Wrapping MESA in OpenGL

[ocaisa]

At JSC, we are moving away from MESA to providing an OpenGL that "does the right thing". Just so people get an idea what is going on, see the easyconfig below (also requires some patches).

easyblock = 'Bundle'

name = 'OpenGL'
version = '2019a'

homepage = 'http://www.opengl.org/'
description = """
Open Graphics Library (OpenGL) is a cross-language, cross-platform application programming interface (API) for rendering
2D and 3D vector graphics. Mesa is an open-source implementation of the OpenGL specification - a system for rendering
interactive 3D graphics. NVIDIA supports OpenGL and a complete set of OpenGL extensions, designed to give a maximum
performance on NVIDIA GPUs.

This is a GL vendor neutral dispatch (GLVND) installation with Mesa and NVIDIA in the same lib-directory. Mesa or NVIDIA
OpenGL is set individually for each XScreen.
"""

toolchain = {'name': 'GCCcore', 'version': '8.3.0'}

# The %(pyver)s does not work since the template resolution is not working when using build dependencies and minimal
# toolchains. See: https://github.com/easybuilders/easybuild-framework/issues/3300
local_pyver = '3.6.8'

builddependencies = [
    ('Python', local_pyver),
    ('binutils', '2.32'),
    ('flex', '2.6.4'),
    ('Bison', '3.3.2'),
    ('Autotools', '20180311'),
    ('pkg-config', '0.29.2'),
    ('expat', '2.2.6'),
    ('libxml2', '2.9.9', '-Python-%s' % local_pyver),
    ('Meson', '0.50.0', '-Python-%s' % local_pyver),
    ('Ninja', '1.9.0'),
    ('CMake', '3.14.0'),
]

dependencies = [
    ('zlib', '1.2.11'),
    ('nettle', '3.4'),
    ('libdrm', '2.4.97'),
    ('LLVM', '8.0.0'),
    ('X11', '20190311'),
    ('libunwind', '1.3.1'),
    ('nvidia', 'driver', '', SYSTEM),
]

default_easyblock = 'ConfigureMake'

default_component_specs = {
    'sources': [SOURCE_TAR_GZ],
    'start_dir': '%(name)s-%(version)s',
}

local_pkg_config = ('export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:%(installdir)s/lib/pkgconfig && '
                    'export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:%(installdir)s/lib64/pkgconfig && ')

