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ladybird/Userland/Libraries/LibWeb/CSS/StyleResolver.cpp
Andreas Kling d965a9552f LibWeb: Start implementing the CSS cascade 
The 'C' in "CSS" is for Cascade, so let's actually implement the cascade
in LibWeb. :^)

StyleResolver::resolve_style() now begins by collecting all the matching
CSS rules for the given DOM::Element. Rules are then processed in the
spec's cascade order (instead of in the order we encounter them.)

With this, "!important" is now honored on CSS properties.

After performing the cascade, we do another pass of what the spec calls
"defaulting" where we resolve "inherit" and "initial" values.
I've left a FIXME about supporting correct "initial" values for every
property, since we're currently lacking some coverage there.

Note that this mechanism now resolves every known CSS property. This is
*not* space-efficient and we'll eventually need to come up with some
strategies to reduce memory usage around this. However, this will do
fine until we have more of the engine working correctly. :^)
2021-09-21 12:49:28 +02:00

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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, the SerenityOS developers.
* Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/QuickSort.h>
#include <LibWeb/CSS/CSSStyleRule.h>
#include <LibWeb/CSS/Parser/Parser.h>
#include <LibWeb/CSS/SelectorEngine.h>
#include <LibWeb/CSS/StyleResolver.h>
#include <LibWeb/CSS/StyleSheet.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/Element.h>
#include <LibWeb/Dump.h>
#include <ctype.h>
#include <stdio.h>
namespace Web::CSS {
StyleResolver::StyleResolver(DOM::Document& document)
: m_document(document)
{
}
StyleResolver::~StyleResolver()
{
}
static StyleSheet& default_stylesheet()
{
static StyleSheet* sheet;
if (!sheet) {
extern char const default_stylesheet_source[];
String css = default_stylesheet_source;
sheet = parse_css(CSS::ParsingContext(), css).leak_ref();
}
return *sheet;
}
static StyleSheet& quirks_mode_stylesheet()
{
static StyleSheet* sheet;
if (!sheet) {
extern char const quirks_mode_stylesheet_source[];
String css = quirks_mode_stylesheet_source;
sheet = parse_css(CSS::ParsingContext(), css).leak_ref();
}
return *sheet;
}
template<typename Callback>
void StyleResolver::for_each_stylesheet(CascadeOrigin cascade_origin, Callback callback) const
{
if (cascade_origin == CascadeOrigin::Any || cascade_origin == CascadeOrigin::UserAgent) {
callback(default_stylesheet());
if (document().in_quirks_mode())
callback(quirks_mode_stylesheet());
}
if (cascade_origin == CascadeOrigin::Any || cascade_origin == CascadeOrigin::Author) {
for (auto& sheet : document().style_sheets().sheets()) {
callback(sheet);
}
}
}
Vector<MatchingRule> StyleResolver::collect_matching_rules(DOM::Element const& element, CascadeOrigin declaration_type) const
{
Vector<MatchingRule> matching_rules;
size_t style_sheet_index = 0;
for_each_stylesheet(declaration_type, [&](auto& sheet) {
size_t rule_index = 0;
static_cast<CSSStyleSheet const&>(sheet).for_each_effective_style_rule([&](auto& rule) {
size_t selector_index = 0;
for (auto& selector : rule.selectors()) {
if (SelectorEngine::matches(selector, element)) {
matching_rules.append({ rule, style_sheet_index, rule_index, selector_index, selector.specificity() });
break;
}
++selector_index;
}
++rule_index;
});
++style_sheet_index;
});
return matching_rules;
}
void StyleResolver::sort_matching_rules(Vector<MatchingRule>& matching_rules) const
{
quick_sort(matching_rules, [&](MatchingRule& a, MatchingRule& b) {
auto& a_selector = a.rule->selectors()[a.selector_index];
auto& b_selector = b.rule->selectors()[b.selector_index];
auto a_specificity = a_selector.specificity();
auto b_specificity = b_selector.specificity();
if (a_selector.specificity() == b_selector.specificity()) {
if (a.style_sheet_index == b.style_sheet_index)
return a.rule_index < b.rule_index;
return a.style_sheet_index < b.style_sheet_index;
}
return a_specificity < b_specificity;
});
}
enum class Edge {
