[matplotlib-devel] Gtk stuff in mlab.py

There are some Gtk-specific functions at the bottom of mlab.py.  It 
tries to "import gtk" and then will either define them or not.

On one of my recent profiling fests, I noticed that this "import gtk" 
(if gtk is installed, and running with some non-Gtk backend) accounts 
for between 1-2% of the total running time over all the examples in 
backend_driver.py.  Not a huge amount, but it seems like it might be a 
good idea to avoid importing something as large as gtk unless we 
actually need to.

We can either import gtk "on demand", when one of these gtk-related 
functions is called, or perhaps better yet move this to another module, 
that would only be imported when needed.  In light of recent 
pylab.py/mlab.py refactorings, are there any opinions on this?

Cheers,
Mike

-- 
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA