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.

## Table of contents

- [Features](#features)
- [Design decisions](#design-decisions)
- [Current status](#current-status)
- [Build](#build)
- [Run](#run)
- [Using the GUI](#using-the-gui)
- [Documentation](#documentation)
- [Diagnostics](#diagnostics)
- [Suggested first agent task](#suggested-first-agent-task)
- [License](#license)

## Features

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

### Audio

- 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.
- 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.

### Mixing and routing

- 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).

### Plugins and instruments

- 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.
- `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.
- [Steinberg SDK integration](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](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).

### MIDI and composition

- 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.

### Editing and project workflow

- 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.
- 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).

### Engine and release

- 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.
- Effect automation/controllers, editing commands, v7 project-folder media paths, performance baselines and release/installation checks are also supported.
- 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.

## 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.
- **Optional JUCE GUI:** build `xtc-juce` with `-DXTC_BUILD_JUCE_GUI=ON -DXTC_JUCE_ROOT=/path/to/JUCE`. Keep or disable FLTK independently with `XTC_BUILD_GUI`. See [the JUCE frontend](src/gui/JUCE/README.md) for build/run instructions and SDK licensing.
- **FLTK/C++ GUI:** C++ is confined to the graphical interface and calls the core through a C API. The sequencer coordinates nested ruler, track, header, clip and velocity widgets; see [GUI ownership](docs/ARCHITECTURE.md#sequencer-widget-ownership).
- **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 default optional GUI needs C++17 and FLTK; a separately selectable JUCE frontend uses an external JUCE SDK; 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 -DXTC_BUILD_JUCE_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

Run the GUI:

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

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

Clean generated files:

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

## Using the GUI

- 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.
- Click the small arrow beside a track name to expand its MIDI velocity lane downward. Drag a note bar’s cap vertically to set velocity (1–127); Escape cancels and Ctrl+Z undoes. Click the arrow again to collapse. See the [expanded-track screenshot](screenshots/track-velocity-expanded.png).
- Audio tracks open an **audio velocity** level envelope in the same lane. Click anywhere to add a gain point (0–400%), drag a point vertically to adjust it, or right-click its cap to remove it. Positions are independent of the snap grid; Escape cancels and undo/redo is supported. This is the track’s saved gain automation, shared with the mixer. See the [audio envelope screenshot](screenshots/audio-velocity-expanded.png).
- 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.

## Documentation

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.

## Diagnostics

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.

## 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.

## Authors

- Johannes Findeisen <you@hanez.org> — Core developer and Founder

For a song that needs no MIDI hardware, media or plugins, open the
[playback test example](examples/projects/README.md#playback-test).

## License

The project is scaffolded under the MIT License; see `LICENSE`. Review the licenses of any future dependencies before distribution. See also [docs/LICENSES.md](docs/LICENSES.md).