Add Nix flake for out-of-the-box NixOS support

.gitignore

@@ -6,3 +6,4 @@ midimech.spec
 build/
 dist/
 .idea/
+result

README.md

@@ -83,6 +83,38 @@ After downloading, make sure to follow the instructions under `Setup`.
 
 *Note: These builds are not always up to date.*
 
+### NixOS / Nix
+
+The included Nix flake handles everything automatically — Python environment, all dependencies, and a virtual MIDI cable (equivalent to loopMIDI on Windows).
+
+**Try it (no install):**
+```
+nix run github:flipcoder/midimech
+```
+
+**NixOS module (recommended):**
+
+Add to your `flake.nix` inputs:
+```nix
+midimech.url = "github:flipcoder/midimech";
+```
+
+Then in your NixOS configuration:
+```nix
+{ midimech, ... }:
+{
+  imports = [ midimech.nixosModules.default ];
+  services.midimech.enable = true;
+}
+```
+
+This installs midimech system-wide with:
+- Desktop entry with icon (shows in GNOME, KDE, etc.)
+- Virtual MIDI cable — equivalent to loopMIDI on Windows, started automatically
+- Removes the "Midi Through" phantom MIDI port (`snd_seq_dummy`)
+
+Point your DAW/synth (e.g. SurgeXT) at the **midimech** MIDI input to receive notes.
+
 ### Mac, Linux, and Running from Git
 
 - Download the project by typing the following commands in terminal:

