Short:        Patches gfx.lib to v40 on CyberGraphX systems
Author:       Andre Osterhues (su0583@studserver.uni-dortmund.de)
Uploader:     Andre Osterhues (su0583 studserver uni-dortmund de)
Type:         util/misc
Replaces:     GFXPatch.lha
Requires:     CyberGraphX, OS3.0
Architecture: m68k-amigaos

What is this patch for?
=======================
Some programs (like AmigaAMP) require OS3.1 as they use WriteChunkyPixels()
from graphics.library v40+. Unfortunately, this function does not exist on
OS3.0 Amigas. But we can cheat ;^)

For example, the AmigaAMP readme states that OS3.1 AND PowerUP are needed for
the spectrum analyser. This is not true. OS3.0, CyberGraphX and (of course) a
PowerPC will also do.


How do I install this patch?
============================
All you need is to run this patch AFTER CyberGraphX is initialized.
Copy gfxpatch to C: and insert the line

Run >NIL: C:gfxpatch

into S:Startup-Sequence. IMPORTANT: Place it after(!) the monitors are
started.
The patch does not need to be started in the Startup-Sequence, you can
also run it before starting a "OS3.1 only" program.


What does this patch do?
========================
This program sets the version of graphics.library to 40.0 and patches two
functions:

1) WriteChunkyPixels()
   This function is mapped to the equivalent CyberGraphX function,
   WritePixelArray().

2) NextDisplayInfo()
   This is needed as CyberGraphX treats OS3.0 display IDs different than those
   of OS3.1. The patch temporarily resets the gfx.lib version, runs the
   original function, and sets the gfx.lib version to 40.0 again.
   When using the first (now obsolete) version of this patch, the ScreenMode
   program did not show any CyberGraphX screen modes. This should be fixed by
   this patch.


Why is it safe?
===============
1) The programmers of graphics v39.xx held enough place for future functions.
   In fact, there is room for 4 functions. On my machine, all of these jump
   to 0xfab606, and there is just a return(0):

   fab606       moveq        #0,d0
   fab608       rts

2) If the graphics.library NegSize is smaller than 1058, the patch will not be
   installed.

3) If run on a non-CyberGraphX system, the patch will not be installed.


Note:
=====
This patch might also work on Picasso96 systems, but it was not tested.


Thanks to:
==========
Frank Mariak for the wonderful CyberGraphX system



Have fun with it!

Andre Osterhues