anchor.diff:      "SYSTEMD_USERS_DIRECTORY=$(out)/lib/sysusers.d"
       "SYSTEMD_FILES_DIRECTORY=$(out)/lib/tmpfiles.d"
       "UDEV_LIBRARY_DIRECTORY=$(out)/lib/udev"
  +    "UDEV_RULES_TYPE=all"
       "POLKIT_POLICY_DIR=$(out)/share/polkit-1/actions"
       "POLKIT_RULE_DIR=$(out)/share/polkit-1/rules.d"
     ];
  
positive.code: { lib, stdenv, fetchurl, pkg-config, python3, bluez
  , tcl, acl, kmod, coreutils, shadow
  , alsaSupport ? stdenv.isLinux, alsaLib
  , systemdSupport ? stdenv.isLinux, systemd
  }:
  
negative.code:       substituteInPlace systemd/system/brltty@.service \
          --replace '/usr/lib' "$out/lib" \
          --replace '/sbin/modprobe' '${kmod}/bin/modprobe'
        # Ensure the systemd-wrapper script uses the correct path to the brltty binary
        sed "/^Environment=\"BRLTTY_EXECUTABLE_ARGUMENTS.*/a Environment=\"BRLTTY_EXECUTABLE_PATH=$out/bin/brltty\"" -i systemd/system/brltty@.service
        substituteInPlace systemd/system/brltty-device@.service \
          --replace '/usr/bin/true' '${coreutils}/bin/true'
        substituteInPlace udev/rules.d/90-brltty-uinput.rules \
  