Blink and Compositor Stacking Contexts
Blink28625 Sep 2025

Blink and Compositor Stacking Contexts

These sources provide an extensive technical explanation of how CSS stacking contexts are implemented within the Chromium rendering engine, focusing on the collaboration between the Blink renderer and the cc compositor. The process begins in Blink, where elements triggering a stacking context (via properties like opacity or z-index) are identified, leading to the creation of internal structures like PaintLayer and EffectPaintPropertyNode to manage z-ordering. Blink then produces a PaintArtifact consisting of drawing commands grouped into paint chunks, each linked to a specific set of property nodes that define the context's position, clipping, and effects. This artifact is passed to the cc compositor, which converts the Blink properties into its own PropertyTrees (especially the EffectNode), using this data to decide which stacking contexts require an isolated drawing buffer, known as a RenderSurfaceImpl, for final GPU compositing and accurate visual blending. Ultimately, Blink determines what is painted and ordered, and cc determines how to composite those results efficiently.

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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