nixos/opengl: add mesaPackage option

      package = mkOption {

        type = types.package;

        internal = true;

        default = cfg.mesaPackage;

        description = lib.mdDoc ''

          The package that provides the OpenGL implementation.

          The default is Mesa's drivers which should cover all OpenGL-capable

          hardware. If you want to use another Mesa version, adjust

          {option}`mesaPackage`.

        '';

      };

      package32 = mkOption {

        type = types.package;

        internal = true;

        default = cfg.mesaPackage32;

        description = lib.mdDoc ''

          Same as {option}`package` but for the 32-bit OpenGL implementation on

          64-bit systems. Used when {option}`driSupport32Bit` is set.

        '';

      };

      mesaPackage = mkOption {

        type = types.package;

        default = pkgs.mesa;

        defaultText = literalExpression "pkgs.mesa";

        example = literalExpression "pkgs.mesa_23";

        description = lib.mdDoc ''

          The package that provides the 32-bit OpenGL implementation on

          64-bit systems. Used when {option}`driSupport32Bit` is

          set.

          The Mesa driver package used for rendering support on the system.

          You should only need to adjust this if you require a newer Mesa

          version for your hardware or because you need to patch a bug.

        '';

        apply = mesa: mesa.drivers or throw "`mesa` package must have a `drivers` output.";

      };

      mesaPackage32 = mkOption {

        type = types.package;

        default = pkgs.pkgsi686Linux.mesa;

        defaultText = literalExpression "pkgs.pkgsi686Linux.mesa";

        example = literalExpression "pkgs.pkgsi686Linux.mesa_23";

        description = lib.mdDoc ''

          Same as {option}`mesaPackage` but for the 32-bit Mesa on 64-bit

          systems. Used when {option}`driSupport32Bit` is set.

        '';

        apply = mesa: mesa.drivers or throw "`mesa` package must have a `drivers` output.";

      };

      extraPackages = mkOption {

          :::

        '';

      };

      extraPackages32 = mkOption {

        type = types.listOf types.package;

        default = [];

    environment.sessionVariables.LD_LIBRARY_PATH = mkIf cfg.setLdLibraryPath

      ([ "/run/opengl-driver/lib" ] ++ optional cfg.driSupport32Bit "/run/opengl-driver-32/lib");

    hardware.opengl.package = mkDefault pkgs.mesa.drivers;

    hardware.opengl.package32 = mkDefault pkgs.pkgsi686Linux.mesa.drivers;

    boot.extraModulePackages = optional (elem "virtualbox" videoDrivers) kernelPackages.virtualboxGuestAdditions;

  };

}