Re: matplotlib broken

[ludo@gnu.org (Ludovic Courtès)]

Federico Beffa <beffa@ieee.org> skribis:

> ludo@gnu.org (Ludovic Courtès) writes:
>
>> I don’t know if I’m missing something, but when I type ‘matplotlib’ at
>> the prompt, I get:
>>
>> /gnu/store/g4m8q73cq4lym3v1ag7pnk5zv49mdifs-python-matplotlib-1.4.2/lib/python3.4/site-packages/matplotlib-1.4.2-py3.4-linux-x86_64.egg/matplotlib/backends/backend_gtk3.py in <module>()
>>      19 except ValueError:
>>      20     raise ImportError(
>> ---> 21         "Gtk3 backend requires the GObject introspection bindings for Gtk 3 "
>>      22         "to be installed.")
>>      23
>>
>> ImportError: Gtk3 backend requires the GObject introspection bindings for Gtk 3 to be installed.
>>
>> This may well be related to <http://bugs.gnu.org/20765>: Because Guix
>> has incomplete dependency information, it might GC some of the things
>> that these eggs refer to, and so things may or may not work depending on
>> whether they have been GC’d.
>
> To solve this error I think you need to set
> export GI_TYPELIB_PATH="$HOME/.guix-profile/lib/girepository-1.0"
> We should probably add a search path specification for that.

Oh right.  It’s actually in gobject-introspection, which makes sense but
is inconvenient in this case.  Not sure how to handle it.

> For me it does display a window as expected, but it doesn't show the
> curve (line in this case).

Indeed, in:

  guix environment --pure --ad-hoc gobject-introspection pango gtk+ python-ipython -E ipython

I get the behavior you describe, and the console shows alarming
warnings like:

  TypeError: Couldn't find foreign struct converter for 'cairo.Context'

which explains the blank page, I guess.  If Python’s FFI uses GIR files,
then that’s probably because it couldn’t find Cairo’s GIR files in
$GI_TYPELIB_PATH?

My 2¢,
Ludo’.