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LibWeb: Reduce HashMap thrashing during custom property cascade
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Build the final custom property map right away instead of first making
a temporary pointer-only map. We also precompute the final needed
capacity for the map to avoid incremental rehashing.
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@awesomekling
awesomekling committed Mar 3, 2022
1 parent e4fdb40 commit 205208d
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Showing 3 changed files with 23 additions and 25 deletions.
35 changes: 19 additions & 16 deletions Userland/Libraries/LibWeb/CSS/StyleComputer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -439,7 +439,7 @@ static void set_property_expanding_shorthands(StyleProperties& style, CSS::Prope
style.set_property(property_id, value);
}

bool StyleComputer::expand_unresolved_values(DOM::Element& element, StringView property_name, HashMap<FlyString, NonnullRefPtr<PropertyDependencyNode>>& dependencies, Vector<StyleComponentValueRule> const& source, Vector<StyleComponentValueRule>& dest, size_t source_start_index, HashMap<FlyString, StyleProperty const*> const& custom_properties) const
bool StyleComputer::expand_unresolved_values(DOM::Element& element, StringView property_name, HashMap<FlyString, NonnullRefPtr<PropertyDependencyNode>>& dependencies, Vector<StyleComponentValueRule> const& source, Vector<StyleComponentValueRule>& dest, size_t source_start_index, HashMap<FlyString, StyleProperty> const& custom_properties) const
{
// FIXME: Do this better!
// We build a copy of the tree of StyleComponentValueRules, with all var()s replaced with their contents.
Expand All @@ -456,7 +456,7 @@ bool StyleComputer::expand_unresolved_values(DOM::Element& element, StringView p
auto get_custom_property = [&custom_properties](auto& name) -> RefPtr<StyleValue> {
auto it = custom_properties.find(name);
if (it != custom_properties.end())
return it->value->value;
return it->value.value;
return nullptr;
};

Expand Down Expand Up @@ -532,7 +532,7 @@ bool StyleComputer::expand_unresolved_values(DOM::Element& element, StringView p
return true;
}

RefPtr<StyleValue> StyleComputer::resolve_unresolved_style_value(DOM::Element& element, PropertyID property_id, UnresolvedStyleValue const& unresolved, HashMap<FlyString, StyleProperty const*> const& custom_properties) const
RefPtr<StyleValue> StyleComputer::resolve_unresolved_style_value(DOM::Element& element, PropertyID property_id, UnresolvedStyleValue const& unresolved, HashMap<FlyString, StyleProperty> const& custom_properties) const
{
// Unresolved always contains a var(), unless it is a custom property's value, in which case we shouldn't be trying
// to produce a different StyleValue from it.
Expand All @@ -549,7 +549,7 @@ RefPtr<StyleValue> StyleComputer::resolve_unresolved_style_value(DOM::Element& e
return {};
}

void StyleComputer::cascade_declarations(StyleProperties& style, DOM::Element& element, Vector<MatchingRule> const& matching_rules, CascadeOrigin cascade_origin, Important important, HashMap<FlyString, StyleProperty const*> const& custom_properties) const
void StyleComputer::cascade_declarations(StyleProperties& style, DOM::Element& element, Vector<MatchingRule> const& matching_rules, CascadeOrigin cascade_origin, Important important, HashMap<FlyString, StyleProperty> const& custom_properties) const
{
for (auto const& match : matching_rules) {
for (auto const& property : verify_cast<PropertyOwningCSSStyleDeclaration>(match.rule->declaration()).properties()) {
Expand All @@ -575,26 +575,29 @@ void StyleComputer::cascade_declarations(StyleProperties& style, DOM::Element& e
}
}

static HashMap<FlyString, StyleProperty const*> cascade_custom_properties(DOM::Element& element, Vector<MatchingRule> const& matching_rules)
static HashMap<FlyString, StyleProperty> const& cascade_custom_properties(DOM::Element& element, Vector<MatchingRule> const& matching_rules)
{
HashMap<FlyString, StyleProperty const*> custom_properties;
size_t needed_capacity = 0;
if (auto* parent_element = element.parent_element())
needed_capacity += parent_element->custom_properties().size();
for (auto const& matching_rule : matching_rules)
needed_capacity += verify_cast<PropertyOwningCSSStyleDeclaration>(matching_rule.rule->declaration()).custom_properties().size();

