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LibWeb: Parse and resolve UnresolvedStyleValues
If a property is custom or contains a `var()` reference, it cannot be parsed into a proper StyleValue immediately, so we store it as an UnresolvedStyleValue until the property is compute. Then, at compute time, we resolve them by expanding out any `var()` references, and parsing the result. The implementation here is very naive, and involves copying the UnresolvedStyleValue's tree of StyleComponentValueRules while copying the contents of any `var()`s it finds along the way. This is quite an expensive operation to do every time that the style is computed.
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6 changed files with 138 additions and 6 deletions
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@ -3435,8 +3435,19 @@ RefPtr<StyleValue> Parser::parse_as_css_value(PropertyID property_id)
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Result<NonnullRefPtr<StyleValue>, Parser::ParsingResult> Parser::parse_css_value(PropertyID property_id, TokenStream<StyleComponentValueRule>& tokens)
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{
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auto block_contains_var = [](StyleBlockRule const& block, auto&& recurse) -> bool {
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for (auto const& token : block.values()) {
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if (token.is_function() && token.function().name().equals_ignoring_case("var"sv))
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return true;
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if (token.is_block() && recurse(token.block(), recurse))
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return true;
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}
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return false;
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};
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m_context.set_current_property_id(property_id);
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Vector<StyleComponentValueRule> component_values;
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bool contains_var = false;
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while (tokens.has_next_token()) {
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auto& token = tokens.next_token();
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@ -3446,15 +3457,27 @@ Result<NonnullRefPtr<StyleValue>, Parser::ParsingResult> Parser::parse_css_value
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break;
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}
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if (token.is(Token::Type::Whitespace))
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continue;
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if (property_id != PropertyID::Custom) {
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if (token.is(Token::Type::Whitespace))
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continue;
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if (token.is(Token::Type::Ident) && has_ignored_vendor_prefix(token.token().ident()))
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return ParsingResult::IncludesIgnoredVendorPrefix;
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if (token.is(Token::Type::Ident) && has_ignored_vendor_prefix(token.token().ident()))
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return ParsingResult::IncludesIgnoredVendorPrefix;
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}
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if (!contains_var) {
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if (token.is_function() && token.function().name().equals_ignoring_case("var"sv))
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contains_var = true;
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else if (token.is_block() && block_contains_var(token.block(), block_contains_var))
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contains_var = true;
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}
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component_values.append(token);
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}
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if (property_id == PropertyID::Custom || contains_var)
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return { UnresolvedStyleValue::create(move(component_values), contains_var) };
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if (component_values.is_empty())
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return ParsingResult::SyntaxError;
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@ -4167,6 +4190,19 @@ bool Parser::has_ignored_vendor_prefix(StringView string)
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return true;
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}
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RefPtr<StyleValue> Parser::parse_css_value(Badge<StyleComputer>, ParsingContext const& context, PropertyID property_id, Vector<StyleComponentValueRule> const& tokens)
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{
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if (tokens.is_empty() || property_id == CSS::PropertyID::Invalid || property_id == CSS::PropertyID::Custom)
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return {};
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CSS::Parser parser(context, "");
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CSS::TokenStream<CSS::StyleComponentValueRule> token_stream { tokens };
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auto result = parser.parse_css_value(property_id, token_stream);
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if (result.is_error())
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return {};
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return result.release_value();
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}
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}
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namespace Web {
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