The source provides an extensive architectural deep dive into the implementation of Scroll-driven Animations (SDA) within the Chromium project, specifically focusing on the Blink rendering engine and the Compositor (CC). It details how SDA fundamentally redesigns web rendering by abstracting scroll position into a time value, enabling animations to be executed directly on the compositor thread to eliminate visual jank caused by main-thread latency. The explanation covers the historical limitations of JavaScript-based scroll events and examines the technical components, including the ScrollTimeline and ViewTimeline primitives, the complex synchronization during the Commit cycle, and the rigorous checks required (CheckCanStartAnimationOnCompositor) to ensure animations are successfully accelerated off the main thread for high-performance interaction. The document serves as a comprehensive reference, analyzing performance trade-offs among CSS declarations, AnimationWorklets, and legacy JavaScript.