HashMap<FlyString, StyleProperty> custom_properties;
custom_properties.ensure_capacity(needed_capacity);

if (auto* parent_element = element.parent_element()) {
for (auto const& it : parent_element->custom_properties())
custom_properties.set(it.key, &it.value);
custom_properties.set(it.key, it.value);
}

for (auto const& matching_rule : matching_rules) {
for (auto const& it : verify_cast<PropertyOwningCSSStyleDeclaration>(matching_rule.rule->declaration()).custom_properties()) {
custom_properties.set(it.key, &it.value);
}
for (auto const& it : verify_cast<PropertyOwningCSSStyleDeclaration>(matching_rule.rule->declaration()).custom_properties())
custom_properties.set(it.key, it.value);
}

element.custom_properties().clear();
for (auto& it : custom_properties)
element.add_custom_property(it.key, *it.value);

return custom_properties;
element.set_custom_properties(move(custom_properties));
return element.custom_properties();
}

// https://www.w3.org/TR/css-cascade/#cascading
Expand All @@ -608,7 +611,7 @@ void StyleComputer::compute_cascaded_values(StyleProperties& style, DOM::Element
sort_matching_rules(matching_rule_set.author_rules);

// Then we resolve all the CSS custom properties ("variables") for this element:
auto custom_properties = cascade_custom_properties(element, matching_rule_set.author_rules);
auto const& custom_properties = cascade_custom_properties(element, matching_rule_set.author_rules);

// Then we apply the declarations from the matched rules in cascade order:

Expand Down
6 changes: 3 additions & 3 deletions Userland/Libraries/LibWeb/CSS/StyleComputer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -78,8 +78,8 @@ class StyleComputer {

void compute_defaulted_property_value(StyleProperties&, DOM::Element const*, CSS::PropertyID, Optional<CSS::Selector::PseudoElement>) const;

RefPtr<StyleValue> resolve_unresolved_style_value(DOM::Element&, PropertyID, UnresolvedStyleValue const&, HashMap<FlyString, StyleProperty const*> const&) const;
bool expand_unresolved_values(DOM::Element&, StringView property_name, HashMap<FlyString, NonnullRefPtr<PropertyDependencyNode>>& dependencies, Vector<StyleComponentValueRule> const& source, Vector<StyleComponentValueRule>& dest, size_t source_start_index, HashMap<FlyString, StyleProperty const*> const& custom_properties) const;
RefPtr<StyleValue> resolve_unresolved_style_value(DOM::Element&, PropertyID, UnresolvedStyleValue const&, HashMap<FlyString, StyleProperty> const&) const;
bool expand_unresolved_values(DOM::Element&, StringView property_name, HashMap<FlyString, NonnullRefPtr<PropertyDependencyNode>>& dependencies, Vector<StyleComponentValueRule> const& source, Vector<StyleComponentValueRule>& dest, size_t source_start_index, HashMap<FlyString, StyleProperty> const& custom_properties) const;

template<typename Callback>
void for_each_stylesheet(CascadeOrigin, Callback) const;
Expand All @@ -89,7 +89,7 @@ class StyleComputer {
Vector<MatchingRule> author_rules;
};

void cascade_declarations(StyleProperties&, DOM::Element&, Vector<MatchingRule> const&, CascadeOrigin, Important important, HashMap<FlyString, StyleProperty const*> const&) const;
void cascade_declarations(StyleProperties&, DOM::Element&, Vector<MatchingRule> const&, CascadeOrigin, Important important, HashMap<FlyString, StyleProperty> const&) const;

void build_rule_cache();
void build_rule_cache_if_needed() const;
Expand Down
7 changes: 1 addition & 6 deletions Userland/Libraries/LibWeb/DOM/Element.h
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Original file line number Diff line number Diff line change
Expand Up @@ -113,13 +113,8 @@ class Element
const ShadowRoot* shadow_root() const { return m_shadow_root; }
void set_shadow_root(RefPtr<ShadowRoot>);

void add_custom_property(String custom_property_name, CSS::StyleProperty style_property)
{
m_custom_properties.set(move(custom_property_name), move(style_property));
}

void set_custom_properties(HashMap<FlyString, CSS::StyleProperty> custom_properties) { m_custom_properties = move(custom_properties); }
HashMap<FlyString, CSS::StyleProperty> const& custom_properties() const { return m_custom_properties; }
HashMap<FlyString, CSS::StyleProperty>& custom_properties() { return m_custom_properties; }

void queue_an_element_task(HTML::Task::Source, Function<void()>);

Expand Down

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