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LibWeb: Implement CSS::Parse::parse_nth_child_pattern()

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This is a modified copy of the code from Selector.cpp, to work on a
TokenStream instead of a String.
This commit is contained in:
Sam Atkins 2021-07-08 13:44:01 +01:00 • committed by Andreas Kling
parent cf333574ac
commit 9cfbc07c24
2 changed files with 105 additions and 3 deletions
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106
Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
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@ -1,4 +1,5 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020-2021, the SerenityOS developers.
* Copyright (c) 2021, Sam Atkins <atkinssj@gmail.com>
*
@ -437,16 +438,30 @@ Optional<Selector> Parser::parse_single_selector(TokenStream<T>& tokens, bool is
auto& pseudo_function = current_value.function();
if (pseudo_function.name().equals_ignoring_case("nth-child")) {
simple_selector.pseudo_class = Selector::SimpleSelector::PseudoClass::NthChild;
simple_selector.nth_child_pattern = Selector::SimpleSelector::NthChildPattern::parse(pseudo_function.values_as_string());
auto function_values = TokenStream<StyleComponentValueRule>(pseudo_function.values());
auto nth_child_pattern = parse_nth_child_pattern(function_values);
if (nth_child_pattern.has_value()) {
simple_selector.nth_child_pattern = nth_child_pattern.value();
} else {
dbgln("Invalid nth-child format");
return {};
}
} else if (pseudo_function.name().equals_ignoring_case("nth-last-child")) {
simple_selector.pseudo_class = Selector::SimpleSelector::PseudoClass::NthLastChild;
simple_selector.nth_child_pattern = Selector::SimpleSelector::NthChildPattern::parse(pseudo_function.values_as_string());
auto function_values = TokenStream<StyleComponentValueRule>(pseudo_function.values());
auto nth_child_pattern = parse_nth_child_pattern(function_values);
if (nth_child_pattern.has_value()) {
simple_selector.nth_child_pattern = nth_child_pattern.value();
} else {
dbgln("Invalid nth-child format");
return {};
}
} else if (pseudo_function.name().equals_ignoring_case("not")) {
simple_selector.pseudo_class = Selector::SimpleSelector::PseudoClass::Not;
simple_selector.not_selector = pseudo_function.values_as_string();
} else {
dbgln("Unknown pseudo class: '{}'()", pseudo_function.name());
return simple_selector;
return {};
}
} else {
dbgln("Unexpected Block in pseudo-class name, expected a function or identifier. '{}'", current_value.to_debug_string());
@ -1350,4 +1365,89 @@ RefPtr<StyleValue> Parser::parse_css_value(PropertyID property_id, TokenStream<S
return {};
}
Optional<Selector::SimpleSelector::NthChildPattern> Parser::parse_nth_child_pattern(TokenStream<StyleComponentValueRule>& values)
{
Selector::SimpleSelector::NthChildPattern pattern;
auto current_value = values.next_token();
if (current_value.is(Token::Type::Ident)) {
auto ident = current_value.token().ident();
if (ident.equals_ignoring_case("odd")) {
pattern.step_size = 2;
pattern.offset = 1;
return pattern;
} else if (ident.equals_ignoring_case("even")) {
pattern.step_size = 2;
return pattern;
}
}
// 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).
auto is_n = [](StyleComponentValueRule value) -> bool {
return value.is(Token::Type::Ident) && value.token().ident().equals_ignoring_case("n");
};
auto is_delim = [](StyleComponentValueRule value, StringView delim) -> bool {
return value.is(Token::Type::Delim) && value.token().delim().equals_ignoring_case(delim);
};
int step_size_or_offset = 0;
// "When a=1, or a=-1, the 1 may be omitted from the rule."
if (is_n(current_value)) {
step_size_or_offset = +1;
} else if (is_delim(current_value, "+"sv) && is_n(values.peek_token())) {
step_size_or_offset = +1;
values.next_token();
} else if (is_delim(current_value, "-"sv) && is_n(values.peek_token())) {
step_size_or_offset = -1;
values.next_token();
} else if (current_value.is(Token::Type::Number)) {
step_size_or_offset = current_value.token().integer();
} else {
values.reconsume_current_input_token();
}
current_value = values.next_token();
if (is_n(current_value)) {
values.skip_whitespace();
auto next_value = values.peek_token();
if (is_delim(next_value, "+") || is_delim(next_value, "-")) {
const auto sign = is_delim(next_value, "+") ? 1 : -1;
values.next_token();
values.skip_whitespace();
// "An+B" pattern
auto number = values.next_token();
if (!number.is(Token::Type::Number))
return {};
pattern.step_size = step_size_or_offset;
pattern.offset = sign * number.token().integer();
} else {
// "An" pattern
pattern.step_size = step_size_or_offset;
}
} else {
// "B" pattern
pattern.offset = step_size_or_offset;
}
if (values.has_next_token())
return {};
return pattern;
}
}