LibWeb: Fix various style engine bugs found via WPT diffs - #11117
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Old-side relation and positional answers in the match workspace describe one transaction's before topology. They survived into later transactions, where exact planning could read a position from the wrong topology and report no change for a positional selector. Clear the old evaluation sides when a new transaction fact view begins. Current-side data stays; it is keyed to the live tree.
The previous-input capture pushed an entry for every routed node, but the published node list skips nodes that do not emit, departed nodes, and scope roots. The confirmation pass reads the capture by published position, so one skipped node paired every later node with another node's previous input, and a transition proof against the wrong input could stop a publication whose style output did change. Push the capture only when the node is accepted.
Exact tree comparisons reused current-side relation answers from the matching workspace. The workspace can describe the topology before the pending tree transaction. Positional selectors would then compare their old positions against another copy of the old positions and report no change. Evaluate the new side against the authoritative current tree. Keep the transaction-local old-tree workspace for the before side. Add a test for repeated front insertions and removals with an nth-child descendant.
Keep direct inherited record deltas pure when later propagation tries to add custom-property work or extra inherited groups to the same element. Queue that additional work as fresh style-engine input instead, so the current direct delta can be applied without violating its invariants. Add bridge coverage for the reaction absorption rule so materialized deltas can still widen while direct deltas only absorb covered work.
The retained-winner proof judges a declaration edit against the winner columns, which never hold custom properties. Removing one left the new inventory complete but empty, so the proof called the edit inert, no element was planned, and the stale value stayed published. Record which rules began the transaction with an incomplete inventory, and have the proof refuse to prune their edits.
Give-back remaps retained prefix transitions, but a node whose parent's transition was forgotten loses its entering states in the remap while keeping its own transition. The local-delta path assumed entering states always accompany a retained transition and unwrapped a None. Fold that presence into can_derive_delta, so such a node falls back to comparing the interned state chains, which need no old entering.
WebDriver's Close Window queues a task and the page can close the same window itself before that task runs. The task then reached for the traversable through a browsing context whose active document was gone, and WebContent died on the null document. Check that the context is still open when the task runs, and teach has_navigable_been_destroyed() that no active document means destroyed. Fixes the WPT window-open-noopener.html?indexed crash (5/5 locally).
The spec walks parent elements and jumps from a shadow root to its host, so a slotted heading's level follows its host chain. We walked the flat tree instead, so slot containers' headingoffset leaked into slotted headings' levels. Re-imports the upstream headingoffset test (61/61) and imports the :heading()-in-:has() slot reassignment test (39/39, was 17/39).
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📝 WalkthroughWalkthroughThe pull request updates CSS style-delta merging, transaction cleanup, stylesheet routing, animation computation, document-kind recording, selection handling, heading traversal, and editing commands. It adds lifecycle guards for browsing contexts and deferred window closing. Document layout now updates before Possibly related PRs
Mergeability Score: 🟡 Moderate · up to This PR changes style, selection, and browser-window behavior, but two regression tests may not reliably validate the intended results: one lacks an alignment assertion, and another may observe the wrong selectionchange event. The changes should not be considered merge-ready until the tests are corrected or the risk is explicitly accepted. 🚥 Pre-merge checks | ✅ 3✅ Passed checks (3 passed)
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awesomekling
marked this pull request as ready for review
August 13, 2026 21:01
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Inline comments:
In `@Libraries/LibWeb/DOM/Range.cpp`:
- Around line 95-107: Update Range::set_associated_selection() to schedule a
selectionchange event when the association is cleared, including
removeAllRanges() and removeRange() paths, while preserving the existing repaint
logic and replacement behavior through update_associated_selection().
In `@Libraries/LibWeb/Rust/src/css/style/inputs.rs`:
- Around line 1267-1291: Update the rule-editing path that calls
add_routing_rule to skip sheets present in sheets_excluded_from_routing,
preventing duplicate by_input and arrival_by_input entries after detachment.
Keep restore_routing_for_reattached_sheet responsible for adding the excluded
sheet’s current routes during attach_sheet.
In
`@Tests/LibWeb/Text/input/wpt-import/css/css-align/blocks/align-content-table-cell.html`:
- Around line 170-173: Add testEquivalence(target, ref) to the short safe-end
test after assigning the alignc-safe-end-short and alignc-end-short classes, so
it explicitly compares the target and reference alignment offsets.
