References — bi-09 Paint, Display Items & Property Trees

Primary sources first. In-tree Chromium docs beat any external source, including these modules.

Specifications

CSS 2.2 Appendix E — Elaborate description of stacking contexts — the normative painting order. Still the definitive statement.
CSS Positioned Layout Level 3 — stacking contexts
CSS Transforms Level 2 · Filter Effects · Compositing and Blending

Source

third_party/blink/renderer/core/paint/README.md — primary; the best in-tree explanation of the paint phase
core/paint/
platform/graphics/paint/ — display items and paint artifacts
Property trees — transform, clip, effect and scroll trees; the data structure that made composited scrolling tractable

Talks

Life of a Pixel — paint and property-tree sections

bi-08 — Layout — the input to paint
bi-10 — Compositor & GPU — what consumes the display list
fe-05 — CSS architecture (sibling project) — contain: paint, and the stacking contexts it silently creates

When a claim here proves stale, record it in PROGRESS.md section 7.