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SCI: Fix QFG3 event bugs at the Laibon's hut
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Fixes some well known deadend bugs in the original game:
- Not being able to give the Laibon the horn
- Not being able to enter the Laibon's hut

Bug #11425
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@sluicebox
sluicebox committed May 24, 2022
1 parent f45a5ef commit 6e743a9
Showing 1 changed file with 179 additions and 0 deletions.
179 changes: 179 additions & 0 deletions engines/sci/engine/script_patches.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14112,6 +14112,179 @@ static const uint16 qfg3PatchRingRopePrize[] = {
PATCH_END
};

// The Laibon's hut has complex script bugs that create unintentional dead ends.
// After the Laibon requests a dinosaur horn from fighters and paladins, the
// player is unable to give the horn on subsequent visits if they have the
// bride's price items. Upon leaving the hut, they are unable to return.
//
// rm450:init sets an event number based on game state. The problem events are:
// - Event 5: Fighters/paladins give the horn to begin initiation.
// - Event 6: The bride's price can be paid, but fighters/paladins must have
// given the horn in event 5 for the Laibon to accept the price.
//
// The main problem is that rm450:init tests for event 6 before event 5. If the
// preconditions for event 6 are met then event 5 is suppressed. This is a
// conflict because event 6 can't be completed until event 5 has been, but the
// horn can only be given in event 5. More inconsistencies: some code enforces
// an incorrect rule that these events can only occur once, despite event 6
// being designed to reoccur and event 5 allowing the player to leave without
// giving the horn in version 1.0. Finally, the hut's event logic is out of
// sync between the entrance (room 420) and interior (450). The entrance blocks
// events from recurring even if they weren't completed and is missing a flag
// check, but unlike room 450 it does test the events in the correct order.
//
// We fix this by allowing room 450 to select event 5 (giving the horn) even if
// the preconditions for event 6 are met. We also allow both events to reoccur.
// Finally, we patch the relevant entrance logic to match the interior's.
// Although these patches touch a lot of logic, they only affect the game when
// it is in a state where the player wouldn't have been allowed to proceed with
// events that they've met the preconditions for. Note that these changes are
// broken up into smaller patches to be compatible with the many different
// versions of these scripts, including the NRS fan patches that GOG includes,
// and the comprehensive QFG3 Unofficial Update fan patches.
//
// Applies to: All versions
// Responsible methods: rm450:init, rm420:init
// Fixes bug: #11425
static const uint16 qfg3SignatureLaibonHutEvents1[] = {
0x88, SIG_MAGICDWORD, // lsg 0188 [ johari state ]
SIG_UINT16(0x0188),
0x35, 0x01, // ldi 01
0x1a, // eq? [ Laibon said the bride price ]
SIG_END
};

static const uint16 qfg3PatchLaibonHutEvents1[] = {
PATCH_ADDTOOFFSET(+5),
0x20, // ge? [ Laibon said the bride price OR you've tried to pay before ]
PATCH_END
};

static const uint16 qfg3SignatureLaibonHutEvents2[] = {
SIG_MAGICDWORD,
0x35, 0x06, // ldi 06
0xa3, 0x0b, // sal 0b [ room event = 6 ]
0x32, // jmp [ end of cond ]
SIG_END
};

static const uint16 qfg3PatchLaibonHutEvents2[] = {
PATCH_ADDTOOFFSET(+4),
0x32, PATCH_UINT16(0x0000), // jmp [ continue evaluating room events ]
PATCH_END
};

static const uint16 qfg3SignatureLaibonHutEvents3[] = {
0x31, 0x2b, // bnt 2b [ next room event ]
SIG_ADDTOOFFSET(+7),
0x31, 0x22, // bnt 22 [ next room event ]
SIG_ADDTOOFFSET(+10),
0x31, 0x16, // bnt 16 [ next room event ]
SIG_ADDTOOFFSET(+6),
0x2f, SIG_ADDTOOFFSET(+1), // bt (06, but 08 in QFG3 Unofficial Update)
0x88, SIG_UINT16(0x016a), // lsg 016a [ character class ]
0x35, 0x03, // ldi 03 [ impossible value ]
0x1a, // eq?
0x31, 0x06, // bnt 06 [ always false ]
SIG_MAGICDWORD,
0x35, 0x05, // ldi 05
0xa3, 0x0b, // sal 0b [ room event = 5 ]
0x33, // jmp [ exit cond ]
SIG_END
};

static const uint16 qfg3PatchLaibonHutEvents3[] = {
0x31, 0x23, // bnt 23 [ next room event ]
PATCH_ADDTOOFFSET(+7),
0x31, 0x1a, // bnt 1a [ next room event ]
PATCH_ADDTOOFFSET(+10),
0x31, 0x0e, // bnt 0e [ next room event ]
PATCH_ADDTOOFFSET(+6),
0x31, 0x06, // bnt 06
0x35, 0x05, // ldi 05
0xa3, 0x0b, // sal 0b [ room event = 5 ]
0x33, 0x06, // jmp 06 [ exit cond ]
0x8a, PATCH_UINT16(0x000b), // lsl 000b
0x35, 0x06, // ldi 06
0x1a, // eq? [ is room event 6? ]
0x2f, // bt [ exit cond ]
PATCH_END
};

