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343 lines
8.9 KiB
Markdown
343 lines
8.9 KiB
Markdown
# PREREQ-003: Document Canvas Overlay Pattern - CHANGELOG
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## Status: ✅ COMPLETED
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**Started:** January 3, 2026
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**Completed:** January 3, 2026
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**Time Spent:** ~8 hours
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---
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## Overview
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Successfully documented the Canvas Overlay Pattern by studying CommentLayer implementation and extracting reusable patterns for future Phase 4 visualization overlays (Data Lineage, Impact Radar, Semantic Layers).
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The pattern is now comprehensively documented across five modular documentation files with practical examples, code snippets, and best practices.
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---
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## Deliverables Completed
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### 📚 Documentation Created
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Five comprehensive documentation files in `dev-docs/reference/`:
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1. **CANVAS-OVERLAY-PATTERN.md** (Overview)
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- Main entry point with quick start example
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- Key concepts and architecture overview
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- Links to all specialized docs
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- Common gotchas and best practices
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2. **CANVAS-OVERLAY-ARCHITECTURE.md** (Integration)
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- How overlays integrate with NodeGraphEditor
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- DOM structure and z-index layering
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- Two-layer system (background + foreground)
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- EventDispatcher subscription patterns
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- Complete lifecycle (creation → disposal)
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- Full example overlay implementation
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3. **CANVAS-OVERLAY-COORDINATES.md** (Coordinate Systems)
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- Canvas space vs Screen space transformations
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- Transform math (canvasToScreen/screenToCanvas)
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- React component positioning via parent container transform
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- Scale-dependent vs scale-independent sizing
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- Common patterns (badges, highlights, hit testing)
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4. **CANVAS-OVERLAY-EVENTS.md** (Mouse Event Handling)
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- Event handling when overlay sits in front of canvas
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- Three-step mouse event forwarding solution
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- Event flow diagrams
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- Preventing infinite loops
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- Pointer events CSS strategies
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- Special cases (wheel, drag, multi-select)
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5. **CANVAS-OVERLAY-REACT.md** (React 19 Patterns)
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- React root management with createRoot API
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- Root reuse pattern (create once, render many)
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- State management approaches
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- Scale prop special handling for react-rnd
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- Async rendering workarounds
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- Performance optimizations
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- Common React-specific gotchas
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---
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## Key Technical Discoveries
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### 🎯 CSS Transform Strategy
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The most elegant solution for coordinate transformation:
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- Parent container uses `transform: scale() translate()`
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- React children automatically positioned in canvas coordinates
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- No manual recalculation needed for each element
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```css
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.overlay-container {
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transform: scale(${scale}) translate(${pan.x}px, ${pan.y}px);
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}
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```
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### 🔄 React 19 Root Reuse Pattern
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Critical pattern for performance:
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```typescript
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// ✅ CORRECT - Create once, reuse
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this.root = createRoot(container);
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this.root.render(<Component />); // Update many times
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// ❌ WRONG - Creates new root each render
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createRoot(container).render(<Component />);
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```
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### 🎭 Two-Layer System
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CommentLayer uses two overlay layers:
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- **Background Layer** - Behind canvas for comment boxes with shadows
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- **Foreground Layer** - In front of canvas for interactive controls
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This allows sophisticated layering without z-index conflicts.
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### 🖱️ Smart Mouse Event Forwarding
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Three-step solution for click-through:
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1. Capture all mouse events on overlay
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2. Check if event target is interactive UI (has pointer-events: auto)
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3. If not, forward event to canvas
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Prevents infinite loops while maintaining both overlay and canvas interactivity.
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### 📐 EventDispatcher Context Pattern
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Must use context object for proper cleanup:
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```typescript
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const context = {};
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editor.on('viewportChanged', handler, context);
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return () => editor.off(context); // Cleanup all listeners
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```
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React hook wrappers handle this automatically.
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---
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## Files Analyzed
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### Primary Source
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- `packages/noodl-editor/src/editor/src/views/nodegrapheditor/commentlayer.ts` (~500 lines)
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- Production-ready overlay implementation
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- All patterns extracted from this working example
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### Related Files
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- `packages/noodl-editor/src/editor/src/views/CommentLayer/CommentLayerView.tsx`
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- `packages/noodl-editor/src/editor/src/views/CommentLayer/CommentForeground.tsx`
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- `packages/noodl-editor/src/editor/src/views/CommentLayer/CommentBackground.tsx`
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---
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## Design Decisions
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### Modular Documentation Structure
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**Decision:** Split documentation into 5 focused files instead of one large file.
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**Rationale:**
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- Initial attempt at single file exceeded API size limits
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- Modular structure easier to navigate
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- Each file covers one concern (SRP)
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- Cross-referenced with links for discoverability
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**Files:**
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- Pattern overview (entry point)
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- Architecture (integration)
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- Coordinates (math)
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- Events (interaction)
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- React (rendering)
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### Documentation Approach
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**Decision:** Document existing patterns rather than create new infrastructure.
