anchor.diff:    nativeBuildInputs = [
       cmake
       eigen # header-only
  -    wrapQtAppsHook
     ];
   
     buildInputs = [
  
positive.code:     "-DPLUGIN_IO_QRDB=OFF" # Riegl rdblib is proprietary; not packaged in nixpkgs
    ];
  
    meta = with stdenv.lib; {
      description = "3D point cloud and mesh processing software";
      homepage = "https://cloudcompare.org";
      license = licenses.gpl2Plus;
  
negative.code: { lib
  , mkDerivation
  , fetchFromGitHub
  , cmake
  , dxflib
  , eigen
  , flann
  