!! Will I bagged the code and now it is part of my 
  ACCSTART.S and other .S goodies I use.


Well I now have the ACC shell on some disks where a shell is handy.
It still is very simple lacking a full cp command. But if your like
me you hate to exit a PRG to do cp, df, mf or ls commands.

For the rest of you who are interested and saying where is it now
that I've spilt the beans. You'll have to wait till I finish
implementing the basics like - cp, fgrep, 10 line history, stty,
set, setenv, and everything else. When I think I've done enough
I'll pass around the ACC and PRG. I have some .S stuff I wrote
that people might like which I'll passout on request.

--
Anthony C. Howe                         achowe@watmsg.waterloo.edu

"The definition of flying: throwing yourself at the ground and missing."
		- Douglas Adam's  "Life, the Universe and Everything"