The render layer had no CSS Grid support, so Vector 2022's page layout
(three nested grids) collapsed to a vertical stack with the article
landing tens of thousands of pixels down the page. Wikipedia rendered
as a near-blank page and Hacker News only worked through per-site
hardcoded CSS overrides.
Removed the HN-specific hardcoding and fixed the general engine instead:
- CSS Grid layout (grid-template-areas/columns/rows via taffy's grid mode)
- Indexed, specificity-correct cascade in a new css.rs, replacing the
old test-every-selector-against-every-node scan. Cascade time on
Wikipedia went from 9.5s to under 200ms.
- Ancestor bloom-filter fast-rejection for selector matching in
obscura-dom, needed to make the indexed cascade actually fast on
descendant combinators.
- :link/:visited pseudo-classes were previously unparseable, so any
rule using them (a:link{color:...}, extremely common) silently
dropped the whole rule from the cascade.
- overflow:hidden clipping, fixing the pervasive visually-hidden-but-
accessible pattern used for skip links and screen-reader-only labels.
- @media parser robustness: it did a literal substring search for
max-width: and silently dropped the constraint on max-width : 750px
(space before colon) or max-width:calc(750px - 1px), treating
mobile-only or narrow-viewport rules as always active. The calc()
case was hiding Wikipedia's TOC sidebar via a rule meant only for
narrow screens.
- Table auto-layout approximation: the trailing auto-width td in a row
absorbs leftover space, so a width:100% table's unsized last column
reaches the right edge instead of shrinking to content.
- Inline formatting context approximation: a block holding inline-level
children (a paragraph or list item with links) is promoted to a
wrapping flex row so text and links read as continuous prose instead
of one fragment per line.
- Whitespace-only text nodes no longer get a full line-height box. They
used to stack up as blank rows, turning Wikipedia's collapsed TOC
subsections and the page header into hundreds of pixels of dead space.
- SVG rendering via resvg/usvg, plus resolving relative image URLs
against the page's base URL.
- background-image support including background-size/background-position
for correctly sized and positioned icons.
- Per-screenshot image fetch cache.
- Fixed the layout-only (no paint feature) build, which didn't compile
due to an unconditional call into paint-gated code.
SGavrl
920977776c