anchor.diff:  { lib, stdenv, fetchurl, perl, kbd, bdftopcf
   , libfaketime, fonttosfnt, mkfontscale
   }:
  -
  -with lib;
   
   stdenv.mkDerivation {
     name = "uni-vga";
  
positive.code:   nativeBuildInputs =
      [ bdftopcf libfaketime
        fonttosfnt mkfontscale
      ] ++ optionals stdenv.isLinux [ perl kbd ];
  
    postPatch = "patchShebangs .";
  
  
negative.code:     # convert bdf font to otb
      faketime -f "1970-01-01 00:00:01" \
      fonttosfnt -v -o u_vga16.otb u_vga16.bdf
    '' + lib.optionalString stdenv.isLinux ''
      # convert font to compressed psf
      ./bdf2psf.pl -s UniCyrX.sfm u_vga16.bdf \
        | psfaddtable - UniCyrX.sfm - \
  