callback functions (and OnMenuCommand), and nearly all event handling will be done by functions taking a single event argument.
So in future you will have code like:
-{\small\begin{verbatim}
+{\small
+\begin{verbatim}
void MyFrame::OnOK(wxCommandEvent& event)
{
...
simplify your application's allocation and deallocation of memory for the returned string,
and simply assign the result to a wxString object. For example, replace this:
-{\small\begin{verbatim}
+{\small
+\begin{verbatim}
char* s = wxFunctionThatReturnsString();
s = copystring(s); // Take a copy in case it is temporary
.... // Do something with it
with this:
-{\small\begin{verbatim}
+{\small
+\begin{verbatim}
wxString s = wxFunctionThatReturnsString();
.... // Do something with it
\end{verbatim}