---
phase: 04-timeline-editor
plan: 04
subsystem: ui
tags: [canvas, timeline, inspector, color-picker, command-pattern, undo-redo]
dependency_graph:
  requires:
    - phase: 04-timeline-editor/04-02
      provides: CommandHistory, DeleteBlockCommand, syncBlock, selectedBlock, _onSelectBlock callback
  provides:
    - UpdateParamsCommand (undoable color/speed/direction/length changes)
    - BlockInspector class rendering compact strip with all param controls
    - Inspector show/hide wired to block selection via _onSelectBlock
    - Block canvas fill uses params.color for visual distinction
    - Undo/redo refreshes inspector values via re-triggered _onSelectBlock
  affects: []

tech-stack:
  added: []
  patterns:
    - "BlockInspector wired via callback: timeline._onSelectBlock = (block) => inspector.show(block)"
    - "Inspector delete wires via _onDelete callback to fire DeleteBlockCommand through timeline.history"
    - "UpdateParamsCommand uses module-level currentShowId (same pattern as existing commands)"
    - "Color change committed on 'change' event not 'input' — avoids command flood during color drag"
    - "Block canvas fill uses blockColor + '1a' hex suffix for ~10% opacity color accent"

key-files:
  created:
    - lightsync/frontend/timeline/inspector.js
  modified:
    - lightsync/frontend/timeline/commands.js
    - lightsync/frontend/timeline/timeline.js
    - lightsync/frontend/app.js

key-decisions:
  - "UpdateParamsCommand uses currentShowId (module-level var) not this._showId — matches existing command pattern in commands.js"
  - "Color input fires 'change' (not 'input') to create command — avoids flooding command history during native color picker drag"

patterns-established:
  - "Inspector callbacks: _onSelectBlock and _onDelete on inspector — app.js wires both after creating inspector"

requirements-completed: [TL-04]

duration: 4min
completed: 2026-04-06
---

# Phase 04 Plan 04: Block Inspector Panel Summary

**Compact inspector strip between timeline and transport bar — shows animation label, color swatch, speed/direction/length controls — all param changes go through UpdateParamsCommand for full undo/redo support.**

## Performance

- **Duration:** ~4 min
- **Started:** 2026-04-06T23:51:12Z
- **Completed:** 2026-04-06T23:55:00Z
- **Tasks:** 2
- **Files modified:** 4 (1 created, 3 modified)

## Accomplishments

- `UpdateParamsCommand` added to commands.js with execute/undo storing old/new params shallow copies
- `BlockInspector` class rendering inspector strip: animation label, color swatch → hidden color input, SPEED number, DIR select, LEN number, remove button
- Inspector show/hide wired to block selection via `timeline._onSelectBlock` callback in app.js
- Inspector delete wired via `_onDelete` → `DeleteBlockCommand` through `timeline.history`
- Block fill on canvas uses `params.color + '1a'` for subtle color accent — color changes visible immediately
- Undo/redo handlers re-trigger `_onSelectBlock(selectedBlock)` to refresh inspector values after command reversal
- Docker build: clean (no errors)

## Task Commits

1. **Task 1: UpdateParamsCommand + BlockInspector module** - `e82fc4a` (feat)
2. **Task 2: Wire inspector into timeline and app.js** - `8e084ca` (feat)

## Files Created/Modified

- `lightsync/frontend/timeline/inspector.js` — BlockInspector class with show/hide/_render/_wireEvents, imports UpdateParamsCommand
- `lightsync/frontend/timeline/commands.js` — UpdateParamsCommand added with currentShowId-based sync
- `lightsync/frontend/app.js` — imports BlockInspector + DeleteBlockCommand, wires inspector to timeline
- `lightsync/frontend/timeline/timeline.js` — block color accent from params.color, undo/redo re-triggers inspector refresh

## Decisions Made

| Decision | Rationale |
|----------|-----------|
| UpdateParamsCommand uses `currentShowId` not `this._showId` | The plan's code had `this._showId` which doesn't exist — commands.js uses module-level `currentShowId`, same as all other commands |
| Color change on `change` not `input` | Native color pickers fire `input` continuously during drag; committing on `change` prevents hundreds of undo steps for one color change |

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] Fixed UpdateParamsCommand._showId → currentShowId**
- **Found during:** Task 1 (UpdateParamsCommand implementation)
- **Issue:** Plan's code used `this._showId` in syncBlock call, but commands.js uses module-level `currentShowId` — `this._showId` is undefined
- **Fix:** Used `currentShowId` (module-level variable) matching the exact pattern of PlaceBlockCommand, MoveBlockCommand etc.
- **Files modified:** `lightsync/frontend/timeline/commands.js`
- **Committed in:** e82fc4a

---

**Total deviations:** 1 auto-fixed (Rule 1 - Bug)
**Impact on plan:** Essential fix — `this._showId` would be undefined at runtime, breaking backend sync for all param changes.

## Issues Encountered

None — all other implementation matched the plan exactly.

## Known Stubs

None — inspector is fully wired. All param changes route through UpdateParamsCommand. Color accent on canvas reflects actual block color. Remove button fires DeleteBlockCommand. Undo/redo refreshes inspector.

## Self-Check: PASSED

- `lightsync/frontend/timeline/inspector.js` exists: YES (e82fc4a)
- `inspector.js` exports `BlockInspector`: YES
- `commands.js` has `UpdateParamsCommand`: YES (e82fc4a)
- `app.js` imports `BlockInspector` and `DeleteBlockCommand`: YES (8e084ca)
- `app.js` wires `_onSelectBlock` and `_onDelete`: YES (8e084ca)
- `timeline.js` uses `blockColor + '1a'` for fill: YES (8e084ca)
- `timeline.js` undo/redo re-triggers `_onSelectBlock`: YES (8e084ca)
- Docker build: SUCCESS (clean)

## Next Phase Readiness

- Timeline editor is feature-complete: block place/move/resize/delete/params all undoable
- Inspector provides full visual feedback for selected block parameters
- Phase 04 is complete — all 4 plans done
- No blockers

---
*Phase: 04-timeline-editor*
*Completed: 2026-04-06*