CSS filter may affect contenteditable performance

Phenomenon

When a contenteditable element has CSS filters applied (blur, brightness, etc.), editing performance may be degraded. Typing may lag, and selection may be slow to update.

Reproduction example

1. Create a contenteditable div with filter: blur(2px) brightness(1.2).
2. Type text rapidly.
3. Observe typing lag or jank.
4. Try to select text and observe responsiveness.
5. Compare performance with a contenteditable without filters.

Observed behavior

• In Chrome on macOS, CSS filters may cause performance issues.
• Typing may lag or stutter.
• Selection updates may be slow.
• The UI may become unresponsive during rapid editing.

Expected behavior

• CSS filters should not significantly impact editing performance.
• Or, filters should be optimized for contenteditable use cases.
• Performance should remain acceptable with filters applied.