The CSS Z-Axis: Stacking Contexts and Z-Index
Blink28626 Marras 2025

The CSS Z-Axis: Stacking Contexts and Z-Index

The source provides an exhaustive technical analysis of CSS stacking contexts, defining this fundamental concept as the hierarchical structure that controls the layering of elements along the z-axis. It meticulously outlines the strict, multi-step painting algorithm derived from the CSS2.1 specification, which defines the order in which all elements, from backgrounds and borders to floats and inline content, are painted within a context. A major focus is placed on how the z-index property, utilizing negative, zero, and positive values, determines an element’s precise stack level and whether it forms a new, isolating stacking group for its descendants. The document also addresses the complexities introduced by modern CSS, covering how elements with opacity or transform, or specific layout types like Flexbox/Grid items, automatically trigger new stacking contexts. Furthermore, the analysis differentiates stacking from related layout concepts like containing blocks and formatting contexts and maps the theoretical model to practical implementation details used by rendering engines like Blink/Chrome to manage compositing layers.


Jaksot(460)

blink::PaintArtifact

blink::PaintArtifact

The immutable package of paint chunks + display items for this frame, used to drive compositing without re‑painting.

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blink::TransformPaintPropertyNode / ClipPaintPropertyNode / EffectPaintPropertyNode / ScrollPaintPropertyNode

blink::TransformPaintPropertyNode / ClipPaintPropertyNode / EffectPaintPropertyNode / ScrollPaintPropertyNode

The paint property trees captured during painting (transform, clip, effect/opacity, scroll offset) that define visual & coordinate‑space state.

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blink::PaintController

blink::PaintController

Records drawing into a DisplayItemList, segmenting it into PaintChunks keyed by property‑tree state. (Output: a PaintArtifact.)

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blink::LayoutView (root of the layout tree)

blink::LayoutView (root of the layout tree)

Computes geometry for boxes when layout is dirty.

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blink::StyleEngine / style resolver

blink::StyleEngine / style resolver

Recalculates computed styles that changed since last frame (if any).

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blink::Page → blink::LocalFrame / LocalFrameView

blink::Page → blink::LocalFrame / LocalFrameView

The document’s frame & viewport; LocalFrameView is the scrollable root that triggers layout/paint when needed. provided source outlines the fundamental components of the Blink rendering engine, specif...

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blink::WebViewImpl

blink::WebViewImpl

The source text provides an in-depth explanation of the blink::WebViewImpl class within Chromium's Blink rendering engine, characterizing it as the central control point on the renderer's main thread ...

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cc::LayerTreeHost in Chromium's Compositor

cc::LayerTreeHost in Chromium's Compositor

The source provides an extensive technical explanation of the cc::LayerTreeHost class, which acts as the central main-thread component in the Chromium compositor architecture. It details how this comp...

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