I am trying to run the RectangleSelector example here. I am using a Mac, so I added the lines

import matplotlib
matplotlib.use('TkAgg')

immediately after the module docstring.

Everything works fine, except when I try to resize the rectangle using the mid-edge control points. The rectangle disappears if my cursor is above the control point when I release. If I move my cursor perpendicular to the control direction, so that my cursor is away from the control point when I release, the rectangle remains.

OSX
Anaconda Python 2.7
Matplotlib 1.5.1