Motivation for this change

Update and fix virtualgl. Also added instructions to wiki

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

Edit: copy of instructions since struggling with wiki update...

OpenGL

OpenGL must break purity due to the need for hardware-specific linkage. Intel, AMD, and Nvidia will have different libraries for example. On NixOS, these libraries are mounted at /run/opengl-driver/lib and /run/opengl-driver-32/lib.

When a program is installed in your environment, these libraries should be found automatically. However, this is not the case in a nix-shell. To fix, add this line to your shell.nix:
LD_LIBRARY_PATH="/run/opengl-driver/lib:/run/opengl-driver-32/lib";

VirtualGL

X11 forwarding does not work for OpenGL applications. Instead, we can use VirtualGL. You'll need to install VirtualGL on both client and server (nixpkgs.virtualgl). Then, from client

  > vglconnect <server>
  $ export LD_LIBRARY_PATH=/run/opengl-driver/lib/
  $ vglrun -c proxy  glxgears

For nvidia hardware, an additional workaround is needed to avoid 1 fps framerate. First, run nvidia-settings and save a xorg.conffile in /tmp.

  environment.etc = {
    # needed for virtualgl to fix 1 fps problem, see:
    # https://wiki.archlinux.org/index.php/VirtualGL
    "X11/xorg.conf.d/20-nvidia.conf".text = ''
      <text from xorg.conf here>
      Section "Screen"
        [...]
        Option         "HardDPMS" "false"
      EndSection
    ''';
  }