Chromium Compositor PictureLayerImpl Deep Dive
Blink28631 Loka 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.

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cc::LayerTreeHostImpl (Input Handler & Scroll Logic)

cc::LayerTreeHostImpl (Input Handler & Scroll Logic)

Scroll processing and overscroll detection in the compositor. The LayerTreeHostImpl in cc implements the compositor-thread InputHandler that processes gesture scroll updates and flings. It manages the...

23 Syys 202527min

blink::EventHandler (Blink core input handling)

blink::EventHandler (Blink core input handling)

Scroll chain builder and overscroll chaining logic. Blink’s EventHandler is responsible for building the scroll chain (the sequence of nested scrollable ancestors) when the user scrolls an element . I...

23 Syys 202526min

blink::ElasticOverscrollController

blink::ElasticOverscrollController

Overscroll orchestration and animation. This Blink-side controller manages the rubber-banding (elastic stretch and rebound) effect when a scrollable area is overscrolled. It observes gesture scroll ev...

23 Syys 202526min

viz::Surface / SurfaceAggregator

viz::Surface / SurfaceAggregator

Receives frames from one or more surfaces (main page and OOPIFs), aggregates them into a single display frame.

23 Syys 202535min

viz::CompositorFrameSink (client side)

viz::CompositorFrameSink (client side)

The submission interface used by cc to hand the frame to viz.

23 Syys 202531min

viz::CompositorFrame

viz::CompositorFrame

The packaged frame (passes + quads + metadata) submitted to the display compositor.

23 Syys 202549min

viz::RenderPass & viz::DrawQuad

viz::RenderPass & viz::DrawQuad

builds render passes and quads to describe what to draw this frame.

22 Syys 202537min

cc::TileManager & raster pipeline

cc::TileManager & raster pipeline

Schedules raster of picture tiles (Skia) into GPU resources as needed before draw.

22 Syys 202536min