[vtkusers] Many VTK build tests fail when run from Jenkins/Bamboo or VNC display, even when DISPLAY is set to good opengl-enabled display

[Ben Boeckel]

On Mon, Jan 01, 2018 at 13:58:17 +1030, John wrote:
> MESA_GL_VERSION_OVERRIDE=3.2 made a huge difference to running the tests
> on vnc.
> 
> With the override set, I'm able to run tests on vnc with only 102
> failures, and most of those failures are from the TestGPURayCast group.
> So there's obviously something about that group which doesn't like the
> VNC/Mesa, but almost everything else is good.

Your Mesa build probably lacks floating point texture support. Most
distros disable it due to patent licensing issues. Building it yourself
(assuming a license) would suffice. I'd recommend *not* overwriting the
system Mesa, but using LD_LIBRARY_PATH instead.

> I do find this situation incredibly frustrating and utterly depressing
> though. Once again, I wonder why I ever began to use Linux. What sort of
> utter garbage is this, when having a monitor turn off due to DPMS
> suddenly breaks applications?!?!

This is nvidia behavior, not Linux/Mesa/etc. behavior (I have no such
issues with the nouveau driver). Their driver "optimize" on-screen draws
that aren't actually being displayed by just not doing them. You can see
this if you overlap a window partially on top of a test window and see a
black rectangle in that area. There may be some obscure setting in their
settings app to disable this. If so, I'd like to know about it as well
;) (I haven't been in there in ages, so it may be new).

--Ben