To use the OpenGL versions of the graphical display sinks, you must ensure
that you have Python wrappers for OpenGL installed and are using a version
of wxPython that supports it.  Then you must enable this mode by creating or
editing an entry in the GNU Radio preferences file at:

~/.gnuradio/config.conf

[wxgui]
style=gl


The style parameter accepts 'nongl', 'gl', and 'auto', and defaults to 'auto'.

'nongl' forces the use of the non-GL (current) sinks.  

'gl' forces the use of the new GL based sinks, and will raise an exception if the
appropriate GL support does not exist.

'auto' currently equates to 'nongl'; however, in release 3.2, this will change to
use GL if possible and if not, fallback to the non-GL versions.