yellowjacket/.planning/phases/14-performance-optimization/14-03-SUMMARY.md

phase, plan, subsystem, tags, requires, provides, affects, tech-stack, key-files, key-decisions, patterns-established, requirements-completed, duration, completed

phase	plan	subsystem	tags	requires	provides	affects	tech-stack	key-files	key-decisions	patterns-established	requirements-completed	duration	completed
14-performance-optimization	03	performance	event-delegation queueMicrotask closure-elimination scroll-perf store-batching	phase provides 14-01 CSS containment and GPU scroll promotion for scroll containers	Zero per-item closure allocation during scroll rendering in track-list and queue-panel queueMicrotask notification batching in queue store changeGeneration counter in library store for granular update skipping	14-04 ui-performance	added patterns Event delegation via data-index attributes replacing per-item inline closures queueMicrotask batching for store notifications (now consistent across all stores) changeGeneration counter to skip requestUpdate on loading-only state transitions	created modified frontend/src/components/track-list/track-list.ts frontend/src/components/queue-panel/queue-panel.ts frontend/src/store/queue-store.ts frontend/src/store/library-store.ts frontend/src/store/controllers/library-controller.ts	Event delegation via data-index + closest() instead of bound-method-per-row pattern changeGeneration counter in library store instead of typed per-data subscriptions	Event delegation: attach handlers on virtualizer element, resolve item via closest + data-index Store change generation: monotonic counter for data-only changes, skip updates on loading toggles	PERF-RENDER-01 PERF-RENDER-02	4min	2026-03-14

Phase 14 Plan 03: Render & Store Optimization Summary

Event delegation eliminates per-scroll-frame closure allocation; queueMicrotask batching and changeGeneration counter reduce unnecessary re-renders

Performance

• Duration: 4 min
• Started: 2026-03-14T17:49:45Z
• Completed: 2026-03-14T17:54:13Z
• Tasks: 2
• Files modified: 5

Accomplishments

• Eliminated all inline arrow function closures from renderTrackRow (track-list) and renderTrackItem (queue-panel), removing GC pressure during rapid scrolling
• Added queueMicrotask-based notification batching to queue store, matching the library store pattern
• Added changeGeneration counter to library store so LibraryController skips requestUpdate when only loading flags toggle (no actual data change)
• Confirmed cover-grid already uses event delegation — no changes needed

Task Commits

Each task was committed atomically:

1. Task 1: Eliminate per-item closure allocation in render hot paths - 2f7ed70 (perf)
2. Task 2: Add notification batching to queue store and granular subscriptions to library store - d0c05dc (perf)

Files Created/Modified

• frontend/src/components/track-list/track-list.ts - Event delegation via data-index; removed 5 inline closures per row from renderTrackRow
• frontend/src/components/queue-panel/queue-panel.ts - Event delegation via data-index; removed 5 inline closures per item from renderTrackItem
• frontend/src/store/queue-store.ts - queueMicrotask batching for notify()
• frontend/src/store/library-store.ts - changeGeneration counter incremented on actual data changes
• frontend/src/store/controllers/library-controller.ts - Checks changeGeneration before requestUpdate

Decisions Made

• Event delegation via data-index + closest() — chosen over per-row bound method references because it requires zero function objects in renderItem, not just stable ones. The virtualizer and its children share the same shadow root so event.target.closest() works correctly.
• changeGeneration counter — chosen over typed per-data subscriptions (subscribeTo('tracks')) because it's simpler, backward-compatible, and eliminates the biggest source of unnecessary re-renders (loading flag transitions during eagerFetch cause 8+ requestUpdate calls) without requiring store API changes for existing subscribers.

Deviations from Plan

Auto-fixed Issues

1. [Rule 1 - Bug] Removed unused handleRemoveTrack method

• Found during: Task 1 (queue-panel event delegation)
• Issue: After delegating remove-button click to the virtualizer handler, the old handleRemoveTrack method became unused, causing a TypeScript error (TS6133)
• Fix: Removed the unused method; remove logic is now in onDelegatedClick which checks closest('.remove-button')
• Files modified: frontend/src/components/queue-panel/queue-panel.ts
• Verification: Build passes, pre-commit typecheck passes
• Committed in: 2f7ed70 (Task 1 commit)

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Total deviations: 1 auto-fixed (1 bug) Impact on plan: Trivial cleanup of dead code after refactoring. No scope creep.

Issues Encountered

None

User Setup Required

None - no external service configuration required.

Next Phase Readiness

• Plans 14-01, 14-02, 14-03 complete
• Ready for 14-04 (remaining rendering optimizations)

Self-Check: PASSED

All 5 modified files verified on disk. Both task commits (2f7ed70, d0c05dc) verified in git history.

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Phase: 14-performance-optimization Completed: 2026-03-14