xtc/README.md

# xtc — a lightweight, modular DAW

`xtc` is a new, energyXT-inspired digital audio workstation project. It is not a clone and contains no energyXT source code or assets.

![xtc promotional overview: arrangement, piano roll, mixer and modular effects](screenshots/overview.png)

## Design decisions

- **Modular engine first:** sequencer, instruments, effects, mixers and I/O are nodes in one processing graph.
- **C core:** project model, graph, DSP and audio engine are implemented in C.
- **FLTK/C++ GUI:** C++ is confined to the graphical interface and calls the core through a C API.
- **Linux first:** keep backend-specific details behind an interface.
- **Small increments:** build and test each milestone before adding features.

## Current status

This repository is a starter scaffold, not a production DAW. It currently provides:
- a small C library/API;
- a mono graph model with port validation, cycle rejection and topological ordering;
- compiled offline plans with preallocated buffers, sine oscillator, audio source, gain, meter and output nodes;
- C tests for deterministic rendering, routing, validation and lifecycle;
- an optional JACK-compatible backend with mono input and mono/stereo output with start/stop, routing and status;
- safe control/audio plan handoff and concurrent replacement tests;
- an optional FLTK shell with engine controls, view switching and backend status;
- a modular graph editor with transactional edits and live plan adoption status;
- versioned project save/load and a timeline for tracks and clips;
- sample-counted transport, selection, move/trim, timeline zoom and scrolling;
- WAV import/graph playback, bounded recording and missing-asset relinking;
- MIDI clips, a sine instrument, JACK MIDI input and a basic piano roll;
- stereo track/bus gain/pan/mute/solo, dBFS peak meters and gain/pan automation lanes;
- bounded undo/redo with keyboard shortcuts;
- configurable boundary fades, gain ramps and graceful GUI playback transitions;
- native C processors, deterministic source packaging and staged install/uninstall;
- architecture, format, GUI, roadmap, and decision documents.

The JACK backend has passed software-loopback testing; physical-device playback
and capture are unverified. MIDI recording remains deferred. Bounded LADSPA
hosting supports the compatible mono processors documented in
[PLUGIN_HOSTING.md](docs/PLUGIN_HOSTING.md).

## Build

Requirements: CMake 3.25+, a C99 compiler, Python 3.12+ and a build backend
such as Ninja or Unix Makefiles. The optional GUI needs C++17 and FLTK; JACK and
LADSPA development files enable their optional integrations.

```sh
cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug
cmake --build build --parallel
ctest --test-dir build --output-on-failure
```

For quick development, the optional Make wrapper provides the same workflow:

```sh
make          # configure and build
make test     # build and run CTest
make gui      # build just the FLTK application
make run      # build and launch it
make clean    # clean products; keep the CMake cache
```

Override `BUILD_DIR`, `BUILD_TYPE` or `JOBS` as needed, for example
`make BUILD_DIR=build/release BUILD_TYPE=Release JOBS=8`. Pass additional options
with `CMAKE_ARGS` and `CTEST_ARGS`. CMake remains the authoritative build system.

This builds `libxtc.a`, the headless `xtc-check`, tests, examples and the FLTK
application when available. Live JACK tests are opt-in. Use `-DXTC_BUILD_GUI=OFF`
for the C-only build, or the `debug`, `release`, `minimal` and `sanitize` presets
for separate configurations. See [docs/BUILD.md](docs/BUILD.md) for options,
focused tests, installation and IDE setup. [Phase 108](docs/ROADMAP.md#phase-108--complete-cmake-build-migration) records
the CMake migration.

Run the GUI:

```sh
./build/xtc
```

See [the minimal music-making workflow](docs/WORKFLOW.md) for creating, saving,
reopening and playing a project.

