running examples with the WX backend

Hi, I accidentally deleted a message from Jeremy in which

    > he had code snippets that worked with the WX backend in
    > its current CVS incarnation.

Have you read
There is nothing special about invoking the wx backend. The two ways
of invoking a given backend are described on that page.

If it's not clear after reading, please let me know so I can update
the documentation (or provide suggestions for what can be clearer).