The source provides a detailed technical analysis of how the Chromium web browser manages user input to ensure a responsive and smooth user experience, even when the main thread is occupied. It centers on two critical components operating on the separate compositor thread: the cc::InputHandler and the blink::InputHandlerProxy. The InputHandlerProxy acts as the gatekeeper, receiving events and deciding if they can be handled immediately on the compositor thread for fast results, or if they need to be passed to the main thread. Conversely, the InputHandler is the mechanical engine that directly manipulates the webpage's visual components, such as applying scroll or pinch updates, without waiting for the slower main thread. This architecture enables key features like threaded scrolling, which significantly reduces latency by processing gestures asynchronously.