Top,
Right,
Bottom,
Left,
All,
};
static bool contains(Edge a, Edge b)
{
return a == b || b == Edge::All;
}
static void set_property_expanding_shorthands(StyleProperties& style, CSS::PropertyID property_id, StyleValue const& value, DOM::Document& document, bool is_internally_generated_pseudo_property = false)
{
if (is_pseudo_property(property_id) && !is_internally_generated_pseudo_property) {
dbgln("Ignoring non-internally-generated pseudo property: {}", string_from_property_id(property_id));
return;
}
auto assign_edge_values = [&style](PropertyID top_property, PropertyID right_property, PropertyID bottom_property, PropertyID left_property, auto const& values) {
if (values.size() == 4) {
style.set_property(top_property, values[0]);
style.set_property(right_property, values[1]);
style.set_property(bottom_property, values[2]);
style.set_property(left_property, values[3]);
} else if (values.size() == 3) {
style.set_property(top_property, values[0]);
style.set_property(right_property, values[1]);
style.set_property(bottom_property, values[2]);
style.set_property(left_property, values[1]);
} else if (values.size() == 2) {
style.set_property(top_property, values[0]);
style.set_property(right_property, values[1]);
style.set_property(bottom_property, values[0]);
style.set_property(left_property, values[1]);
} else if (values.size() == 1) {
style.set_property(top_property, values[0]);
style.set_property(right_property, values[0]);
style.set_property(bottom_property, values[0]);
style.set_property(left_property, values[0]);
}
};
if (property_id == CSS::PropertyID::TextDecoration) {
if (value.is_text_decoration()) {
auto& text_decoration = static_cast<TextDecorationStyleValue const&>(value);
style.set_property(CSS::PropertyID::TextDecorationLine, text_decoration.line());
style.set_property(CSS::PropertyID::TextDecorationStyle, text_decoration.style());
style.set_property(CSS::PropertyID::TextDecorationColor, text_decoration.color());
return;
}
if (value.is_builtin()) {
style.set_property(CSS::PropertyID::TextDecorationLine, value);
style.set_property(CSS::PropertyID::TextDecorationStyle, value);
style.set_property(CSS::PropertyID::TextDecorationColor, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::Overflow) {
if (value.is_overflow()) {
auto& overflow = static_cast<OverflowStyleValue const&>(value);
style.set_property(CSS::PropertyID::OverflowX, overflow.overflow_x());
style.set_property(CSS::PropertyID::OverflowY, overflow.overflow_y());
return;
}
if (value.is_builtin()) {
style.set_property(CSS::PropertyID::OverflowX, value);
style.set_property(CSS::PropertyID::OverflowY, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::Border) {
set_property_expanding_shorthands(style, CSS::PropertyID::BorderTop, value, document);
set_property_expanding_shorthands(style, CSS::PropertyID::BorderRight, value, document);
set_property_expanding_shorthands(style, CSS::PropertyID::BorderBottom, value, document);
set_property_expanding_shorthands(style, CSS::PropertyID::BorderLeft, value, document);
// FIXME: Also reset border-image, in line with the spec: https://www.w3.org/TR/css-backgrounds-3/#border-shorthands
return;
}
if (property_id == CSS::PropertyID::BorderRadius) {
if (value.is_value_list()) {
auto& values_list = static_cast<StyleValueList const&>(value);
assign_edge_values(PropertyID::BorderTopLeftRadius, PropertyID::BorderTopRightRadius, PropertyID::BorderBottomRightRadius, PropertyID::BorderBottomLeftRadius, values_list.values());
return;
}
if (value.is_builtin()) {
style.set_property(CSS::PropertyID::BorderTopLeftRadius, value);
style.set_property(CSS::PropertyID::BorderTopRightRadius, value);
style.set_property(CSS::PropertyID::BorderBottomRightRadius, value);
style.set_property(CSS::PropertyID::BorderBottomLeftRadius, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::BorderTop
|| property_id == CSS::PropertyID::BorderRight
|| property_id == CSS::PropertyID::BorderBottom
|| property_id == CSS::PropertyID::BorderLeft) {
Edge edge = Edge::All;
switch (property_id) {
