feat(editor): toggleable follow-playhead (Shift+L)

[ChrisBeWithYou]

Roadmap 2.3 (parity cluster). The other 2.3 items — seek-to-note / next-prev note/beat/grid/anchor — already shipped in the earlier waves; this adds the missing follow toggle.

What

The playback auto-scroll (view jumps once the playhead crosses 80% of the window, landing it at 30%) was unconditional. It''s now gated on a follow pref — default ON, behavior unchanged — so an author can pin the view on one passage and keep editing while the song plays on. New registry command toggleFollow, bound Shift+L in both FeedBack Native and EOF Legacy profiles (collision-checked). Editor pref only, never pack data. The scroll policy math moves into a @pure:follow-scroll block.

Tests

tests/follow_toggle.test.js: the 80%-trigger/30%-landing policy pinned exactly, the at-threshold non-trigger, and the follow-off null (fails on main, where the scroll is unconditional). Full JS suite: 42 files green.

Fresh region vs the open queue — playbackTick''s scroll block + registry rows only.

🤖 Generated with Claude Code

https://claude.ai/code/session_01JEoFeTPSnz4NpwwCG52hnu

Summary by CodeRabbit

• New Features

  • Added a Follow-playhead editor preference controlled via Shift+L to toggle auto-follow during playback.

• Bug Fixes

  • Playback auto-scrolling is no longer unconditional; it now follows the configured setting (defaults to on) and only applies after the trigger point.

• Tests

  • Added tests covering follow-enabled vs follow-disabled scrolling behavior, including threshold and scroll target expectations.

• Documentation

  • Updated the Unreleased changelog entry for the new preference/shortcut.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a Shift+L follow-playhead toggle. Playback auto-scroll now depends on a persisted editor preference that defaults on, with a test covering the scroll target behavior and a changelog update.

Changes

Follow-playhead toggle

Layer / File(s)	Summary
Shortcut registration and dispatch screen.js	Adds toggleFollow shortcut registration, maps Shift+L in two key handlers, and routes the action to _editorToggleFollow().
Follow-gated playback auto-scroll screen.js, tests/follow_toggle.test.js, CHANGELOG.md	Adds follow-aware scroll targeting, localStorage-backed preference persistence, status text updates for toggle state, a test for enabled/disabled follow behavior, and a changelog entry for the new preference.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• got-feedBack/feedBack-plugin-editor#83: Also updates keyboard shortcut and action wiring in screen.js, with similar key-mapping and dispatcher changes.

🚥 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 summarizes the main change: a toggleable editor follow-playhead feature bound to Shift+L.
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 docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/editor-follow-toggle

Warning

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🔧 ast-grep (0.44.1)

screen.js

ast-grep timed out on this file

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[coderabbitai]

🧹 Nitpick comments (1)

tests/follow_toggle.test.js (1)

16-24: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Fragile regex+eval extraction for the pure block.

Extracting _followScrollTargetPure via regex on comment markers and evaluating with new Function is brittle — reformatting the @pure:follow-scroll markers or block whitespace in screen.js would silently break this test's ability to locate/eval the function. Consider having screen.js export the pure function (e.g., conditional module.exports for Node) and require it directly instead.

♻️ Suggested direction (screen.js side)

+if (typeof module !== 'undefined' && module.exports) {
+  module.exports = { _followScrollTargetPure };
+}

// tests/follow_toggle.test.js
const { _followScrollTargetPure } = require('../screen.js');

🤖 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/follow_toggle.test.js` around lines 16 - 24, The current test setup in
follow_toggle.test.js is brittle because it locates _followScrollTargetPure by
regexing the `@pure`:follow-scroll markers in screen.js and then evaluating the
block with new Function. Update screen.js to expose _followScrollTargetPure as a
normal export for Node so the test can load it directly with require, and remove
the marker-based extraction logic from the test while keeping the existing
function name and 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/follow_toggle.test.js`:
- Around line 16-24: The current test setup in follow_toggle.test.js is brittle
because it locates _followScrollTargetPure by regexing the `@pure`:follow-scroll
markers in screen.js and then evaluating the block with new Function. Update
screen.js to expose _followScrollTargetPure as a normal export for Node so the
test can load it directly with require, and remove the marker-based extraction
logic from the test while keeping the existing function name and behavior
unchanged.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: a46318cb-9ccd-41d8-b803-d9c13ee3ed9d

📥 Commits

Reviewing files that changed from the base of the PR and between 2d8f56a and 2119566.

📒 Files selected for processing (3)

• CHANGELOG.md
• screen.js
• tests/follow_toggle.test.js

✅ Files skipped from review due to trivial changes (1)

• CHANGELOG.md

🚧 Files skipped from review as they are similar to previous changes (1)

• screen.js

[byrongamatos]

@coderabbitai Thanks — skipping the module.exports suggestion on this one. The @pure-block regex + new Function extraction is the established convention across all 47 test files in this repo (scroll_bounds, eof_shortcuts, audio_mixer, …), and screen.js is intentionally a single browser IIFE with zero module.exports by design. Adding a Node export just for this one function would be inconsistent with the codebase and break the single-IIFE contract. The marker-based extraction is deliberately uniform, so keeping it consistent here is the lower-risk choice.

[coderabbitai]

Tip

For best results, initiate chat on the files or code changes.

@byrongamatos Understood, that makes sense — thanks for the context. Given screen.js is intentionally a single browser IIFE and the @pure:... marker + new Function extraction pattern is the uniform convention across all test files in this repo, adding a one-off module.exports here would indeed be inconsistent. Withdrawing that suggestion.

(⁀ᗢ⁀) noted for future reviews

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✏️ Learnings added

Learnt from: byrongamatos
URL: https://github.com/got-feedBack/feedBack-plugin-editor/pull/113

Timestamp: 2026-07-07T23:04:25.521Z
Learning: In this repository (feedBack-plugin-editor), `screen.js` is intentionally a single browser IIFE with zero `module.exports` by design. Tests extract pure functions from it using an `pure:<name>` marker-comment block convention parsed via regex and evaluated with `new Function`, rather than via `module.exports`. This marker-based extraction convention is used uniformly across all test files in the repo (e.g., `scroll_bounds`, `eof_shortcuts`, `audio_mixer`, `follow_toggle`). Do not suggest adding `module.exports` to `screen.js` for testability; instead expect/require the `pure:<name>` block convention for newly extracted pure functions.

Note: Learnings are effective only in the context of similar code segments. To apply general coding guidelines, please configure review instructions. You can manage existing learnings in the app.