cc::EffectTree

The source provides an extensive technical explanation of the Effect Property Tree within the Chromium compositor, which is crucial for managing how visual effects are applied to web content. This tree structure, composed of EffectNodes, decouples effects (such as opacity, filters, and blending modes) from the traditional layer hierarchy to centralize calculations, improving rendering performance. A primary function of the effect tree is determining when content must be rendered into a separate RenderSurface (an offscreen texture) for correct compositing, flagged by the render_surface_reason field for complex needs like filters or non-standard blend modes. The document details the structure of an EffectNode, including fields that track cumulative properties like screen_space_opacity and visibility flags like is_drawn, and explains how the effect tree seamlessly interacts with the Transform and Clip property trees to ensure correct coordinate spaces and boundaries are maintained during effect application. Finally, it addresses the tree's role in facilitating performant CSS animations by allowing real-time property updates on the compositor thread and ensuring stability through element identification.