case CSS::PropertyID::BorderTop:
edge = Edge::Top;
break;
case CSS::PropertyID::BorderRight:
edge = Edge::Right;
break;
case CSS::PropertyID::BorderBottom:
edge = Edge::Bottom;
break;
case CSS::PropertyID::BorderLeft:
edge = Edge::Left;
break;
default:
break;
}
if (value.is_border()) {
auto& border = static_cast<BorderStyleValue const&>(value);
if (contains(Edge::Top, edge)) {
style.set_property(PropertyID::BorderTopWidth, border.border_width());
style.set_property(PropertyID::BorderTopStyle, border.border_style());
style.set_property(PropertyID::BorderTopColor, border.border_color());
}
if (contains(Edge::Right, edge)) {
style.set_property(PropertyID::BorderRightWidth, border.border_width());
style.set_property(PropertyID::BorderRightStyle, border.border_style());
style.set_property(PropertyID::BorderRightColor, border.border_color());
}
if (contains(Edge::Bottom, edge)) {
style.set_property(PropertyID::BorderBottomWidth, border.border_width());
style.set_property(PropertyID::BorderBottomStyle, border.border_style());
style.set_property(PropertyID::BorderBottomColor, border.border_color());
}
if (contains(Edge::Left, edge)) {
style.set_property(PropertyID::BorderLeftWidth, border.border_width());
style.set_property(PropertyID::BorderLeftStyle, border.border_style());
style.set_property(PropertyID::BorderLeftColor, border.border_color());
}
return;
}
return;
}
if (property_id == CSS::PropertyID::BorderStyle) {
if (value.is_value_list()) {
auto& values_list = static_cast<StyleValueList const&>(value);
assign_edge_values(PropertyID::BorderTopStyle, PropertyID::BorderRightStyle, PropertyID::BorderBottomStyle, PropertyID::BorderLeftStyle, values_list.values());
return;
}
if (value.is_builtin()) {
style.set_property(CSS::PropertyID::BorderTopStyle, value);
style.set_property(CSS::PropertyID::BorderRightStyle, value);
style.set_property(CSS::PropertyID::BorderBottomStyle, value);
style.set_property(CSS::PropertyID::BorderLeftStyle, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::BorderWidth) {
if (value.is_value_list()) {
auto& values_list = static_cast<StyleValueList const&>(value);
assign_edge_values(PropertyID::BorderTopWidth, PropertyID::BorderRightWidth, PropertyID::BorderBottomWidth, PropertyID::BorderLeftWidth, values_list.values());
return;
}
if (value.is_builtin()) {
style.set_property(CSS::PropertyID::BorderTopWidth, value);
style.set_property(CSS::PropertyID::BorderRightWidth, value);
style.set_property(CSS::PropertyID::BorderBottomWidth, value);
style.set_property(CSS::PropertyID::BorderLeftWidth, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::BorderColor) {
if (value.is_value_list()) {
auto& values_list = static_cast<StyleValueList const&>(value);
assign_edge_values(PropertyID::BorderTopColor, PropertyID::BorderRightColor, PropertyID::BorderBottomColor, PropertyID::BorderLeftColor, values_list.values());
return;
}
if (value.is_builtin()) {
style.set_property(CSS::PropertyID::BorderTopColor, value);
style.set_property(CSS::PropertyID::BorderRightColor, value);
style.set_property(CSS::PropertyID::BorderBottomColor, value);
style.set_property(CSS::PropertyID::BorderLeftColor, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::Background) {
auto set_single_background = [&](CSS::BackgroundStyleValue const& background) {
set_property_expanding_shorthands(style, CSS::PropertyID::BackgroundColor, background.color(), document);
set_property_expanding_shorthands(style, CSS::PropertyID::BackgroundImage, background.image(), document);
set_property_expanding_shorthands(style, CSS::PropertyID::BackgroundRepeatX, background.repeat_x(), document, true);
set_property_expanding_shorthands(style, CSS::PropertyID::BackgroundRepeatY, background.repeat_y(), document, true);
};
if (value.is_background()) {
auto& background = static_cast<CSS::BackgroundStyleValue const&>(value);
set_single_background(background);
return;
}
if (value.is_value_list()) {
auto& background_list = static_cast<CSS::StyleValueList const&>(value).values();
// FIXME: Handle multiple backgrounds.