components = [
    # A vendor neutral dispatch layer
    ('libglvnd', '1.2.0', {
        'source_urls': [
            'https://github.com/NVIDIA/libglvnd/archive/'
        ],
        'sources': ['v%(version)s.tar.gz'],
        'checksums': ['37981bd3320261f14140b8aef6e2e6c08c7e75b6a98dcea034670017f3f1312a'],
        'preconfigopts': './autogen.sh && '
    }),
    # Mesa for software rendering, not hardware rendering.
    ('Mesa', '19.2.1', {
        # We build:
        # - llvmpipe: the high-performance Gallium LLVM driver (only possible with glx=gallium-xlib)
        # - swr: Intel's OpenSWR
        'easyblock': 'MesonNinja',
        'source_urls': [
            'https://mesa.freedesktop.org/archive/',
            'https://mesa.freedesktop.org/archive/%(version)s',
            'ftp://ftp.freedesktop.org/pub/mesa/%(version)s',
            'ftp://ftp.freedesktop.org/pub/mesa/older-versions/%(version_major)s.x/%(version)s',
            'ftp://ftp.freedesktop.org/pub/mesa/older-versions/%(version_major)s.x',
        ],
        'sources': [SOURCELOWER_TAR_XZ],
        'checksums': [
            '4cc53ca1a8d12c6ff0e5ea44a5213c05c88447ab50d7e28bb350cd29199f01e9',
            '8997808ec140990141669d7ad7a536bba541aadbde85fdc1ec9cf849a945caa9',
            'f448455984b6234ef99ac348f9f641ec650eccfe659232ead0292c99441b9840',
        ],
        'start_dir': '%(namelower)s-%(version)s',
        'separate_build_dir': True,
        'patches': [
            'Mesa-19.2.1-match-swrast-loosely.patch',
            'Mesa-19.2.1-meson-avoid-march.patch',
        ],
        'preconfigopts': local_pkg_config,
        'configopts': (' -D libdir=%(installdir)s/lib'
                       ' -D gbm=true'
                       ' -D glx=auto'
                       ' -D osmesa=gallium'
                       ' -D llvm=true'
                       ' -D shared-llvm=true'
                       ' -D dri-drivers=""'
                       ' -D gallium-drivers="swr,swrast"'
                       ' -D swr-arches=avx,avx2,skx,knl'
                       ' -D vulkan-drivers=""'
                       ' -D platforms=x11,drm,surfaceless'
                       ' -D glvnd=true'
                       ' -D libunwind=true'
                       ' -D egl=true'
                       ' -D gles1=true -Dgles2=true'
                       ' -D shared-glapi=true'
                       ' -D gallium-omx=disabled'
                       ' -D buildtype=release'),
    }),
    # OpenGL Extension Wrangler Library - determines which OpenGL extensions are supported at run-time
    # This is just GLEW for GLX (which requires DISPLAY to be set) and not GLEW for EGL as GLEW selects GLX/EGL at
    # compile-time and not run-time (https://github.com/nigels-com/glew/issues/172#issuecomment-357400019)
    # Compile+Load GLEW-EGL on top to enable GLEW for EGL
    ('glew', '2.2.0', {
        'source_urls': [
            'https://sourceforge.net/projects/glew/files/glew/snapshots/',
        ],
        'sources': [
            'glew-20200115.tgz',
        ],
        'checksums': [
            '314219ba1db50d49b99705e8eb00e83b230ee7e2135289a00b5b570e4a4db43a',
        ],
        'skipsteps': ['configure'],
        'buildopts': ('GLEW_PREFIX=%(installdir)s GLEW_DEST=%(installdir)s LIBDIR=%(installdir)s/lib '
                      'LDFLAGS.EXTRA="-L${EBROOTX11}/lib/ -lX11" LDFLAGS.GL="-L%(installdir)s/lib -lGL"'),
        'installopts': 'GLEW_PREFIX=%(installdir)s GLEW_DEST=%(installdir)s LIBDIR=%(installdir)s/lib ',
        'install_cmd': 'make install.all ',
    }),
    # OpenGL Utility Library - offers higher level GL-graphics functions
    ('glu', '9.0.1', {
        'source_urls': [
            'ftp://ftp.freedesktop.org/pub/mesa/glu/'
        ],
        'sources': [
            'glu-%(version)s.tar.gz'
        ],
        'checksums': [
            'f6f484cfcd51e489afe88031afdea1e173aa652697e4c19ddbcb8260579a10f7',
        ],
    }),
    ('demos', '95c1a57cfdd1ef2852c828cba4659a72575c5c5d', {
        'source_urls': [
            'https://gitlab.freedesktop.org/mesa/demos/-/archive/%(version)s/',
        ],
        'sources': [SOURCELOWER_TAR_GZ],
        'checksums': [
            '7738beca8f6f6981ba04c8a22fde24d69d6b2aaab1758ac695c9475bf704249c',
        ],
        'preconfigopts': ('./autogen.sh && ' +
                          local_pkg_config +
                          'GLEW_CFLAGS="-I%(installdir)s/include/" GLEW_LIBS="-L%(installdir)s/lib/ -lGLEW -lGL" '
                          'EGL_CFLAGS="-I%(installdir)s/include/" EGL_LIBS="-L%(installdir)s/lib/ -lEGL" '),
        'configopts': '--disable-osmesa ',
    }),
]

