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LibWeb: Implement :nth-child pseudo-class
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6 changed files with 161 additions and 36 deletions
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@ -4,7 +4,10 @@
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "Selector.h"
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#include <AK/StringUtils.h>
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#include <LibWeb/CSS/Selector.h>
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#include <ctype.h>
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namespace Web::CSS {
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@ -44,4 +47,73 @@ u32 Selector::specificity() const
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return ids * 0x10000 + classes * 0x100 + tag_names;
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}
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Selector::SimpleSelector::NthChildPattern Selector::SimpleSelector::NthChildPattern::parse(const StringView& args)
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{
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CSS::Selector::SimpleSelector::NthChildPattern pattern;
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if (args.equals_ignoring_case("odd")) {
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pattern.step_size = 2;
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pattern.offset = 1;
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} else if (args.equals_ignoring_case("even")) {
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pattern.step_size = 2;
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} else {
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const auto consume_int = [](GenericLexer& lexer) -> Optional<int> {
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return AK::StringUtils::convert_to_int(lexer.consume_while([](char c) -> bool {
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return isdigit(c) || c == '+' || c == '-';
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}));
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};
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// Try to match any of following patterns:
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// 1. An+B
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// 2. An
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// 3. B
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// ...where "A" is "step_size", "B" is "offset" and rest are literals.
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// "A" can be omitted, in that case "A" = 1.
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// "A" may have "+" or "-" sign, "B" always must be predated by sign for pattern (1).
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int step_size_or_offset = 0;
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GenericLexer lexer { args };
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// "When a=1, or a=-1, the 1 may be omitted from the rule."
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if (lexer.consume_specific("n") || lexer.consume_specific("+n")) {
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step_size_or_offset = +1;
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lexer.retreat();
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} else if (lexer.consume_specific("-n")) {
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step_size_or_offset = -1;
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lexer.retreat();
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} else {
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const auto value = consume_int(lexer);
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if (!value.has_value())
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return {};
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step_size_or_offset = value.value();
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}
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if (lexer.consume_specific("n")) {
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lexer.ignore_while(isspace);
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if (lexer.next_is('+') || lexer.next_is('-')) {
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const auto sign = lexer.next_is('+') ? 1 : -1;
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lexer.ignore();
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lexer.ignore_while(isspace);
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// "An+B" pattern
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const auto offset = consume_int(lexer);
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if (!offset.has_value())
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return {};
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pattern.step_size = step_size_or_offset;
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pattern.offset = sign * offset.value();
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} else {
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// "An" pattern
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pattern.step_size = step_size_or_offset;
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}
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} else {
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// "B" pattern
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pattern.offset = step_size_or_offset;
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}
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if (lexer.remaining().length() > 0)
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return {};
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}
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return pattern;
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}
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}
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