Track transform, filter, backdrop-filter, perspective, containment,
will-change, and content-visibility triggers independently. Use the combined
state for absolute and fixed containing-block ancestry.
Track every non-none transform as a containing-block trigger, including
unsupported visual transforms. Keep separate nearest-ancestor maps so
positioned boxes capture absolute descendants while only transforms capture
fixed descendants.
Reparent inset-positioned absolute boxes to the nearest non-static ancestor
and fixed boxes to the initial containing block. Keep auto-axis boxes on the
existing static-position path, distinguish fixed from absolute, and blockify
positioned inline boxes and floats.
Paint order was pure tree order, so a dropdown/overlay declared before a
later sibling lost to it and a z:-1 decorative backdrop covered its own
content. A positioned element with a non-zero z-index now lifts its
whole subtree into a separate paint layer: negative layers under the
normal flow, positive above it, each sorted ascending with tree order
preserved within equal z. Nested z roots paint inside their ancestor
root's subtree in tree order, the pragmatic core of CSS stacking
contexts.
clear (left/right/both, previously unparsed) now ends the float zone,
so a clearfix element drops below the float at full width instead of
joining the flow column beside it.
Repro-verified: an earlier z:10 overlay paints over a later sibling, a
later z:-1 backdrop paints under earlier content, and the clear repro
matches Chromium within 3px on every measure. Spot set unchanged or
slightly improved; obstacle course 33/33.
Cells now vertical-align the way tables actually do: middle by default
(the effective UA behavior), with author top/middle/bottom parsed and
applied to whichever shape the cell took: main-axis alignment on the
flex-column stand-in, line alignment on a promoted inline context, or a
pinned-origin offset for the pure-text leaf path where the shaped text
height is known at finalize.
Specified column widths finally apply. <col>/<colgroup> widths (style
or attribute, with span) and colspan-1 cell widths are recorded per
column at build time and pinned inside the column-balancing pass: px
directly, percent against the table's content width, with each column's
content min-content still flooring it. The cell's own width is
neutralized once it has fed the column, so the cell box fills its grid
area instead of shrinking to a fraction of its own already-sized track
(a width:50% cell previously ended up at 25 percent). Unspecified
columns keep content sizing but stretch to fill a definite table width
instead of leaving a dead strip of table background. Row and cell
heights act as row minimums.
Verified against Chromium on a 5-case repro (column from cell width,
row backgrounds, vertical alignment, col element width, percent cell in
a fixed table): all match. Wikipedia and the prose spot set unchanged;
obstacle course 33/33.
paint_image clipped an object-fit:cover overflow to the element box but
ignored the ancestor overflow:hidden clip entirely, so a partially
visible image (a half-scrolled carousel slide, a hero cropped by its
section) painted its full raster past the viewport edge. Pass the
already clip-intersected visible rect down and mask against it whenever
the destination exceeds it on any side.
Broken images now fall back the way browsers do: a non-empty alt renders
as text in place of the image with no placeholder box, alt="" renders
nothing (declared decorative), and only a missing alt keeps the neutral
grey placeholder.
Verified with a repro covering the half-clipped cover slide and all
three alt variants; no movement on the image-heavy spot set; obstacle
course 33/33.
The srcset picker already normalized every candidate to a pixel density
(x descriptor, or w / source-size) to choose one, then threw the density
away, so layout sized the image from the file's raw pixels. Every 2x
responsive asset occupied twice its design size.
Return the picked candidate's density alongside its URL (img srcset,
data-srcset, and picture source paths alike) and divide the fetched
intrinsic dimensions by it, so layout sees CSS px.
Verified: srcset "x.png 2x" of a 648px file lays out at 324 CSS px and
"648w" with sizes=300px at 300, while a bare src stays at raw size; no
regressions on the image-heavy spot set (a bbc delta traced to homepage
content drift against a days-old baseline, 8.0 vs 7.8 percent when
recaptured same-time); obstacle course 33/33.
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