postinstallcmds = [
    'cd %(installdir)s/lib && ln -sf libGL.so.1.7.0 libGL.so.1',
    'rm %(installdir)s/lib/*.la',
    'cd %(installdir)s/lib && ln -sf ${EBROOTNVIDIA}/lib64/libEGL_nvidia.so.0 .',
    'cd %(installdir)s/lib && ln -sf ${EBROOTNVIDIA}/lib64/libGLX_nvidia.so.0 .',
    'cd %(installdir)s/lib && ln -sf libGLX_mesa.so.0 libGLX_indirect.so.0',
    'cd %(installdir)s/lib && ln -sf ${EBROOTNVIDIA}/lib64/libGLESv1_CM_nvidia.so.1 .',
    'cd %(installdir)s/lib && ln -sf ${EBROOTNVIDIA}/lib64/libGLESv2_nvidia.so.2 .',
    # EGL vendor ICDs
    'echo "{"                                               >  %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "  \"file_format_version\" : \"1.0.0\","          >> %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "  \"ICD\" : {"                                   >> %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "      \"library_path\" : \"libEGL_nvidia.so.0\"" >> %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "  }"                                             >> %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "}"                                               >> %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "{"                                               >  %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',
    'echo "  \"file_format_version\" : \"1.0.0\","          >> %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',
    'echo "  \"ICD\" : {"                                   >> %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',
    'echo "      \"library_path\" : \"libEGL_mesa.so.0\""   >> %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',
    'echo "  }"                                             >> %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',
    'echo "}"                                             >> %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',
    # correct pkg-config of GLEW
    'sed -i "/^libdir=/c\libdir=\${exec_prefix}\/lib" %(installdir)s/lib/pkgconfig/glew.pc',
    'sed -i "/^prefix=/c\prefix=%(installdir)s"       %(installdir)s/lib/pkgconfig/glew.pc',
]

modextravars = {
    '__EGL_VENDOR_LIBRARY_FILENAMES': ('%(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json:'
                                       '%(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json'),
    'EGL_PLATFORM': 'surfaceless',
    'EGL_DRIVER': 'swr',
    'EGL_LOG_LEVEL': 'fatal',
    'GALLIUM_DRIVER': 'swr',
    'KNOB_MAX_WORKER_THREADS': '65535',
}

modluafooter = '''
add_property("arch","gpu")

conflict("Mesa")
conflict("libGLU")
'''

sanity_check_paths = {
    'files': [
        'lib/libEGL_mesa.%s' % SHLIB_EXT, 'lib/libOSMesa.%s' % SHLIB_EXT,
        'include/GL/glext.h', 'include/GL/gl_mangle.h', 'include/GL/glx.h',
        'include/GL/osmesa.h', 'include/GL/gl.h', 'include/GL/glxext.h',
        'include/GL/glx_mangle.h', 'include/GLES/gl.h', 'include/GLES2/gl2.h', 'include/GLES3/gl3.h',
        'lib/libOpenGL.%s' % SHLIB_EXT,
        'lib/libGLEW.a', 'lib/libGLEW.%s' % SHLIB_EXT,
        'bin/glewinfo', 'bin/visualinfo',
        'include/GL/glew.h', 'include/GL/glxew.h', 'include/GL/wglew.h',
    ],
    'dirs': []
}

moduleclass = 'vis'

[ocaisa]

This is here as an FYI, it needs to be turned into an easyblock.

[ocaisa]

This is being developed by @jhgoebbert but I know that people in the maintainer list are interested in this

[paulmelis]

This is really nice! A much better approach than using Mesa as a dep in every package that uses OpenGL. However, it seems to be based on the idea of having a separate package/module for the NVIDIA driver binaries (I see EBROOTNVIDIA) instead of using the driver installer?

[paulmelis]

But how would an easyblock version of the above work?

[Thyre]

Let us revive this issue, due to recent discussion at the 10th EasyBuild User Meeting (slides + recording) and the last EasyBuilders meeting (notes).

@jhgoebbert is still mainly working on providing the OpenGL module for JSC. Up to 2025a here in easybuild-easyconfigs, we've been using Mesa, libglvnd and so on as separate components.

