Thread: Window Hook

With SetWindowsHookEx() you can either specify a dll in hMod and use 0 for dwThreadId which gives you a system wide hook, or you use NULL for hMod and specify your programs thread id in dwThreadId to hook your program.
Now if i happen to have a thread id for another program can i create a hook which will only hook that program. I have tried a couple versions of SetWindowsHookEx() with and without a dll but i cant get it to work yet, has anyone done this before?

The documentation suggests that you can. I haven't tried it.

Originally Posted by MSDN_SetWindowsHookEx

lpfn
[in] Pointer to the hook procedure. If the dwThreadId parameter is zero or specifies the identifier of a thread created by a different process, the lpfn parameter must point to a hook procedure in a dynamic-link library (DLL). Otherwise, lpfn can point to a hook procedure in the code associated with the current process.

Which hook are you trying to use? Could you post your hook setup code?

has anyone done this before?

Yes, several times. Just pass SetWindowHookEx() the ID of the thread you want to hook.

I'm not sure where you are getting your error description from but my list of system error codes says:

Originally Posted by MSDN System Error Codes

1428 Cannot set nonlocal hook without a module handle. ERROR_HOOK_NEEDS_HMOD

This makes it clear that the hook procedure must be in a DLL and you must provide its hInstance to SetWindowsHookEx().

Also, your GetMsgProc needs the CALLBACK calling convention:

Code:

LRESULT CALLBACK GetMsg( int code, WPARAM wParam, LPARAM lParam )

The Error description came from msdn, i just searched for 'error 1428', i guess maybe different things use the same codes, will try it in a dll. I was hoping to do away with the hassle of a dll, it may as well be systemwide if i got to use a dll.
Thanks for the help dude