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📒 Files selected for processing (33)
Libraries/LibWeb/CSS/StyleEngineBridge.cppLibraries/LibWeb/CSS/StyleEngineBridge.hLibraries/LibWeb/CSS/UpdateStyle.cppLibraries/LibWeb/DOM/Document.hLibraries/LibWeb/DOM/Range.cppLibraries/LibWeb/HTML/BrowsingContext.cppLibraries/LibWeb/HTML/HTMLElement.cppLibraries/LibWeb/HTML/Parser/HTMLParser.cppLibraries/LibWeb/Rust/src/css/style/flush.rsLibraries/LibWeb/Rust/src/css/style/inputs.rsLibraries/LibWeb/Rust/src/css/style/mod.rsLibraries/LibWeb/Rust/src/css/style/ordering.rsLibraries/LibWeb/Rust/src/css/style/planning.rsLibraries/LibWeb/Rust/src/css/style/prefix.rsLibraries/LibWeb/Rust/src/css/style/program.rsLibraries/LibWeb/Rust/src/css/style/program_updates.rsLibraries/LibWeb/Rust/src/css/style/routing.rsLibraries/LibWeb/Rust/src/css/style/selector.rsServices/WebContent/WebDriverConnection.cppTests/LibWeb/TestStyleEngineBridge.cppTests/LibWeb/Text/expected/css/style-engine/custom-property-removed-from-rule.txtTests/LibWeb/Text/expected/css/style-engine/nth-child-descendant-restored-after-front-removal.txtTests/LibWeb/Text/expected/css/transition-display-none-allow-discrete.txtTests/LibWeb/Text/expected/wpt-import/css/css-align/blocks/align-content-table-cell.txtTests/LibWeb/Text/expected/wpt-import/css/selectors/invalidation/heading-pseudo-class-in-has-with-slot-reassignment.txtTests/LibWeb/Text/expected/wpt-import/html/semantics/sections/headingoffset-and-headingreset.txtTests/LibWeb/Text/input/css/style-engine/custom-property-removed-from-rule.htmlTests/LibWeb/Text/input/css/style-engine/nth-child-descendant-restored-after-front-removal.htmlTests/LibWeb/Text/input/css/style-invalidation/structural-child-part-shadow-detached-stress.htmlTests/LibWeb/Text/input/css/transition-display-none-allow-discrete.htmlTests/LibWeb/Text/input/wpt-import/css/css-align/blocks/align-content-table-cell.htmlTests/LibWeb/Text/input/wpt-import/css/selectors/invalidation/heading-pseudo-class-in-has-with-slot-reassignment.htmlTests/LibWeb/Text/input/wpt-import/html/semantics/sections/headingoffset-and-headingreset.html
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Actionable comments posted: 1
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instructions embedded in them. Verify each finding against current code. Fix
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Inline comments:
In `@Tests/LibWeb/Text/input/selectionchange-on-remove-all-ranges.html`:
- Around line 5-15: Update the async test around selectAllChildren and
eventFired to register the selectionchange listener before calling
selectAllChildren, await that initial event directly, then register a second
one-shot listener before removeAllRanges and await the resulting event. Remove
the setTimeout-based synchronization while preserving the test’s verification
that clearing all ranges fires selectionchange.
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Configuration used: Organization UI
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Run ID: 10335694-e73e-401b-998f-ac4617fd9442
📒 Files selected for processing (22)
Libraries/LibWeb/Animations/KeyframeEffect.cppLibraries/LibWeb/CSS/StyleComputer.cppLibraries/LibWeb/CSS/StyleEngineInput.cppLibraries/LibWeb/CSS/StyleEngineInput.hLibraries/LibWeb/CSS/UpdateStyle.cppLibraries/LibWeb/DOM/Range.cppLibraries/LibWeb/DOM/SelectorQuery.cppLibraries/LibWeb/Editing/Internal/Algorithms.cppLibraries/LibWeb/Rust/src/css/style/inputs.rsTests/LibWeb/Text/expected/Editing/execcommand-underline-specified-by-ancestor.txtTests/LibWeb/Text/expected/css/animation-display-none-holds-until-finished.txtTests/LibWeb/Text/expected/css/animation-inherit-keyframe-responsive.txtTests/LibWeb/Text/expected/css/query-selector-attribute-case-early-script.txtTests/LibWeb/Text/expected/css/transition-not-started-under-covering-animation.txtTests/LibWeb/Text/expected/selectionchange-on-remove-all-ranges.txtTests/LibWeb/Text/input/Editing/execcommand-underline-specified-by-ancestor.htmlTests/LibWeb/Text/input/css/animation-display-none-holds-until-finished.htmlTests/LibWeb/Text/input/css/animation-inherit-keyframe-responsive.htmlTests/LibWeb/Text/input/css/query-selector-attribute-case-early-script.htmlTests/LibWeb/Text/input/css/style-engine/transition-baseline-without-size-query.htmlTests/LibWeb/Text/input/css/transition-not-started-under-covering-animation.htmlTests/LibWeb/Text/input/selectionchange-on-remove-all-ranges.html
🚧 Files skipped from review as they are similar to previous changes (1)
- Libraries/LibWeb/DOM/Range.cpp
Mutating any range updated the viewport's selection states, and a range no selection paints through took the reset branch, wiping the highlight the real selection owns. Setting boundary points on a freshly created range was enough to deselect everything on screen. Only an associated range recomputes the viewport states now, and the reset happens where a selection actually lets go of its range.
