Upon updating Ubuntu Linux to the latest version I find that something
has changed in the environment to produce a problem in the beta version
of Visual. The rendering thread (the code that generates the OpenGL
display) has to lock out the computational thread (your own Python code)
in order to avoid conflicts in reading or writing common resources. The
rendering routine for faces (in faces.cpp) tries to acquire the lock and
fails, hanging forever, while the computational thread goes merrily on
its way forever. Because faces are used to draw vertical and horizontal
bars in the graph package, bar graphs hang. Oddly, if the faces are
inside a frame, there is no problem.
The good news is that the problem is absolutely reproducible, on several
different computers including computers with brand new clean installs of
the latest Ubuntu. The bad news is that I haven't had much time to
devote to the problem and don't know its cause, and I don't have
experience debugging a thread lock problem. I would welcome suggestions.
Bruce Sherwood
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