The framework calls this member function when the size, position, or Z-order has changed as a result of a call to the SetWindowPos member function or another window-management function.
The default implementation sends the WM_SIZE and WM_MOVE messages to the window. These messages are not sent if an application handles the OnWindowPosChanged call without calling its base class. It is more efficient to perform any move or size change processing during the call to OnWindowPosChanged without 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.