CContainedWindowT::m_pfnSuperWindowProc
If the contained window is subclassed, m_pfnSuperWindowProc points to the original window procedure of the window class.
WNDPROC m_pfnSuperWindowProc;
Remarks
If the contained window is superclassed, meaning it is based on a window class that modifies an existing class, m_pfnSuperWindowProc points to the existing window class's window procedure.
The DefWindowProc method sends message information to the window procedure saved in m_pfnSuperWindowProc.
Requirements
Header: atlwin.h