Was sind die Unterschiede zwischen WH_MOUSE und WH_MOUSE_LL Haken?

Habe ich herausgefunden, dass WH_MOUSE ist nicht immer genannt. Könnte das problem sein, dass ich mit WH_MOUSE und nicht WH_MOUSE_LL?

Code:

class MouseHook
{
public:
  static signal<void(UINT, const MOUSEHOOKSTRUCT&)> clickEvent;

  static bool install() 
  {
    if (isInstalled()) return true;
    hook = ::SetWindowsHookEx(WH_MOUSE, (HOOKPROC)&mouseProc,  
                                ::GetModuleHandle(NULL), NULL);
    return(hook != NULL);
  }

  static bool uninstall() 
  {
    if (hook == NULL) return TRUE;
    bool fOk = ::UnhookWindowsHookEx(hook);
    hook = NULL;
    return fOk != FALSE;
  }

  static bool isInstalled() { return hook != NULL; }

private:
   static LRESULT CALLBACK mouseProc(int nCode, WPARAM wParam, LPARAM lParam)
   {            
      if (nCode == HC_ACTION && 
        (wParam == WM_LBUTTONDOWN || wParam == WM_NCLBUTTONDOWN ||
         wParam == WM_RBUTTONDOWN || wParam == WM_NCRBUTTONDOWN ||
         wParam == WM_MBUTTONDOWN || wParam == WM_NCMBUTTONDOWN ))
      {
        MOUSEHOOKSTRUCT* mhs = (MOUSEHOOKSTRUCT*) lParam;
        clickEvent(wParam, *mhs);
      }         

      return ::CallNextHookEx(hook, nCode, wParam, lParam);
    }

   static HHOOK hook;
};