The framework calls this member function after gaining the input focus.
Contains the CWnd object that loses the input focus (may be NULL). The pointer may be temporary and should not be stored for later use.
To display a caret, CWnd should call the appropriate caret functions at this point.
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.