Window Procedures as Virtual Function inside classes.

#include <Windows.h>
#include <tchar.h>

/** BASE WINDOW CLASS | AS A TEMPLATE **/
class CWnd
{
public:
	virtual void Init(HINSTANCE hInstance)	//Registers, Creates, Shows the Window
	{
		HWND         hwnd ;
		WNDCLASS     wndclass ;

		wndclass.style         = 0 ;
		wndclass.lpfnWndProc   = WndProc ;
		wndclass.cbClsExtra    = 0 ;
		wndclass.cbWndExtra    = 0 ;
		wndclass.hInstance     = hInstance ;
		wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
		wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
		wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
		wndclass.lpszMenuName  = NULL ;
		wndclass.lpszClassName = L"CWndMy32" ;

		RegisterClass (&wndclass);
     
		hwnd = CreateWindow (L"CWndMy32", TEXT ("The Hello Program"), 
                                      WS_OVERLAPPEDWINDOW,
			              CW_USEDEFAULT,CW_USEDEFAULT,
                                      CW_USEDEFAULT,CW_USEDEFAULT,
				     NULL,NULL,hInstance,
                                      (LPVOID)this) ; 
    //attach a pointer of the 
        //  class (Cwnd *) to the			                                            //window using the last parameter
                     // of CreateWindow

		ShowWindow (hwnd, SW_SHOWNORMAL) ;

		UpdateWindow (hwnd) ;
	}

protected:
	HINSTANCE hInst;
	HWND m_hwnd;
private:
	//Window Procedure for all of the windows (derived classes like the one below) created by this TEMPLATE CLASS
	static LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
	{
		CWnd * _this = (CWnd *) GetWindowLong(hwnd, GWL_USERDATA);
		if(msg == WM_NCCREATE)
		{
			_this = new CWnd;
			_this->hInst = GetModuleHandle(0);
			_this->m_hwnd = hwnd;
			SetWindowLong(hwnd, GWL_USERDATA, (LONG) _this);
			return TRUE;
		}

		return _this->VirtualProc(hwnd, msg, wParam, lParam);
	}

	//Virtual Procedure Function to override in derived classes
	virtual LRESULT VirtualProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM        
        lParam)
	{
		return DefWindowProc(hwnd, msg, wParam, lParam);
	}
};

/** A CLASS FOR USING THE TEMPLATE CLASS | WHICH IS CWnd **/
class CMyWnd : public CWnd
{
private:
	//This virtual function Overides the 'VirtualProc' function of the 'CWnd' Class
	LRESULT VirtualProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
	{
		if(msg == WM_LBUTTONDOWN)
			MessageBox(0, 0, 0, 0);	//To Test if it words, if so, an empty message box will appear when the window is clicked
		return DefWindowProc(hwnd, msg, wParam, lParam);
	}
};

/** Windows Entry **/
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int nCmdShow)
{
	CMyWnd wnd;				//Object of the Template Used Class | CMyWnd : public CWnd
	wnd.Init(hInstance);

	MSG msg;
	while(GetMessage(&msg, 0, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}

	return msg.wParam;
}