The Architecture of Chromium's Safe Callback Cancellation
Blink28629 Marras 2025

The Architecture of Chromium's Safe Callback Cancellation

The source material provides a comprehensive examination of Chromium's CancelableCallback utility, which was introduced to allow for the safe and explicit cancellation of tasks that have been scheduled to run asynchronously. This mechanism wraps existing callbacks and supplies a handle that, when Cancel() is invoked, prevents the wrapped operation from executing, thereby avoiding potential race conditions or resource leaks. Crucially, the system is implemented using base::WeakPtr internally, where canceling the callback invalidates the weak pointer, causing any outstanding posted task to become a no-op upon firing. However, the system is designed to be sequence-affine, meaning all usage and cancellation must occur on the same thread, directing users who require cross-thread cancellation toward the CancelableTaskTracker instead. Although highly versatile for general asynchronous tasks and timeouts, the documentation explicitly advises developers to generally prefer WeakPtr binding when cancellation can be cleanly tied to the destruction of a specific object.

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blink::NGPhysicalFragment and friends

blink::NGPhysicalFragment and friends

Layout takes the styled DOM and produces a fragment tree of positioned boxes. In modern Blink this is LayoutNG; the core artifact is NGPhysicalFragment, which stores geometry and is used downstream fo...

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blink::StyleEngine

blink::StyleEngine

style invalidation & resolution (recalc). 
Given DOM/style changes since the last frame, StyleEngine computes updated ComputedStyles, manages active stylesheets/media query state, and marks the right ...

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blink::Document & blink::DocumentLifecycle

blink::Document & blink::DocumentLifecycle

states that gate phases. The document owns the DOM and keeps a DocumentLifecycle state machine that ensures we do things in phase order (style before layout, pre‑paint before paint, etc.). Lifecycle t...

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blink::LocalFrameView

blink::LocalFrameView

orchestrates style → layout → pre‑paint/paint for a frame. This is the workhorse that actually runs lifecycle phases. On a frame tick from WebFrameWidgetImpl, it goes through style recalc, layout (Lay...

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blink::LocalFrame

blink::LocalFrame

the document host and local‑root boundary.
The local frame owns the Document and its LocalFrameView. The local root frame coordinates lifecycle for its subtree (including OOPIF boundaries handled late...

9 Loka 202532min

blink::Page

blink::Page

the page container and animation clock keeper. Page holds frame trees and the PageAnimator that services script‑driven animations on each tick. It’s the top‑level context for the document/view that We...

9 Loka 202534min

blink::WebFrameWidgetImpl

blink::WebFrameWidgetImpl

renderer‑main entry to Blink’s lifecycle. This is where a compositor BeginFrame (coming in via content/public and mojo plumbing) first turns into Blink work on the renderer main thread. It receives th...

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Blink's ComputedStyle: An In-Depth Analysis

Blink's ComputedStyle: An In-Depth Analysis

The collection of sources provides a detailed technical analysis of the ComputedStyle object within Blink, the rendering engine for Chromium. The primary source, an in-depth analysis document, explain...

9 Loka 202545min