Coding for IIgs?

[lyricalnanoha <lyricalnanoha@usotsuki.hoshinet.org>]

I've just gotten to thinking.

I don't know a lot about the IIgs under the hood, though I've kind-of 
wondered how hard it would be to code for it.  And maybe I'm being a bit 
of a masochist here by wanting to do all of this without recourse to 
GS/OS, but at least what I want to do is keep my DOS 3.3 comfort zone 
(thank ghed for UniDOS and its ability to use the DOS 3.3 api on 3.5" 
disks xD).

So I've been wondering about how hard it would be (keep in mind the only 
tool I have for assembling 65816 code is CA65, though it seems that should 
be adequate) to do some simple stuff.  Like...

1. Good place to locate this stuff in RAM?  I wouldn't want to step on 
anything and I don't know the GS's memory map, though I'd need to load the 
stuff into the "Contiguous 48" and then move it up... prolly isn't that 
hard as 65816 is 6502 extended...

2. Set the 320x200 mode, (is it paletted? mb set it up with RGBI, the CGA 
palette? would be more familiar for me) draw pixels on it, possibly write 
on it in Shaston 8 (if not, I can always crack out a PC font), cursors 
etc.

3. Set the 640x200 mode, same as above

4. I wonder how hard GUI stuff is at low-level?  Like, mouse, menus, 
windows.  And how much of that is done by the toolbox, and how much by 
ProDOS-16 / GS/OS?

This really sounds noob, I know - but I'd just like to try some of this 
stuff.  Prolly my first experiment will be something simple, like taking a 
6502 BASIC interpreter, and engineering it to use graphics routines for 
text i/o.  (Or FPBASIC "&" hacks to use them?)

-uso.