cc::LayerTreeHostImpl (Input Handler & Scroll Logic)
Blink28623 Syys 2025

cc::LayerTreeHostImpl (Input Handler & Scroll Logic)

Scroll processing and overscroll detection in the compositor. The LayerTreeHostImpl in cc implements the compositor-thread InputHandler that processes gesture scroll updates and flings. It manages the scroll state of all scroll nodes (via the ScrollTree) and determines when a scroll has hit the extent of an element. Currently, this is where overscroll is detected and reported – but only for the root/viewport. For example, the InputHandler sets did_overscroll_root in the scroll result when the root scroll node reaches its boundary , triggering the elastic effect on the root. To support elastic overscroll on non-root elements, this logic in LayerTreeHostImpl (and its ScrollTree/ScrollNode handling) needs to be generalized: it must detect overscroll on any scrollable node and initiate the overscroll animation (via the helper/controller) for that node instead of chaining upward. Understanding LayerTreeHostImpl and how it yields overscroll information (e.g. populating InputHandlerScrollResult.unused_scroll_delta, accumulated overscroll, and overscroll_behavior flags ) is key, as changes here will route overscroll into the ElasticOverscrollController for the right element rather than exclusively the root.

Jaksot(403)

CSS Scroll Mechanics and Blink Implementation Deep Dive

CSS Scroll Mechanics and Blink Implementation Deep Dive

The provided text is a deep technical analysis of CSS layout, scrolling, and Blink (Chromium) implementation, focusing heavily on modern web engine architecture. It begins by explaining fundamental CS...

14 Joulu 202559min

CSS Selectors Level 4: Specificity, Performance, and Scoping

CSS Selectors Level 4: Specificity, Performance, and Scoping

The provided text offers a comprehensive technical overview of CSS Selectors Level 4, detailing its fundamental role in binding style declarations to elements and its broad utility across CSS and Java...

13 Joulu 202528min

CSS Values and Units Level 4: The Foundation

CSS Values and Units Level 4: The Foundation

The provided document is an extensive technical overview of the CSS Values and Units Module Level 4, which defines the foundational system for how all values, units, and mathematical expressions are p...

13 Joulu 202527min

The Grammar and Parsing of CSS Syntax

The Grammar and Parsing of CSS Syntax

The provided source discusses the critical role of the CSS Syntax Module Level 3 specification as the fundamental grammar and parsing model for the entire CSS platform. This specification, which repla...

13 Joulu 202528min

Chromium Feature Toggles: Switches, Flags, and Blink Runtime

Chromium Feature Toggles: Switches, Flags, and Blink Runtime

The provided text offers a comprehensive technical overview of the four primary mechanisms utilized in Chromium for toggling features and behaviors at runtime. It distinguishes between command-line sw...

13 Joulu 202538min

Chrome's Raster-Inducing Scroll Architecture Deep Dive

Chrome's Raster-Inducing Scroll Architecture Deep Dive

The provided text details the architecture and mechanisms of raster-inducing scrolling within the Google Chrome rendering engine, explaining how Chrome balances scrolling performance with visual quali...

13 Joulu 202531min

W3C CSS Snapshot of 2025: An Analysis of Specification Stability

W3C CSS Snapshot of 2025: An Analysis of Specification Stability

The sources consist of **excerpts from the W3C’s latest CSS Snapshot (2025)**, along with supporting context from **prior snapshots and Working Group publications**, which provide an in-depth analysis...

13 Joulu 202527min

Compositor Scheduler Lifecycle: Commit and Invalidation Coalescing

Compositor Scheduler Lifecycle: Commit and Invalidation Coalescing

These sources explain the lifecycle management of rendering trees within the Chromium compositor (cc), focusing on how the scheduler handles requests for updates. A core principle established is that ...

12 Joulu 202527min