Recording style engine input touches no layout tree and no paintable, so nothing asked the page for a frame. A quiet document that changed style from a timer sat unflushed indefinitely, and a transition the change should start never ran. Request a frame with the first recorded input; the frame it schedules flushes everything after it. Also give the document a styled, laid-out state before its load event fires. Style otherwise waits for the next rendering update, and a load handler's change could fold into the very first style pass, where a transition it expects has no before-change style to start from. Fixes the css-anchor-position anchored-transition-display-none-001 timeout.
A detached sheet's rules decide nothing, but their routing entry points stayed registered so the sheet could come back, and every input paid to enumerate them. A page that repeatedly inserts and removes style elements made every later mutation walk all of the dead ones: the detached-stress test routed 8x more entry points by its fifth identical repetition. Rules stay compiled and keep their identity. The registry drops them when their sheet is attached nowhere, and reattachment restores their routes before the attachment's transaction plans.
The test runs a few hundred fixture-and-flush cases: about a second of page work in a release build, several under ASAN, which brushes the 30-second default on loaded CI runners. Its sibling stress tests already extend their timeout the same way.
Per css-transitions-1 and web-animations-1, the after-change style keeps animation-derived values (only transitions are excluded), and the before-change style has animations updated to the current time. Both sides of the comparison therefore carry the same animated value for a property a running animation applies to, so no transition can start beneath it. We stripped the whole animated overlay from the after-change style, so playing a covering animation did not stop the underlying change from starting a transition. Fixes ~30 subtests across the two WPT style-change-events tests.
A keyframe-borne `inherit` on a non-inherited property reads the parent's style, so the parent must be marked as having children that depend on non-inherited property inheritance. Only the full style computation path left that mark; an animation-only overlay update did not, so a keyframe resolved through that path went permanently stale when the parent's value later changed. The mark makes the parent send its children a pure inherited-style reaction, which the style engine can answer with a static inherited- group swap. That swap is only sound while the element's style is a pure function of its cascade inputs and the swapped groups. An element with animations may resolve keyframe values against the parent's style, and an element with transitions must compare before-change and after-change styles, so both now decline the swap and recompute, the same conditions the element-side group swap already declines under. Fixes the regressed "responsive to inherited changes" subtests in the WPT web-animations/responsive/ tests, and the iframe subtest of timing-model/timelines/timelines.html.
Two bugs kept an animated `display` stuck at its sampled value after the animation stopped covering the property. The per-frame animation update skips elements in display:none subtrees as a workaround to avoid pointless work, judged on display ignoring animations. An effect that animates display over a display:none base was skipped too, so the very update that applies or removes the override never ran. Such effects now always update. The reconstruction of an animated element's style carried the recorded pre-box-type-transformation display, which tracks the animated display while one is applied. When the update dropped the animated value, the re-adjustment pass fed that stale display back in and resurrected it. Reconstruction now starts over from the base style's display whenever the overlay covers `display`. Fixes the WPT web-animations display animation-type test.
Whether HTML attribute-name folding applies is a fact about the document, and a compiled selector carries it. The engine learned it when the first style sheet attached, but a script that runs before that can compile a selector query, and the compiled query is cached, so `[viewBox]` permanently stopped matching HTML elements when the first querySelector call came early enough. Publish the document kind at query compilation too, as the isolated engine for disconnected trees already does. Fixes WPT dom/nodes/querySelector-mixed-case.html.
Three bugs kept the underline and strikethrough commands from seeing text decorations they had to remove. The specified command value read the `text-decoration` shorthand from the style attribute and looked for line keywords in a value list, but the attribute stores expanded longhands and the reconstructed shorthand is a ShorthandStyleValue, so the check always failed and toggling never removed a parent block's decoration. Clearing the value had the same mismatch, plus a VERIFY that the shorthand is a value list. Both now operate on the `text-decoration-line` longhand. The effective command value's ancestor walk advanced the ancestor but kept querying the starting node's resolved value, so a decoration set above the editing host was invisible and toggling wrapped already decorated text in another <u> or <s>. The WPT editing removing-inline-style-specified-by-parent-block test now passes all subtests in all three variants.
Setting an empty user style left the page holding an engaged, empty source, and shadow scopes only share style caches while no user style is present, so sharing stayed disabled for the lifetime of the page. A page outlives the documents a test runner loads into it. The style-engine test that exercises user styles cleans up by setting the empty string, so every test that later ran in the same WebContent process lost scope cache sharing, and the shadow-scopes-share test failed with scopeRuleCacheBuilds=4 whenever the scheduler put it after that test in one process. This is the intermittent CI failure seen on the sanitizer job.
This was referenced Aug 15, 2026
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Fixes found while working through the WPT regressions from the style engine landing: stale old-side workspace answers, a parallel-array shear that swallowed real publications, custom-property removal never invalidating, a prefix interner give-back crash, routing entry points leaking from detached sheets, and a stalled rendering loop that let load handlers run before the first style pass.
Also fixed nearby: heading offsets now walk the host chain per spec (both heading WPT tests fully pass and are imported in-tree), mutating a free-standing Range no longer wipes the selection highlight, and WebDriver no longer crashes closing a window the page already closed.