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MakeVPort_Patch.doc
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1992-05-21
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MakeVPort_Patch
by Sebastiano Vigna
MakeVPort_Patch is a very small 2.04-only utility that patches the
graphics.library function MakeVPort() in such a way to avoid an annoying bug
that keeps multipalette pictures from being correctly scrolled (multipalette
pictures contain the new PCHG chunk which specifies line-by-line palette
changes; hundreds of colors can be displayed even in hi-res with
multitasking and full system compatibility). When a laced viewport with a
user CopperList is moved on an odd DyOffset, the user CopperList is merged
incorrectly. Commodore has presently no plans to fix this bug, hence this
few lines of C and Assembler that will decrement by one the DyOffset of such
ViewPorts. To my knowledge, this is more or less what used to happen under
1.3.
You should put MakeVPort_Patch in your startup-sequence as follows:
Run >NIL: <NIL: MakeVPort_Patch
The MakeVPort_Patch source and executables are in the public domain. This
software is provided "AS IS" without warranty of any kind, either expressed
or implied. By using MakeVPort_Patch, you agree to accept the entire risk as
to the quality and performance of the program.
Comments, complaints, desiderata are welcome.
Sebastiano Vigna
Via Valparaiso 18
I-20144 Milano MI
BIX: svigna
INTERNET: vigna@imiucca.csi.unimi.it
UUCP:cbmehq!cbmita!sebamiga!seba@cbmvax.cbm.commodore.com
...{uunet|pyramid|rutgers}!cbmvax!cbmehq!cbmita!sebamiga!seba
FIDO: 2:331/301.6 (aka 2:21301/6 Sebastiano Vigna@f301.n331.z2.fidonet.org)