Alternative fix for the toggle of the Salem (#94)

Depends on: FAForever/fa#6499

README.md

@@ -197,9 +197,6 @@ These new features have been added in a backwards compatible manner
     - section/LuaFuncRegs.cpp
 - Maximum sim rate up to 50
     - hooks/DelClampMaxSimRate.cpp
-- Adds an amphibious mode toggle to the Salem
-    - hooks/luaSimGetStat.cpp
-    - section/luaSimGetStat.cpp
 - Adds GetDepositsAroundPoint to Sim and UI
     - section/SimGetDepositsAroundPoint.cpp
     - section/LuaFuncRegs.cpp
@@ -225,3 +222,6 @@ These new features have been added in a backwards compatible manner
     - section/BuildUnit.cpp
     - section/SelectUnit.cpp
     - section/SimArmyCreate.cpp
+- Add `Unit:ForceAltFootPrint` that forces game to use AltFootprint for the unit (applied to Salem in particular)
+    - hooks/EntityGetFootprint.cpp
+    - section/EntityGetFootprint.cpp

hooks/EntityGetFootprint.cpp

@@ -0,0 +1,14 @@
+#define SECTION(index, address) ".section h"#index"; .set h"#index","#address";"
+#include "../define.h"
+
+asm(
+// Moho::Entity::Entity
+SECTION(0, 0x00677BC9)
+    "mov dword ptr [esi+0x1F8], ebx;" // 0x1F9 bool forceAltFootprint
+
+//  Moho::Entity::GetFootprint
+SECTION(1, 0x006788A5)
+    "jmp "QU(asm__GetFootprint)";"
+    "nop;"
+    "nop;"
+);

section/EntityGetFootprint.cpp

@@ -0,0 +1,39 @@
+#include "include/CObject.h"
+#include "include/magic_classes.h"
+#include "include/moho.h"
+
+int ForceAltFootPrint(lua_State *L)
+{
+
+    if (lua_gettop(L) != 2)
+        L->LuaState->Error(s_ExpectedButGot, __FUNCTION__, 2, lua_gettop(L));
+    auto res = GetCScriptObject<Unit>(L, 1);
+    if (res.IsFail())
+        L->LuaState->Error("%s", res.reason);
+
+    void *unit = res.object;
+    bool flag = lua_toboolean(L, 2);
+
+    GetField<bool>(unit, 8+0x1F9) = flag; // bool forceAltFootprint
+
+    return 0;
+}
+using UnitMethodReg = SimRegFunc<0x00E2D550, 0x00F8D704>;
+
+UnitMethodReg UseAltFootPrintReg{
+    "ForceAltFootPrint",
+    "",
+    ForceAltFootPrint,
+    "Unit"};
+
+
+void asm__GetFootprint()
+{
+    asm(
+        "cmp   byte ptr [ecx+0x11C], 0;" //  this->sstiData.usingAltFp
+        "jnz   0x006788AE;"
+        "cmp   byte ptr [ecx+0x1F9], 0;" // bool forceAltFootprint
+        "jnz   0x006788AE;"
+        "jmp   0x006788C2;"
+    );
+}

section/include/global.h

@@ -152,4 +152,16 @@ struct Result {
   constexpr static Result<T> Success(void *data) { return {(T *)data, nullptr}; }
 
   inline bool IsFail() { return reason != nullptr; }
-};
+};
+
+template <typename T>
+T Offset(void *ptr, size_t offset)
+{
+    return (T)(((char *)ptr) + offset);
+}
+
+template <typename T>
+T &GetField(void *ptr, size_t offset)
+{
+    return *Offset<T *>(ptr, offset);
+}

section/include/moho.h

@@ -821,6 +821,7 @@ struct UnitIntel
 
 struct Unit : WeakObject
 {//0x006A5422, 0x6A8 bytes
+	using Type = ObjectType<0x010C6FC8, 0x00F6A1E4>;
 	//WeakObject WeakObject;
 	// at 0x8
 	//Entity Entity; to 0x278