import of graph_tool hangs (Ubuntu 15.10)

graph-tool
1

I have followed the instructions for Ubuntu here

https://graph-tool.skewed.de/download#debian

to install the precompiled version of graph-tool onto my Ubuntu 15.10
system.
It went okay except that I got the complaint, even after installing the key,
that the graph-tool package wasn't verified.

After installation, there seems to be a conflict between graph_tool and
pylab.
I usually start python 2.7 under ipython with ipython --pdb --pylab

After doing so, the following works alright

from graph_tool import Graph

However, the following hangs forever:

from graph_tool.all import graph_draw
/usr/lib/python2.7/dist-packages/gi/module.py:176: Warning: cannot register
existing type 'GtkWidget'
  g_type = info.get_g_type()
/usr/lib/python2.7/dist-packages/gi/module.py:176: Warning: cannot add class
private field to invalid type '<invalid>'
  g_type = info.get_g_type()
/usr/lib/python2.7/dist-packages/gi/module.py:176: Warning: cannot add
private field to invalid (non-instantiatable) type '<invalid>'
  g_type = info.get_g_type()
/usr/lib/python2.7/dist-packages/gi/module.py:176: Warning:
g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE
(instance_type)' failed
  g_type = info.get_g_type()
/usr/lib/python2.7/dist-packages/gi/module.py:176: Warning: cannot register
existing type 'GtkBuildable'
  g_type = info.get_g_type()
/usr/lib/python2.7/dist-packages/gi/module.py:176: Warning:
g_type_interface_add_prerequisite: assertion 'G_TYPE_IS_INTERFACE
(interface_type)' failed
  g_type = info.get_g_type()
/usr/lib/python2.7/dist-packages/gi/module.py:176: Warning:
g_once_init_leave: assertion 'result != 0' failed
  g_type = info.get_g_type()

I don't understand the errors, but possibly some test could avert the
hang/crash outcome?

Thanks,
Chris

2

This looks like a GTK+ problem. Do you known which matplotlib backend you
are using?

Best,
Tiago

3

Using matplotlib backend: Qt4Agg

Thanks,
Chris

4

What happens if you change this to GTK3Cairo?

5

Then graph-tool.all imports just fine.

I can't remember whether I have chosen my backend for a reason, but I
can try using what you suggest.

However, this is still undesirable behavior, is it not?

Chris

6

I said:

I can't remember whether I have chosen my backend for a reason,

Oh, btw: it's because with GTK3Cairo, the plot windows become modal. If I
use matplotlib.show(), I have to close the plot window to continue.

Thanks!
Chris

7

Yes, but it is not graph-tool's fault. What is happening is probably
that the Qt backend is using GTK version 2 to do the drawing, and GTK 2
and 3 (which is used in graph-tool) are incompatible; they cannot be
loaded simultaneously in the same program.

An alternative fix is for you to configure Qt to use a "native" theme
that does not use GTK at all.

Best,
Tiago