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LibWeb: Implement :nth-[last-]child(n of foo) syntax

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In Selectors level 4, `:nth-child()` and `:nth-last-child()` can both
optionally take a selector-list argument. This selector-list acts as a
filter, so that only elements matching the list are counted. For
example, this means that the following are equivalent:

```css
:nth-child(2n+1 of p) {}
p:nth-of-type(2n+1) {}
```
This commit is contained in:
Sam Atkins 2022-03-17 19:13:51 +00:00 • committed by Andreas Kling
parent 0e4c35b4b2
commit 5b0187477b
5 changed files with 92 additions and 25 deletions
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34
Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
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@ -571,15 +571,37 @@ Result<Selector::SimpleSelector, Parser::ParsingResult> Parser::parse_simple_sel
} else if (pseudo_class_token.is_function()) {
auto parse_nth_child_pattern = [this](auto& simple_selector, auto& pseudo_function) -> bool {
auto parse_nth_child_pattern = [this](Selector::SimpleSelector& simple_selector, StyleFunctionRule const& pseudo_function, bool allow_of = false) -> bool {
auto function_values = TokenStream<StyleComponentValueRule>(pseudo_function.values());
auto nth_child_pattern = parse_a_n_plus_b_pattern(function_values);
auto nth_child_pattern = parse_a_n_plus_b_pattern(function_values, allow_of ? AllowTrailingTokens::Yes : AllowTrailingTokens::No);
if (nth_child_pattern.has_value()) {
simple_selector.pseudo_class.nth_child_pattern = nth_child_pattern.value();
} else {
dbgln_if(CSS_PARSER_DEBUG, "!!! Invalid format for {}", pseudo_function.name());
return false;
}
if (!allow_of)
return true;
function_values.skip_whitespace();
if (!function_values.has_next_token())
return true;
// Parse the `of <selector-list>` syntax
auto& maybe_of = function_values.next_token();
if (!(maybe_of.is(Token::Type::Ident) && maybe_of.token().ident().equals_ignoring_case("of"sv)))
return false;
function_values.skip_whitespace();
auto selector_list = parse_a_selector_list(function_values);
if (selector_list.is_error())
return false;
function_values.skip_whitespace();
if (function_values.has_next_token())
return false;
simple_selector.pseudo_class.argument_selector_list = selector_list.value();
return true;
};
@ -606,11 +628,11 @@ Result<Selector::SimpleSelector, Parser::ParsingResult> Parser::parse_simple_sel
simple_selector.pseudo_class.argument_selector_list = not_selector.release_value();
} else if (pseudo_function.name().equals_ignoring_case("nth-child"sv)) {
simple_selector.pseudo_class.type = Selector::SimpleSelector::PseudoClass::Type::NthChild;
if (!parse_nth_child_pattern(simple_selector, pseudo_function))
if (!parse_nth_child_pattern(simple_selector, pseudo_function, true))
return ParsingResult::SyntaxError;
} else if (pseudo_function.name().equals_ignoring_case("nth-last-child"sv)) {
simple_selector.pseudo_class.type = Selector::SimpleSelector::PseudoClass::Type::NthLastChild;
if (!parse_nth_child_pattern(simple_selector, pseudo_function))
if (!parse_nth_child_pattern(simple_selector, pseudo_function, true))
return ParsingResult::SyntaxError;
} else if (pseudo_function.name().equals_ignoring_case("nth-of-type"sv)) {
simple_selector.pseudo_class.type = Selector::SimpleSelector::PseudoClass::Type::NthOfType;
@ -4129,7 +4151,7 @@ RefPtr<StyleValue> Parser::parse_css_value(StyleComponentValueRule const& compon
return {};
}
Optional<Selector::SimpleSelector::ANPlusBPattern> Parser::parse_a_n_plus_b_pattern(TokenStream<StyleComponentValueRule>& values)
Optional<Selector::SimpleSelector::ANPlusBPattern> Parser::parse_a_n_plus_b_pattern(TokenStream<StyleComponentValueRule>& values, AllowTrailingTokens allow_trailing_tokens)
{
int a = 0;
int b = 0;
@ -4145,7 +4167,7 @@ Optional<Selector::SimpleSelector::ANPlusBPattern> Parser::parse_a_n_plus_b_patt
auto make_return_value = [&]() -> Optional<Selector::SimpleSelector::ANPlusBPattern> {
// When we think we are done, but there are more non-whitespace tokens, then it's a parse error.
values.skip_whitespace();
if (values.has_next_token()) {
if (values.has_next_token() && allow_trailing_tokens == AllowTrailingTokens::No) {
if constexpr (CSS_PARSER_DEBUG) {
dbgln_if(CSS_PARSER_DEBUG, "Extra tokens at end of An+B value:");
values.dump_all_tokens();