34 lines
3.0 KiB
Markdown
34 lines
3.0 KiB
Markdown
# P2 · arrangement, render, agent
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P2 turns the loop into a thing that can be played, rendered and performed with an agent. It is delivered in three slices.
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## P2a · the arrangement
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Four 2-bar sections (A–D) form an 8-bar loop. Each section is a full `Pattern` (5 rows × 16 steps, with per-row faces). The engine walks 64 steps, picks the section and the pattern step, and triggers the section's rows; the bar clock runs 1–8. The state carries `arrangement: [Pattern; 4]`, `active_section`, and `pattern` = the active section for the editors.
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Commands: `select_section { index }`, `clear_section { index }`, `copy_section { from, to }`, event `arrangement { sections, active }`. Pattern edits apply to the active section. Select is persisted but not undoable; clear/copy push history. Sections, the active index and their history are stored in SQLite (`arrangement`, `active_section` columns, migrated with `ensure_column`) and restored on load.
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Surface: the quarry gets a section strip (A–D with note counts, copy →, clear); the pattern grid edits the active section. The descent draws the 64-step road, bar labels 01–08, section seams and letters A–D, with the active section emphasized; the playhead follows the 8-bar clock.
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Verification:
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- `cargo test -p zhila-core arrangement`: sections independent, select/copy/clear, undo, material carries four sections, loop_bars = 8.
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- `node scripts/persistence-smoke.mjs`: imports, edits section B, copies A→C, cuts, restarts, verifies the arrangement, active B, B's step 0 = 0, C = A, and undo/redo.
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- `npm --prefix ui run arrangement-smoke`: four sections, select B, edit a step, switch to the nave, play, screenshot `preview-p2-arrangement.png`.
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Limits: exactly four sections of two bars; no insert/reorder/length; select is not undoable; no per-section mute.
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## P2b · render
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`zhila_engine::render_arrangement(RenderRequest)` drives the same `AudioState` offline: no cpal device, the same voices, sample faces, gains, master and the 8-bar sections, plus a 1.5 s tail. `Command::render` is intercepted by the host, rendered in `spawn_blocking`, written with `hound` as 48 kHz stereo 32-bit float to `<project>/renders/<project>-<ms>.wav`, and announced with `Event::rendered { path, duration_sec }`; the command result is the unchanged state. Render is not a project edit and does not push history.
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Surface: `render` in the top rail; the wire logs the send and the `rendered` path; the button's title keeps the last path.
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Verification: `cargo test -p zhila-engine` (non-silent 16.5 s buffer, correct frame count); `node scripts/render-smoke.mjs` (status 16.5 s, peak 0.442, 6.3 MB, float 48 kHz stereo, event duration matches); `npm --prefix ui run render-ui-smoke` (button → wire path, screenshot `preview-p2-render.png`).
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Limits: WAV only, stereo float, fixed 48 kHz and 1.5 s tail; no stems, normalisation or section ranges.
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## P2c · agent (next)
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An in-app LLM agent on the same verbs, with state/sound context and approval for project edits.
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