AltTabFix.c

#include "stdafx.h"
#include "PluginAPI.h"
#include "SafeWrite.h"
#include <stdio.h>
#include <intrin.h>

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
					 )
{
	return TRUE;
}

extern "C"
{
	// the alt+tab crash usually happens because the two funcs below get null class pointers passed to them somehow
	// we just reimplement those functions, but add a check to make sure it's not NULL first, and if it is then we just return 0 (which is fine, doesn't seem to break anything)
	// these functions are pretty much 1:1 with the originals, with the addition of the NULL check
	static const UInt32 kAltTabFixXAddr = 0x004C9A80;
	static const UInt32 kAltTabFixYAddr = 0x004C9AA0;

	typedef void(*_Console_Print)(const char * buf, ...);
	const _Console_Print Console_Print = (_Console_Print)0x00579B9B;

	int __fastcall AltTabFixXHook(uint8_t *thisPtr, void* unused)
	{
		if (!thisPtr) // NULL check
		{
			Console_Print("(AltTabFix) !! Prevented X-coord crash !!");
			return 0;
		}

		int* data = *(int**)(thisPtr + 0x3C);
		if (*(uint8_t*)(thisPtr + 0x24) & 1)
			return 0;

		if (data == 0)
			return 0;

		return *data;
	}

	int __fastcall AltTabFixYHook(uint8_t *thisPtr, void* unused)
	{
		if (!thisPtr) // NULL check
		{
			Console_Print("(AltTabFix) !! Prevented Y-coord crash !!");
			return 0;
		}

		int* data = *(int**)(thisPtr + 0x3C);
		if (*(uint8_t*)(thisPtr + 0x24) & 1)
			return 0;

		if (data == 0)
			return 0;

		return *(data + 1);
	}

	bool __declspec(dllexport) OBSEPlugin_Query(const OBSEInterface * obse, PluginInfo * info)
	{
		// fill out the info structure
		if (info)
		{
			info->infoVersion = PluginInfo::kInfoVersion;
			info->name = "alt_tab_fix";
			info->version = 1;
		}

		// version checks
		if (obse->isEditor)
			return false;

		if (obse->oblivionVersion != 0x010201A0) // 1.2.416
			return false;

		return true;
	}

	bool __declspec(dllexport) OBSEPlugin_Load(const OBSEInterface * obse)
	{
		if (!OBSEPlugin_Query(obse, 0))
			return false;

		WriteRelJump(kAltTabFixXAddr, (UInt32)&AltTabFixXHook);
		WriteRelJump(kAltTabFixYAddr, (UInt32)&AltTabFixYHook);

		return true;
	}
}