---

What are the main differences between JSC & upstream

JSC combines all OpenGL / EGL related stuff into one single module. This includes:

• libglvnd for switching between Mesa & NVIDIA
• Mesa for software rendering
• glu for higher level GL-graphics
• glew (in the GLX variant) for OpenGL extension detection
• "demos", mainly for eglinfo

All of them are available in separate modules upstream. For 2024a e.g., we have:

• Mesa-24.1.3-GCCcore-13.3.0.eb
• Mesa-demos-9.0.0-GCCcore-13.3.0.eb
• libGLU-9.0.3-GCCcore-13.3.0.eb
• glew-2.2.0-GCCcore-13.3.0-egl.eb
• libglvnd-1.7.0-GCCcore-13.3.0.eb

For glew, upstream is missing the GLX variant used in OpenGL at JSC. At JSC, we don't have the EGL variant.
Combining all of this into a single EasyConfigs has the significant benefit that users only need to load a single module for full OpenGL functionality. A similar principle applies to writing EasyConfigs using OpenGL in some form...

---

Specific differences in EasyConfigs

libglvnd

At JSC, we create explicit vendor files for glvnd to use NVIDIA & Mesa. These are located in %(installdir)s/share/glvnd/egl_vendor.d/ and added via __EGL_VENDOR_LIBRARY_FILENAMES.
Upstream uses "__EGL_VENDOR_LIBRARY_DIRS": ['/etc/glvnd/egl_vendor.d', '/usr/share/glvnd/egl_vendor.d'], relying on the OS to provide these files.

I feel like the approach by JSC, providing the files ourselves, should be considered as well. While all my systems have /usr/share/glvnd/egl_vendor.d/, a simple Ubuntu Server installation is missing these files by default. So we might end up with a libglvnd installation without config files for it.
We should probably do both: Add the files ourselves, but also consider "global" files. One would need to figure out the precedence order of __EGL_VENDOR_LIBRARY_DIRS.

Mesa

At JSC, we don't use the Mesa EasyBlock at the moment. That's something we should adopt.
At the same time, we should take a look at e.g. in the EasyBlock:

        # Mesa fails to build with libunwind on aarch64
        # See https://github.com/easybuilders/easybuild-easyblocks/issues/2150
        if get_cpu_architecture() == AARCH64:
            given_config_opts = self.cfg.get('configopts')
            if "-Dlibunwind=true" in given_config_opts:
                self.log.warning('libunwind not supported on aarch64, stripping from configopts!')
                configopts_libunwind_stripped = given_config_opts.replace('-Dlibunwind=true', '-Dlibunwind=false')
                self.cfg.set_keys({'configopts': configopts_libunwind_stripped})
                self.log.warning('New configopts after stripping: ' + self.cfg.get('configopts'))

We've been enabling libunwind on JEDI / JUPITER without issues, so this part of the EasyBlock can probably be removed by now (which needs to be verified).

With increased support for AMD GPUs in EasyBuild, we should also explore if we can enable radeonsi for Mesa. Yeah, the MI[xxx] GPUs don't support rendering (similar to NVIDIAs H200), but there are also consumer GPUs which would really benefit.

Lastly, we set some options, but I don't know what they're for exactly:

    'EGL_PLATFORM': 'surfaceless',
    'EGL_LOG_LEVEL': 'fatal',
    'KNOB_MAX_WORKER_THREADS': '65535',

[Thyre]

Regarding libunwind (see easybuilders/easybuild-easyblocks#2150):

Instead of fully disabling libunwind for Mesa, we should probably patch libunwind like this:
https://sources.debian.org/patches/libunwind/1.3.2-2/0001-aarch64-Use-__asm__-instead-of-asm-89.patch/

Since that specific libunwind version is long removed from EasyBuild, we should check newer versions of libunwind, if they switched from asm to __asm__. The latest one does, but what about v1.4.0?

[paulmelis]

With increased support for AMD GPUs in EasyBuild, we should also explore if we can enable radeonsi for Mesa. Yeah, the MI[xxx] GPUs don't support rendering (similar to NVIDIAs H200), but there are also consumer GPUs which would really benefit.

I don't know about the H200 as we don't have them, but I was shocked when I found out our H100's did provide OpenGL rendering, even though there's nothing mentioned about that in the NVIDIA datasheets. This is with EGL under VirtualGL and VNC, but still. But perhaps the H200 is even further stripped in terms of graphics capabilities?

