anchor.diff:  { cairo, cmake, fetchFromGitHub, libXdmcp, libpthreadstubs, libxcb, pcre, pkgconfig
  -, python2, stdenv, xcbproto, xcbutil, xcbutilcursor, xcbutilimage
  +, python3, stdenv, xcbproto, xcbutil, xcbutilcursor, xcbutilimage
   , xcbutilrenderutil, xcbutilwm, xcbutilxrm, makeWrapper
   
   # optional packages-- override the variables ending in 'Support' to enable or
  
positive.code: assert i3Support     -> ! i3GapsSupport && jsoncpp != null && i3      != null;
  assert i3GapsSupport -> ! i3Support     && jsoncpp != null && i3-gaps != null;
  
  stdenv.mkDerivation rec {
      pname = "polybar";
      version = "3.4.0";
  
      src = fetchFromGitHub {
        owner = "jaagr";
        repo = pname;
        rev = version;
        sha256 = "1g3zj0788cdlm8inpl19279bw8zjcy7dzj7q4f1l2d8c8g1jhv0m";
        fetchSubmodules = true;
      };
  
  
negative.code:     };
  
      buildInputs = [
        cairo libXdmcp libpthreadstubs libxcb pcre python3 xcbproto-py3 xcbutil
        xcbutilcursor xcbutilimage xcbutilrenderutil xcbutilwm xcbutilxrm
  
        (if alsaSupport   then alsaLib       else null)
  