flake.nix

# https://github.com/nix-community/nix-direnv
# https://github.com/oxalica/rust-overlay
{
  description = "A basic flake with a shell";
  nixConfig.bash-prompt = "\[rust-plot\]($(parse_git_branch))$ ";

  inputs.nixpkgs-pinned.url = "github:NixOS/nixpkgs?rev=85f1ba3e51676fa8cc604a3d863d729026a6b8eb";
  inputs.flake-utils.url = "github:numtide/flake-utils";
  inputs.rust-overlay.url = "github:oxalica/rust-overlay";

  outputs = { self, nixpkgs-pinned, rust-overlay, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system: 
    let
      overlays = [ (import rust-overlay) ];
      pkgs = import nixpkgs-pinned {
        inherit system overlays;
      };

      jetbrains-idea-community-override = pkgs.jetbrains.idea-community.override {
        vmopts = "-Xmx8g";
      };


      #pkgs.rust-bin.beta.latest
      #pkgs.rust-bin.stable.latest
      #pkgs.rust-bin.selectLatestNightlyWith (toolchain: toolchain.default)
      #pkgs.rust-bin.beta."2021-01-01"
      #pkgs.rust-bin.nightly."2020-12-31"

      rust_version = pkgs.rust-bin.stable."1.69.0";
    in
    with pkgs;
      {
        devShells.default = mkShell rec {

          nativeBuildInputs = [
            bashInteractive

            cmake gnumake expat pkg-config fontconfig
          ];

          buildInputs = [
            rust_version.default

            jetbrains-idea-community-override

            freetype
            libxkbcommon
            libGL
            # WINIT_UNIX_BACKEND=wayland
            wayland
            # WINIT_UNIX_BACKEND=x11
            xorg.libXcursor
            xorg.libXrandr
            xorg.libXi
            xorg.libX11

            ## utilities
            xorg.xdpyinfo
          ];

          shellHook = ''
            parse_git_branch() {
              git rev-parse --abbrev-ref HEAD 2> /dev/null
            }

            export CARGO_HOME="$PWD/.cargo"
            export PATH=$PATH:$CARGO_HOME/bin

            # XDG environment variable exports are needed for Intellij Idea to work properly when launched from terminal. Only XDG_DATA_HOME is definitely needed.
#           export XDG_STATE_HOME="$PWD/.XDG/state"
            export XDG_DATA_HOME="$PWD/.XDG/share"
#           export XDG_CONFIG_HOME="$PWD/.XDG/config"
#           export XDG_CACHE_HOME="$PWD/.XDG/cache"

            #using the $PWD for the XDG_DATA_HOME avoids this error:
            #/nix/store/hl5v6vjsf3yhi9a2fyf5vnq06w6c257r-rust-default-1.64.0/bin/cargo check --message-format json --workspace --all-targets -Z unstable-options --keep-going
            #error: failed to run `rustc` to learn about target-specific information
            #error: failed to run `rustc` to learn about target-specific information
            #Caused by:
            #  could not execute process `/home/username/.local/share/JetBrains/IdeaIC2023.1/intellij-rust/bin/linux/x86-64/intellij-rust-native-helper /nix/store/hl5v6vjsf3yhi9a2fyf5vnq06w6c257r-rust-default-1.64.0/bin/rustc - --crate-name ___ --print=file-names --crate-type bin --crate-type rlib --crate-type dylib --crate-type cdylib --crate-type staticlib --crate-type proc-macro --print=sysroot --print=cfg` (never executed)
            #Caused by:
            #  No such file or directory (os error 2)

            echo ""
            echo "impure environment loaded for project: rust-plot"
            echo "to enter a pure environment from this one use command: 'nix develop -i'"
            echo ""
            echo "launch development IDE in this environment with '@idea'"

          '';

          LD_LIBRARY_PATH = "${nixpkgs-pinned.lib.makeLibraryPath buildInputs}";
          RUSTUP_TOOLCHAIN = rust_version.rustc.version;

          ## an old method to set rust compiler flags. This might be different now that I use the rust overlay.
          #  RUSTFLAGS = (builtins.map (a: ''-L ${a}/lib'') []);
          #  RUSTFLAGS =
          #    "-C link-arg=-Wl,-dynamic-linker,/lib/ld-linux-armhf.so.3 " +
          #    "-C target-feature=+crt-static";

          ########################################3
          #### variables required when running in pure mode nix develop -i

          ## Setting this prevents error "Wayland status: XdgRuntimeDirNotSet"
          XDG_RUNTIME_DIR="/run/user/1000";

          # This corrects another x11 error. this could need to be sometimes changed to DISPLAY=":0";
          DISPLAY=":1";

          # prevents error: Authorization required, but no authorization protocol specified...Failed to initialize any backend! Wayland status: NoCompositorListening X11 status: XOpenDisplayFailed
          XAUTHORITY="/run/user/1000/gdm/Xauthority";
          #########################################


          # extra debugging flags
          #RUST_BACKTRACE=1;
          #LIBGL_DEBUG = "verbose";
          #WAYLAND_DEBUG=1;
          #RUST_LOG="debug";
        };

      }
    );
}

There are buildinputs and nativebuildinputs in this file that are specifically required for my application. You will want to remove those if you copy this. Best to look at the rust-overlay flake.nix example and add lines to that as needed.