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LibWeb: Use fast CSS selector matching in default matches() code path
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Before this change, checking if fast selector matching could be used was
only enabled in style recalculation and hover invalidation. With this
change it's enabled for all callers of SelectorEngine::matches() by
default. This way APIs like `Element.matches()` and `querySelector()`
could take advantage of this optimization.
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@kalenikaliaksandr @gmta
kalenikaliaksandr authored and gmta committed Feb 3, 2025
1 parent 17c0d44 commit 0f17ad9
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Showing 7 changed files with 59 additions and 66 deletions.
46 changes: 46 additions & 0 deletions Libraries/LibWeb/CSS/Selector.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,50 @@ static bool component_value_contains_nesting_selector(Parser::ComponentValue con
return false;
}

static bool can_selector_use_fast_matches(CSS::Selector const& selector)
{
for (auto const& compound_selector : selector.compound_selectors()) {
if (compound_selector.combinator != CSS::Selector::Combinator::None
&& compound_selector.combinator != CSS::Selector::Combinator::Descendant
&& compound_selector.combinator != CSS::Selector::Combinator::ImmediateChild) {
return false;
}

for (auto const& simple_selector : compound_selector.simple_selectors) {
if (simple_selector.type == CSS::Selector::SimpleSelector::Type::PseudoClass) {
auto const pseudo_class = simple_selector.pseudo_class().type;
if (pseudo_class != CSS::PseudoClass::FirstChild
&& pseudo_class != CSS::PseudoClass::LastChild
&& pseudo_class != CSS::PseudoClass::OnlyChild
&& pseudo_class != CSS::PseudoClass::Hover
&& pseudo_class != CSS::PseudoClass::Active
&& pseudo_class != CSS::PseudoClass::Focus
&& pseudo_class != CSS::PseudoClass::FocusVisible
&& pseudo_class != CSS::PseudoClass::FocusWithin
&& pseudo_class != CSS::PseudoClass::Link
&& pseudo_class != CSS::PseudoClass::AnyLink
&& pseudo_class != CSS::PseudoClass::Visited
&& pseudo_class != CSS::PseudoClass::LocalLink
&& pseudo_class != CSS::PseudoClass::Empty
&& pseudo_class != CSS::PseudoClass::Root
&& pseudo_class != CSS::PseudoClass::Enabled
&& pseudo_class != CSS::PseudoClass::Disabled
&& pseudo_class != CSS::PseudoClass::Checked) {
return false;
}
} else if (simple_selector.type != CSS::Selector::SimpleSelector::Type::TagName
&& simple_selector.type != CSS::Selector::SimpleSelector::Type::Universal
&& simple_selector.type != CSS::Selector::SimpleSelector::Type::Class
&& simple_selector.type != CSS::Selector::SimpleSelector::Type::Id
&& simple_selector.type != CSS::Selector::SimpleSelector::Type::Attribute) {
return false;
}
}
}

return true;
}

Selector::Selector(Vector<CompoundSelector>&& compound_selectors)
: m_compound_selectors(move(compound_selectors))
{
Expand Down Expand Up @@ -88,6 +132,8 @@ Selector::Selector(Vector<CompoundSelector>&& compound_selectors)
}

collect_ancestor_hashes();

m_can_use_fast_matches = can_selector_use_fast_matches(*this);
}

void Selector::collect_ancestor_hashes()
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3 changes: 3 additions & 0 deletions Libraries/LibWeb/CSS/Selector.h
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Original file line number Diff line number Diff line change
Expand Up @@ -268,12 +268,15 @@ class Selector : public RefCounted<Selector> {

auto const& ancestor_hashes() const { return m_ancestor_hashes; }

bool can_use_fast_matches() const { return m_can_use_fast_matches; }

private:
explicit Selector(Vector<CompoundSelector>&&);

Vector<CompoundSelector> m_compound_selectors;
mutable Optional<u32> m_specificity;
Optional<Selector::PseudoElement> m_pseudo_element;
bool m_can_use_fast_matches { false };
bool m_contains_the_nesting_selector { false };
bool m_contains_hover_pseudo_class { false };

Expand Down
51 changes: 6 additions & 45 deletions Libraries/LibWeb/CSS/SelectorEngine.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -157,7 +157,7 @@ static inline bool matches_link_pseudo_class(DOM::Element const& element)
return element.has_attribute(HTML::AttributeNames::href);
}

bool matches_hover_pseudo_class(DOM::Element const& element)
static bool matches_hover_pseudo_class(DOM::Element const& element)
{
auto* hovered_node = element.document().hovered_node();
if (!hovered_node)
Expand Down Expand Up @@ -899,8 +899,13 @@ bool matches(CSS::Selector const& selector, int component_list_index, DOM::Eleme
VERIFY_NOT_REACHED();
}

bool fast_matches(CSS::Selector const& selector, DOM::Element const& element_to_match, GC::Ptr<DOM::Element const> shadow_host, MatchContext& context);

bool matches(CSS::Selector const& selector, DOM::Element const& element, GC::Ptr<DOM::Element const> shadow_host, MatchContext& context, Optional<CSS::Selector::PseudoElement::Type> pseudo_element, GC::Ptr<DOM::ParentNode const> scope, SelectorKind selector_kind, GC::Ptr<DOM::Element const> anchor)
{
if (selector_kind == SelectorKind::Normal && selector.can_use_fast_matches()) {
return fast_matches(selector, element, shadow_host, context);
}
VERIFY(!selector.compound_selectors().is_empty());
if (pseudo_element.has_value() && selector.pseudo_element().has_value() && selector.pseudo_element().value().type() != pseudo_element)
return false;
Expand Down Expand Up @@ -1011,48 +1016,4 @@ bool fast_matches(CSS::Selector const& selector, DOM::Element const& element_to_
}
}

