ladybird/Libraries/LibWeb/CSS/Parser/DescriptorParsing.cpp

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/*
* Copyright (c) 2025, Sam Atkins <sam@ladybird.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/CSS/Parser/ErrorReporter.h>
#include <LibWeb/CSS/Parser/Parser.h>
#include <LibWeb/CSS/StyleValues/FontSourceStyleValue.h>
#include <LibWeb/CSS/StyleValues/KeywordStyleValue.h>
#include <LibWeb/CSS/StyleValues/LengthStyleValue.h>
#include <LibWeb/CSS/StyleValues/PercentageStyleValue.h>
#include <LibWeb/CSS/StyleValues/StringStyleValue.h>
#include <LibWeb/CSS/StyleValues/StyleValueList.h>
#include <LibWeb/CSS/StyleValues/UnicodeRangeStyleValue.h>
#include <LibWeb/CSS/StyleValues/UnresolvedStyleValue.h>
namespace Web::CSS::Parser {
Parser::ParseErrorOr<NonnullRefPtr<StyleValue const>> Parser::parse_descriptor_value(AtRuleID at_rule_id, DescriptorID descriptor_id, TokenStream<ComponentValue>& unprocessed_tokens)
{
if (!at_rule_supports_descriptor(at_rule_id, descriptor_id)) {
ErrorReporter::the().report(UnknownPropertyError {
.rule_name = to_string(at_rule_id),
.property_name = to_string(descriptor_id),
});
return ParseError::SyntaxError;
}
auto context_guard = push_temporary_value_parsing_context(DescriptorContext { at_rule_id, descriptor_id });
Vector<ComponentValue> component_values;
while (unprocessed_tokens.has_next_token()) {
if (unprocessed_tokens.peek_token().is(Token::Type::Semicolon))
break;
auto const& token = unprocessed_tokens.consume_a_token();
component_values.append(token);
}
TokenStream tokens { component_values };
auto metadata = get_descriptor_metadata(at_rule_id, descriptor_id);
for (auto const& option : metadata.syntax) {
auto transaction = tokens.begin_transaction();
auto parsed_style_value = option.visit(
[&](Keyword keyword) {
return parse_all_as_single_keyword_value(tokens, keyword);
},
[&](PropertyID property_id) -> RefPtr<StyleValue const> {
auto value_or_error = parse_css_value(property_id, tokens);
if (value_or_error.is_error())
return nullptr;
auto value_for_property = value_or_error.release_value();
// Descriptors don't accept the following, which properties do:
// - CSS-wide keywords
// - Arbitrary substitution functions (so, UnresolvedStyleValue)
if (value_for_property->is_css_wide_keyword() || value_for_property->is_unresolved())
return nullptr;
return value_for_property;
},
[&](DescriptorMetadata::ValueType value_type) -> RefPtr<StyleValue const> {
switch (value_type) {
case DescriptorMetadata::ValueType::CropOrCross: {
// crop || cross
auto first = parse_keyword_value(tokens);
tokens.discard_whitespace();
auto second = parse_keyword_value(tokens);
if (!first)
return nullptr;
RefPtr<StyleValue const> crop;
RefPtr<StyleValue const> cross;
if (first->to_keyword() == Keyword::Crop)
crop = first;
else if (first->to_keyword() == Keyword::Cross)
cross = first;
else
return nullptr;
if (!second)
return first.release_nonnull();
if (crop.is_null() && second->to_keyword() == Keyword::Crop)
crop = second.release_nonnull();
else if (cross.is_null() && second->to_keyword() == Keyword::Cross)
cross = second.release_nonnull();
else
return nullptr;
return StyleValueList::create(StyleValueVector { crop.release_nonnull(), cross.release_nonnull() }, StyleValueList::Separator::Space);
}
case DescriptorMetadata::ValueType::FamilyName:
return parse_family_name_value(tokens);
case DescriptorMetadata::ValueType::FontSrcList: {
// "If a component value is parsed correctly and is of a font format or font tech that the UA
// supports, add it to the list of supported sources. If parsing a component value results in a
// parsing error or its format or tech are unsupported, do not add it to the list of supported
// sources.
// If there are no supported entries at the end of this process, the value for the src descriptor
// is a parse error.
// These parsing rules allow for graceful fallback of fonts for user agents which don’t support a
// particular font tech or font format."
