anchor.diff:      [ librsvg sane-backends sane-frontends ] ++
       (with perlPackages; [
         Gtk3
  +      Gtk3ImageView
         Gtk3SimpleList
         Cairo
         CairoGObject
         Glib
         GlibObjectIntrospection
         GooCanvas2
  +      GraphicsTIFF
  +      IPCSystemSimple
         LocaleCodes
         LocaleGettext
  -      PDFAPI2
  +      PDFBuilder
  +      ImagePNGLibpng
         ImageSane
         SetIntSpan
         PerlMagick
  
positive.code:     xvfb_run
      file
      tesseract # tests are expecting tesseract 3.x precisely
    ];
  
    checkPhase = ''
      xvfb-run -s '-screen 0 800x600x24' \
        make test
    '';
  
negative.code: 
  perlPackages.buildPerlPackage rec {
    pname = "gscan2pdf";
    version = "2.11.1";
  
    src = fetchurl {
      url = "mirror://sourceforge/gscan2pdf/${version}/${pname}-${version}.tar.xz";
      sha256 = "0aigngfi5dbjihn43c6sg865i1ybfzj0w81zclzy8r9nqiqq0wma";
    };
  
    nativeBuildInputs = [ wrapGAppsHook ];
  