thirdparty/scummvm
2
0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

SCUMM: Patch the MI2 Mac boot script

Browse source 
There are (at least) two different versions of MI2 for the Mac. The one
that was distributed with the LucasArts Mac CD Game Pack II has a
modified boot script that completely removes the copy protection screen
(yay!) and the difficulty selection (boo!).

To re-instastate the difficulty selection, patch the boot script to be
identical to the other version, which was presumably released on
floppies.

This patching is only done if the boot script has the exact expected
length of the CD version's script, and if the patched script matches the
floppy version's. That should be safe enough.
This commit is contained in:
Torbjörn Andersson 2021-07-12 14:28:47 +02:00 • committed by Eugene Sandulenko
parent 36ab29e546
commit 8522ef0f4f
1 changed files with 69 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

71
engines/scumm/resource.cpp
View file

@ -20,7 +20,9 @@
*
*/
#include "common/md5.h"
#include "common/str.h"
#include "common/memstream.h"
#include "common/macresman.h"
#ifndef MACOSX
#include "common/config-manager.h"
@ -700,6 +702,8 @@ int ScummEngine::loadResource(ResType type, ResId idx) {
applyWorkaroundIfNeeded(type, idx);
// NB: The workaround may have changed the resource size, so don't rely on 'size' after this.
// dump the resource if requested
if (_dumpScripts && type == rtScript) {
dumpResource("script-", idx, getResourceAddress(rtScript, idx));
@ -1645,13 +1649,14 @@ const char *nameOfResType(ResType type) {
}
}
void ScummEngine::applyWorkaroundIfNeeded(ResType type, int idx) {
int size = getResourceSize(type, idx);
// WORKAROUND: FM-TOWNS Zak used the extra 40 pixels at the bottom to increase the inventory to 10 items
// if we trim to 200 pixels, we can show only 6 items
// therefore we patch the inventory script (20)
// replacing the 5 occurences of 10 as limit to 6
if (_game.platform == Common::kPlatformFMTowns && _game.id == GID_ZAK && ConfMan.getBool("trim_fmtowns_to_200_pixels"))
if (_game.platform == Common::kPlatformFMTowns && _game.id == GID_ZAK && ConfMan.getBool("trim_fmtowns_to_200_pixels")) {
if (type == rtScript && idx == 20) {
byte *ptr = getResourceAddress(rtScript, idx);
for (int cnt = 5; cnt; ptr++) {
@ -1661,6 +1666,68 @@ void ScummEngine::applyWorkaroundIfNeeded(ResType type, int idx) {
}
}
}
}
// WORKAROUND: The Mac version of Monkey Island 2 that was distributed
// on CD as the LucasArts Adventure Game Pack II is missing the part of
// the boot script that shows the copy protection and difficulty
// selection screen. Presumably it didn't include the code wheel. In
// fact, none of the games on this CD have any copy protection.
//
// The games on the first Game Pack CD does have copy protection, but
// since I only own the discs I can neither confirm nor deny if the
// necessary documentation was included.
//
// However, this means that there is no way to pick the difficulty
// level. Since ScummVM bypasses the copy protection check, there is
// no harm in showing the screen by simply re-inserging the missing
// part of the script.
else if (_game.id == GID_MONKEY2 && _game.platform == Common::kPlatformMacintosh && type == rtScript && idx == 1 && size == 6718) {
byte *unpatchedScript = getResourceAddress(type, idx);
const byte patch[] = {
0x48, 0x00, 0x40, 0x00, 0x00, 0x13, 0x00, // if (Local[0] == 0) {
0x33, 0x03, 0x00, 0x00, 0xc8, 0x00, // SetScreen(0,200);
0x0a, 0x82, 0xff, // startScript(130,[]);
0x80, // breakHere();
0x68, 0x00, 0x00, 0x82, // VAR_RESULT = isScriptRunning(130);
0x28, 0x00, 0x00, 0xf6, 0xff, // unless (!VAR_RESULT) goto 0955;
// }
0x48, 0x00, 0x40, 0x3f, 0xe1, 0x1d, 0x00, // if (Local[0] == -7873) [
0x1a, 0x32, 0x00, 0x3f, 0x01, // VAR_MAINMENU_KEY = 319;
0x33, 0x03, 0x00, 0x00, 0xc8, 0x00, // SetScreen(0,200);
0x0a, 0x82, 0xff, // startScript(130,[]);
0x80, // breakHere();
0x68, 0x00, 0x00, 0x82, // VAR_RESULT = isScriptRunning(130);
0x28, 0x00, 0x00, 0xf6, 0xff, // unless (!VAR_RESULT) goto 0955;
0x1a, 0x00, 0x40, 0x00, 0x00 // Local[0] = 0;
// }
};
byte *patchedScript = new byte[6780];
memcpy(patchedScript, unpatchedScript, 2350);
memcpy(patchedScript + 2350, patch, sizeof(patch));
memcpy(patchedScript + 2350 + sizeof(patch), unpatchedScript + 2350, 6718 - 2350);
WRITE_BE_UINT32(patchedScript + 4, 6780);
Common::MemoryReadStream stream(patchedScript, 6780);
// Just to be completely safe, check that the patched script now
// matches the boot script from the other known Mac version.
// Only if it does can we replace the unpatched script.
Common::String md5 = Common::computeStreamMD5AsString(stream);
if (md5 == "92b1cb7902b57d02b8e7434903d8508b") {
byte *newResource = _res->createResource(type, idx, 6780);
memcpy(newResource, patchedScript, 6780);
} else
warning("Could not patch MI2 Mac boot script: Bad checksum '%s'", md5.c_str());
delete[] patchedScript;
}
}