dom-layout-shim

1a58c8d: Include accessible linked stylesheets and constructable stylesheets in layout. The engine now follows document and adoption order and automatically recomputes geometry after CSSOM edits or changes to document.adoptedStyleSheets.

  const sheet = new window.CSSStyleSheet();
  sheet.replaceSync(".dialog { position: fixed; inset: 0 }");
  window.document.adoptedStyleSheets = [sheet];

  await attachLayoutEngine({ window });

  // Now covers the configured viewport; previously this sheet was ignored.
  dialog.getBoundingClientRect();

5189aa2: Apply responsive stylesheet @media rules against the viewport configured for the layout engine. Media types, dimensions, orientation, aspect ratio, query lists, conjunctions, and nested rules now select the same branches as Chromium.

Previously, media rules were rejected by the unsupported CSS policy. After upgrading, matching rules contribute layout:

  document.head.innerHTML = `
    <style>@media (max-width: 600px) { #panel { width: 100px } }</style>
  `;
  document.body.innerHTML = '<div id="panel"></div>';

  await attachLayoutEngine({ window, viewport: { width: 480, height: 800 } });
  document.querySelector("#panel").offsetWidth; // 100

2b49074: Support rectangular named grid templates through grid-template-areas and single-name grid-area placement. Named areas can span rows and columns and may be arranged around unnamed . cells.

Previously, named templates were rejected as unsupported CSS. After upgrading, items use the declared area bounds:

  document.body.innerHTML = `
    <main style='display:grid; grid-template-columns:80px 120px;
      grid-template-areas:"nav content"'>
      <article id="content" style="grid-area:content"></article>
    </main>
  `;

  await attachLayoutEngine({ window });
  document.querySelector("#content").offsetLeft; // 80

c86fc03: Resolve CSS custom properties before parsing supported layout declarations. Inherited values, local overrides, forward references, nested fallbacks, and cyclic references now follow their CSS variable semantics, while values that remain unresolved route through unsupportedCss.

Previously, a supported declaration such as width: var(--card-width) was ignored as an unsupported value. After upgrading, it contributes layout:

  document.body.innerHTML = `
    <main style="--card-width: 240px">
      <article id="card" style="width:var(--card-width)"></article>
    </main>
  `;

  await attachLayoutEngine({ window });
  document.querySelector("#card").offsetWidth; // 240

97a9a85: Support position: sticky for physical insets, scrolling ancestors, viewport scrolling, containing-block limits, hit testing, and simple table headers.

  scroller.scrollTop = 50;

  // Now remains at the scroller's top inset; previously `sticky` was rejected.
  toolbar.getBoundingClientRect().top;

fa4068f: Make CSS support evidence explain the independently supported behaviors within each topic. The exported inventory now provides descriptive, behavior-specific claims instead of broad current-supported-scope entries, and its prose marks CSS syntax and API names as inline code for documentation renderers.

  const grid = cssSupportInventory.find((topic) => topic.id === "grid-layout");

  // Now identifies explicit tracks, auto flow, line placement, area placement,
  // and shared placement behavior as separate claims with their own evidence.
  grid?.claims.map((claim) => claim.id);

The CSS support explorer also separates implementation support from Chromium verification, explains metadata with tooltips, groups dense claim sections, and previews parity test sources without leaving the page.

a8f464c: Make documentation navigation respond immediately after the initial page load. The shared shell now swaps internal page content and styles without reloading the document, while direct URLs, refreshes, Back and Forward navigation, scroll restoration, page-specific behavior, and no-JavaScript fallback navigation continue to work normally.

For example, following the CSS support navigation link updates the URL and support explorer in place instead of triggering another document load.

a2963e2: Add explicit deterministic native-control profile selection and per-control metric overrides. The initial portable profile names and preserves the package's existing intrinsic control geometry instead of deriving it from the runtime host. Overrides can specialize one metric or replace the complete profile.

  await attachLayoutEngine({
    window,
    nativeControls: {
      profile: "portable",
      overrides: { textInput: { width: 220 } },
    },
  });

  // An unstyled text input is 220×23 on Linux, macOS, and Windows:
  // the width is overridden while the portable height remains in effect.
  document.querySelector("input")?.getBoundingClientRect();

d61c212: Support two-dimensional translation and scaling through both transform functions and the individual translate and scale properties. Percentage values, transform origins, ordered function lists, transformed descendants, client rectangles, and point queries are included.

  /* Transform functions are now reflected in geometry and hit testing. */
  .dialog {
    transform: translate(20px, 10px) scale(1.25);
    transform-origin: left top;
  }

  /* The equivalent individual properties are also supported. */
  .popover {
    translate: 50% 8px;
    scale: 1.25;
  }

Layout flow and offset/client dimensions remain untransformed, matching browser behavior.

ee791b0: Update the documentation site with a complete usage guide, syntax-highlighted code examples, highlighted CSS support search matches, automatic light and dark themes, and a package changelog that separates pending Changesets under Upcoming from versions confirmed by release tags. Navigation is consistent and marks the current page, bracket pairs are depth-colored, CSS support results are relevance-ranked in a denser layout, and changelog commit references link to their source. Shared styles, flash-free generated navigation, responsive menus, visible release context, keyboard focus treatment, and reduced-motion support keep the experience consistent across pages and devices.

