The framework calls this member function when the size, position, or Z-order is about to change as a result of a call to the SetWindowPos member function or another window-management function.
afx_msg void OnWindowPosChanging( WINDOWPOS* lpwndpos );
Points to a WINDOWPOS data structure that contains information about the window's new size and position.
An application can prevent changes to the window by setting or clearing the appropriate bits in the flags member of the WINDOWPOS structure.
For a window with the WS_OVERLAPPED or WS_THICKFRAME style, the default implementation sends a WM_GETMINMAXINFO message to the window. This is done to validate the new size and position of the window and to enforce the CS_BYTEALIGNCLIENT and CS_BYTEALIGN client styles. An application can override this functionality by not calling its base class.
This member function is called by the framework to allow your application to handle a Windows message. The parameters passed to your function reflect the parameters received by the framework when the message was received. If you call the base-class implementation of this function, that implementation will use the parameters originally passed with the message and not the parameters you supply to the function.