scroll direction incorrectly reported by TkAgg

In my interactive plots that connect with mouse scroll events
(event.button), I just noticed that TkAgg reports the opposite - 'up'
when the scroll direction is down and vice versa. GTKAgg and WxAgg
report the correct value.

I noticed this after installing ipython in a virtualenv and having
problems with interactive plotting using GTKAgg and WxAgg. Figure
windows would not appear, or would appear and hang the interpreter - a
threading issue I guess. So I switched to TkAgg, which solved the
problem, but then scrolling was mixed up.

This is using stock packages for Ubuntu 10.04, with ipython 0.10.1
installed in the virtualenv with pip. I compiled and installed
matplotlib 1.0 in the same virtualenv and saw the same behavior.

Anyone else had these issues?