> For the complete documentation index, see [llms.txt](https://docs.wellcomecollection.org/request-for-comments-rfcs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.wellcomecollection.org/request-for-comments-rfcs/086-item-viewer-refactor/12-phase-6-duplicate-calls.md).

# Phase 6: Eliminate Duplicate Index Calls

[← Back to Index](/request-for-comments-rfcs/086-item-viewer-refactor.md)

**Effort:** 30 minutes\
**Risk:** Low\
**Priority:** Medium\
**Previous:** [Phase 5: Restriction Status](/request-for-comments-rfcs/086-item-viewer-refactor/11-phase-5-restriction-status.md)\
**Next:** [Phase 7: Cleanup](/request-for-comments-rfcs/086-item-viewer-refactor/13-phase-7-cleanup.md)

## Goal

Since `currentCanvasIndex` is now in context (from Phase 1), remove all duplicate `queryParamToArrayIndex(query.canvas)` calls across components.

## Why?

**Before:**

```typescript
// Thumbnails.tsx
const index = queryParamToArrayIndex(query.canvas);

// NoScriptImage.tsx
const index = queryParamToArrayIndex(query.canvas);

// MultipleManifestList.tsx
const index = queryParamToArrayIndex(query.canvas);
```

**Problem:** Same calculation repeated in 3+ files.

**After:**

```typescript
const { currentCanvasIndex } = useItemViewerContextV2();
```

Single source of truth!

## Files to Update

Find all occurrences:

```bash
cd content/webapp
grep -r "queryParamToArrayIndex(query.canvas)" .
```

### Expected files (update each):

1. **`Thumbnails.tsx`** (lines 38, 49)
2. **`NoScriptImage.tsx`** (line 42)
3. **`MultipleManifestList.tsx`** (lines 23, 37)
4. Any others found

### Replace pattern:

```typescript
// OLD:
const index = queryParamToArrayIndex(query.canvas);
// or
queryParamToArrayIndex(query.canvas)

// NEW:
const { currentCanvasIndex } = useItemViewerContextV2();
// or just use currentCanvasIndex directly
```

## Testing

* [ ] Thumbnails highlight correct canvas
* [ ] NoScript image shows correct canvas
* [ ] Multiple manifest list shows correct position
* [ ] All components that use index still work

## Success Criteria

* [ ] No more `queryParamToArrayIndex(query.canvas)` calls in consuming components
* [ ] All components use `currentCanvasIndex` from context
* [ ] Test coverage maintained

## Time: \~30 minutes

***

**Next:** [Phase 7: Cleanup](/request-for-comments-rfcs/086-item-viewer-refactor/13-phase-7-cleanup.md)