The new get_cursor_data() function has an indexing bug. If the user pans an image such that there is a gap between the edge of the image and the axes edges, and you mouse over that area, IndexError exceptions are thrown all over the place.

@joferkington 's mpl data cursor takes care of this correctly, IIRC, and I know I covered this in my book as well. Hopefully, someone will buy a copy and take a look and adapt it to get_cursor_data().