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::PaintArtifact

blink::PaintArtifact

The immutable package of paint chunks + display items for this frame, used to drive compositing without re‑painting.

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blink::TransformPaintPropertyNode / ClipPaintPropertyNode / EffectPaintPropertyNode / ScrollPaintPropertyNode

blink::TransformPaintPropertyNode / ClipPaintPropertyNode / EffectPaintPropertyNode / ScrollPaintPropertyNode

The paint property trees captured during painting (transform, clip, effect/opacity, scroll offset) that define visual & coordinate‑space state.

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blink::PaintController

blink::PaintController

Records drawing into a DisplayItemList, segmenting it into PaintChunks keyed by property‑tree state. (Output: a PaintArtifact.)

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blink::LayoutView (root of the layout tree)

blink::LayoutView (root of the layout tree)

Computes geometry for boxes when layout is dirty.

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blink::StyleEngine / style resolver

blink::StyleEngine / style resolver

Recalculates computed styles that changed since last frame (if any).

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blink::Page → blink::LocalFrame / LocalFrameView

blink::Page → blink::LocalFrame / LocalFrameView

The document’s frame & viewport; LocalFrameView is the scrollable root that triggers layout/paint when needed. provided source outlines the fundamental components of the Blink rendering engine, specif...

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blink::WebViewImpl

blink::WebViewImpl

The source text provides an in-depth explanation of the blink::WebViewImpl class within Chromium's Blink rendering engine, characterizing it as the central control point on the renderer's main thread ...

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cc::LayerTreeHost in Chromium's Compositor

cc::LayerTreeHost in Chromium's Compositor

The source provides an extensive technical explanation of the cc::LayerTreeHost class, which acts as the central main-thread component in the Chromium compositor architecture. It details how this comp...

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