For example, after a feature merges but before its package release, its entry is shown as:

  Upcoming
    Add the newly merged feature.

After the release tag is created, the same changelog section is shown under its published version instead.

For example, searching the CSS support explorer for flex now places an exact property match before records that only mention flex in supporting notes:

  Flex layout — exact property match
  Display model — supporting evidence match
  Grid layout — supporting evidence match

Support searches now report the filtered result count, expose labeled and resettable controls, and give every support area a stable link such as css-support-status.html#flex-layout. Guide navigation follows the currently visible section and accounts for the sticky header when following a section link. The changelog likewise keeps the current version visible while scrolling, also identifies the current major, minor, or patch section, links directly to release headings, and can filter entries by release type. External references open in a separate tab, and Chromium parity fixtures are styled as source links rather than inert metadata chips.

The generated website is deployed from an ignored build directory rather than being bundled into the npm package. Authored Markdown and machine-readable documentation remain included in the package.

Internal pages are prefetched and prerendered where the browser supports it, so documentation navigation responds immediately without an artificial transition delay.

4d6d9f3: Improve browser-compatible wrapping in canvas-capable runtimes by updating Pretext to 0.0.8. Text such as foo!bar, foo/bar, and foo♂bar now keeps symbols that browsers treat as part of the word within the same breakable run. When wrapping at a soft hyphen, the line now ends at the rendered hyphen instead of incorrectly pulling letters from after the break onto the preceding line.

For example, at a constrained width, a soft-hyphen break changes from:

  trans-a | tlantic

to the browser-compatible break:

  trans- | atlantic

Runtimes without Canvas 2D text measurement continue to use the deterministic fallback measurer and are unaffected by these Pretext-specific corrections.

ff1ef3b: Patch offsetTop, offsetLeft, and offsetParent from the layout snapshot.

Previously, these properties came from the host DOM implementation and could disagree with the engine's geometry:

  element.offsetTop;
  element.offsetLeft;
  element.offsetParent;

They now describe the element relative to its layout-backed CSS offset parent, including positioned ancestors, borders, margins, and scrolling.

a6bdc8b: Implement Element.scrollIntoView() against the layout snapshot so calls consistently affect layout-backed geometry instead of relying on the host DOM implementation.

The method scrolls nested containers and the configured viewport using boolean or block/inline alignment options. Smooth behavior is applied immediately to keep test layout deterministic.

8be6e4f: Support adjacent (+) and general (~) sibling combinators in stylesheet selectors.

68fc5d9: Answer window.matchMedia() queries from the configured layout viewport.

Previously, matchMedia() used the DOM environment's viewport, which could disagree with the dimensions used by the layout engine:

  await attachLayoutEngine({
    window,
    viewport: { width: 320, height: 640 },
  });

  // Previously: false when the DOM environment was wider than 500px
  window.matchMedia("(max-width: 500px)").matches;

It now evaluates the query against the configured 320px-wide layout viewport:

  // Now: true
  window.matchMedia("(max-width: 500px)").matches;

3724069: Recompute layout after style elements are added or changed and after existing CSSOM rules are edited or deleted.

b26f8ce: Add an unsupported CSS reporter that reduces warning streams to a stable adoption-cost summary across a test suite.

Previously, consumers had to build their own aggregation around onWarning:

  const warnings = [];

  await attachLayoutEngine({
    window,
    unsupportedCss: {
      onWarning: (warning) => warnings.push(warning),
    },
  });

The reporter now deduplicates declarations and exposes one headline count with sorted diagnostic details:

  const reporter = createUnsupportedCssReporter();

  await attachLayoutEngine({
    window,
    unsupportedCss: { onWarning: reporter.onWarning },
  });

  const { unsupportedDeclarationCount, declarations } = reporter.getSummary();

9d8958b: Release the package into the public domain under the Unlicense, permitting use, copying, modification, publishing, compilation, sale, and distribution for any commercial or non-commercial purpose.

0bb1dbe: Establish the package as DOM Layout Shim, published as dom-layout-shim, with repository, issue tracker, and documentation metadata for the renamed project.

7334dfa: Continue layout with deduplicated, actionable warnings when CSS is unsupported. Strict failures and deliberate suppression remain available through unsupportedCss: { default: 'throw' } and { default: 'ignore' }.

100c77b: Clarify Chromium parity evidence for native text and form-control metrics that vary across host platforms while retaining exact checks for stable dimensions and author-sized time inputs and textareas.