The framework calls this member function immediately before losing the input focus.
Specifies a pointer to the window that receives the input focus (may be NULL or may be temporary).
If the CWnd object is displaying a caret, the caret should be destroyed 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.