Blink Compositor Promotion of CSS Animations
Blink2866 Marras 2025

Blink Compositor Promotion of CSS Animations

The technical sources provide an extensive analysis of how the Blink rendering engine (used in Chromium/Chrome) determines whether a CSS animation can be executed on the compositor thread instead of the main thread to improve performance and achieve smooth frame rates. This process involves a complex pipeline, beginning with style calculation and proceeding through layout and layer assignment, where an element must be assigned a composited layer and corresponding property tree nodes to be eligible for acceleration. The critical decision is made by the function CheckCanStartAnimationOnCompositor(), which only permits animations on a limited set of properties—primarily transform, opacity, filter, and backdrop-filter—while rejecting anything affecting layout or requiring frame-by-frame repainting. If accelerated, the animation’s keyframes are converted into CompositorAnimation objects and run by the GPU-assisted compositor, allowing the main thread to remain free for other tasks.

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blink::PropertyTreeManager

blink::PropertyTreeManager

bridges Blink property trees → cc property trees. Given Blink’s Transform/Clip/Effect/Scroll nodes (from paint property trees), this class creates/updates the cc counterparts (cc::TransformNode, cc::C...

10 Loka 202546min

blink::PaintArtifactCompositor

blink::PaintArtifactCompositor

turns chunks into compositor layers & updates cc property trees. Consumes the new PaintArtifact and does the layerization and property‑tree updates required for compositor draw. It supports fast paths...

10 Loka 202529min

blink::PaintChunk and blink::DisplayItemList

blink::PaintChunk and blink::DisplayItemList

grouping and content. PaintChunk: groups sequential display items that share the same property‑tree state and cull/visibility; it’s the unit we layerize and invalidate.DisplayItemList: the recorded Sk...

10 Loka 202537min

blink::PaintArtifact

blink::PaintArtifact

the immutable “what to draw” package for this frame. A PaintArtifact is the product of Blink painting: a DisplayItemList plus an ordered vector of PaintChunks. It is immutable post‑creation and design...

10 Loka 202531min

blink::PaintController

blink::PaintController

builds the display list + paint chunks and manages caching. As painters call into GraphicsContext, they also drive a PaintController which groups drawing into display items and paint chunks (each keye...

10 Loka 202529min

blink::GraphicsContext

blink::GraphicsContext

immediate drawing API that records to a display list. Painters for layout objects use GraphicsContext to “draw”—but in modern Blink those calls get recorded into a display list (PaintRecord) backed by...

10 Loka 202544min

blink::TransformPaintPropertyNode / ClipPaintPropertyNode / EffectPaintPropertyNode / ScrollPaintPropertyNode

blink::TransformPaintPropertyNode / ClipPaintPropertyNode / EffectPaintPropertyNode / ScrollPaintPropertyNode

These are the nodes within those four trees. Every piece of painted content (a “paint chunk”) is associated with a tuple of (Transform, Clip, Effect, Scroll) nodes—its PropertyTreeState. This precisel...

10 Loka 202533min

blink::PaintPropertyTreeBuilder

blink::PaintPropertyTreeBuilder

builds/updates paint property trees.Consumes the layout/fragment data and produces the four paint property trees (Transform, Clip, Effect, Scroll) for the current frame. These trees encode coordinate ...

10 Loka 202547min