CALLBACK GlobalWndProc(...HWND hWnd, message...){  for (int i=0; i<g_iNumActiveCRendererObjects; ++i)  {    if (hWnd==g_renderer[i].GetHWND())    {      return g_renderer[i].LocalWndProc( hWnd, message );    }  }  return DefWndProc(...)}  

  class Thing{...  void OpenOrInitialiseWindow();protected:  static BOOL CALLBACK WndProc( HWND hWnd, UINT uMsg, ... )  virtual BOOL OnWndProc( HWND hWnd, UINT uMsg, ... )};void Thing::OpenOrInitialiseWindow(){  WNDCLASS wc;  ...  wc.lpfnWndProc = Thing::WndProc;  ...  RegisterClass();  hWnd = CreateWindow(...);  // stash a ptr to the object in window  SetWindowLong( hWnd, GWL_USERDATA, this );}BOOL CALLBACK Thing::WndProc( HWND hWnd, UINT uMsg, ... ){  Thing* pthis = (Thing*)GetWindowLong(hWnd,GWL_USERDATA);  // need to check this pointer , because we''ll get NCCREATE  // messages before we get a chance to SetWindowLong()  if (pthis)  {    return pthis->OnWndProc( hWnd, uMsg, ... );  }  return DefWndProc(...);}  

    //Observer.hpp#include <list>#define FOR_EACH_OBSERVER_CALL(mthd) 	{	tyListObserver::iterator it = m_listObserver.beign();	tyListObserver::iterator itStop = m_listObserver.end();	for(;it!=itStop; it++)		{		(*it)->mthd;		}	}//maybe the pre-processor isn't evil afterall...template <class TObserver>CObservable	{	public:		void AddObserver(TObserver* pObserver)			{			m_listObserver.insert(m_listObserver.end(), pObserver);			}		void RemoveObserver(TObserver*)			{			m_listObserver.remove(pObserver);			}	private:		typedef std::list<TObserver*> tyListObserver;		tyListObserver m_listObserver;	};//Engine classesclass IObserverOfMyClass	{	virtual void OnSomeEvent(int)=0;	};class CMyClass : public IObservable<IObserverOfMyClass>{	private:		void SomeEvent(...)			{			FOR_EACH_OBSERVER_CALL(OnSomeEvent(-1));			}}//UI Class(es)class CWnd : public IOberverOfMyClass	{		CWnd()		{		m_MyInst.AddOberver(this);		}	~CWnd()		{		m_MyInst.RemoveOberver(this);		}		virtual void OnSomeEvent(int i)		{//SomeEvent triggered		_ASSERT(i==-1);		}	private:		CMyClass m_MyInst;	};