Observe opened windows with SetWindowsHookEx - c++

Question

I'm trying to observe opening and closing windows with a global Windows hook. Therefore I'm trying to pass callback functions to the DLL containing my hook procedure. However, the hook procedure itself never gets called.
/** Handle to this DLL */
HINSTANCE dllModule = 0;
/** Hook procedure */
HHOOK windowHook = 0;
/** Callbacks are called when a new window is opened, or closed. */
HWND_CALLBACK windowOpenCallback = 0;
HWND_CALLBACK windowCloseCallback = 0;
WINDOWHOOK_API int WINAPI DllMain(HINSTANCE hInstance, DWORD reason, LPVOID reserved)
{
if(reason == DLL_PROCESS_ATTACH)
{
dllModule = hInstance;
std::cout << "Process attached." << std::endl;
}
else if (reason == DLL_PROCESS_DETACH)
{
std::cout << "Process detached." << std::endl;
}
else if (reason == DLL_THREAD_ATTACH)
{
}
else if (reason == DLL_THREAD_DETACH)
{
}
return 1;
}
WINDOWHOOK_API bool setWindowHook(HWND_CALLBACK openCallback, HWND_CALLBACK closeCallback)
{
if(windowHook != 0 || windowOpenCallback != 0 || windowCloseCallback != 0)
{
return false;
}
windowOpenCallback = openCallback;
windowCloseCallback = closeCallback;
windowHook = SetWindowsHookEx(WH_SHELL, (HOOKPROC)hookCallback, dllModule, 0);
return windowHook != 0;
}
WINDOWHOOK_API bool releaseWindowHook()
{
bool result = windowHook != 0 && UnhookWindowsHookEx(windowHook) != 0;
windowHook = 0;
windowOpenCallback = 0;
windowCloseCallback = 0;
return result;
}
LRESULT CALLBACK hookCallback(int nCode, WPARAM wParam, LPARAM lParam)
{
std::cout << "Hook callback" << std::endl;
return CallNextHookEx(windowHook, nCode, wParam, lParam);
}
From my main program, I load the library and call the setWindowHook procedure. I then simply start an infinite loop and wait for the hook to be called, but although the setWindowHook doesn't fail, the hook procedure is never called. I don't understand why.
I tried setting a WH_KEYBOARD hook. With that, the hook procedure got called on keypresses, but only if they were inside the console window of my program.
I'm compiling this to 32bit on a 64bit machine. However, shouldn't it at least work for all my 32bit applications?
Thanks in advance.

Answer 1

Thanks, I got it to work with the DLL and SetWindowsHookEx, however the SetWinEventHook solution works even better and you don't need a DLL for that.
The only problem was, that the WINEVENTHOOK has no LPVOID pointer attribute that we can pass a class instance to. So if you're looking for an OO-approach and are struggling with that, this codeproject link might help.
Also make sure, that whatever thread you set the hook from, has a message loop, or you won't receive any events.
while (!stopped)
{
if (PeekMessage(&msg, 0, 0, 0, PM_REMOVE))
{
// you don't have to do anything here
}
}