LibWeb: Parse color values using TokenStream

Author: https://github.com/AtkinsSJ
Commit: e4e048f278
Pull-request: https://github.com/SerenityOS/serenity/pull/24062
Reviewed-by: https://github.com/Hendiadyoin1

Userland/Libraries/LibWeb/CSS/Parser/GradientParsing.cpp

@@ -30,15 +30,14 @@ Optional<Vector<TElement>> Parser::parse_color_stop_list(TokenStream<ComponentVa
         tokens.skip_whitespace();
         if (!tokens.has_next_token())
             return ElementType::Garbage;
-        auto const& token = tokens.next_token();
 
         RefPtr<StyleValue> color;
         Optional<typename TElement::PositionType> position;
         Optional<typename TElement::PositionType> second_position;
-        auto dimension = parse_dimension(token);
+        if (auto dimension = parse_dimension(tokens.peek_token()); dimension.has_value() && is_position(*dimension)) {
-        if (dimension.has_value() && is_position(*dimension)) {
             // [<T-percentage> <color>] or [<T-percentage>]
             position = get_position(*dimension);
+            (void)tokens.next_token(); // dimension
             tokens.skip_whitespace();
             // <T-percentage>
             if (!tokens.has_next_token() || tokens.peek_token().is(Token::Type::Comma)) {
@@ -46,13 +45,13 @@ Optional<Vector<TElement>> Parser::parse_color_stop_list(TokenStream<ComponentVa
                 return ElementType::ColorHint;
             }
             // <T-percentage> <color>
-            auto maybe_color = parse_color_value(tokens.next_token());
+            auto maybe_color = parse_color_value(tokens);
             if (!maybe_color)
                 return ElementType::Garbage;
             color = maybe_color.release_nonnull();
         } else {
             // [<color> <T-percentage>?]
-            auto maybe_color = parse_color_value(token);
+            auto maybe_color = parse_color_value(tokens);
             if (!maybe_color)
                 return ElementType::Garbage;
             color = maybe_color.release_nonnull();
@@ -61,8 +60,7 @@ Optional<Vector<TElement>> Parser::parse_color_stop_list(TokenStream<ComponentVa
             // Note: Double-position color stops only appear to be valid in this order.
             for (auto stop_position : Array { &position, &second_position }) {
                 if (tokens.has_next_token() && !tokens.peek_token().is(Token::Type::Comma)) {
-                    auto token = tokens.next_token();
+                    auto dimension = parse_dimension(tokens.next_token());
-                    auto dimension = parse_dimension(token);
                     if (!dimension.has_value() || !is_position(*dimension))
                         return ElementType::Garbage;
                     *stop_position = get_position(*dimension);

Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp

@@ -2502,16 +2502,22 @@ Optional<Color> Parser::parse_color(ComponentValue const& component_value)
     return {};
 }
 
-RefPtr<StyleValue> Parser::parse_color_value(ComponentValue const& component_value)
+RefPtr<StyleValue> Parser::parse_color_value(TokenStream<ComponentValue>& tokens)
 {
-    auto color = parse_color(component_value);
+    auto transaction = tokens.begin_transaction();
-    if (color.has_value())
+    auto component_value = tokens.next_token();
+
+    if (auto color = parse_color(component_value); color.has_value()) {
+        transaction.commit();
         return ColorStyleValue::create(color.value());
+    }
 
     if (component_value.is(Token::Type::Ident)) {
         auto ident = value_id_from_string(component_value.token().ident());
-        if (ident.has_value() && IdentifierStyleValue::is_color(ident.value()))
+        if (ident.has_value() && IdentifierStyleValue::is_color(ident.value())) {
+            transaction.commit();
             return IdentifierStyleValue::create(ident.value());
+        }
     }
 
     return nullptr;
@@ -2565,10 +2571,8 @@ RefPtr<StyleValue> Parser::parse_paint_value(TokenStream<ComponentValue>& tokens
     // `<paint> = none | <color> | <url> [none | <color>]? | context-fill | context-stroke`
 
     auto parse_color_or_none = [&]() -> Optional<RefPtr<StyleValue>> {
-        if (auto color = parse_color_value(tokens.peek_token())) {
+        if (auto color = parse_color_value(tokens))
-            (void)tokens.next_token();
             return color;
-        }
 
         // NOTE: <color> also accepts identifiers, so we do this identifier check last.
         if (tokens.peek_token().is(Token::Type::Ident)) {
@@ -6499,10 +6503,8 @@ Optional<Parser::PropertyAndValue> Parser::parse_css_value_for_properties(Readon
     }
 
     if (auto property = any_property_accepts_type(property_ids, ValueType::Color); property.has_value()) {
-        if (auto maybe_color = parse_color_value(peek_token)) {
+        if (auto maybe_color = parse_color_value(tokens))
-            (void)tokens.next_token();
             return PropertyAndValue { *property, maybe_color };
-        }
     }
 
     if (auto property = any_property_accepts_type(property_ids, ValueType::Image); property.has_value()) {

Userland/Libraries/LibWeb/CSS/Parser/Parser.h

@@ -224,7 +224,7 @@ private:
     RefPtr<StyleValue> parse_number_value(TokenStream<ComponentValue>&);
     RefPtr<StyleValue> parse_number_or_percentage_value(TokenStream<ComponentValue>&);
     RefPtr<StyleValue> parse_identifier_value(ComponentValue const&);
-    RefPtr<StyleValue> parse_color_value(ComponentValue const&);
+    RefPtr<StyleValue> parse_color_value(TokenStream<ComponentValue>&);
     RefPtr<StyleValue> parse_rect_value(TokenStream<ComponentValue>&);
     RefPtr<StyleValue> parse_ratio_value(TokenStream<ComponentValue>&);
     RefPtr<StyleValue> parse_string_value(TokenStream<ComponentValue>&);