diff --git a/flake.nix b/flake.nix
index c5ea5b37..44369377 100644
--- a/flake.nix
+++ b/flake.nix
@@ -130,9 +130,9 @@
                 #doxygen = prev.doxygen;
 
                 pybind11 = pythonPackages.pybind11;
-                #breathe = python3Packages.breathe;
-                #sphinx = python3Packages.sphinx;
-                #sphinx-rtd-theme = python3Packages.sphinx-rtd-theme;
+                #breathe = pythonPackages.breathe;
+                #sphinx = pythonPackages.sphinx;
+                #sphinx-rtd-theme = pythonPackages.sphinx-rtd-theme;
 
                 #extras1 = { boost = boost; };
                 #extras2 = { boost = boost; python3Packages = python3Packages; pybind11 = pybind11; };
@@ -164,7 +164,10 @@
 
                 xo-unit =
                   (prev.callPackage ./pkgs/xo-unit.nix { xo-cmake = xo-cmake;
-                                                         xo-reflect = xo-reflect; }).overrideAttrs
+                                                         xo-reflect = xo-reflect;
+                                                         python = python;
+                                                         pythonPackages = pythonPackages;
+                                                       }).overrideAttrs
                     (old: { src = ./.; });
 
                 # placeholder-D
diff --git a/pkgs/xo-unit.nix b/pkgs/xo-unit.nix
index 093c3091..e3ee6d43 100644
--- a/pkgs/xo-unit.nix
+++ b/pkgs/xo-unit.nix
@@ -1,8 +1,27 @@
 {
-  # nixpkgs dependencies
+  # 1. nixpkgs dependencies
+  # 1.1. python
+  python, pythonPackages,
+
+  # 1.2. particular python packages
+  sphinx ? pythonPackages.sphinx,
+  sphinx-rtd-theme ? pythonPackages.sphinx-rtd-theme,
+  breathe ? pythonPackages.breathe,
+
+  # 1.3. document-generation packages
+  #      use of makeFontsConf adapted from nixpkgs/development/libraries/gtkmm/4.x.nix
+  #
+  doxygen, graphviz,
+  #fontconfig,
+  makeFontsConf,
+
+  # used for graphviz (dot) see docs/Doxyfile.in
+  helvetica-neue-lt-std,
+
+  # 1.4. c++ build/utest chain
   stdenv, cmake, catch2, # ... other deps here
 
-  # xo dependencies
+  # 2. xo dependencies
   xo-cmake, xo-reflect,
 
   # args
@@ -31,7 +50,32 @@ stdenv.mkDerivation (finalattrs:
     });
 
     cmakeFlags = ["-DCMAKE_MODULE_PATH=${xo-cmake}/share/cmake"];
+
+    FONTCONFIG_FILE = makeFontsConf { fontDirectories = [ helvetica-neue-lt-std ]; };
+
+    # move HOME so fontconfig can do sensible things
+    buildPhase = ''
+      set -x
+
+      echo "FONTCONFIG_FILE=$FONTCONFIG_FILE"
+
+      #export FONTCONFIG_FILE=$fontconfig.out/etc/fonts/fonts.conf
+      export HOME=$TMPDIR
+      export XDG_CONFIG_HOME=$TMPDIR
+
+      mkdir $XDG_CONFIG_HOME/fontconfig
+
+      #grep xdg $FONTCONFIG_FILE
+
+      #$fontconfig.out/bin/fc-cache -v
+
+      make && make docs
+    '';
+
+    # NOTE: helvetic-neue-lt-std has unfree license
+    #FONTCONFIG_FILE = makeFontsConf { fontDirectories = [ helvetica-neue-lt-std ]; };
+
     doCheck = true;
-    nativeBuildInputs = [ cmake catch2 ];
-    propagatedBuildInputs = [ ];
+    nativeBuildInputs = [ cmake catch2 doxygen graphviz sphinx sphinx-rtd-theme breathe ];
+    propagatedBuildInputs = [ xo-reflect ];
   })