[Thyre]

I don't know about the H200 as we don't have them, but I was shocked when I found out our H100's did provide OpenGL rendering, even though there's nothing mentioned about that in the NVIDIA datasheets. This is with EGL under VirtualGL and VNC, but still. But perhaps the H200 is even further stripped in terms of graphics capabilities?

Interesting! We have one test system with an H100 and then our GH200 nodes. Would be great if OpenGL rendering would still work, even if not officially documented.

[jhgoebbert]

I don't know about the H200 as we don't have them, but I was shocked when I found out our H100's did provide OpenGL rendering, even though there's nothing mentioned about that in the NVIDIA datasheets. This is with EGL under VirtualGL and VNC, but still. But perhaps the H200 is even further stripped in terms of graphics capabilities?

I can hardly believe that but this would be fantastic!

[paulmelis]

Also, similar output from Blender's system info (same OpenGL calls to get that info, of course):

GPU:
====================================

renderer:       'NVIDIA H100/PCIe/SSE2'
vendor:         'NVIDIA Corporation'
version:        '4.6.0 NVIDIA 575.57.08'
device type:    'NVIDIA'
backend type:   'OPENGL'
extensions:
        GL_AMD_multi_draw_indirect
        GL_AMD_seamless_cubemap_per_texture
        GL_AMD_vertex_shader_layer
        GL_AMD_vertex_shader_viewport_index
...

[Thyre]

I can verify that eglinfo & glxinfo also both show NVIDIA when __GLX_VENDOR_LIBRARY_NAME=nvidia is set, and glxgears at least did show some usage in nvidia-smi on GH200.
So it may actually still work.

[Micket]

Sorry for being late to this party, I'm afraid i still have some comments on this whole approach;

libglvnd

I always expected this to be provided by the OS, since the OS still needs to provide the GPU drivers and nvidia libs anyway.
nvidia-driver-libs (RHEL) or nvidia-gl (ubuntu), both are strict requirements of doing any nvidia 3D acceleration both also supply the glvnd ICDs /usr/share/glvnd/egl_vendor.d/10_nvidia.json (from what i can tell from https://packages.ubuntu.com/noble/amd64/libnvidia-gl-535/filelist ). So I think this assumption holds; you'll not find anyone who packages the EGL (or vulkan) drivers without also including the corresponding ICDs; they are strict package deal.

So, what is inside this ('nvidia', 'driver', '', SYSTEM), i don't know. I'm guessing that this is a repackaged nvidia-gl rpm maybe? This package really must include the ICD files as well, just like they do for all other backends when you install.
Why wouldn't this module supply the ICD via __EGL_VENDOR_LIBRARY_DIRS ?

It seems needlessly complex to rely on a different package to manually re-write the same ICD on it's behalf.

If there was ever anything outside of EB that wanted 3D rendering (like some tool in a apptainer container), then they would of course also need this ICD and accompanying nvidia libraries.

vulkan

Just a side note, I'll just note the existence of the same situation for Vulkan as well (/usr/share/vulkan/icd.d/nvidia_icd.json).
I'm no expert and we barely have anything that even touches vulkan yet, but from the start, vulkan included this dispatch mechanism similar to glvnd into it's design (via vulkan-loader).
Vulkan-loader relies on VK_ADD_DRIVER_FILES to list all the icd's from any path. So a nvidia system module should also append it's vk ICD to that environment variable (if it's not a standard OS path)
With vulkan, it's entirely up to the application to select the GPU(s) based on metadata, so there is no need to care about filename priority here.

bundle

Symlinking files over from nvidia

I really don't understand why this is done at all. There is nothing special that comes from these libraries being in the same path.
Just leave those files exactly where they are, don't symlink any of them. If GLVND can find the libraries in this OpenGL bundle, then there is no reason why it wouldn't find them in their original location just as well; it's just library paths in the end.

