feat(editor): GM roll — a piano-roll layout for the drum editor

[ChrisBeWithYou]

Why

Kisscool's "no piano roll for drum MIDI" report (recorded in the dogfood handoff as a known design gap, and as view-modality open question 3) + Christian's 07-18 commitment to ship it for the nightly. Drummers arriving from DAWs read drums on General-MIDI percussion rows; the editor offered only the physical-kit piece order (Full) and the community 7-row family shape (Compact).

What

The Rows toggle gains a third density: GM roll.

• One row per piece on its canonical GM note, pitch-descending top→bottom — the piano-roll convention (57 Crash R on top, 36 Kick near the bottom, the no-GM stack sinking last). Labels carry the GM number: 38 Snare, 42 HH cl.
• Implemented exactly the way the view-modality design demands (V6: one grid, density presets, never a second data path): a new 'midi' branch in _drumLaneTablePure. Same grid, same piece-ids, same editing/selection/colors in every mode — only row order and labels change.
• DRUM_PIECE_GM defines the canonical piece→note map in drum.js (primary notes only; the pad strip's GM_DRUM_MAP keeps the 35/40/41/47/59 aliases — and importing it from there would create a drum ← drum-pad-strip cycle).
• Cycle is Full → Compact → GM roll → Full (_drumDensityNextPure); the preference round-trips 'midi' through localStorage like the existing modes; button text + status copy + User Guide updated.

Tests

drum_density.test.mjs extended — all new assertions fail on main: every piece appears exactly once; strict pitch-descending order (crash_r top, kick lowest GM row, stack last with gm: null); per-row gm agrees with the map; map hygiene (exactly the chart pieces, nothing extra); the 3-way cycle incl. junk recovery. npm test 209/209 · lint 0 errors.

Runtime verification (real host + Playwright)

Loaded a pack with a drum tab, entered the drum editor: Rows cycles Full → Compact → GM roll → Full; the GM rows render pitch-ordered with numbered labels and the fixture's hits land on their rows; the status line describes the mode; the preference persists (editorDrumDensity = midi).

🤖 Generated with Claude Code

https://claude.ai/code/session_01929LgKdJMyPGLf8N1WpEVW

Summary by CodeRabbit

• New Features

  • Added a GM roll drum-editor layout with one row per General MIDI percussion piece.
  • Rows are ordered by pitch and labeled with their GM note numbers.
  • The Rows toggle now cycles through Full, Compact, and GM roll modes.
  • The selected layout persists between sessions.

• Documentation

  • Updated the user guide and changelog with details about GM roll mode.

[coderabbitai]

Warning

Review limit reached

@ChrisBeWithYou, you've reached your PR review limit, so we couldn't start this review.

Next review available in: 38 minutes

Enable usage-based reviews in Billing to review now. Otherwise, wait until the next included review is available.
You're only billed for reviews past your plan's rate limits ($0.25/file).

How can I continue?

After more reviews become available, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

To avoid repeated limits, reduce automatic review volume by pausing incremental auto-reviews earlier, using label-based review opt-in, excluding WIP or generated PR titles, or requesting reviews manually when the PR is ready. If your team needs uninterrupted high-volume reviews, an organization admin can enable usage-based reviews.

How do review limits work?

CodeRabbit enforces per-developer PR review limits for each organization. Most developers receive the normal plan review availability.

For paid Pro and Pro+ PR reviews, CodeRabbit uses adaptive limits for sustained high-volume activity. When a developer's recent PR review activity reaches the 95th percentile or higher among CodeRabbit users, additional reviews become available more gradually as earlier reviews age out of the rolling window.

Please refer docs for additional details.

Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: b934c24d-967d-4eed-9e75-7b2152c8e05d

📥 Commits

Reviewing files that changed from the base of the PR and between 8d8dcee and 3ee0940.

📒 Files selected for processing (4)

• CHANGELOG.md
• docs/USER-GUIDE.md
• src/drum.js
• tests/drum_density.test.mjs

📝 Walkthrough

Walkthrough

The drum editor adds a persisted GM roll density mode with one General MIDI percussion piece per pitch-ordered row, GM-number labels, updated controls, documentation, changelog coverage, and tests for mapping and cycling.

