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using Manic Miner and Jet Set Willy game engines
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Message: 5901
Author: Daniel
Date: 19/08/2006
Subject: A technical question about J. G. Harston's patch - items problem
I have tried applying J. G. Harston's Intel Hex 7-bit rooms patch
(message # 5879 and 5881), following John Elliott's instructions
given at http://www.seasip.demon.co.uk/Jsw/patches.html and using his
Hexpat utility.
The results very varied, but never quite satisfactory so far.
When I applied the patch to a .TAP file I am currently working on
(the bug-free version of Steve Worek's "Jet Set Emily"), the items
look good in JSWED 2.2.9, but when I load the game into an emulator,
they are visible, but all in the wrong places.
When I applied the patch to a .TAP file of Philip Bee's gamma-
released "JSW (again!)", in the emulator the items were not visible
at all - there seemed to be no items.
When I applied the patch to a .TAP file of my own gamma-
released "Willy's New Mansion", no items were visible, either. What's
more, I noted a glitch in the room "The Multi-Toilet Bathroom" - the
toilet sprite seems to have been slightly modified (even though in
JSWED it looks OK).
In JSWED 2.2.9 all of the above-mentioned game files after applying
the patch seem OK, i.e. the items are visible and in the right places.
I haven't had the time to experiment further with other files, but my
main question at this point is: what else needs to be done after
applying the patch so that when playing the game in the emulator the
items are visible and in the right places?
J. G. Harston says on his website
(http://mdfs.net/Software/JSW/JGH/Docs/Rooms.htm) that after applying
the POKEs he gives (which the patch does as well, if I understand
things correctly):
"The JSW48 object table remains in memory from &A3FF to &A5FF. &A3FF
holds 255-number of object to collect, &A4xx holds the room number in
bits 0-6 and bit 8 of the object position (x+32*y) in bit 7. &A5xx
holds bits 0-7 of the object position."
So I guess - thinking aloud - that after applying the patch, the
addresses &A4xx would have to be modified manually (in JSWED's Hex
editor, I guess). But what needs to be done exactly?
Also, why are the items invisible (in the emulator) in case of some
TAP files (after applying the patch), but they are visible and in the
wrong places in case of other TAP files? Does it have something to do
with the fact that J. G. Harston's patch moves the "item collected"
flag to bit6 of the bytes in page &A6. Does the value of the
addresses &A6xx need to be corrected as well? If so, how exactly?
Any help will be appreciated! (in as detailed and simple terms as
possible :-) ).
Daniel
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