---
phase: 08-frontend-performance-ux
plan: 02
subsystem: ui
tags: [lit, virtualizer, repeat-directive, dom-recycling, performance]

# Dependency graph
requires:
  - phase: 08-frontend-performance-ux
    provides: "Phase context with virtualizer component analysis"
provides:
  - "All 7 lit-virtualizer instances use repeat() with stable keys for efficient DOM reuse"
  - "Keyed rendering: FilePath (tracks), album.ID (covers), QueueTrack.id (queue), artist.ID (artists), genre.name (genres)"
affects: [08-frontend-performance-ux]

# Tech tracking
tech-stack:
  added: []
  patterns: ["repeat() directive with stable keys on all lit-virtualizer instances"]

key-files:
  created: []
  modified:
    - frontend/src/components/track-list/track-list.ts
    - frontend/src/components/queue-panel/queue-panel.ts
    - frontend/src/components/cover-grid/cover-grid.ts
    - frontend/src/components/artists-view/artists-view.ts
    - frontend/src/components/genres-view/genres-view.ts

key-decisions:
  - "Inline album.ID key in repeat() calls instead of keeping gridKeyFunction method"
  - "Use genre.name (lowercase) as key matching Genre interface, not genre.Name from plan"

patterns-established:
  - "Virtualizer pattern: always use repeat() with stable entity key as child of lit-virtualizer, keep .items for sizing"

requirements-completed: [PERF-05, UX-02]

# Metrics
duration: 3min
completed: 2026-03-05
---

# Phase 8 Plan 02: Virtualizer repeat() Directive Migration Summary

**Migrated all 7 lit-virtualizer instances across 5 components to repeat() directive with stable entity keys for efficient DOM recycling during scrolling and filtering**

## Performance

- **Duration:** 3 min
- **Started:** 2026-03-05T04:13:34Z
- **Completed:** 2026-03-05T04:17:06Z
- **Tasks:** 2
- **Files modified:** 5

## Accomplishments
- All 7 virtualizer instances now use repeat() with stable keys for DOM node reuse
- Removed .renderItem and .keyFunction properties from all lit-virtualizer elements
- Removed dead gridKeyFunction method from cover-grid component
- Stable keys: FilePath (tracks), QueueTrack.id (queue), album.ID (covers), artist.ID (artists), genre.name (genres)

## Task Commits

Each task was committed atomically:

1. **Task 1: Migrate track-list and queue-panel virtualizers** - `d2d7d8c` (perf)
2. **Task 2: Migrate cover-grid, artists-view, and genres-view virtualizers** - `1c3514d` (perf)

## Files Created/Modified
- `frontend/src/components/track-list/track-list.ts` - repeat() with FilePath key for track virtualizer
- `frontend/src/components/queue-panel/queue-panel.ts` - repeat() with QueueTrack.id key for queue virtualizer
- `frontend/src/components/cover-grid/cover-grid.ts` - repeat() with album.ID key for all 3 cover grid virtualizers, removed gridKeyFunction
- `frontend/src/components/artists-view/artists-view.ts` - repeat() with artist.ID key
- `frontend/src/components/genres-view/genres-view.ts` - repeat() with genre.name key

## Decisions Made
- **Inlined album.ID key instead of keeping gridKeyFunction:** The gridKeyFunction method was only used for .keyFunction property bindings. Since repeat() takes an inline key function, the method became dead code and was removed for cleanliness.
- **Used genre.name (lowercase) not genre.Name:** The Genre interface in genres-view uses lowercase `name` field, not the Go-model-style `Name`. Plan referenced `genre.Name` but actual code uses `genre.name`.

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] Fixed renderGridEntry call signature in cover-grid repeat()**
- **Found during:** Task 2 (cover-grid migration)
- **Issue:** Plan template used `(entry, index) => this.renderGridEntry(entry, index)` but renderGridEntry only accepts 1 argument (GridEntry), not 2
- **Fix:** Changed to `(entry) => this.renderGridEntry(entry)` for all 3 cover-grid virtualizers
- **Files modified:** frontend/src/components/cover-grid/cover-grid.ts
- **Verification:** TypeScript compiles without errors
- **Committed in:** 1c3514d (Task 2 commit)

**2. [Rule 1 - Bug] Corrected genre key from genre.Name to genre.name**
- **Found during:** Task 2 (genres-view migration)
- **Issue:** Plan specified `entry.genre.Name` but Genre interface uses lowercase `name` field
- **Fix:** Used `entry.genre.name` as the repeat() key
- **Files modified:** frontend/src/components/genres-view/genres-view.ts
- **Verification:** TypeScript compiles without errors
- **Committed in:** 1c3514d (Task 2 commit)

---

**Total deviations:** 2 auto-fixed (2 bugs)
**Impact on plan:** Both fixes necessary for TypeScript correctness. No scope creep.

## Issues Encountered
None

## User Setup Required
None - no external service configuration required.

## Next Phase Readiness
- All virtualizer components now use repeat() with stable keys
- Ready for remaining Phase 8 plans (08-03, 08-04)

---
*Phase: 08-frontend-performance-ux*
*Completed: 2026-03-05*