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ladybird/Libraries/LibWeb/CSS/StyleResolver.cpp
Andreas Kling 731685468a LibWeb: Start fleshing out support for relative CSS units 
This patch introduces support for more than just "absolute px" units in
our Length class. It now also supports "em" and "rem", which are units
relative to the font-size of the current layout node and the <html>
element's layout node respectively.
2020-06-07 17:55:46 +02:00

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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#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 <LibWeb/Parser/CSSParser.h>
#include <ctype.h>
#include <stdio.h>
namespace Web {
StyleResolver::StyleResolver(Document& document)
: m_document(document)
{
}
StyleResolver::~StyleResolver()
{
}
static StyleSheet& default_stylesheet()
{
static StyleSheet* sheet;
if (!sheet) {
extern const char default_stylesheet_source[];
String css = default_stylesheet_source;
sheet = parse_css(css).leak_ref();
}
return *sheet;
}
template<typename Callback>
void StyleResolver::for_each_stylesheet(Callback callback) const
{
callback(default_stylesheet());
for (auto& sheet : document().style_sheets().sheets()) {
callback(sheet);
}
}
NonnullRefPtrVector<StyleRule> StyleResolver::collect_matching_rules(const Element& element) const
{
NonnullRefPtrVector<StyleRule> matching_rules;
for_each_stylesheet([&](auto& sheet) {
for (auto& rule : sheet.rules()) {
for (auto& selector : rule.selectors()) {
if (SelectorEngine::matches(selector, element)) {
matching_rules.append(rule);
break;
}
}
}
});
#ifdef HTML_DEBUG
dbgprintf("Rules matching Element{%p}\n", &element);
for (auto& rule : matching_rules) {
dump_rule(rule);
}
#endif
return matching_rules;
}
bool StyleResolver::is_inherited_property(CSS::PropertyID property_id)
{
static HashTable<CSS::PropertyID> inherited_properties;
if (inherited_properties.is_empty()) {
inherited_properties.set(CSS::PropertyID::BorderCollapse);
inherited_properties.set(CSS::PropertyID::BorderSpacing);
inherited_properties.set(CSS::PropertyID::Color);
inherited_properties.set(CSS::PropertyID::FontFamily);
inherited_properties.set(CSS::PropertyID::FontSize);
inherited_properties.set(CSS::PropertyID::FontStyle);
inherited_properties.set(CSS::PropertyID::FontVariant);
inherited_properties.set(CSS::PropertyID::FontWeight);
inherited_properties.set(CSS::PropertyID::LetterSpacing);
inherited_properties.set(CSS::PropertyID::LineHeight);
inherited_properties.set(CSS::PropertyID::ListStyle);
inherited_properties.set(CSS::PropertyID::ListStyleImage);
inherited_properties.set(CSS::PropertyID::ListStylePosition);
inherited_properties.set(CSS::PropertyID::ListStyleType);
inherited_properties.set(CSS::PropertyID::TextAlign);
inherited_properties.set(CSS::PropertyID::TextIndent);
inherited_properties.set(CSS::PropertyID::TextTransform);
inherited_properties.set(CSS::PropertyID::Visibility);
inherited_properties.set(CSS::PropertyID::WhiteSpace);
inherited_properties.set(CSS::PropertyID::WordSpacing);
// FIXME: This property is not supposed to be inherited, but we currently
// rely on inheritance to propagate decorations into line boxes.
inherited_properties.set(CSS::PropertyID::TextDecoration);
}
return inherited_properties.contains(property_id);
}
static Vector<String> split_on_whitespace(const StringView& string)
{
if (string.is_empty())
return {};
Vector<String> v;
size_t substart = 0;
for (size_t i = 0; i < string.length(); ++i) {
char ch = string.characters_without_null_termination()[i];
if (isspace(ch)) {
size_t sublen = i - substart;
if (sublen != 0)
v.append(string.substring_view(substart, sublen));
substart = i + 1;
}
}
size_t taillen = string.length() - substart;
if (taillen != 0)
v.append(string.substring_view(substart, taillen));
return v;
}
static inline void set_property_border_width(StyleProperties& style, const StyleValue& value)
{
ASSERT(value.is_length());
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);
}
static inline void set_property_border_color(StyleProperties& style, const StyleValue& value)
{
ASSERT(value.is_color());
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);
}
static inline void set_property_border_style(StyleProperties& style, const StyleValue& value)
{
ASSERT(value.is_string());
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);
}
static void set_property_expanding_shorthands(StyleProperties& style, CSS::PropertyID property_id, const StyleValue& value)
{
if (property_id == CSS::PropertyID::Border) {
auto parts = split_on_whitespace(value.to_string());
if (value.is_length()) {
set_property_border_width(style, value);
return;
}
if (value.is_color()) {
set_property_border_color(style, value);
return;
}
if (value.is_string()) {
auto parts = split_on_whitespace(value.to_string());
if (parts.size() == 1) {
if (auto value = parse_line_style(parts[0])) {
set_property_border_style(style, value.release_nonnull());
set_property_border_color(style, ColorStyleValue::create(Gfx::Color::Black));
set_property_border_width(style, LengthStyleValue::create(Length(3, Length::Type::Px)));
return;
}
}
RefPtr<LengthStyleValue> line_width_value;
RefPtr<ColorStyleValue> color_value;
RefPtr<StringStyleValue> line_style_value;
for (auto& part : parts) {
if (auto value = parse_line_width(part)) {
if (line_width_value)
return;
line_width_value = move(value);
continue;
}
