Re: the nvidia/osmesa dilema

[Daniel J Sebald]

On 05/04/2016 02:15 PM, John W. Eaton wrote:
> Umm, I wonder if the issue discussed here is the same as our problem:
> https://sourceforge.net/p/mesa3d/mailman/message/24581439/

It sounds like the same problem, but the solution they have doesn't seem 
very robust.


> tl;dr:  As I understand it, mixing OpenGL and OSMesa calls requires some
> care to ensure that you are only calling the functions from the OSMesa
> library when the OSMesa gl context is active.  It doesn't appear that we
> are doing this correctly.  I guess somehow it works with some OpenGL
> library implementations but not the Nvidia one (at least).

Not sure.  My impression is that OSMesa is somewhat tied into OSMesa, 
development wise, so it should mesh pretty well.

After doing a bit of searching and reading, I'm thinking the issue is 
that Qt (GUI) is using X11 and the nVidia driver might be adhering more 
rigorously to the X11 standard than other drivers, in particular on the 
matter of multiple threads.  I wrote some notes about this here:

https://savannah.gnu.org/bugs/?47849#comment6

The quotes from GLX manual are perhaps helpful.

What hunk of software/driver is using what standard is mere guessing for 
me, but here's a rundown on nVidia drivers for Linux:

https://wiki.gentoo.org/wiki/NVidia/nvidia-drivers

and even more, this bit

https://wiki.gentoo.org/wiki/NVidia/nvidia-drivers#Enable_OpenGL.2FOpenCL

makes me think that nVidia driver might be intentionally restricting an 
application that tries to use openGL on its resources without being 
configured properly.

If there were a way to use openGL rendering in non-visible plots pretty 
much the same as visible plots but somehow the context memory simply 
isn't mapped into the screen video memory, that would be the best 
solution.  Then __osmesa_print__ could be used for only the case where 
there is no Qt toolkit or FLTK toolkit...and that could be the case used 
for generating the documentation---hence no Qt/FLTK needed for docs. 
Just __osmesa_print__.

Dan