[Paraview] Chromium and 'Unable to open display' in client-server mode

[Joel Welling]

Hi folks;
  We have modified VTK/Rendering/vtkXOpenGLRenderWindow.cxx so that, if the 
server process cannot access the DISPLAY environment variable, it attempts 
create an OpenGL context using the Chromium API.  This works very well, and 
we've had wonderful success running the server rendering processes across 
Chromium under ParaView up through (I believe) 2.0.1.
  In version 2.4.1 there is apparently some trap code which prevents this, 
however.  I know the code at line 448 of GUI/Client/vtkPVCompositeRenderModuleU
I.cxx (rev. 1.30) is getting called, and giving its associated error message 
'Unable to open display'.  The associated text says that this happens when one 
of the servers cannot get a valid DISPLAY environment variable.  Of course 
this message is getting displayed on the client side, and the source of the 
message is somewhere on the server side.
  The servers may not be able to open the DISPLAY, but they have a perfectly 
good graphics context.  Can someone direct me to the code where the server 
DISPLAY is tested so that I can disable it?  I believe I've covered all the 
uses of DISPLAY in vtkXOpenGLRenderWindow and I'm not sure where else to look.

Thanks,
-Joel Welling
 welling at psc.edu