# xtc user manual (0.1.0 development build)

xtc is a bounded Linux music-making prototype. Start with a copy of an important
project and keep backups of its WAV media. Supported limits and unfinished areas
are listed in KNOWN_LIMITATIONS.md; no production/device qualification is implied.

## Build or install

Follow BUILD.md and LINUX.md. Core: `make all test`; GUI: `make gui`, then
`./build/xtc`. Use an existing JACK-compatible server and reconnect with F6.
Connect `midi_in` to a controller, `input` to mono capture and `output` /
`output_right` to left/right playback using your JACK routing application.
No server, physical routing or system configuration is changed automatically.
`xtc --version`, `xtc --help` and `xtc --diagnose` need no display/server.

For a source install stage with `make install-gui DESTDIR="$PWD/build/stage"
PREFIX=/usr`, inspect the stage, and use your normal deployment process. A user
prefix is supported (for example an absolute path to your `.local` folder).
`make uninstall` with the same DESTDIR/PREFIX removes only that version's known
files. See LINUX.md for package extraction, dependencies and removal. Never use
a release built for a different system ABI without rebuilding/testing it.

## Make a short project

1. New/Open starts in Sequencer. Add track; use F2 to name it.
2. Add MIDI clip, select it and open Piano roll (Ctrl+4). Left-click to draw
   notes, drag to move, drag a right edge to resize, Delete/right-click to remove.
3. Alternatively Import WAV (Ctrl+I). It creates/routes an Audio clips source;
   supported WAV formats and preload limits are in AUDIO_FILES.md.
4. Drag clips to arrange them and edges to trim. View/Snap sets the timeline
   grid; +/- zoom buttons and scrollbars navigate. Ctrl+D duplicates a clip after
   its end, retaining its complete source. F2 names clips; right-click offers
   duplicate/rename/delete. Alt+Up/Down with timeline focus reorders tracks.
5. Play/F5 starts; Pause/F7 or Stop/F8 leaves the position for resuming. Home
   returns to start while stopped (or stops first); click the ruler to seek.
   Recording uses Stop, not Pause. F9 Panic releases the instrument.
6. Mixer (Ctrl+2) offers track gain/pan/mute/solo and Gain/Pan automation lanes.
   Click to add points, right-click to remove. CONTROL.md explains timing and
   live CC7 volume, CC10 pan and CC64 sustain.
7. Save (Ctrl+S), close, reopen and continue editing. Ctrl+Z undoes and
   Ctrl+Shift+Z/Ctrl+Y redoes. New/Open resets history after unsaved-change handling.

Modular Graph (Ctrl+3) exposes routing. Drag output to input to connect, select a
wire/node and Delete to remove; cycles and invalid ports are rejected. Keep an
Output route for playback. GUI changes show queued/active graph status. Graph
positions are session-only; music/routing/automation are saved. Edits that prepare
new plans stop playback; disk/compilation may pause the GUI, never run in audio.

## Record and retain media

Choose a project folder and save the project there first. Record/Shift+F5 asks for
an unused WAV path. Stop finalizes the take and inserts it. Existing destinations
are protected, including a file created while recording. Undo/removing a take
removes its reference, never the recorded file. Imported external files are also
never deleted. WAVs inside the save folder become relative references; move the
folder and media together. Save As preserves the same source media, not a copy.

On write failure the GUI reports a retained path. Keep it and recover complete
frames to a different, unused destination:

```sh
xtc-check --recover-recording take.wav.tmp.XXXXXX recovered.wav
```

Only xtc's canonical float32 mono temporary format is salvaged. Incomplete trailing
frames are omitted. The source is retained. Import/relink the recovered WAV.
Missing/unreadable media is silent and reported; select the clip and use File/
Relink selected audio. See RECOVERY.md for interruption, disk-full and power-loss
limits. Close/project operations are refused while recording; finish the take first.

## Trusted effects and sources

File/Load LADSPA plugin lists compatible descriptor indices from the chosen `.so`.
Loading executes native code. Select a documented compatible mono plugin, connect
its graph ports, then use Edit/Selected plugin control. Edit/Selected plugin
automation adds/removes tick-based linear or step points. Control names/ranges
appear in the dialogs. Module identity/control values/lanes save with the project;
module binaries and DSP history do not. The initial amp/inverter/sine set and
unsupported layouts are listed in PLUGIN_HOSTING.md. Missing plugins reject GUI
Open with identity/path information and preserve the saved/current documents.
Restore the compatible module at that path and retry. Plugins are not sandboxed.

## Diagnose a problem

Run `xtc-check --diagnose` and capture the version, architecture, compiled features,
GUI error text and steps to reproduce. `xtc-check --validate song.xtc` checks
metadata without opening plugins/media; it does not certify playback resources.
Check JACK routing, sample rate/format and xrun/process status in the GUI. After
server loss/rate change stop/reconnect and retry. Keep the original project,
media and retained temporary files before recovery attempts.

A native plugin can crash/hang the process. There is no crash-isolation guarantee.
Use the operating system's core-dump/debugger tools if available; xtc does not
install signal handlers, change core limits or upload crash reports. Debugger/
core files may contain media paths and audio memory; share only what you intend.
Report bugs following MAINTENANCE.md, including whether the issue reproduces
without plugins. Physical listening and independent human install/usability
acceptance remain pending.