So, I would suggest, removing this:

    'cd %(installdir)s/lib && ln -sf ${EBROOTNVIDIA}/lib64/libEGL_nvidia.so.0 .',
    'cd %(installdir)s/lib && ln -sf ${EBROOTNVIDIA}/lib64/libGLX_nvidia.so.0 .',
    'cd %(installdir)s/lib && ln -sf ${EBROOTNVIDIA}/lib64/libGLESv1_CM_nvidia.so.1 .',
    'cd %(installdir)s/lib && ln -sf ${EBROOTNVIDIA}/lib64/libGLESv2_nvidia.so.2 .',

and, the ICD part

    # EGL vendor ICDs
    'echo "{"                                               >  %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "  \"file_format_version\" : \"1.0.0\","          >> %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "  \"ICD\" : {"                                   >> %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "      \"library_path\" : \"libEGL_nvidia.so.0\"" >> %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "  }"                                             >> %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',
    'echo "}"                                               >> %(installdir)s/share/glvnd/egl_vendor.d/10_nvidia.json',

should just be included in the ('nvidia', 'driver', '', SYSTEM), package (surely that module already has this json file).
After all, there is nothing special about %(installdir)s/lib or %(installdir)s/share/glvnd/egl_vendor.d/ that requires a monolithic approach to this.

The other json blob is also already generated by a normal Mesa install

    'echo "  \"file_format_version\" : \"1.0.0\","          >> %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',
    'echo "  \"ICD\" : {"                                   >> %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',
    'echo "      \"library_path\" : \"libEGL_mesa.so.0\""   >> %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',
    'echo "  }"                                             >> %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',
    'echo "}"                                             >> %(installdir)s/share/glvnd/egl_vendor.d/50_mesa.json',

so this also seems pointless to repeat manually? My Mesa installs already include this without being manually generated by any extra step. So, just delete this code?
(It also generates the neccessary vulkan icd for Lavapipe software rendering in share/vulkan/icd.d/ )

GLEW

GLEW seems like a questionable inclusion I.M.H.O.; it's by no means a standard package, and the fact that it only supports one backend at the time (with conflicting library symbols), makes it even more cumbersome; the GLX and EGL variants must conflict with each other, and this is lost here. . Shadowing it with a separate module only works as you never use the first one.
The only saving grace here is that GLEW isn't actually that popular among our easyconfigs so we don't see these conflicts.
Do we have anything apart from only ParaView that uses it? Paraview happens to be one of the few things I'd actually want to build with EGL support so i would still need to use glew-egl on top of this easyconfig, and it would make it a hidden incompatibility with anything that might use glew-glx. I hope they all use RPATH otherwise it's segfault all day long.

It's not like we pull in everything else 3D, things like GLFW/togl/epoxy/freeglut/SDL2 or even GLAD (which is a more modern approach to this type of problem, though it's a generator), so, it's not really a one-stop shop, and it really never can be.

In fact, I just found out that VTK ditched GLEW for GLAD a while back https://gitlab.kitware.com/paraview/paraview/-/merge_requests/7030 (yaaaay!)
So, as far as I know, there isn't anything in EB that depends on GLEW (but my grep-fu might be weak).

One giant build?

I don't understand what benefit bringing glvnd into the same module, instead of just being a dependency like the many other things. It just makes for a longer build when something needs to be re-built/tested etc.
I'm not going to die on this hill, but it seems to me like some special meaning is given to the fact that they are using the same installdir here, but there is nothing special about that. GLVND library will happily look into all the paths you tell it.

OpenGL (or vulkan?!)

This actually isn't just OpenGL. It's also Vulkan, and this cannot be separated out.
I haven't had time to think this one through completely, but I think it's really important that we support this from the start.

At this point, i think maybe it would be sufficient if i where to make my Vulkan package depend on this OpenGL package.
The Mesa (and your nvidia package) would need to add their respective vk icd paths to VK_ADD_DRIVER_FILES. I think this can just point to a directory, despite what the name suggests.
There is also VK_ADDITIONAL_EXPLICIT_LAYER_PATH_ENV_VAR and VK_ADDITIONAL_IMPLICIT_LAYER_PATH_ENV_VAR that should be set via modextrapaths. Potentially, we should set VK_IMPLICIT_LAYER_PATH_ENV_VAR and maybe VK_EXPLICIT_LAYER_PATH_ENV_VAR to intentionally override any old OS installed layers, as they might not be compatible if they are really old. But i'm just guessing here.