Changes

Drum GM roll mode

Layer / File(s)	Summary
GM lane mapping and ordering src/drum.js, tests/drum_density.test.mjs	Adds GM note mappings and generates one midi-density lane per piece, ordered by descending pitch with stack unmapped; tests validate lane structure, ordering, and mapping coverage.
Density cycling and editor rendering src/drum.js, docs/USER-GUIDE.md, CHANGELOG.md, tests/drum_density.test.mjs	Adds full → compact → midi → full cycling, persists valid density values, renders GM labels, updates control text, and documents the GM roll mode.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant DensityButton
  participant DrumEditor
  participant LocalStorage
  DensityButton->>DrumEditor: Toggle drum density
  DrumEditor->>DrumEditor: Compute next density
  DrumEditor->>LocalStorage: Persist editorDrumDensity
  DrumEditor->>DrumEditor: Rebuild lane table and render labels

Loading

Possibly related PRs

• got-feedBack/feedBack-plugin-editor#120: Introduced the drum-grid row density system extended by this GM roll mode.
• got-feedBack/feedBack-plugin-editor#166: Established the drum lane-table and density machinery used by this feature.

Suggested reviewers: byrongamatos

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding GM roll piano-roll layout support for the drum editor.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/drum-gm-roll

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[ChrisBeWithYou]

Planned follow-up (Christian's call, 07-18): surface this in the view dropdown.

This PR puts the GM roll behind the Rows button (Full → Compact → GM roll). #316 separately turns the view switcher into a dropdown that, for drum tracks, offers Drum grid · Notation. So today a user checking the dropdown for "what layouts does this track have?" sees no piano roll, even though this PR ships one.

Once both this and #316 are merged, a small follow-up commit lands on whichever merged second: the drum dropdown becomes Drum grid · Piano roll · Notation (Piano roll = GM-roll density), while Full / Compact stay here on the Rows button — they're densities of the kit-ordered grid; GM roll is a different axis (pitch). Both controls read _drumDensityMode() so they can't drift, and returning to Drum grid restores the last non-GM density rather than resetting to Full.

Nothing to change in this PR — noting it so the two don't stay disconnected.

[ChrisBeWithYou]

Update — the follow-up landed early, in #316. Christian is merging these himself after a Codex review, which removes the merge-order risk that had me deferring this.

This PR is unchanged and still independently mergeable. #316 now has this branch merged into it and adds the unification on top: the drum dropdown becomes Drum grid · Piano roll · Notation, where Piano roll selects the GM-roll density from this PR. Full/Compact stay here on the Rows button, and both controls route through one setter so they can't drift.

Merge order: this PR first, then #316.

[coderabbitai]

🧹 Nitpick comments (1)

tests/drum_density.test.mjs (1)

106-112: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Update test description to match assertion behavior.

The test description mentions junk recovers to compact-first, but the assertion _drumDensityNextPure('banana') === 'full' verifies that junk input correctly recovers to 'full'.

♻️ Proposed fix

-t('density cycle: Full → Compact → GM roll → Full; junk recovers to compact-first', () => {
+t('density cycle: Full → Compact → GM roll → Full; junk recovers to full', () => {
     assert.strictEqual(_drumDensityNextPure('full'), 'compact');
     assert.strictEqual(_drumDensityNextPure('compact'), 'midi');

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@tests/drum_density.test.mjs` around lines 106 - 112, Update the test
description for the `_drumDensityNextPure` cycle test to state that junk input
recovers to “full,” matching the existing `'banana'` assertion. Leave the
assertions and test behavior unchanged.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@tests/drum_density.test.mjs`:
- Around line 106-112: Update the test description for the
`_drumDensityNextPure` cycle test to state that junk input recovers to “full,”
matching the existing `'banana'` assertion. Leave the assertions and test
behavior unchanged.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 57b45e27-0dc1-4ffd-90b3-3eb3d3cd6316

📥 Commits

Reviewing files that changed from the base of the PR and between 6243cf8 and 8d8dcee.

📒 Files selected for processing (4)

• CHANGELOG.md
• docs/USER-GUIDE.md
• src/drum.js
• tests/drum_density.test.mjs