-In fact, they should better all start with \_\_WX instead of \_\_ only,
-so please start any new defines with \_\_WX.
+There are two wxWidgets ports to Mac OS. One of them, wxMac, exists in two versions: Classic and
+Carbon. The Classic version is the only one to work on Mac OS version 8. The
+Carbon version may be built either as CFM or Mach-O (binary format, like ELF)
+and the former may run under OS 9 while the latter only runs under OS X.
+Finally, there is a new Cocoa port which can only be used under OS X. To
+summarize:
+
+\begin{itemize}
+\item If you want to test for all Mac platforms, classic and OS X, you
+should test both \texttt{\_\_WXMAC\_\_} and \texttt{\_\_WXCOCOA\_\_}.
+\item If you want to test for any GUI Mac port under OS X, use
+\texttt{\_\_WXOSX\_\_}.
+\item If you want to test for any port under Mac OS X, including, for
+example, wxGTK and also wxBase, use \texttt{\_\_DARWIN\_\_} (see below).
+\end{itemize}
+
+The convention is to use the \texttt{\_\_WX} prefix for these
+symbols, although this has not always been followed.