a11y-dom

The abstraction over the document: a DOM-shaped tree as a trait, plus capability tiers. This lets the same rule run over a parsed HTML tree, over a browser AX tree and over the live page.

Status

0.26.0 on crates.io. Used by accname, a11y-rules and all hosts; auditmysite builds a tree from CDP data out of it in dom_document.rs.

Structure

Public surface

Type	Purpose
Document	the minimum: tree, elements, attributes
Semantics, Rendering	tiers a host offers only if it really has the data
Rendering host measurements	default methods, None = not measured: layout, scroll_overflow_px, visually_hidden, sampled_backdrop, frame_reachable (#132), box_transform (#134), paste_probe (#133), focus_cover (#135), text_spacing_clip (#136)
BoxTransform	computed transform and rotate of an element as strings, via Rendering::box_transform() (default None); a method instead of two ComputedStyle fields because new fields on that non-non_exhaustive struct break hosts that build it as a literal
PasteProbe	raw observations of a synthetic paste event at a password or code field (cancelled, inserted), via Rendering::paste_probe() (default None); the host runs it as an opt-in pass because it executes page handlers and writes value
FocusCover	after the host focused and scrolled a control: sample points, how many are covered by a fixed or sticky foreign element painted above it, and the blocker; via Rendering::focus_cover() (default None); the host records how it scrolled
SpacingClip	the model for text spacing: one fact per element, taken twice (before, after the host applied the 1.4.12 override): whether it clips its own text through hidden overflow; via Rendering::text_spacing_clip() (default None). The host injects the override, measures, removes it, and reports whether injection worked (None otherwise)
Layout	layout information for heuristic rules, via Rendering::layout() (default None)
Arena, ArenaBuilder, ArenaNode	ready-made implementation for tests and parser-based hosts

Parse tree adapter

With the optional feature html5-parser, html5_parser::Document itself implements Document (handle type Html5Node), so a host can run rules over the parse tree without copying it into an Arena. Comments and doctype are skipped, <template> content appears as children of the <template> element, and document_order walks the tree because the parser’s node ids follow allocation order. The feature is off by default.

Dependencies

Downward: nothing except serde (optional). Upward: accname, a11y-rules, host adapters.

Limits

A tier is a promise about availability, not about quality. A host that offers Rendering promises layout data — not that it is correct. If a tier is missing, the rules built on it return NotRun, not “passed”.