if (!background_list.is_empty()) {
auto& background = background_list.first();
if (background.is_background())
set_single_background(static_cast<CSS::BackgroundStyleValue const&>(background));
}
return;
}
if (value.is_builtin()) {
set_property_expanding_shorthands(style, CSS::PropertyID::BackgroundColor, value, document);
set_property_expanding_shorthands(style, CSS::PropertyID::BackgroundImage, value, document);
set_property_expanding_shorthands(style, CSS::PropertyID::BackgroundRepeatX, value, document, true);
set_property_expanding_shorthands(style, CSS::PropertyID::BackgroundRepeatY, value, document, true);
return;
}
return;
}
if (property_id == CSS::PropertyID::BackgroundImage) {
if (value.is_value_list()) {
auto& background_image_list = static_cast<CSS::StyleValueList const&>(value).values();
// FIXME: Handle multiple backgrounds.
if (!background_image_list.is_empty()) {
auto& background_image = background_image_list.first();
style.set_property(CSS::PropertyID::BackgroundImage, background_image);
}
return;
}
if (value.is_builtin() || value.is_image() || value.to_identifier() == ValueID::None) {
style.set_property(CSS::PropertyID::BackgroundImage, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::BackgroundRepeat) {
if (value.is_value_list()) {
auto& background_repeat_list = static_cast<CSS::StyleValueList const&>(value).values();
// FIXME: Handle multiple backgrounds.
if (!background_repeat_list.is_empty()) {
auto& maybe_background_repeat = background_repeat_list.first();
if (maybe_background_repeat.is_background_repeat()) {
auto& background_repeat = static_cast<BackgroundRepeatStyleValue const&>(maybe_background_repeat);
set_property_expanding_shorthands(style, PropertyID::BackgroundRepeatX, background_repeat.repeat_x(), document, true);
set_property_expanding_shorthands(style, PropertyID::BackgroundRepeatY, background_repeat.repeat_y(), document, true);
}
}
return;
}
if (value.is_background_repeat()) {
auto& background_repeat = static_cast<BackgroundRepeatStyleValue const&>(value);
set_property_expanding_shorthands(style, PropertyID::BackgroundRepeatX, background_repeat.repeat_x(), document, true);
set_property_expanding_shorthands(style, PropertyID::BackgroundRepeatY, background_repeat.repeat_y(), document, true);
return;
}
if (value.is_builtin()) {
set_property_expanding_shorthands(style, PropertyID::BackgroundRepeatX, value, document, true);
set_property_expanding_shorthands(style, PropertyID::BackgroundRepeatY, value, document, true);
return;
}
return;
}
if (property_id == CSS::PropertyID::BackgroundRepeatX || property_id == CSS::PropertyID::BackgroundRepeatY) {
auto value_id = value.to_identifier();
if (value_id == CSS::ValueID::RepeatX || value_id == CSS::ValueID::RepeatY)
return;
style.set_property(property_id, value);
return;
}
if (property_id == CSS::PropertyID::Margin) {
if (value.is_value_list()) {
auto& values_list = static_cast<StyleValueList const&>(value);
assign_edge_values(PropertyID::MarginTop, PropertyID::MarginRight, PropertyID::MarginBottom, PropertyID::MarginLeft, values_list.values());
return;
}
if (value.is_length() || value.is_builtin()) {
style.set_property(CSS::PropertyID::MarginTop, value);
style.set_property(CSS::PropertyID::MarginRight, value);
style.set_property(CSS::PropertyID::MarginBottom, value);
style.set_property(CSS::PropertyID::MarginLeft, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::Padding) {
if (value.is_value_list()) {
auto& values_list = static_cast<StyleValueList const&>(value);
assign_edge_values(PropertyID::PaddingTop, PropertyID::PaddingRight, PropertyID::PaddingBottom, PropertyID::PaddingLeft, values_list.values());
return;
}
if (value.is_length() || value.is_builtin()) {
style.set_property(CSS::PropertyID::PaddingTop, value);
style.set_property(CSS::PropertyID::PaddingRight, value);
style.set_property(CSS::PropertyID::PaddingBottom, value);
style.set_property(CSS::PropertyID::PaddingLeft, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::ListStyle) {
if (value.is_list_style()) {
auto& list_style = static_cast<CSS::ListStyleStyleValue const&>(value);
style.set_property(CSS::PropertyID::ListStylePosition, list_style.position());
style.set_property(CSS::PropertyID::ListStyleImage, list_style.image());