if (auto value = parse_color(part)) {
if (color_value)
return;
color_value = move(value);
continue;
}
if (auto value = parse_line_style(part)) {
if (line_style_value)
return;
line_style_value = move(value);
continue;
}
}
if (line_width_value)
set_property_border_width(style, line_width_value.release_nonnull());
if (color_value)
set_property_border_color(style, color_value.release_nonnull());
if (line_style_value)
set_property_border_style(style, line_style_value.release_nonnull());
return;
}
return;
}
if (property_id == CSS::PropertyID::BorderStyle) {
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;
}
if (property_id == CSS::PropertyID::BorderWidth) {
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;
}
if (property_id == CSS::PropertyID::BorderColor) {
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;
}
if (property_id == CSS::PropertyID::Background) {
auto parts = split_on_whitespace(value.to_string());
NonnullRefPtrVector<StyleValue> values;
for (auto& part : parts) {
values.append(parse_css_value(part));
}
if (values[0].is_color())
style.set_property(CSS::PropertyID::BackgroundColor, values[0]);
return;
}
if (property_id == CSS::PropertyID::Margin) {
if (value.is_length()) {
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;
}
if (value.is_string()) {
auto parts = split_on_whitespace(value.to_string());
if (parts.size() == 2) {
auto vertical = parse_css_value(parts[0]);
auto horizontal = parse_css_value(parts[1]);
style.set_property(CSS::PropertyID::MarginTop, vertical);
style.set_property(CSS::PropertyID::MarginBottom, vertical);
style.set_property(CSS::PropertyID::MarginLeft, horizontal);
style.set_property(CSS::PropertyID::MarginRight, horizontal);
return;
}
if (parts.size() == 3) {
auto top = parse_css_value(parts[0]);
auto horizontal = parse_css_value(parts[1]);
auto bottom = parse_css_value(parts[2]);
style.set_property(CSS::PropertyID::MarginTop, top);
style.set_property(CSS::PropertyID::MarginBottom, bottom);
style.set_property(CSS::PropertyID::MarginLeft, horizontal);
style.set_property(CSS::PropertyID::MarginRight, horizontal);
return;
}
if (parts.size() == 4) {
auto top = parse_css_value(parts[0]);
auto right = parse_css_value(parts[1]);
auto bottom = parse_css_value(parts[2]);
auto left = parse_css_value(parts[3]);
style.set_property(CSS::PropertyID::MarginTop, top);
style.set_property(CSS::PropertyID::MarginBottom, bottom);
style.set_property(CSS::PropertyID::MarginLeft, left);
style.set_property(CSS::PropertyID::MarginRight, right);
return;
}
dbg() << "Unsure what to do with CSS margin value '" << value.to_string() << "'";
return;
}
return;
}
if (property_id == CSS::PropertyID::Padding) {
if (value.is_length()) {
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;
}
if (value.is_string()) {
auto parts = split_on_whitespace(value.to_string());
if (parts.size() == 2) {
auto vertical = parse_css_value(parts[0]);
auto horizontal = parse_css_value(parts[1]);
style.set_property(CSS::PropertyID::PaddingTop, vertical);
style.set_property(CSS::PropertyID::PaddingBottom, vertical);
style.set_property(CSS::PropertyID::PaddingLeft, horizontal);
style.set_property(CSS::PropertyID::PaddingRight, horizontal);
return;
}
if (parts.size() == 3) {
auto top = parse_css_value(parts[0]);
auto horizontal = parse_css_value(parts[1]);
auto bottom = parse_css_value(parts[2]);
style.set_property(CSS::PropertyID::PaddingTop, top);
style.set_property(CSS::PropertyID::PaddingBottom, bottom);
style.set_property(CSS::PropertyID::PaddingLeft, horizontal);
style.set_property(CSS::PropertyID::PaddingRight, horizontal);
return;
}
if (parts.size() == 4) {
auto top = parse_css_value(parts[0]);
auto right = parse_css_value(parts[1]);
auto bottom = parse_css_value(parts[2]);
auto left = parse_css_value(parts[3]);
style.set_property(CSS::PropertyID::PaddingTop, top);
style.set_property(CSS::PropertyID::PaddingBottom, bottom);
style.set_property(CSS::PropertyID::PaddingLeft, left);
style.set_property(CSS::PropertyID::PaddingRight, right);
return;
}
dbg() << "Unsure what to do with CSS padding value '" << value.to_string() << "'";
return;
}
return;
}
if (property_id == CSS::PropertyID::ListStyle) {
auto parts = split_on_whitespace(value.to_string());
if (!parts.is_empty()) {
auto value = parse_css_value(parts[0]);
style.set_property(CSS::PropertyID::ListStyleType, value);
}
return;
}
style.set_property(property_id, value);
}
NonnullRefPtr<StyleProperties> StyleResolver::resolve_style(const Element& element, const StyleProperties* parent_style) const
{
auto style = StyleProperties::create();
if (parent_style) {
parent_style->for_each_property([&](auto property_id, auto& value) {
if (is_inherited_property(property_id))
set_property_expanding_shorthands(style, property_id, value);
});
}
element.apply_presentational_hints(*style);
auto matching_rules = collect_matching_rules(element);
for (auto& rule : matching_rules) {
for (auto& property : rule.declaration().properties()) {
set_property_expanding_shorthands(style, property.property_id, property.value);
}
}
auto style_attribute = element.attribute(HTML::AttributeNames::style);
if (!style_attribute.is_null()) {
if (auto declaration = parse_css_declaration(style_attribute)) {
for (auto& property : declaration->properties()) {
set_property_expanding_shorthands(style, property.property_id, property.value);
}
}
}
return style;
}
}
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