flake.nix

@@ -0,0 +1,209 @@
+{
+  description = "Midimech - Isomorphic musical layout engine for LinnStrument and Launchpad X";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      system = "x86_64-linux";
+      pkgs = import nixpkgs { inherit system; };
+      python = pkgs.python312;
+
+      # --- Custom Python packages not in nixpkgs ---
+
+      # rtmidi2: Cython wrapper around RtMidi C++ library.
+      # Uses pre-built manylinux wheel + autoPatchelfHook since no sdist is published.
+      rtmidi2 = python.pkgs.buildPythonPackage rec {
+        pname = "rtmidi2";
+        version = "1.4.1";
+        format = "wheel";
+        src = pkgs.fetchurl {
+          url = "https://files.pythonhosted.org/packages/cc/08/e426f1a8dae34acb8a13a0eca47970a78955a0c00395efe89a94ef04ad49/rtmidi2-1.4.1-cp312-cp312-manylinux_2_17_x86_64.manylinux2014_x86_64.whl";
+          hash = "sha256:2270b773302806209eb3aec341156ef841e2f5ea7a83f5b242311d0da1df3a76";
+        };
+        nativeBuildInputs = [ pkgs.autoPatchelfHook ];
+        buildInputs = [
+          pkgs.alsa-lib
+          pkgs.libjack2
+          pkgs.stdenv.cc.cc.lib  # libstdc++
+        ];
+        pythonImportsCheck = [ "rtmidi2" ];
+      };
+
+      # launchpad-py: Pure Python Novation Launchpad control suite
+      launchpad-py = python.pkgs.buildPythonPackage rec {
+        pname = "launchpad-py";
+        version = "0.9.1";
+        pyproject = true;
+        src = python.pkgs.fetchPypi {
+          pname = "launchpad_py";
+          inherit version;
+          hash = "sha256:9c70885a9079d9960a066515f4b83727e7c475543da8ef68786f00a8ef10727c";
+        };
+        build-system = [ python.pkgs.setuptools ];
+        dependencies = [ python.pkgs.pygame-ce ];
+        pythonImportsCheck = [ "launchpad_py" ];
+        doCheck = false;
+      };
+
+      # mido-fix: Fork of mido (MIDI Objects), required by musicpy
+      mido-fix = python.pkgs.buildPythonPackage rec {
+        pname = "mido-fix";
+        version = "1.2.12";
+        pyproject = true;
+        src = python.pkgs.fetchPypi {
+          pname = "mido_fix";
+          inherit version;
+          hash = "sha256:8ce7ad87f847de36c7dd3048876581113c4d83367d1f392e5a7a9f9562b3374e";
+        };
+        build-system = [ python.pkgs.setuptools ];
+        pythonImportsCheck = [ "mido_fix" ];
+        doCheck = false;
+      };
+
+      # musicpy: Music programming language / theory library
+      # musicpy declares mido-fix + dataclasses as deps; midimech only uses
+      # musicpy for chord analysis (not MIDI I/O), so we skip the runtime
+      # deps check and provide pygame-ce which musicpy actually imports.
+      musicpy = python.pkgs.buildPythonPackage rec {
+        pname = "musicpy";
+        version = "7.11";
+        pyproject = true;
+        src = python.pkgs.fetchPypi {
+          inherit pname version;
+          hash = "sha256:7957971dc1be5b310a83253acd8dd8d3ce803ba47f67d88603904667badde993";
+        };
+        build-system = [ python.pkgs.setuptools ];
+        dependencies = [ python.pkgs.pygame-ce mido-fix ];
+        pythonImportsCheck = [ "musicpy" ];
+        dontCheckRuntimeDeps = true;
+        doCheck = false;
+      };
+
+      # --- Python environment with all deps ---
+
+      pythonEnv = python.withPackages (ps: [
+        ps.pygame-ce
+        ps.pygame-gui
+        ps.pyglm
+        rtmidi2
+        launchpad-py
+        musicpy
+        ps.pyyaml
+        ps.webcolors
+      ]);
+
+      runtimeLibs = pkgs.lib.makeLibraryPath [
+        pkgs.SDL2
+        pkgs.SDL2_image
+        pkgs.SDL2_mixer
+        pkgs.SDL2_ttf
+        pkgs.alsa-lib
+        pkgs.libjack2
+      ];
+
+    in {
+      packages.${system} = {
+        midimech = pkgs.stdenv.mkDerivation {
+          pname = "midimech";
+          version = "0.1.0";
+          src = self;
+
+          nativeBuildInputs = [ pkgs.makeWrapper pkgs.pkg-config ];
+          buildInputs = [ pythonEnv pkgs.alsa-lib ];
+
+          buildPhase = ''
+            # Compile the native MIDI virtual cable (zero-overhead loopMIDI equivalent)
+            cc -O2 -Wall $(pkg-config --cflags --libs alsa) \
+              midimech-vport.c -o midimech-vport
+          '';
+
+          installPhase = ''
+            mkdir -p $out/share/midimech $out/bin
+            cp -r . $out/share/midimech/
+
+            # Install the native MIDI virtual cable
+            install -m755 midimech-vport $out/bin/midimech-vport
+
+            # Main entry point: starts virtual MIDI cable + midimech
+            cat > $out/bin/midimech <<LAUNCHER
+            #!/bin/sh
+            cleanup() { kill "\$VPORT_PID" 2>/dev/null; wait "\$VPORT_PID" 2>/dev/null; }
+            trap cleanup EXIT INT TERM
+            $out/bin/midimech-vport &
+            VPORT_PID=\$!
+            sleep 0.3
+            cd $out/share/midimech
+            exec ${pythonEnv}/bin/python3 $out/share/midimech/midimech.py "\$@"
+            LAUNCHER
+            chmod +x $out/bin/midimech
+            patchShebangs $out/bin/midimech
+
+            # Wrap to include runtime libraries + set window class for desktop icon matching
+            wrapProgram $out/bin/midimech \
+              --prefix LD_LIBRARY_PATH : "${runtimeLibs}" \
+              --set ALSA_CONFIG_PATH "${pkgs.alsa-lib}/share/alsa/alsa.conf" \
+              --set SDL_VIDEO_WAYLAND_WMCLASS midimech \
+              --set SDL_VIDEO_X11_WMCLASS midimech \
+              --set SDL_APP_ID midimech
+
+            # Desktop entry for application launchers
+            mkdir -p $out/share/applications $out/share/icons/hicolor/256x256/apps
+            cp $out/share/midimech/icon.png $out/share/icons/hicolor/256x256/apps/midimech.png
+            cat > $out/share/applications/midimech.desktop <<DESKTOP
+            [Desktop Entry]
+            Name=Midimech
+            Comment=Isomorphic musical layout engine for LinnStrument and Launchpad X
+            Exec=$out/bin/midimech
+            Icon=midimech
+            Terminal=false
+            Type=Application
+            Categories=Audio;Music;Midi;
+            StartupWMClass=midimech
+            DESKTOP
+
+          '';
+
+          meta = with pkgs.lib; {
+            description = "Isomorphic musical layout engine for LinnStrument and Launchpad X";
+            homepage = "https://github.com/zitongcharliedeng/midimech";
+            license = licenses.mit;
+            platforms = [ "x86_64-linux" ];
+          };
+        };
+
+        default = self.packages.${system}.midimech;
+      };
+
+      apps.${system}.default = {
+        type = "app";
+        program = "${self.packages.${system}.midimech}/bin/midimech";
+      };
+
+      # NixOS module: installs midimech system-wide with clean MIDI setup.
+      #
+      # Usage in your NixOS config:
+      #   imports = [ midimech-flake.nixosModules.default ];
+      #   services.midimech.enable = true;
+      nixosModules.default = { config, lib, ... }:
+        let
+          cfg = config.services.midimech;
+        in {
+          options.services.midimech = {
+            enable = lib.mkEnableOption "midimech isomorphic MIDI layout engine";
+          };
+
+          config = lib.mkIf cfg.enable {
+            environment.systemPackages = [
+              self.packages.${system}.midimech
+            ];
+
+            # Remove the "Midi Through" phantom port that clutters MIDI device lists.
+            # midimech provides its own virtual MIDI cable; snd_seq_dummy is redundant.
+            boot.blacklistedKernelModules = [ "snd_seq_dummy" ];
+          };
+        };
+    };
+}