// same as above but for the NRS script due its wide branch offsets
static const uint16 qfg3SignatureNrsLaibonHutEvents3[] = {
0x30, SIG_UINT16(0x0031), // bnt 0031 [ next room event ]
SIG_ADDTOOFFSET(+8),
0x30, SIG_UINT16(0x0026), // bnt 0026 [ next room event ]
SIG_ADDTOOFFSET(+10),
0x30, SIG_UINT16(0x0019), // bnt 0019 [ next room event ]
SIG_ADDTOOFFSET(+6),
0x2e, SIG_UINT16(0x0006), // bt 0006
0x88, SIG_UINT16(0x016a), // lsg 016a [ character class ]
0x35, 0x03, // ldi 03 [ impossible value ]
0x1a, // eq?
0x30, SIG_UINT16(0x0007), // bnt 0007 [ always false ]
SIG_MAGICDWORD,
0x35, 0x05, // ldi 05
0xa3, 0x0b, // sal 0b [ room event = 5 ]
0x32, // jmp [ exit cond ]
SIG_END
};

static const uint16 qfg3PatchNrsLaibonHutEvents3[] = {
0x30, PATCH_UINT16(0x0028), // bnt 0028 [ next room event ]
PATCH_ADDTOOFFSET(+8),
0x30, PATCH_UINT16(0x001d), // bnt 001d [ next room event ]
PATCH_ADDTOOFFSET(+10),
0x30, PATCH_UINT16(0x0010), // bnt 0010 [ next room event ]
PATCH_ADDTOOFFSET(+6),
0x30, PATCH_UINT16(0x0007), // bnt 0007
0x35, 0x05, // ldi 05
0xa3, 0x0b, // sal 0b [ room event = 5 ]
0x32, PATCH_UINT16(0x0006), // jmp 0006 [ exit cond ]
0x8a, PATCH_UINT16(0x000b), // lsl 000b
0x35, 0x06, // ldi 06
0x1a, // eq? [ is room event 6? ]
0x2e, // bt [ exit cond ]
PATCH_END
};

static const uint16 qfg3SignatureLaibonHutEntrance1[] = {
0x88, SIG_MAGICDWORD, // lsg 016e [ entrance event ]
SIG_UINT16(0x016e),
0x35, 0x09, // ldi 09
0x1c, // ne? [ global366 != 9 (haven't entered for event 5) ]
SIG_END
};

static const uint16 qfg3PatchLaibonHutEntrance1[] = {
0x78, // push1
0x39, 0x26, // pushi 26 [ flag 38 ]
0x45, 0x06, 0x02, // callb proc0_6 [ is flag 38 set? (dispelled Johari) ]
PATCH_END
};

static const uint16 qfg3SignatureLaibonHutEntrance2[] = {
0x88, SIG_MAGICDWORD, // lsg 0188 [ johari state ]
SIG_UINT16(0x0188),
0x35, 0x01, // ldi 01
0x1a, // eq? [ Laibon said the bride price ]
SIG_ADDTOOFFSET(+59),
0x88, SIG_UINT16(0x016e), // lsg 016e [ entrance event ]
0x35, 0x0d, // ldi 0d
0x1c, // ne? [ global366 != 13 (haven't entered for event 6) ]
SIG_END
};

static const uint16 qfg3PatchLaibonHutEntrance2[] = {
PATCH_ADDTOOFFSET(+5),
0x20, // ge? [ Laibon said the bride price OR you've tried to pay before ]
PATCH_ADDTOOFFSET(+59),
0x88, PATCH_UINT16(0x0188), // lsg 0188
0x35, 0x04, // ldi 04
PATCH_END // ne? [ Haven't paid Laibon the bride price ]
};

// script, description, signature patch
static const SciScriptPatcherEntry qfg3Signatures[] = {
{ true, 944, "import dialog continuous calls", 1, qfg3SignatureImportDialog, qfg3PatchImportDialog },
Expand All @@ -14124,6 +14297,12 @@ static const SciScriptPatcherEntry qfg3Signatures[] = {
{ true, 285, "missing points for telling about initiation heap", 1, qfg3SignatureMissingPoints1, qfg3PatchMissingPoints1 },
{ true, 285, "missing points for telling about initiation script", 1, qfg3SignatureMissingPoints2a, qfg3PatchMissingPoints2 },
{ true, 285, "missing points for telling about initiation script", 1, qfg3SignatureMissingPoints2b, qfg3PatchMissingPoints2 },
{ true, 420, "laibon hut entrance (1/2)", 1, qfg3SignatureLaibonHutEntrance1, qfg3PatchLaibonHutEntrance1 },
{ true, 420, "laibon hut entrance (2/2)", 1, qfg3SignatureLaibonHutEntrance2, qfg3PatchLaibonHutEntrance2 },
{ true, 450, "laibon hut events (1/3)", 1, qfg3SignatureLaibonHutEvents1, qfg3PatchLaibonHutEvents1 },
{ true, 450, "laibon hut events (2/3)", 1, qfg3SignatureLaibonHutEvents2, qfg3PatchLaibonHutEvents2 },
{ true, 450, "laibon hut events (3/3)", 1, qfg3SignatureLaibonHutEvents3, qfg3PatchLaibonHutEvents3 },
{ true, 450, "NRS: laibon hut events (3/3)", 1, qfg3SignatureNrsLaibonHutEvents3, qfg3PatchNrsLaibonHutEvents3 },
{ true, 460, "NRS: floating spears", 1, qfg3SignatureNrsFloatingSpears, qfg3PatchNrsFloatingSpears },
{ true, 510, "ring rope prize", 1, qfg3SignatureRingRopePrize, qfg3PatchRingRopePrize },
{ true, 550, "combat speed throttling script", 1, qfg3SignatureCombatSpeedThrottling1, qfg3PatchCombatSpeedThrottling1 },
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