Add Nix flake for out-of-the-box NixOS support#16
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zitongcharliedeng wants to merge 13 commits intoflipcoder:mainfrom
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Add Nix flake for out-of-the-box NixOS support#16zitongcharliedeng wants to merge 13 commits intoflipcoder:mainfrom
zitongcharliedeng wants to merge 13 commits intoflipcoder:mainfrom
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- flake.nix: self-contained Nix package with all Python deps (rtmidi2, launchpad-py, musicpy, mido-fix) and native MIDI virtual cable (midimech-vport) - midimech-vport.c: native C ALSA sequencer virtual MIDI cable, equivalent to loopMIDI on Windows - midimech-launch.py: launcher that starts vport + midimech - NixOS module with snd_seq_dummy blacklist for clean MIDI ports - Fix launchpad_py crash on Linux ALSA when no Launchpad connected Usage: nix run github:zitongcharliedeng/midimech#midimech Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The launcher is trivial shell glue (start vport, sleep, exec midimech). Convention: flake handles its own wrappers in installPhase. Repo now has only flake.nix, flake.lock, and midimech-vport.c as nix-related files. midimech-vport.c is real Linux source code, not nix plumbing. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Known limitation: extra "RtMidi" ports visible on LinuxOn Linux ALSA, each This is an rtmidi2/ALSA behavior, not something we can fix at the midimech level without replacing rtmidi2 with direct ALSA sequencer bindings. Functionally harmless — users just need to select the "midimech" port and ignore the RtMidi entries. |
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Note: audio glitches at very low ALSA buffer sizesAt buffer sizes below 128 samples (2.9ms), audio through ALSA/PipeWire can become distorted and glitchy under heavy polyphony. This is an ALSA + PipeWire scheduling limitation, not a midimech issue — the same behavior occurs with any MIDI source at those buffer sizes on Linux. 128 samples / 44100 Hz (2.9ms) is a solid sweet spot for low latency without artifacts. |
Installs midimech.desktop and icon so desktop environments can show midimech in their application menu. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Without this, GNOME shows a generic gear icon in alt-tab and the taskbar because it can't associate the pygame/SDL2 window with the desktop entry. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Documents nix run, nix profile install, and NixOS module usage with the recommended virtual MIDI cable setup. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Removed misleading claim that nix profile install creates desktop entries. Only the NixOS module provides full desktop integration. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The virtual MIDI cable is always started with midimech. No need for a separate binary without it. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Virtual cable starts by default (recommended). Pass --no-vport to skip it for users who manage MIDI routing themselves. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The flake is NixOS-only. The vport IS the point — it's the loopMIDI equivalent. Users who don't want it run midimech.py directly, same as on Windows/Mac. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Version was incorrectly set to 0.1.0-chromatic-quantize despite nix-support being based on main. Set SDL hints for icon matching on both Wayland and X11 backends. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Okay the icon seems to be working in alt-tab Wayland GNOME too now.
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The Python launcher (removed in b4a648e) set cwd= to the midimech directory. The inlined shell launcher did not, so scales.yaml and settings.ini were not found when launched from a .desktop file. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
GNOME desktop launches don't inherit NixOS shell environment. Without ALSA_CONFIG_PATH, rtmidi2 can't find alsa.conf, fails to create a sequencer client, and pygame segfaults on MIDI init. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
I made this to run midimech easily on my NixOS machines at home. Single command, zero manual setup:
This sets up everything automatically — Python environment, all dependencies, and a virtual MIDI cable (equivalent to loopMIDI on Windows). Been using this daily on two NixOS machines over the past few days with no issues.
What's included
flake.nix— Self-contained Nix package. Builds all Python deps from PyPI (rtmidi2, launchpad-py, musicpy, mido-fix), compiles the native MIDI virtual cable, and bundles everything into a singlemidimechcommand. Includes desktop entry with icon for GNOME/KDE.midimech-vport.c— Tiny C program that creates an ALSA sequencer virtual MIDI port named "midimech". Equivalent to loopMIDI on Windows. Started automatically when you runmidimech. Any synth (SurgeXT, etc.) subscribes to this port to receive MIDI.NixOS module — System-wide install via
services.midimech.enable = true. Installs desktop entry with icon and blacklistssnd_seq_dummyto remove the "Midi Through Port-0" phantom device.Bug fix included
Wrapped launchpad detection (
src/core.py) in try/except —launchpad_py'sCheck()/Open()calls throwRtMidiErroron Linux ALSA when the requested port index doesn't exist (on Windows WinMM it returnsFalsegracefully). This crashed midimech on any Linux system without a Launchpad connected.Tested
Smoke tested and used daily on NixOS unstable (x86_64-linux) with PipeWire + ALSA, LinnStrument → midimech → SurgeXT. Full MIDI chain working, LEDs working, no crash without Launchpad connected.
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