Chromium Compositor PictureLayerImpl Deep Dive
Blink28631 Okt 2025

Chromium Compositor PictureLayerImpl Deep Dive

The source provides an extensive technical overview of the cc::PictureLayerImpl class, a critical component in the rendering architecture of Chromium's compositor, responsible for processing content on the compositor thread. This class manages the complex process of tiled rasterization, breaking a layer's drawing commands (from the main thread) into Tile textures at various scales for display performance, particularly during zooming and animation. The text details the class's fields, including the PictureLayerTilingSet (which holds multiple resolution tilings), scale factors (ideal vs. raster), and invalidation tracking. Furthermore, it explains key methods like PushPropertiesTo (transferring state to the active layer) and the AppendQuads process, which converts ready tiles into draw commands for the final rendering output, while managing optimizations for animated images, solid colors, and LCD text.

Avsnitt(395)

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 Okt 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 Okt 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 Okt 202531min

blink::NGPhysicalFragment and friends

blink::NGPhysicalFragment and friends

Layout takes the styled DOM and produces a fragment tree of positioned boxes. In modern Blink this is LayoutNG; the core artifact is NGPhysicalFragment, which stores geometry and is used downstream fo...

10 Okt 202537min

blink::StyleEngine

blink::StyleEngine

style invalidation & resolution (recalc). 
Given DOM/style changes since the last frame, StyleEngine computes updated ComputedStyles, manages active stylesheets/media query state, and marks the right ...

10 Okt 202534min

blink::Document & blink::DocumentLifecycle

blink::Document & blink::DocumentLifecycle

states that gate phases. The document owns the DOM and keeps a DocumentLifecycle state machine that ensures we do things in phase order (style before layout, pre‑paint before paint, etc.). Lifecycle t...

10 Okt 202535min

blink::LocalFrameView

blink::LocalFrameView

orchestrates style → layout → pre‑paint/paint for a frame. This is the workhorse that actually runs lifecycle phases. On a frame tick from WebFrameWidgetImpl, it goes through style recalc, layout (Lay...

9 Okt 202544min

blink::LocalFrame

blink::LocalFrame

the document host and local‑root boundary.
The local frame owns the Document and its LocalFrameView. The local root frame coordinates lifecycle for its subtree (including OOPIF boundaries handled late...

9 Okt 202532min

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