[matplotlib-devel] Another try at interactive gui thread

[Baptiste C. <bap...@al...>]

Hello,

here is a proposition of a new strategy for interactive plotting in GTK 
(probably also WX), that doesn't need IPython, and runs the mainloop in 
a separate thread from the calculations.
It has no impact on the user unless he chooses to make use of it, and a 
small impact on the backend developper.

It works in two parts:

matplotlib/__init__.py imports a gtk_protect function that returns a 
wrapper around "dangerous" functions or methods.
The one proposed here (protect_mutex.py) encloses the actual function 
call in a gtk.threads_enter() / gtk.threads_leave() pair in order to 
acquire the GTK mutex.
The same strategy seems possible in WX, though I encountered a lot of 
annoying little problems with WX 2.4. If someone is interested in taking 
over that part, please ask me (I usually don't use WX).
For the non-interactive case, matplotlib defines a dummy gtk_protect 
function which returns its own input, i.e. nothing is changed in that case.

Then all the backend as to do is call gtk_protect on dangerous functions 
or methods in order to replace them with a wrapper. The wrapper has 
little overhead, so I may have protected more than needed.

How to use:
after applying the patch, you have to change your rc params to actually 
use it. Change your .matplotlibrc to contain the following:
backend      : GTKAgg # or GTK or GTKCairo
interactive  : True
gui_protect  : Mutex

Afterwards, you can run most of the examples with python -i, and modify 
the plots to your liking :-)

Cheers,
BC