The GUI opens JACK and offers Play/Pause/Stop/To start/Reconnect, backend status and view
switching. The initial empty graph is silent. Modular Graph supports adding,
moving and deleting oscillator/audio/instrument/gain/meter/output nodes and connecting ports.
Import WAV (Ctrl+I) creates playable clips; Add region creates silent placeholders.
Record captures JACK input to a chosen WAV; Stop finalizes and adds the take.
Save the project after recording. External asset paths must remain available;
select a missing clip and use File/Relink selected audio to repair it.
Add MIDI clip on an existing track, then open Piano roll (or Ctrl+5 for the selected track) to draw notes.
Connect a MIDI source to the JACK `midi_in` port for live playing; Panic/F9
silences held notes. See [MIDI workflow and limits](docs/MIDI.md).
See [audio workflow and limits](docs/AUDIO_FILES.md) and the
[sample editor workflows](docs/AUDIO_EDITOR.md).
Mixer (Ctrl+2) selects a track for gain/pan/mute/solo and automation editing.
Ctrl+Z undoes; Ctrl+Shift+Z or Ctrl+Y redoes up to 32 edits.
The GUI now exposes left `output` and `output_right` JACK ports; route both
explicitly for stereo. See [mixer workflow and limits](docs/MIXER.md).
Use Add track/Add region, drag regions or their edges, and Zoom +/-; scrollbars pan.
Ctrl+N/O/S creates, opens or saves a project; Save As chooses another path.
Arrangement edits stop playback; graph edits remain live.
The ruler seeks while stopped. Stop pauses; Reconnect and project load reset position. F5 starts, F8 stops, Space toggles, F6 reconnects, and Ctrl+1/2/3
switches views. Ctrl+Q closes the client and window. No physical ports are
connected automatically. In Modular Graph, drag output to input to connect;
select a node or wire and press Delete to remove it. Invalid edits leave the
active graph intact; queued changes are labeled until the engine adopts them.
See [GUI documentation](docs/GUI.md).
For Linux installation, routing and CLI options see [LINUX.md](docs/LINUX.md);
for native effects/instruments see [NATIVE_API.md](docs/NATIVE_API.md).
The release preset and CMake’s `dist`, `test-install`, `test-release` and
`test-package` targets provide release preparation; see
[RELEASING.md](docs/RELEASING.md) for exact guarantees.
With JACK development files and an existing JACK-compatible server, configure
with `-DXTC_ENABLE_LIVE_TESTS=ON`, build, and run
`ctest --test-dir build --output-on-failure -L live`. These software-loopback
checks connect only test clients. See [engine documentation](docs/AUDIO_ENGINE.md)
for configuration, routing, ownership and recovery.

Clean generated files:

```sh
cmake --build build --target clean
```

## Suggested first agent task

Read `AGENT.md` and `docs/ARCHITECTURE.md`. Inspect the existing implementation, run `cmake --build build --target check`, and report gaps before adding the next feature. Do not jump directly to plugin hosting or a full sequencer.

## License

The project is scaffolded under the MIT License; see `LICENSE`. Review the licenses of any future dependencies before distribution.

Audio timing, transitions, latency limits and listening previews are described
in [docs/AUDIO_QUALITY.md](docs/AUDIO_QUALITY.md). Human listening acceptance
of the transitions remains pending.

The engine adds no-clobber recording/recovery, parameterized native C processors,
and trusted in-process LADSPA hosting with persisted identity/control values.
See [RECOVERY.md](docs/RECOVERY.md), [NATIVE_API.md](docs/NATIVE_API.md) and
[PLUGIN_HOSTING.md](docs/PLUGIN_HOSTING.md) for commands and limits.

For everyday use see [USER_MANUAL.md](docs/USER_MANUAL.md),
[KNOWN_LIMITATIONS.md](docs/KNOWN_LIMITATIONS.md) and
[MAINTENANCE.md](docs/MAINTENANCE.md). `xtc-check --diagnose` reports build features;
`cmake --build build --target test-package` checks a local system-linked Linux binary archive.
Effect automation/controllers, editing commands, v7 project-folder media paths,
performance baselines and release/installation checks are also supported.

Non-destructive audio splitting, clip gain/fades and cached timeline waveforms
are supported, with undo and v8 persistence (reading v1–v7). See
[AUDIO_FILES.md](docs/AUDIO_FILES.md#non-destructive-clip-editing).
`cmake --build build --target test-audio-editing` checks source preservation and exact boundary output.
Time stretching and independent pitch shifting remain deferred.

Signal-flow graph layout, routing diagnostics, direction/role indicators and
atomic unity-gain insertion into a wire are supported. See
[ROUTING.md](docs/ROUTING.md); `cmake --build build --target test-routing` verifies the C routing contract.

