fix(ui): optimize MutationObserver in NoteEditorDialog

[lfnovo]

Summary

• Only observe DOM mutations when the dialog is open
• Prevents unnecessary MutationObserver activity when dialog is closed
• Follow-up optimization to PR feat(notebooks): Enhance dialog content styling for fullscreen mode #305

Related Issue

Follow-up to #305 (merged)

Type of Change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Tested locally with development setup
• Existing tests pass
• Linting passes

Checklist

• My code follows TypeScript best practices
• I have performed a self-review of my code
• My changes generate no new warnings or errors

Co-Authored-By: Claude Opus 4.5 [email protected]

[claude]

Claude finished @lfnovo's task —— View job

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PR Review: MutationObserver Optimization

Todo List:

• Read and analyze the modified NoteEditorDialog.tsx file
• Review code quality and best practices
• Check for potential bugs or issues
• Evaluate performance considerations
• Assess security concerns
• Review test coverage considerations
• Provide comprehensive feedback

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Code Review Feedback

✅ Excellent Performance Optimization

The changes effectively address the performance concern by:

• Early return guard: Adding if (!open) return on line 73 prevents MutationObserver creation when the dialog is closed
• Proper dependency array: Changing from [] to [open] ensures the observer is recreated when dialog state changes
• Clean resource management: Observer is properly disconnected when dialog closes

✅ Code Quality & Best Practices

1. Formatting improvement: Better spacing in observer.observe() call improves readability
2. Logical flow: The early return pattern is a clean, idiomatic React approach
3. Resource management: Proper cleanup in useEffect return function prevents memory leaks

✅ Bug Prevention

The changes prevent a subtle but important issue:

• Before: MutationObserver would run continuously even when dialog was closed, wasting CPU cycles
• After: Observer only runs when needed, improving overall application performance

⚠️ Minor Considerations

1. Effect dependency: While [open] is correct, consider if this creates unnecessary observer recreation on dialog open/close cycles. The current approach is fine since dialog opening/closing should be infrequent.

2. Fullscreen state cleanup: The observer cleanup happens automatically, but consider if setIsEditorFullscreen(false) should be called when dialog closes to ensure consistent state (though this appears to be handled in handleClose on line 114).

🔒 Security Assessment

• No security concerns: The changes don't introduce any security vulnerabilities
• DOM querying: The document.querySelector() call is safe and necessary for the functionality

🧪 Test Coverage Considerations

The changes are low-risk but could benefit from tests verifying:

• Observer is not created when dialog is initially closed
• Observer is created when dialog opens
• Observer is properly cleaned up when dialog closes

However, testing MutationObserver behavior can be complex and may not be worth the effort for this simple optimization.

📊 Performance Impact

Positive impact:

• Eliminates unnecessary DOM mutation monitoring when dialog is closed
• Reduces CPU usage and improves battery life on mobile devices
• Minimal memory footprint improvement

Trade-off:

• Negligible overhead from useEffect re-execution when open changes

Overall Assessment

This is a well-implemented performance optimization that follows React best practices. The changes are:

• ✅ Minimal and focused
• ✅ Properly implemented with correct cleanup
• ✅ Performance-positive with no negative side effects
• ✅ Code quality improvements (formatting)

Recommendation: Approve and merge. This is exactly the type of thoughtful optimization that improves application performance without adding complexity.

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[cubic-dev-ai]

No issues found across 1 file