[PyOpenGL-Devel] Force PyOpenGL to load a specific GL dynamic library

[Tiago N. <ti...@gm...>]

Hi,

My application has the requirement to run in environments that might not
provide hardware-accelerated OpenGL (such as Remote Desktop on Windows).
Since we'd like to use hardware acceleration if available, we have code
that detects the local support at runtime and loads a bundled GL lib
(Mesa+llvmpipe) if necessary.

As far as I understand it, PyOpenGL uses ctypes to load the GL lib at
runtime. On Windows, I can update the PATH environment variable to have
PyOpenGL find my OpenGL32.dll first, and it works as expected.

On Linux, it looks like ctypes does a straight dlopen() on the candidate
names (libGL.so, libGL.so.1, etc). Apparently it's too late to update
LD_LIBRARY_PATH to have the loader find my lib first (ref:
https://stackoverflow.com/questions/856116/changing-ld-library-path-at-runtime-for-ctypes),
so PyOpenGL finds another dynamic library and I end up with two loaded
libs, which as expected doesn't work. My application has other, non-Python
OpenGL dependencies and those are resolved by loading (via ctypes) the full
name to our bundled libGL.so, so PyOpenGL is our last remaining loose end.

I'm writing to ask if my reasoning here is correct and if PyOpenGL has
another mechanism through which I could say "load this dynamic lib please".
I did some research but couldn't find anything. If no mechanism is
available, would the maintainers be interested in adding it? I figured an
environment variable called something like PYOPENGL_GL_LIB_FILE and
pointing to the full path of my local libGL.so would be interesting, and
that would solve my issue. I would be glad to work on a patch to add this
feature, as it looks like I might have to patch our local PyOpenGL build
anyway.

Thank you,

Tiago