midimech-vport.c

@@ -0,0 +1,73 @@
+/*
+ * midimech-vport: Zero-overhead virtual MIDI cable for ALSA sequencer.
+ *
+ * Creates a single ALSA sequencer port named "midimech" that acts as a
+ * pass-through: any MIDI written to it is forwarded to all subscribers.
+ *
+ * This replaces the Python rtmidi2 callback approach, eliminating GIL
+ * overhead and providing jitter-free MIDI forwarding at any buffer size.
+ *
+ * Equivalent to loopMIDI on Windows.
+ */
+
+#include <alsa/asoundlib.h>
+#include <signal.h>
+#include <stdio.h>
+
+static volatile int running = 1;
+
+static void on_signal(int sig) {
+    (void)sig;
+    running = 0;
+}
+
+int main(void) {
+    snd_seq_t *seq;
+    int err;
+
+    err = snd_seq_open(&seq, "default", SND_SEQ_OPEN_DUPLEX, 0);
+    if (err < 0) {
+        fprintf(stderr, "Cannot open ALSA sequencer: %s\n", snd_strerror(err));
+        return 1;
+    }
+
+    snd_seq_set_client_name(seq, "midimech");
+
+    /* Create a single port with both read and write capabilities.
+     * - WRITE + SUBS_WRITE: midimech.py can send MIDI here
+     * - READ + SUBS_READ: SurgeXT (or any synth) can subscribe to receive MIDI
+     */
+    int port = snd_seq_create_simple_port(seq, "midimech",
+        SND_SEQ_PORT_CAP_WRITE | SND_SEQ_PORT_CAP_SUBS_WRITE |
+        SND_SEQ_PORT_CAP_READ  | SND_SEQ_PORT_CAP_SUBS_READ,
+        SND_SEQ_PORT_TYPE_MIDI_GENERIC | SND_SEQ_PORT_TYPE_APPLICATION);
+
+    if (port < 0) {
+        fprintf(stderr, "Cannot create port: %s\n", snd_strerror(port));
+        snd_seq_close(seq);
+        return 1;
+    }
+
+    fprintf(stderr, "[midimech-vport] Virtual MIDI cable 'midimech' ready (port %d)\n", port);
+
+    signal(SIGINT, on_signal);
+    signal(SIGTERM, on_signal);
+
+    /* Event loop: read incoming MIDI events, forward to all subscribers */
+    snd_seq_event_t *ev;
+    while (running) {
+        err = snd_seq_event_input(seq, &ev);
+        if (err < 0) {
+            if (err == -EAGAIN) continue;
+            break;
+        }
+
+        snd_seq_ev_set_source(ev, port);
+        snd_seq_ev_set_subs(ev);
+        snd_seq_ev_set_direct(ev);
+        snd_seq_event_output_direct(seq, ev);
+    }
+
+    snd_seq_close(seq);
+    return 0;
+}