anchor.diff:  { theme ? null, stdenv, fetchurl, dpkg, makeWrapper , alsaLib, atk, cairo,
   cups, curl, dbus, expat, fontconfig, freetype, glib , gnome2, gtk3, gdk_pixbuf,
   libappindicator-gtk3, libnotify, libxcb, nspr, nss, pango , systemd, xorg,
  -at-spi2-atk, libuuid
  +at-spi2-atk, libuuid, nodePackages
   }:
   
   let
  
positive.code:     gtk3  # needed for GSETTINGS_SCHEMAS_PATH
    ];
  
    nativeBuildInputs = [ makeWrapper ];
  
    dontUnpack = true;
    buildCommand = ''
  
negative.code:       --replace /usr/bin/ $out/bin/ \
        --replace /usr/share/ $out/share/
    '' + stdenv.lib.optionalString (theme != null) ''
      asar extract $out/lib/slack/resources/app.asar $out/lib/slack/resources/app.asar.unpacked
      cat <<EOF >> $out/lib/slack/resources/app.asar.unpacked/dist/ssb-interop.bundle.js
  
      var fs = require('fs');
      document.addEventListener('DOMContentLoaded', function() {
        fs.readFile('${theme}/theme.css', 'utf8', function(err, css) {
          let s = document.createElement('style');
          s.type = 'text/css';
          s.innerHTML = css;
          document.head.appendChild(s);
        });
      });
      EOF
      asar pack $out/lib/slack/resources/app.asar.unpacked $out/lib/slack/resources/app.asar
    '';
  
    meta = with stdenv.lib; {
  