cc::CommitState
Blink28625 Sep 2025

cc::CommitState

The provided source offers an extensive architectural analysis of Chromium’s cc::CommitState struct, detailing its critical function as the intermediary data structure that facilitates communication between the main rendering thread and the compositor (impl) thread during frame commits. The core purpose of CommitState is to take a snapshot of the main thread’s compositor state, enabling non-blocking commits by transferring all necessary persistent settings and one-time updates, like resource requests and animation data, in a single package. The document breaks down the structure into persistent fields (settings that carry over between frames) and ephemeral fields (one-time updates that are consumed and cleared after the commit), distinguishing it from the ThreadUnsafeCommitState, which holds non-copyable pointers that require thread synchronization. This design is crucial for performance and safety, as it batches updates and minimizes the duration the main thread must stall during the commitment phase of the rendering pipeline.


Episoder(417)

cc::PropertyTrees

cc::PropertyTrees

(TransformTree / ClipTree / EffectTree / ScrollTree) with nodes cc::TransformNode / ClipNode / EffectNode / ScrollNode — The impl‑side property‑tree state that positions, clips, blends, and scrolls co...

22 Sep 202534min

cc::LayerTreeHostImpl

cc::LayerTreeHostImpl

The compositor‑thread twin that owns the active/pending trees, runs impl‑side animations/scroll, and prepares draw. Implements cc::InputHandler for threaded scrolling/pinch.

22 Sep 202546min

main —> impl cc::LayerTreeHost

main —> impl cc::LayerTreeHost

Packages updated layers/property trees; kicks a commit to the compositor thread (via the proxy).

22 Sep 202536min

blink::PropertyTreeManager

blink::PropertyTreeManager

Bridges Blink’s paint property trees into cc property trees: creates/updates cc TransformNode, ClipNode, EffectNode, and ScrollNode (including inner/outer viewport scroll nodes).

22 Sep 202539min

blink::PaintArtifactCompositor

blink::PaintArtifactCompositor

Decides what needs to be composited and prepares the main‑thread representation to feed cc (layers if needed, scrollbar compositing, etc.).

22 Sep 202542min

blink::PaintArtifact

blink::PaintArtifact

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

21 Sep 202536min

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.

21 Sep 202541min

blink::PaintController

blink::PaintController

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

21 Sep 202533min

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