style.set_property(CSS::PropertyID::ListStyleType, list_style.style_type());
return;
}
if (value.is_builtin()) {
style.set_property(CSS::PropertyID::ListStylePosition, value);
style.set_property(CSS::PropertyID::ListStyleImage, value);
style.set_property(CSS::PropertyID::ListStyleType, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::Font) {
if (value.is_font()) {
auto& font_shorthand = static_cast<CSS::FontStyleValue const&>(value);
style.set_property(CSS::PropertyID::FontSize, font_shorthand.font_size());
style.set_property(CSS::PropertyID::FontFamily, font_shorthand.font_families());
style.set_property(CSS::PropertyID::FontStyle, font_shorthand.font_style());
style.set_property(CSS::PropertyID::FontWeight, font_shorthand.font_weight());
style.set_property(CSS::PropertyID::LineHeight, font_shorthand.line_height());
// FIXME: Implement font-stretch and font-variant
return;
}
if (value.is_builtin()) {
style.set_property(CSS::PropertyID::FontSize, value);
style.set_property(CSS::PropertyID::FontFamily, value);
style.set_property(CSS::PropertyID::FontStyle, value);
style.set_property(CSS::PropertyID::FontWeight, value);
style.set_property(CSS::PropertyID::LineHeight, value);
// FIXME: Implement font-stretch and font-variant
return;
}
return;
}
if (property_id == CSS::PropertyID::Flex) {
if (value.is_flex()) {
auto& flex = static_cast<CSS::FlexStyleValue const&>(value);
style.set_property(CSS::PropertyID::FlexGrow, flex.grow());
style.set_property(CSS::PropertyID::FlexShrink, flex.shrink());
style.set_property(CSS::PropertyID::FlexBasis, flex.basis());
return;
}
if (value.is_builtin()) {
style.set_property(CSS::PropertyID::FlexGrow, value);
style.set_property(CSS::PropertyID::FlexShrink, value);
style.set_property(CSS::PropertyID::FlexBasis, value);
return;
}
return;
}
if (property_id == CSS::PropertyID::FlexFlow) {
if (value.is_flex_flow()) {
auto& flex_flow = static_cast<FlexFlowStyleValue const&>(value);
style.set_property(CSS::PropertyID::FlexDirection, flex_flow.flex_direction());
style.set_property(CSS::PropertyID::FlexWrap, flex_flow.flex_wrap());
return;
}
if (value.is_builtin()) {
style.set_property(CSS::PropertyID::FlexDirection, value);
style.set_property(CSS::PropertyID::FlexWrap, value);
return;
}
return;
}
style.set_property(property_id, value);
}
StyleResolver::CustomPropertyResolutionTuple StyleResolver::resolve_custom_property_with_specificity(DOM::Element& element, String const& custom_property_name) const
{
if (auto maybe_property = element.resolve_custom_property(custom_property_name); maybe_property.has_value())
return maybe_property.value();
auto parent_element = element.parent_element();
CustomPropertyResolutionTuple parent_resolved {};
if (parent_element)
parent_resolved = resolve_custom_property_with_specificity(*parent_element, custom_property_name);
auto matching_rules = collect_matching_rules(element);
sort_matching_rules(matching_rules);
for (int i = matching_rules.size() - 1; i >= 0; --i) {
auto& match = matching_rules[i];
if (match.specificity < parent_resolved.specificity)
continue;
auto custom_property_style = verify_cast<PropertyOwningCSSStyleDeclaration>(match.rule->declaration()).custom_property(custom_property_name);
if (custom_property_style.has_value()) {
element.add_custom_property(custom_property_name, { custom_property_style.value(), match.specificity });
return { custom_property_style.value(), match.specificity };
}
}
return parent_resolved;
}
Optional<StyleProperty> StyleResolver::resolve_custom_property(DOM::Element& element, String const& custom_property_name) const
{
auto resolved_with_specificity = resolve_custom_property_with_specificity(element, custom_property_name);
return resolved_with_specificity.style;
}
struct MatchingDeclarations {
Vector<MatchingRule> user_agent_rules;
Vector<MatchingRule> author_rules;
};
void StyleResolver::cascade_declarations(StyleProperties& style, DOM::Element& element, Vector<MatchingRule> const& matching_rules, CascadeOrigin cascade_origin, bool important) const
{
for (auto& match : matching_rules) {
for (auto& property : verify_cast<PropertyOwningCSSStyleDeclaration>(match.rule->declaration()).properties()) {
