perf(web): optimize cssListener for rapid stylesheet additions#209
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Brentlok merged 2 commits intoDec 6, 2025
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Fixes performance issues when CSS-in-JS libraries inject many stylesheets rapidly (e.g., Emotion's 2000+ style tags in dev mode). Previously, the MutationObserver would call initialize() on every DOM mutation, reprocessing all stylesheets each time, causing O(n²) complexity. Changes: - Debounce initialization with requestIdleCallback (50ms timeout, setTimeout fallback) - Track processed stylesheets with WeakSet to avoid reprocessing - Extract helper functions for cross-platform idle callback scheduling This reduces operations from O(n²) to O(n), improving navigation performance significantly in development environments.
Brentlok
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Dec 6, 2025
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I've done minor refactor to simplify things a bit. Thanks for PR 👌
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Summary
Fixes performance issues when CSS-in-JS libraries inject many stylesheets rapidly (e.g., Emotion's 2000+ style tags in dev mode).
Previously, the MutationObserver would call
initialize()on every DOM mutation, reprocessing all stylesheets each time, causing O(n²) complexity. This resulted in 7+ second navigation delays in development environments.Changes
requestIdleCallback(withsetTimeoutfallback) to batch rapid mutations into a single initialization call (50ms timeout)WeakSetto skip already-processed stylesheetsPerformance Impact
Testing
unbuildRelated
Addresses the performance concerns discussed in #188