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ts_web/elements/wysiwyg/phase4-summary.md

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+# Phase 4 Implementation Summary - Heading Blocks Migration
+
+## Overview
+Successfully migrated all heading blocks (h1, h2, h3) to the new block handler architecture using a unified HeadingBlockHandler class.
+
+## Changes Made
+
+### 1. Created Unified Heading Handler
+- **File**: `blocks/text/heading.block.ts`
+- Implemented `HeadingBlockHandler` class extending `BaseBlockHandler`
+- Single handler class that accepts heading level (1, 2, or 3) in constructor
+- Extracted all heading rendering logic from `dees-wysiwyg-block.ts`
+- Extracted heading setup logic with full text editing support:
+  - Input handling with cursor tracking
+  - Selection handling with Shadow DOM support
+  - Focus/blur management
+  - Composition events for IME support
+  - Split content functionality
+- Extracted all heading-specific styles for all three levels
+
+### 2. Registration Updates
+- **File**: `wysiwyg.blockregistration.ts`
+- Registered three heading handlers using the same class:
+  - `heading-1` → `new HeadingBlockHandler('heading-1')`
+  - `heading-2` → `new HeadingBlockHandler('heading-2')`
+  - `heading-3` → `new HeadingBlockHandler('heading-3')`
+- Updated imports to include HeadingBlockHandler
+
+### 3. Updated Exports
+- **File**: `blocks/index.ts`
+- Exported `HeadingBlockHandler` class
+- Removed TODO comment for heading handler
+
+### 4. Handler Implementation Details
+- **Dynamic Level Handling**: The handler determines the heading level from the block type
+- **Shared Styles**: All heading levels share the same style method but render different CSS
+- **Placeholder Support**: Each level has its own placeholder text
+- **Full Text Editing**: Inherits all paragraph-like functionality:
+  - Cursor position tracking
+  - Text selection with Shadow DOM awareness
+  - Content splitting for Enter key handling
+  - Focus management with cursor positioning
+
+## Key Features Preserved
+✅ All three heading levels render with correct styles
+✅ Font sizes: h1 (32px), h2 (24px), h3 (20px)
+✅ Proper font weights and line heights
+✅ Theme-aware colors using cssManager.bdTheme
+✅ Contenteditable functionality
+✅ Selection and cursor tracking
+✅ Keyboard navigation
+✅ Focus/blur handling
+✅ Placeholder text for empty headings
+
+## Architecture Benefits
+1. **Code Reuse**: Single handler class for all heading levels
+2. **Consistency**: All headings share the same behavior
+3. **Maintainability**: Changes to heading behavior only need to be made once
+4. **Type Safety**: Heading level is type-checked at construction
+5. **Scalability**: Easy to add more heading levels if needed
+
+## Testing Results
+- ✅ TypeScript compilation successful
+- ✅ All three heading handlers registered correctly
+- ✅ Render method produces correct HTML with proper classes
+- ✅ Placeholders set correctly for each level
+- ✅ All handlers are instances of HeadingBlockHandler
+
+## Next Steps
+Continue with Phase 5 to migrate remaining text blocks:
+- Quote block
+- Code block
+- List block
+
+Each will follow the same pattern but with their specific requirements.