Title typing is slow and laggy

[reddpy]

Description

Typing in the title field of the editor has noticeable lag/delay. Each keystroke feels slow and glitchy compared to typing in the body of the note.

Root Cause Analysis

Every keystroke in the title triggers a cascade of work across multiple registerUpdateListener callbacks:

1. TitlePlugin (src/components/editor/plugins/title-plugin.tsx) — calls getTextContent() (tree traversal), then editor.getElementByKey() (DOM lookup), then toggles is-placeholder class, then invokes onTitleChange callback
2. onTitleChange handler (src/components/lexical-editor.tsx) — triggers a Zustand store update (updateDocumentInStore) which can cause sidebar/app re-renders, plus a debounced IPC save
3. BlockPlaceholderPlugin — fires its own update listener doing DOM queries and classList operations
4. FloatingToolbarPlugin — recalculates selection state with DOM tree walks
5. OnChangePlugin — serializes the entire editor state to JSON on every change (debounced at 600ms, but the serialization itself runs synchronously)
6. SectionIndicatorPlugin — mutation listener walks mutations to check parent nodes

All of these fire independently on every single keystroke with no batching or coordination.

Potential Optimizations

• Debounce or throttle the title text extraction and onTitleChange callback
• Batch DOM operations (classList toggles, getElementByKey) via requestAnimationFrame
• Consider a single centralized update listener instead of 4+ independent ones
• Avoid calling getTextContent() on every update — use a dirty flag or mutation listener instead
• Profile whether the Zustand store update from updateDocumentInStore causes unnecessary re-renders in the sidebar

Reproduction

1. Open any note
2. Click into the title
3. Type quickly — noticeable lag/delay between keystrokes and characters appearing