// https://drafts.csswg.org/css-fonts-4/#font-face-src-parsing
auto source_lists = parse_a_comma_separated_list_of_component_values(tokens);
StyleValueVector valid_sources;
for (auto const& source_list : source_lists) {
TokenStream source_tokens { source_list };
if (auto font_source = parse_font_source_value(source_tokens); font_source && !source_tokens.has_next_token())
valid_sources.append(font_source.release_nonnull());
}
if (valid_sources.is_empty())
return nullptr;
return StyleValueList::create(move(valid_sources), StyleValueList::Separator::Comma);
}
case DescriptorMetadata::ValueType::Length:
return parse_length_value(tokens);
case DescriptorMetadata::ValueType::OptionalDeclarationValue: {
// `component_values` already has what we want. Just skip through its tokens so code below knows we consumed them.
while (tokens.has_next_token())
tokens.discard_a_token();
return UnresolvedStyleValue::create(move(component_values));
}
case DescriptorMetadata::ValueType::PageSize: {
// https://drafts.csswg.org/css-page-3/#page-size-prop
// <length [0,∞]>{1,2} | auto | [ <page-size> || [ portrait | landscape ] ]
// auto
if (auto value = parse_all_as_single_keyword_value(tokens, Keyword::Auto))
return value.release_nonnull();
// <length [0,∞]>{1,2}
if (auto first_length = parse_length_value(tokens)) {
if (first_length->is_length() && first_length->as_length().raw_value() < 0)
return nullptr;
tokens.discard_whitespace();
if (auto second_length = parse_length_value(tokens)) {
if (second_length->is_length() && second_length->as_length().raw_value() < 0)
return nullptr;
return StyleValueList::create(StyleValueVector { first_length.release_nonnull(), second_length.release_nonnull() }, StyleValueList::Separator::Space);
}
return first_length.release_nonnull();
}
// [ <page-size> || [ portrait | landscape ] ]
RefPtr<StyleValue const> page_size;
RefPtr<StyleValue const> orientation;
if (auto first_keyword = parse_keyword_value(tokens)) {
if (first_is_one_of(first_keyword->to_keyword(), Keyword::Landscape, Keyword::Portrait)) {
orientation = first_keyword.release_nonnull();
} else if (keyword_to_page_size(first_keyword->to_keyword()).has_value()) {
page_size = first_keyword.release_nonnull();
} else {
return nullptr;
}
} else {
return nullptr;
}
tokens.discard_whitespace();
if (auto second_keyword = parse_keyword_value(tokens)) {
if (orientation.is_null() && first_is_one_of(second_keyword->to_keyword(), Keyword::Landscape, Keyword::Portrait)) {
orientation = second_keyword.release_nonnull();
} else if (page_size.is_null() && keyword_to_page_size(second_keyword->to_keyword()).has_value()) {
page_size = second_keyword.release_nonnull();
} else {
return nullptr;
}
// Portrait is considered the default orientation, so don't include it.
if (orientation->to_keyword() == Keyword::Portrait)
return page_size.release_nonnull();
return StyleValueList::create(StyleValueVector { page_size.release_nonnull(), orientation.release_nonnull() }, StyleValueList::Separator::Space);
}
return page_size ? page_size.release_nonnull() : orientation.release_nonnull();
}
case DescriptorMetadata::ValueType::PositivePercentage: {
if (auto percentage_value = parse_percentage_value(tokens)) {
if (percentage_value->is_percentage()) {
if (percentage_value->as_percentage().raw_value() < 0)
return nullptr;
return percentage_value.release_nonnull();
}
// All calculations in descriptors must be resolvable at parse-time.
if (percentage_value->is_calculated()) {
auto percentage = percentage_value->as_calculated().resolve_percentage({});
if (percentage.has_value() && percentage->value() >= 0)
return PercentageStyleValue::create(percentage.release_value());
return nullptr;
}
}
return nullptr;
}
case DescriptorMetadata::ValueType::String:
return parse_string_value(tokens);
case DescriptorMetadata::ValueType::UnicodeRangeTokens: {
return parse_comma_separated_value_list(tokens, [this](auto& tokens) -> RefPtr<StyleValue const> {
return parse_unicode_range_value(tokens);
});
}
}
return nullptr;
});
if (!parsed_style_value || tokens.has_next_token())
continue;
transaction.commit();
return parsed_style_value.release_nonnull();
}
ErrorReporter::the().report(InvalidPropertyError {
.rule_name = to_string(at_rule_id),
.property_name = to_string(descriptor_id),
.value_string = tokens.dump_string(),
.description = "Failed to parse."_string,
});
return ParseError::SyntaxError;
}
Optional<Descriptor> Parser::convert_to_descriptor(AtRuleID at_rule_id, Declaration const& declaration)
{
auto descriptor_id = descriptor_id_from_string(at_rule_id, declaration.name);
if (!descriptor_id.has_value())
return {};
auto value_token_stream = TokenStream(declaration.value);
auto value = parse_descriptor_value(at_rule_id, descriptor_id.value(), value_token_stream);
if (value.is_error())
return {};
return Descriptor { *descriptor_id, value.release_value() };
}
}