[Matplotlib-users] Possible problem with mpl.axes.Axes.add_collection()

[<jor...@ya...>]

Hi,
I have a strange problem. It seems to me it is related to 
mpl.axes.Axes.add_collection(), but I am too lost to be sure. I have a 
script for visualizing certain aspects of images, built upon many bits 
and pieces I found on the matplotlib example section. It basically lets 
me view an image from two different perspectives, that is, its usual 
representation and another one, for example a scatter plot of red versus 
green. That part is working, but I added later on the possibility to 
select a group of points in either representation and see them 
highlighted in both with the same color. That part works OK, up to the 
third selected region, but when I select the fourth something strange 
happens, as I don't see this region in any of the subplots. I represent 
the regions as collections, and add them to subplot with 
add_collection() method. The collections themselves are created ok, and 
the get_children() method even report having them, but they are not 
visible. What surprises me the most is that it is always the fourth 
selected region the one showing this problem, no matter how big or small 
are the previous ones.I tried to make a scaled down version of the 
script exhibiting the problem, but it works ok then. I could post the 
code here, but then I'll force you to go through a 300 lines script. How 
do you go about debugging these sort of problems?
As a side note, the doc tells that add_collection() returns the 
collection, when it actually returns a NoneType object.
BTW, I am using the gtk backend, ipython is started with ipython 
-gthread -pylab. Matplotlib version is 0.98.5.3

Regards,

Jorge