Interact delegate

**wag321** · 07-12-2011

So I am in the process of converting from asm to delegates. And I noticed that interact (which i c/pd from another thread) looks like

Code:

                    "fs mov eax, [0x2C]",
                    "mov eax, [eax]",
                    "add eax, 0x08",
                    "mov dword [eax], "+ CurMgr
                    "mov ecx, "+ ObjPointer
                    "call "+ ObjInteractPointer
                    "retn"

Unless I'm wrong it's accessing the fs segment register. I couldn't figure out why it would be doing this so I created a delegate ala

Code:

        [UnmanagedFunctionPointer(CallingConvention.ThisCall)]
        private delegate void InteractDelegate(uint target);

Which works fine.
Although it's working I can't help but wonder what that fs magic is all about? Can anyone explain?

**lanman92** · 07-12-2011

It is updating the TLS of the local thread(redundancy?). The object manager is stored in TLS, so you have to update the TLS pointer when you make calls using the object manager most of the time. It is not necessary when you use an EndScene hook for obvious reasons.

**wag321** · 07-12-2011

Ah great thanks!

**namreeb** · 07-12-2011

Note that it is not necessary when called from an EndScene hook ASSUMING that nothing but WoW is calling EndScene. If you are injecting a GUI framework (XNA, SlimDX, etc.), you may still have a problem. The easiest way to handle this scenario is to only execute your EndScene code when the current thread is the main thread.