Keep the charts in State

[batteryviewer] / default.nix

let
  batteryviewer = { lib, stdenv, gtk3, pkg-config, }:
    stdenv.mkDerivation {
      pname = "batteryviewer";
      version = "0.1";

      src = lib.cleanSource ./.;

      nativeBuildInputs = [ pkg-config ];
      buildInputs = [ gtk3 ];

      makeFlags = [ "prefix=$(out)" ];
    };
in { pkgs ? import <nixpkgs> { }, }: {
  batteryviewer = pkgs.callPackage batteryviewer { };
}