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LibWeb: Implement :nth-child pseudo-class

This commit is contained in:
miere43 2021-05-08 23:19:25 +03:00 committed by Andreas Kling
parent 1e0e8b27c0
commit aa83539d7b
6 changed files with 161 additions and 36 deletions

View file

@ -4,7 +4,10 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include "Selector.h"
#include <AK/StringUtils.h>
#include <LibWeb/CSS/Selector.h>
#include <ctype.h>
namespace Web::CSS {
@ -44,4 +47,73 @@ u32 Selector::specificity() const
return ids * 0x10000 + classes * 0x100 + tag_names;
}
Selector::SimpleSelector::NthChildPattern Selector::SimpleSelector::NthChildPattern::parse(const StringView& args)
{
CSS::Selector::SimpleSelector::NthChildPattern pattern;
if (args.equals_ignoring_case("odd")) {
pattern.step_size = 2;
pattern.offset = 1;
} else if (args.equals_ignoring_case("even")) {
pattern.step_size = 2;
} else {
const auto consume_int = [](GenericLexer& lexer) -> Optional<int> {
return AK::StringUtils::convert_to_int(lexer.consume_while([](char c) -> bool {
return isdigit(c) || c == '+' || c == '-';
}));
};
// Try to match any of following patterns:
// 1. An+B
// 2. An
// 3. B
// ...where "A" is "step_size", "B" is "offset" and rest are literals.
// "A" can be omitted, in that case "A" = 1.
// "A" may have "+" or "-" sign, "B" always must be predated by sign for pattern (1).
int step_size_or_offset = 0;
GenericLexer lexer { args };
// "When a=1, or a=-1, the 1 may be omitted from the rule."
if (lexer.consume_specific("n") || lexer.consume_specific("+n")) {
step_size_or_offset = +1;
lexer.retreat();
} else if (lexer.consume_specific("-n")) {
step_size_or_offset = -1;
lexer.retreat();
} else {
const auto value = consume_int(lexer);
if (!value.has_value())
return {};
step_size_or_offset = value.value();
}
if (lexer.consume_specific("n")) {
lexer.ignore_while(isspace);
if (lexer.next_is('+') || lexer.next_is('-')) {
const auto sign = lexer.next_is('+') ? 1 : -1;
lexer.ignore();
lexer.ignore_while(isspace);
// "An+B" pattern
const auto offset = consume_int(lexer);
if (!offset.has_value())
return {};
pattern.step_size = step_size_or_offset;
pattern.offset = sign * offset.value();
} else {
// "An" pattern
pattern.step_size = step_size_or_offset;
}
} else {
// "B" pattern
pattern.offset = step_size_or_offset;
}
if (lexer.remaining().length() > 0)
return {};
}
return pattern;
}
}