One-level mix buses, routing, coherent track/bus peaks and master clipping
indicators are supported, persisted in v9 (reading v1–v8). See [MIXER.md](docs/MIXER.md).

LADSPA descriptor browsing, an identity/parameter editor with reset,
transactional replacement and insertion into graph wires are supported. See
[PLUGIN_HOSTING.md](docs/PLUGIN_HOSTING.md) for compatibility and lifecycle limits.

Common parameter targets, Linear/Hold mixer automation and saved per-channel
live MIDI CC bindings are supported. Project v10 reads v1–v9. See
[CONTROL.md](docs/CONTROL.md) for timing, precedence and qualification limits.

Undo storage is reserved before edits/publication, completed takes are grouped,
surviving editor selections are preserved and context menus/focus feedback are
improved. See [EDITING.md](docs/EDITING.md) for the workflow audit and failure
boundaries.

Project troubleshooting: `xtc-check --validate PROJECT.xtc` reports metadata
errors with the expected record and syntax line. `xtc-check --inspect PROJECT.xtc`
lists resolved media/module paths and plugin identities without executing plugins
or starting JACK. Exit codes: 0 = valid metadata and available files, 2 = missing
or unreadable references, 1 = metadata/I/O error. File availability does not
certify WAV contents or plugin compatibility. See [PROJECT_FORMAT.md](docs/PROJECT_FORMAT.md)
for the compatibility and relocation policy.

**File → Load plugin** supports LADSPA plus an initial Linux
CLAP/VST2/VST3 effect subset. Select the actual module binary (`.clap` or `.so`,
including a VST3 bundle's inner binary). Modern effects require one mono input
and output, float32 and zero latency; they use default configuration. Instruments,
modern parameter editing/automation, opaque state and custom editors are not
implemented. Projects now save v11 and read v1–v11. See PLUGIN_HOSTING.md for the
full contract and test/qualification limits.


A compact sequencer Create menu, optional track inspector and per-track modular
effect chains are supported. Open **View → Track inserts** (or Ctrl+5 for the selected track) to add,
search, reorder, bypass, inspect and mix mono LADSPA/VST2/VST3/CLAP effects or
internal devices. Chains support undo, presets, audio/MIDI rendering and export.
Projects save format 17 and read formats 1–17. See
[track insert workflows and limits](docs/TRACK_INSERTS.md) and the
[screenshot gallery](screenshots/README.md).

Direct selected-track inserts, effect duplication, chain copy/
paste, A/B snapshots, three internal effect templates, bulk rack actions, insert
peak meters, tap tempo, audio crossfades and MIDI chord strumming are supported. See
[creative workflows and limits](docs/CREATIVE_WORKFLOWS.md).

MIDI devices and defaults are configurable in **Preferences → midi**, including
JACK/PipeWire input/output choices, channel filtering and optional thru. Use
**File → Import MIDI** or **Export selected clip as MIDI** to exchange note clips.
Application preferences load from **`~/.xtc.conf`** at startup and save on Apply
and clean exit. See [configuration and MIDI workflows](docs/MIDI_WORKFLOWS.md)
for file support, routing and persistence details.


[Steinberg SDK integration (Phase 106)](docs/STEINBERG.md) adds conventional Linux
VST3 bundle loading, transport context, official-SDK gain/synth examples and
validator checks. Run `cmake -S . -B build -DXTC_VST3_SDK_ROOT=/path/to/vst3sdk -DXTC_BUILD_STEINBERG=ON && cmake --build build --target test-steinberg-sdk`
for optional SDK qualification. A Windows ASIO device diagnostic is provided;
a native ASIO playback/capture backend remains planned.

[JUCE integration (Phase 107)](docs/JUCE.md) provides an optional VST3/standalone
Soft Keys instrument with a native editor, DSP effects, presets, MIDI-to-WAV
rendering and VST3 hosting examples. Build and qualify it with
`cmake -S . -B build -DXTC_JUCE_ROOT=/path/to/JUCE -DXTC_BUILD_JUCE=ON && cmake --build build --target test-juce`; review JUCE’s AGPLv3/commercial licence
before distributing linked binaries. See [the examples](examples/juce/README.md).