[vtkusers] Using vtkpython with X11 on headless Mac OS X systems

[kent williams]

If you want to use VTK Python, I believe you need to also build X11
versions of TCL and TK.  Otherwise you'll get Carbon versions of TK,
and they really don't play nice with X11.

As for whether running OSX headless is the culprit -- don't know.  We
don't use Python at all but we do use Tcl/TK with remote display from
OS X just fine.