if (important != property.important)
continue;
auto property_value = property.value;
if (property.value->is_custom_property()) {
auto custom_property_name = static_cast<CSS::CustomStyleValue const&>(*property.value).custom_property_name();
auto resolved = resolve_custom_property(element, custom_property_name);
if (resolved.has_value()) {
property_value = resolved.value().value;
}
}
set_property_expanding_shorthands(style, property.property_id, property_value, m_document);
}
}
if (cascade_origin == CascadeOrigin::Author) {
if (auto* inline_style = verify_cast<ElementInlineCSSStyleDeclaration>(element.inline_style())) {
for (auto& property : inline_style->properties()) {
if (important != property.important)
continue;
set_property_expanding_shorthands(style, property.property_id, property.value, m_document);
}
}
}
}
// https://drafts.csswg.org/css-cascade/#cascading
void StyleResolver::compute_cascaded_values(StyleProperties& style, DOM::Element& element) const
{
// First, we collect all the CSS rules whose selectors match `element`:
MatchingRuleSet matching_rule_set;
matching_rule_set.user_agent_rules = collect_matching_rules(element, CascadeOrigin::UserAgent);
sort_matching_rules(matching_rule_set.user_agent_rules);
matching_rule_set.author_rules = collect_matching_rules(element, CascadeOrigin::Author);
sort_matching_rules(matching_rule_set.author_rules);
// Then we apply the declarations from the matched rules in cascade order:
// Normal user agent declarations
cascade_declarations(style, element, matching_rule_set.user_agent_rules, CascadeOrigin::UserAgent, false);
// FIXME: Normal user declarations
// Normal author declarations
cascade_declarations(style, element, matching_rule_set.author_rules, CascadeOrigin::Author, false);
// Author presentational hints (NOTE: The spec doesn't say exactly how to prioritize these.)
element.apply_presentational_hints(style);
// FIXME: Animation declarations [css-animations-1]
// Important author declarations
cascade_declarations(style, element, matching_rule_set.author_rules, CascadeOrigin::Author, true);
// FIXME: Important user declarations
// Important user agent declarations
cascade_declarations(style, element, matching_rule_set.user_agent_rules, CascadeOrigin::UserAgent, true);
// FIXME: Transition declarations [css-transitions-1]
}
// https://drafts.csswg.org/css-cascade/#defaulting
void StyleResolver::compute_defaulted_values(StyleProperties& style, DOM::Element const& element) const
{
// FIXME: If we don't know the correct initial value for a property, we fall back to InitialStyleValue.
auto get_initial_value = [&](PropertyID property_id) -> NonnullRefPtr<StyleValue> {
auto value = property_initial_value(property_id);
if (!value)
return InitialStyleValue::the();
return value.release_nonnull();
};
auto get_inherit_value = [&](PropertyID property_id) -> NonnullRefPtr<StyleValue> {
if (!element.parent_element() || !element.parent_element()->specified_css_values())
return get_initial_value(property_id);
auto& map = element.parent_element()->specified_css_values()->m_property_values;
auto it = map.find(property_id);
VERIFY(it != map.end());
return const_cast<StyleValue&>(*it->value);
};
// Walk the list of all known CSS properties and:
// - Add them to `style` if they are missing.
// - Resolve `inherit` and `initial` as needed.
for (auto i = to_underlying(CSS::first_property_id); i <= to_underlying(CSS::last_property_id); ++i) {
auto property_id = (CSS::PropertyID)i;
auto it = style.m_property_values.find(property_id);
if (it == style.m_property_values.end()) {
if (is_inherited_property(property_id))
style.m_property_values.set(property_id, get_inherit_value(property_id));
else
style.m_property_values.set(property_id, get_initial_value(property_id));
continue;
}
if (it->value->is_initial()) {
it->value = get_initial_value(property_id);
continue;
}
if (it->value->is_inherit()) {
it->value = get_inherit_value(property_id);
continue;
}
}
}
NonnullRefPtr<StyleProperties> StyleResolver::resolve_style(DOM::Element& element) const
{
auto style = StyleProperties::create();
compute_cascaded_values(style, element);
compute_defaulted_values(style, element);
return style;
}
}
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