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**Rationale:**
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- CommentLayer already provides production-ready examples
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- Phase 4 can use CommentLayer as reference implementation
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- Premature abstraction avoided
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- Future overlays will reveal common needs organically
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**Next Steps:**
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- VIEW-005, 006, 007 implementations will identify reusable utilities
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- Extract shared code when patterns become clear (not before)
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---
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## Impact on Phase 4
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### Unblocks
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This prerequisite fully unblocks:
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- ✅ **VIEW-005: Data Lineage** - Can implement path highlighting overlay
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- ✅ **VIEW-006: Impact Radar** - Can implement dependency highlighting
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- ✅ **VIEW-007: Semantic Layers** - Can implement visibility filtering UI
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### Provides Foundation
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Each visualization view can now:
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1. Reference CANVAS-OVERLAY-PATTERN.md for quick start
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2. Copy CommentLayer patterns for specific needs
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3. Follow React 19 best practices from documentation
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4. Avoid common gotchas documented in each guide
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---
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## Testing Approach
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**Validation Method:** Documentation verified against working CommentLayer implementation.
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All patterns documented are:
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- Currently in production
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- Battle-tested in real usage
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- Verified to work with React 19
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- Compatible with existing NodeGraphEditor
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No new code created = no new bugs introduced.
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---
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## Lessons Learned
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### What Worked Well
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1. **Studying Production Code**
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- CommentLayer provided real-world patterns
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- No guessing about what actually works
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- Edge cases already handled
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2. **Modular Documentation**
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- Splitting into 5 files prevented API size issues
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- Easier to find specific information
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- Better for future maintenance
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3. **Code Examples**
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- Every concept backed by working code
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- Practical not theoretical
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- Copy-paste friendly snippets
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### Challenges Overcome
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1. **API Size Limits**
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- Initial comprehensive doc too large
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- **Solution:** Modular structure with cross-references
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2. **Complex Coordinate Math**
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- Transform math can be confusing
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- **Solution:** Visual diagrams and step-by-step examples
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3. **React 19 Specifics**
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- New API patterns not well documented elsewhere
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- **Solution:** Dedicated React patterns guide
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### For Future Tasks
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- Start with modular structure for large documentation
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- Include visual diagrams for spatial concepts
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- Balance theory with practical examples
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- Cross-reference between related docs
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---
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## Success Metrics
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✅ **Completeness**
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- All CommentLayer patterns documented
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- All coordinate transformation cases covered
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- All event handling scenarios explained
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- All React 19 patterns captured
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✅ **Clarity**
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- Each doc has clear scope and purpose
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- Code examples for every pattern
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- Common gotchas highlighted
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- Cross-references for navigation
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✅ **Usability**
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- Quick start example provided
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- Copy-paste friendly code snippets
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- Practical not academic tone
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- Real-world examples from CommentLayer
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✅ **Future-Proof**
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- Foundation for VIEW-005, 006, 007
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- Patterns generalizable to other overlays
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- Follows React 19 best practices
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- Compatible with existing architecture
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---
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## Next Steps
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### Immediate
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- [x] Create CHANGELOG.md (this file)
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- [ ] Update LEARNINGS.md with key discoveries
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- [ ] Task marked as complete
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### Future (Phase 4 Views)
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- Implement VIEW-005 (Data Lineage) using these patterns
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- Implement VIEW-006 (Impact Radar) using these patterns
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- Implement VIEW-007 (Semantic Layers) using these patterns
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- Extract shared utilities if patterns emerge across views
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---
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## References
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### Documentation Created
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- `dev-docs/reference/CANVAS-OVERLAY-PATTERN.md`
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- `dev-docs/reference/CANVAS-OVERLAY-ARCHITECTURE.md`
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- `dev-docs/reference/CANVAS-OVERLAY-COORDINATES.md`
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- `dev-docs/reference/CANVAS-OVERLAY-EVENTS.md`
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- `dev-docs/reference/CANVAS-OVERLAY-REACT.md`
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### Source Files Analyzed
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- `packages/noodl-editor/src/editor/src/views/nodegrapheditor/commentlayer.ts`
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- `packages/noodl-editor/src/editor/src/views/CommentLayer/` (React components)
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### Related Tasks
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- PREREQ-001: Webpack Caching (prerequisite, completed)
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- PREREQ-002: React 19 Debug Fixes (parallel, completed)
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- VIEW-005: Data Lineage (unblocked by this task)
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- VIEW-006: Impact Radar (unblocked by this task)
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- VIEW-007: Semantic Layers (unblocked by this task)
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---
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_Task completed: January 3, 2026_
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