The framework calls this member function to inform an application's main window procedure that a modal dialog box or a menu is entering an idle state.
A modal dialog box or menu enters an idle state when no messages are waiting in its queue after it has processed one or more previous messages.
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.