perf(bridge): CSS style engine optimizations + invalidation fixes #806
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andycall
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Jan 16, 2026
- Cache author stylesheets in DOM order via StyleEngine and match against that list to preserve cascade semantics and avoid matching inline/link sheets twice. - Reuse cached UA default HTML stylesheet RuleSet instead of rebuilding per match. - Track pseudo-element matches during normal collection; only resolve ::before/::after when `content` is present, prefilter pseudo selector buckets, and clear stale pseudo styles via a per-element sent mask. - Initialize Document URL from script/module sourceURL (and Dart-provided URL for parseHTML/bytecode eval) so @import/url() never leak about:* bases across the bridge. - Add gtests for pseudo style gating.
UA (user-agent) default styles are now provided by the Dart engine only. This removes the native UA stylesheet pipeline from the C++ bridge: - Drop CSSDefaultStyleSheets and bundled html.css/quirks.css resources - Remove UA rule matching from StyleResolver / ElementRuleCollector - Remove CMake CSS header generation and source list entry - Update tests to stop resetting UA stylesheets
Blink-style declared-value recalc was rebuilding MediaQueryEvaluator for every element during MatchAuthorRules, which is expensive because it constructs dynamic MediaValues. Changes: - Reuse cached author-sheet RuleSets via StyleSheetContents::GetRuleSetShared() and only call EnsureRuleSet() (and thus create a MediaQueryEvaluator) on cache miss. - Lazily construct a single MediaQueryEvaluator per MatchAuthorRules call instead of per element. - Make MatchRequest store the common single RuleSet inline and iterate via ForEachRuleSet() to avoid per-match vector allocations. Tests: - node scripts/run_bridge_unit_test.js (fails: StyleEngineTest.SiblingInvalidationDirectAdjacentOnInsertion)
- Cache viewport width/height + DPR in ExecutingContext and feed via Page resize/DPR callbacks. MediaValues reads cached values first to avoid synchronous GetBindingProperty during MQ eval. - Optimize cascade construction by avoiding per-property stable_sort in StyleCascade::AnalyzeMatchResult. - Speed up selector rule collection: use std::sort (cascade_order is unique) and avoid allocating typed-only ID buckets. - Minor: assign MatchResult directly into StyleCascade in StyleEngine. Also remove noisy style update timing log previously used for profiling. Tests: - cmake --build bridge/cmake-build-macos-arm64 -j 8 - bridge/build/macos/lib/arm64/webf_css_unittests '--gtest_filter=StyleCascadeTest.*' # Conflicts: # webf/example/macos/Runner.xcodeproj/project.pbxproj
…mments - Update cascade origin documentation to provide clearer implementation details. - Adjust bit manipulation logic for important origins to simplify flipping behavior while preserving transition bit. - Refactor constants and inline methods for improved readability and consistency.
…ld options - Eliminated WEBF_LOG_* macros and conditional logging logic. - Simplified CMakeLists.txt by removing log category definitions and build-time switches. - Streamlined logging implementation for maintenance and readability.
- Bridge: cache preferred color scheme in ExecutingContext and reuse it in MediaValuesDynamic::PreferredColorScheme - Bridge: update cached scheme on nativeOnColorSchemeChanged to keep prefers-color-scheme media queries consistent - Dart: on attach/brightness change, dispatch ColorSchemeChangeEvent and notify native Blink when not overridden - Dart: make WebFController.isDarkMode fall back to PlatformDispatcher for consistent system brightness - Example: keep DayNightSwitcherIcon in sync (app toggle sets override; system toggle clears override to null) - macOS example: embed objective_c.framework for plugin linkage
…anges - Ensure descendants of elements transitioning from `display:none` to visible recalculate styles to pick up inline styles and render correctly. - Add handling for `IsDisplayNoneForStyleInvalidation` to trigger subtree recalculation and clear subtree flags.
- Dropped redundant `nativeOnColorSchemeChanged` call, as platform brightness changes no longer notify native Blink.
…equirement - Ensure sibling invalidations occur even when restyle flags are not set by WebF. - Adjust logic to skip unnecessary checks for indirect/direct adjacent rules before scheduling invalidations. - Add safe handling for inserting/removing sibling elements when selector matching is incomplete.
And run generate_ios_mirror_ccs.js --fix - Added logic to detect and remove orphan wrappers no longer matching source files or configuration. - Extended wrapper support to include `.mm` files. - Updated `--fix` flag to remove orphans and prune empty directories. - Improved dry-run mode to clarify removal actions without modifying files.
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Motivation
This branch focuses on CSS correctness and performance in the bridge style engine, especially around stylesheet ordering/base URL, media-query evaluation, and style invalidation.
What changed
CSS correctness
display:noneto visible by forcing subtree style recalculation (prevents descendants from keeping stale styles).Performance
MediaQueryEvaluatorconstruction during rule matching; reuse evaluator via match request context.Refactors / cleanup
Commits (in order)
fix(css): preserve author sheet DOM order and base URLrefactor(bridge): remove UA stylesheet handlingperf(bridge): avoid per-element MediaQueryEvaluator in rule matchingperf(bridge): speed up resize media-query style recalcrefactor(css): clarify cascade origin bit manipulation and improve commentsrefactor(logging): remove per-category logging system and related build optionsfix(theme): sync system color scheme and overridesfix: buildfix(css): recompute subtree styles after display:none -> visible changesRisk / compatibility notes
bridge/core/css/style_engine.cc; please pay extra attention to regressions in selector matching, invalidation, and stylesheet ordering.Testing
node scripts/run_bridge_unit_test.js).