anchor.diff:        ]
         ++ optional (elem "nvidia" driverNames) kernelPackages.nvidia_x11
         ++ optional (elem "nvidiaLegacy" driverNames) kernelPackages.nvidia_x11_legacy
  -      ++ optional (elem "virtualbox" driverNames) xorg.xrefresh;
  +      ++ optional (elem "virtualbox" driverNames) xorg.xrefresh
  +      ++ optional (elem "ati_unfree" driverNames) kernelPackages.ati_drivers_x11;
         
       environment.systemPackages = config.environment.x11Packages;
       
  
positive.code:             LD_LIBRARY_PATH = "${xorg.libX11}/lib:${xorg.libXext}/lib:${kernelPackages.nvidia_x11}/lib";
            } // optionalAttrs (elem "nvidiaLegacy" driverNames) {
              LD_LIBRARY_PATH = "${xorg.libX11}/lib:${xorg.libXext}/lib:${kernelPackages.nvidia_x11_legacy}/lib";
            } // cfg.displayManager.job.environment;
  
          preStart =
  
negative.code:   # Map video driver names to driver packages.
    knownVideoDrivers = {
      ati          = { modules = [ xorg.xf86videoati ]; };
      ati_unfree   = { modules = [ kernelPackages.ati_drivers_x11 ]; driverName = "fglrx"; };
      cirrus       = { modules = [ xorg.xf86videocirrus ]; };
      i810         = { modules = [ xorg.xf86videoi810 ]; };
      intel        = { modules = [ xorg.xf86videointel ]; };
  