Getting extra data from control

You know when you create a control you can add something you want at the very end?

Code:

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HWND CreateWindow(
  LPCTSTR lpClassName,  // pointer to registered class name
  LPCTSTR lpWindowName, // pointer to window name
  DWORD dwStyle,        // window style
  int x,                // horizontal position of window
  int y,                // vertical position of window
  int nWidth,          // window width
  int nHeight,          // window height
  HWND hWndParent,      // handle to parent or owner window
  HMENU hMenu,          // handle to menu or child-window identifier
  HANDLE hInstance,    // handle to application instance
  LPVOID lpParam        // pointer to window-creation data
);

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How can I access that?

Code:

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/*...*/
case WM_CREATE:
{
  CREATESTRUCT* cs = reinterpret_cast<CREATESTRUCT*>(lParam);
  void*  extraData = cs->lpCreateParams;
  /*...*/
  return 0;
}

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Is that the only way?
I'm trying to store a pointer to the controls class,

Code:

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void MCButon::Init()
{
  ctrl = CreateWindow(...,(VOID*)this);
}

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like that, so that if I want to handle it's paint routine I can just subclass it, however I'd like to be able to use the one window proc to do it...which I would just test a member of the class which I would be able to get from that pointer.

Did that even make sense? lol. :)

Maybe you want something like this.

Code:

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SetWindowLongPtr(hwnd, GWLP_USERDATA, (LONG_PTR) ptrToSomething);

...

// and retrieve it later...
ptrToSomething = (cast) GetWindowLongPtr(hwnd, GWLP_USERDATA);

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Excellent, works like a charm..:)