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Engine Fix: Op135 form-to-form transition #119

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Engine Fix: Op135 form-to-form transition #119

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29 changes: 29 additions & 0 deletions EEex/copy/EEex_scripts/EEex_Fix_Patch.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -561,6 +561,35 @@

EEex_JITAt(EEex_Label("Hook-bsearchrange()-FirstInstruction"), {"jmp #L(EEex::Override_bsearchrange)"})

--[[
+------------------------------------------------------------------------------------+
| Fix op135 (CGameEffectPolymorph) form-to-form transition |
| Issue: uses UnequipAll(animationOnly=0) when already polymorphed |
| causing passive equipment bonuses (rings, amulets, etc.) |
| to be stripped instead of preserved. |
| Particularly bad for undroppable items like Edwin's Amulet or Nalia's Ring. |
+------------------------------------------------------------------------------------+
| Root cause: a JNE at the "is already polymorphed?" check incorrectly |
| skips setting edx=1 (animation-only), so the second |
| polymorph always calls UnequipAll with animationOnly=0. |
| Fix: NOP out the 2-byte JNE (75 02) so animationOnly=1 is always used. |
+------------------------------------------------------------------------------------+
--]]

EEex_Utility_NewScope(function()
local jneAddr = EEex_Label("Hook-CGameEffectPolymorph::ApplyEffect()-FormToFormUnequipAllBugJne")
local byte0 = EEex_ReadU8(jneAddr)
if byte0 == 0x90 then return end -- already patched
if byte0 ~= 0x75 then -- sanity: expect JNE short opcode
EEex_Error(string.format(
"[op135 form-to-form bug fix] Unexpected opcode 0x%02X at hook label, cannot patch",
byte0))
return
end
EEex_WriteU8(jneAddr, 0x90) -- NOP (was 0x75 = JNE short)
EEex_WriteU8(jneAddr + 1, 0x90) -- NOP (was 0x02 = rel8 offset)
end)

EEex_EnableCodeProtection()

end)()
7 changes: 7 additions & 0 deletions EEex/loader/InfinityLoader.db
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Original file line number Diff line number Diff line change
Expand Up @@ -2207,6 +2207,13 @@ Operations=ADD 25
Pattern=4889742420574883EC30488BF1488BFA
Operations=ADD 40

; op135 (CGameEffectPolymorph) hooks
; Bug fix: form-to-form transition incorrectly calls UnequipAll(animationOnly=0);
; the JNE at this address should be NOP'd so animationOnly=1 is always used.
[Hook-CGameEffectPolymorph::ApplyEffect()-FormToFormUnequipAllBugJne]
Pattern=4C89AC24D00000004533FF
Operations=ADD 64

[Hook-CGameEffectProtectionCircle::ApplyEffect()-AddTail]
Pattern=488D8E001D0000
Operations=ADD 17
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