Gate baseline export where CSS forbids it (scroll containers, contain:layout, vertical-align) - #684
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Summary
Fixes part of the baseline-export regression group on #627 (Group A). The parley baseline wiring passed Taffy's
first_baselines.ythrough toInlineBox::baselineunconditionally, but CSS requires several classes of atomic inline to synthesize their baseline from the bottom margin edge (baseline: Nonein parley 0.11) instead of exporting their content's baseline.Three gates:
compute_child_layout_internal(mod.rs) — split into a wrapper +compute_child_layout_dispatchso it covers every layout path (including tables/form controls), and suppressfirst_baselineswhen:Display::FlowRoot+ non-visible/clip overflow) — CSS2 §10.8.1; flex/grid containers keep exporting their content baseline even when scrollable (perbaseline-of-scrollable-1a), orcontain: layout(css-contain baseline suppression).inline box update (inline.rs) — parley has no per-box
vertical-align; it always anchors a box's baseline (or bottom edge if unset) to the line baseline. For alignments this cannot approximate (middle,text-bottom,sub, non-zero shifts, …) the baseline is left unset so the box aligns by its bottom edge.vertical-align: topkeeps exporting: its baseline-anchored rendering coincides with WPT reference emulations (* { vertical-align: top }+margin-top), and gating it regressed 4 flexbox vert tests. Also clampsibox.baselineto ≥0 to match the non-negative reserved line space when negativemargin-topis present (fixesflexbox_inline.html).inline container output (inline.rs) — an inline root whose first line has no glyph runs (e.g. only a lone image) no longer exports a
0.0"baseline"; per CSS a box with no in-flow line boxes synthesizes from the bottom margin edge (fixes theobject-view-box-*tests).WPT results (css/CSS2, css-align, css-flexbox, css-grid, css-contain, css-images)
Remaining 9 Group A failures are not fixable in blitz integration code:
baseline-of-scrollable-1b,baseline-block-with-overflow-001: need consumer-dependent suppression of a scrollable block child's baseline during block-layout baseline propagation — a Taffy-side question (Taffy's block algorithm forwards the child baseline; blitz can't see the consumer).grid-baseline-001/002,grid-inline-baseline,grid-inline-items-002,flexbox-baseline-multi-line-horiz-004: Taffy flex/grid baseline synthesis/alignment (e.g. grid's first-row baseline fallback incompute/grid/mod.rs), not blitz wiring.percentage-size-subitems-001(×2 flex/grid variants),scrollbar-gutter-001/002,floats-141.xht: need realvertical-alignsupport in parley (the refs rely onvertical-align: top/line-height details); gating them here regressed previously-passing tests.cargo check --workspace,cargo fmt,cargo clippyare clean.Link to Devin session: https://dioxus.staging.devinenterprise.com/sessions/331985c4732e4248a71184626d9c4a38
Requested by: @nicoburns
WPT results
37 newly passing, 81 newly failing (net -44).
Full diff (118 changed tests)
Generated by the WPT workflow.