nix-install-vendor-gl

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• =nix-install-vendor-gl.sh=

  Ensure that a system-compatible OpenGL driver is available for nix-shell-encapsulated programs.

  This is an attempt at automated solution to https://github.com/NixOS/nixpkgs/issues/9415

  The home of =nix-install-vendor-gl.sh= is at: https://github.com/deepfire/nix-install-vendor-gl

*** Limitations

Currently only nVidia drivers are supported, although the infrastructure is
generalised sufficiently so, that adding support for a new driver stack should
amount to extending case statements in a number of functions -- the list is
here: https://github.com/deepfire/nix-install-vendor-gl/blob/master/nix-install-vendor-gl.sh#L7

*** OS/GPU test matrix

|              | nvidia | nouveau | AMDGPU | radeonsi | Catalyst | Intel |
|--------------+--------+---------+--------+----------+----------+-------|
| SteamOS      | ✅     |         |        |          |          |       |
| Ubuntu 14.04 LTS | ✅     |         |        |          |          |       |
| Ubuntu 16.04 | ✅     |         |        |          |          |       |
| Ubuntu 16.10 | [[https://github.com/deepfire/nix-install-vendor-gl/issues/7][#7]]     |         |        |          |          |       |
| Ubuntu 17.04 |        |         |        |          |          |       |

• Quickstart *** Prerequisites

  1. Nix, obviously.

  2. Both system and Nix-provided =glxinfo='s:

     • system one :: likely, is at =/usr/bin/glxinfo= (if it is elsewhere, you would have to specify its path with =--system-glxinfo=). This one is installed with distro-specific means: =apt-get install mesa-utils=, =dnf install glx-utils=, or similar.

     • Nix-provided :: should be at =~/.nix-profile/bin/glxinfo=, and can also be similarly specified.

*** Typical scenario ::

1. Enter shell, face failure:

   #+BEGIN_SRC bash
   desktop@steamos:~/src/reflex-glfw$ nix-shell

   [nix-shell:~/src/reflex-glfw]$ glxinfo
   name of display: :1
   libGL error: unable to load driver: swrast_dri.so
   libGL error: failed to load driver: swrast
   X Error of failed request:  GLXBadContext
     Major opcode of failed request:  155 (GLX)
     Minor opcode of failed request:  6 (X_GLXIsDirect)
     Serial number of failed request:  54
     Current serial number in output stream:  53
   #+END_SRC

2. Call for rescue (note the =.= dot) -- will require interactive input, due
   to a =sudo= invocation (suggestions on how to improve this are welcome!):

   #+BEGIN_SRC bash
   [nix-shell:~/src/reflex-glfw]$ . ../nix-install-vendor-gl/nix-install-vendor-gl.sh
   INFO: The version of the vendor driver in nixpkgs:  375.26
   doesn't match the system vendor driver version:     367.27
   ..so a semi-automated vendor GL package download is required.

   downloading ‘http://download.nvidia.com/XFree86/Linux-x86_64/367.27/NVIDIA-Linux-x86_64-367.27.run’... [74251/75142 KiB, 3525.9 KiB/s]
   path is ‘/nix/store/lfp9md7r5ms29wqy99bsayql8sh9fwbw-NVIDIA-Linux-x86_64-367.27.run’
   /nix/store/4mxr3p5cl16fvmfqqj780937b5wrv1gn-opengl-drivers
   Nix-compatible vendor GL driver is now installed at /run/opengl-driver

   To make them available to Nix-build applications you can now issue:

      export LD_LIBRARY_PATH=/run/opengl-driver/lib

   (Doing the export, in case you have sourced the file directly.)
   #+END_SRC

3. Proceed happily:

   #+BEGIN_SRC bash
   [nix-shell:~/src/reflex-glfw]$ glxinfo
   name of display: :1
   display: :1  screen: 0
   direct rendering: Yes
   server glx vendor string: NVIDIA Corporation
   server glx version string: 1.4
   server glx extensions:
       GLX_ARB_context_flush_control, GLX_ARB_create_context,
   #+END_SRC

3. The cases of re-activation are handled transparently:

   #+BEGIN_SRC bash
   [nix-shell:~/src/reflex-glfw]$ . ../nix-install-vendor-gl/nix-install-vendor-gl.sh
   INFO: Nix-available GL seems to be okay (according to glxinfo exit status).

   [nix-shell:~/src/reflex-glfw]$ exit
   exit
   desktop@steamos:~/src/reflex-glfw$ nix-shell

   [nix-shell:~/src/reflex-glfw]$ . ../nix-install-vendor-gl/nix-install-vendor-gl.sh
   INFO: A global libGL.so.1 already seems to be installed at
   /run/opengl-driver/lib/libGL.so.1, and it appears to be sufficient for
   the Nix 'glxinfo'.

     export LD_LIBRARY_PATH=/run/opengl-driver/lib
   #+END_SRC

• Troubleshooting

  Firstly, there's an =examine= subcommand that dumps /a lot/ of information, that might prove to be useful in case /something goes wrong/.

  Secondly, still, if anything goes wrong, please:

  1. If the script is obviously failing, repeat the failing invocation with =--verbose=.
  2. File a bug report at https://github.com/deepfire/nix-install-vendor-gl/issues (with the log attached, if #1).

• Why:

  When one uses Nix to run Nix-encapsulated OpenGL software on non-NixOS, it's not unlikely to encounter a similarly-looking error:

  [nix-shell:~/src/reflex-glfw]$ dist/build/reflex-glfw-demo/reflex-glfw-demo libGL error: unable to load driver: swrast_dri.so libGL error: failed to load driver: swrast

  This happens because nix isolates your program from the system, which implies a purposeful ignorance of your host GL libraries.

  However, these /particular/ host GL libraries are essential for your program to be able to talk to your X server.

  The issue is well-known:

  https://github.com/NixOS/nixpkgs/issues/9415

  So, it's a fairly fundamental conflict, and one solution is to supply a sufficiently matching version of GL libraries (yes, that means your nVidia drivers) using Nix itself.

  Thankfully, it's not impossible -- this script attempts to be a proof.