To intercept other events, you used to override virtual functions, such as OnSize. Now, while you can use the OnSize name for such event handlers (or any other name of your choice), it has only a single argument (wxSizeEvent) and must again be 'mapped' using the EVT_SIZE macro. The same goes for all other events, including OnClose (although in fact you can still use the old, virtual form of OnClose for the time being).