Current Overscroll System Architecture Deep Dive

The provided document offers an in-depth technical architectural overview of the overscroll system, primarily within the Chromium browser. It explains how browsers handle scroll gestures that go beyond content boundaries to produce effects like elastic bounce, pull-to-refresh, and history navigation (overscroll navigation). Central to this system is the OverscrollController, which resides in the browser process and manages gesture state, working in conjunction with an OverscrollControllerDelegate to execute high-level actions such as reloading a page or navigating history. Furthermore, the document details the compositor's role in generating smooth, platform-consistent visual feedback, like the rubber-banding effect, often using off-main-thread animations for performance. Finally, it notes that developers can use the CSS overscroll-behavior property to customize or disable these built-in browser effects.