Clip Nodes in the Blink and Chromium Compositor
Blink2862 Tammi

Clip Nodes in the Blink and Chromium Compositor

The provided text explains how Chromium’s Blink engine and the compositor utilize clip nodes within property trees to manage page geometry and visual masking. These nodes define specific regions where content remains visible, specifically handling CSS overflow, clip-paths, and border-radius through a hierarchical structure. The system differentiates between main-thread clipping, which is flexible but CPU-intensive, and compositor-thread clipping, which leverages the GPU for higher performance during scrolling and animations. By separating clipping into dedicated clip trees, the engine ensures that visual restrictions are applied efficiently without redundant calculations. This architectural approach also facilitates precise hit testing and optimized rasterization by identifying which parts of an element are interactive or visible to the user. Overall, the sources detail the lifecycle of clipping data as it moves from initial layout through pre-paint to final GPU compositing.

Jaksot(408)

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

blink::PrePaintTreeWalk

blink::PrePaintTreeWalk

cross‑frame pre‑paint traversal. Runs in the InPrePaint lifecycle phase. Walks the entire layout tree starting at the root LocalFrameView, updating paint invalidation state and computing the context n...

10 Loka 202531min