bool can_use_fast_matches(CSS::Selector const& selector)
{
for (auto const& compound_selector : selector.compound_selectors()) {
if (compound_selector.combinator != CSS::Selector::Combinator::None
&& compound_selector.combinator != CSS::Selector::Combinator::Descendant
&& compound_selector.combinator != CSS::Selector::Combinator::ImmediateChild) {
return false;
}

for (auto const& simple_selector : compound_selector.simple_selectors) {
if (simple_selector.type == CSS::Selector::SimpleSelector::Type::PseudoClass) {
auto const pseudo_class = simple_selector.pseudo_class().type;
if (pseudo_class != CSS::PseudoClass::FirstChild
&& pseudo_class != CSS::PseudoClass::LastChild
&& pseudo_class != CSS::PseudoClass::OnlyChild
&& pseudo_class != CSS::PseudoClass::Hover
&& pseudo_class != CSS::PseudoClass::Active
&& pseudo_class != CSS::PseudoClass::Focus
&& pseudo_class != CSS::PseudoClass::FocusVisible
&& pseudo_class != CSS::PseudoClass::FocusWithin
&& pseudo_class != CSS::PseudoClass::Link
&& pseudo_class != CSS::PseudoClass::AnyLink
&& pseudo_class != CSS::PseudoClass::Visited
&& pseudo_class != CSS::PseudoClass::LocalLink
&& pseudo_class != CSS::PseudoClass::Empty
&& pseudo_class != CSS::PseudoClass::Root
&& pseudo_class != CSS::PseudoClass::Enabled
&& pseudo_class != CSS::PseudoClass::Disabled
&& pseudo_class != CSS::PseudoClass::Checked) {
return false;
}
} else if (simple_selector.type != CSS::Selector::SimpleSelector::Type::TagName
&& simple_selector.type != CSS::Selector::SimpleSelector::Type::Universal
&& simple_selector.type != CSS::Selector::SimpleSelector::Type::Class
&& simple_selector.type != CSS::Selector::SimpleSelector::Type::Id
&& simple_selector.type != CSS::Selector::SimpleSelector::Type::Attribute) {
return false;
}
}
}

return true;
}

}
5 changes: 0 additions & 5 deletions Libraries/LibWeb/CSS/SelectorEngine.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,9 +25,4 @@ struct MatchContext {

bool matches(CSS::Selector const&, DOM::Element const&, GC::Ptr<DOM::Element const> shadow_host, MatchContext& context, Optional<CSS::Selector::PseudoElement::Type> = {}, GC::Ptr<DOM::ParentNode const> scope = {}, SelectorKind selector_kind = SelectorKind::Normal, GC::Ptr<DOM::Element const> anchor = nullptr);

[[nodiscard]] bool fast_matches(CSS::Selector const&, DOM::Element const&, GC::Ptr<DOM::Element const> shadow_host, MatchContext& context);
[[nodiscard]] bool can_use_fast_matches(CSS::Selector const&);

[[nodiscard]] bool matches_hover_pseudo_class(DOM::Element const&);

}
10 changes: 2 additions & 8 deletions Libraries/LibWeb/CSS/StyleComputer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -595,13 +595,8 @@ Vector<MatchingRule const*> StyleComputer::collect_matching_rules(DOM::Element c
if (context.did_match_any_hover_rules)
did_match_any_hover_rules = true;
};
if (rule_to_run.can_use_fast_matches) {
if (!SelectorEngine::fast_matches(selector, element, shadow_host_to_use, context))
continue;
} else {
if (!SelectorEngine::matches(selector, element, shadow_host_to_use, context, pseudo_element))
continue;
}
if (!SelectorEngine::matches(selector, element, shadow_host_to_use, context, pseudo_element))
continue;
matching_rules.append(&rule_to_run);
}

Expand Down Expand Up @@ -2686,7 +2681,6 @@ void StyleComputer::make_rule_cache_for_cascade_origin(CascadeOrigin cascade_ori
selector.specificity(),
cascade_origin,
false,
SelectorEngine::can_use_fast_matches(selector),
false,
};

Expand Down
1 change: 0 additions & 1 deletion Libraries/LibWeb/CSS/StyleComputer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -86,7 +86,6 @@ struct MatchingRule {
u32 specificity { 0 };
CascadeOrigin cascade_origin;
bool contains_pseudo_element { false };
bool can_use_fast_matches { false };
bool must_be_hovered { false };

// Helpers to deal with the fact that `rule` might be a CSSStyleRule or a CSSNestedDeclarations
Expand Down
9 changes: 2 additions & 7 deletions Libraries/LibWeb/DOM/Document.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1728,13 +1728,8 @@ void Document::invalidate_style_for_elements_affected_by_hover_change(Node& old_

SelectorEngine::MatchContext context;
bool selector_matched = false;
if (rule.can_use_fast_matches) {
if (SelectorEngine::fast_matches(selector, element, {}, context))
selector_matched = true;
} else {
if (SelectorEngine::matches(selector, element, {}, context, {}))
selector_matched = true;
}
if (SelectorEngine::matches(selector, element, {}, context, {}))
selector_matched = true;
if (element.has_pseudo_elements()) {
if (SelectorEngine::matches(selector, element, {}, context, CSS::Selector::PseudoElement::Type::Before))
selector_matched = true;
Expand Down

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