LibWeb: Add SVG-presentation-attribute-parsing mode to CSS parser

When parsing these, <number> is allowed anywhere that would usually
allow a <length>, <length-percentage>, or <angle>. The spec is not
clear on exactly how this should work
(see https://github.com/w3c/svgwg/issues/792 ) so I'm using some
artistic license until things are clearer:
- If we expected a <length>, treat the <number> as pixels.
- If we expected an <angle>, treat the <number> as degrees.
- Only allow direct <number> tokens, not calc() or other functions.

From what I can tell this is what the spec *intended* but I may be very
wrong. In any case, telling the ParsingContext whether we're parsing
one of these attributes is a cleaner approach and more correct than
temporarily enabling quirks mode, which we did previously.

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

@@ -6200,6 +6200,25 @@ Optional<Parser::PropertyAndValue> Parser::parse_css_value_for_properties(Readon
         || any_property_accepts_type(property_ids, ValueType::Time).has_value();
 
     if (property_accepts_dimension) {
+        if (peek_token.is(Token::Type::Number) && m_context.is_parsing_svg_presentation_attribute()) {
+            auto transaction = tokens.begin_transaction();
+            auto token = tokens.next_token();
+            // https://svgwg.org/svg2-draft/types.html#presentation-attribute-css-value
+            // We need to allow <number> in any place that expects a <length> or <angle>.
+            // FIXME: How should these numbers be interpreted? https://github.com/w3c/svgwg/issues/792
+            //        For now: Convert them to px lengths, or deg angles.
+            auto angle = Angle::make_degrees(token.token().number_value());
+            if (auto property = any_property_accepts_type(property_ids, ValueType::Angle); property.has_value() && property_accepts_angle(*property, angle)) {
+                transaction.commit();
+                return PropertyAndValue { *property, AngleStyleValue::create(angle) };
+            }
+            auto length = Length::make_px(CSSPixels::nearest_value_for(token.token().number_value()));
+            if (auto property = any_property_accepts_type(property_ids, ValueType::Length); property.has_value() && property_accepts_length(*property, length)) {
+                transaction.commit();
+                return PropertyAndValue { *property, LengthStyleValue::create(length) };
+            }
+        }
+
         auto transaction = tokens.begin_transaction();
         if (auto maybe_dimension = parse_dimension(peek_token); maybe_dimension.has_value()) {
             (void)tokens.next_token();
@@ -6249,6 +6268,9 @@ Optional<Parser::PropertyAndValue> Parser::parse_css_value_for_properties(Readon
             (void)tokens.next_token();
             auto& calculated = *maybe_calculated;
             // This is a bit sensitive to ordering: `<foo>` and `<percentage>` have to be checked before `<foo-percentage>`.
+            // FIXME: When parsing SVG presentation attributes, <number> is permitted wherever <length>, <length-percentage>, or <angle> are.
+            //        The specifics are unclear, so I'm ignoring this for calculated values for now.
+            //        See https://github.com/w3c/svgwg/issues/792
             if (calculated.resolves_to_percentage()) {
                 if (auto property = any_property_accepts_type(property_ids, ValueType::Percentage); property.has_value())
                     return PropertyAndValue { *property, calculated };

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

@@ -13,29 +13,33 @@
 
 namespace Web::CSS::Parser {
 
-ParsingContext::ParsingContext(JS::Realm& realm)
+ParsingContext::ParsingContext(JS::Realm& realm, Mode mode)
     : m_realm(realm)
+    , m_mode(mode)
 {
 }
 
-ParsingContext::ParsingContext(DOM::Document const& document, AK::URL url)
+ParsingContext::ParsingContext(DOM::Document const& document, AK::URL url, Mode mode)
     : m_realm(const_cast<JS::Realm&>(document.realm()))
     , m_document(&document)
     , m_url(move(url))
+    , m_mode(mode)
 {
 }
 
-ParsingContext::ParsingContext(DOM::Document const& document)
+ParsingContext::ParsingContext(DOM::Document const& document, Mode mode)
     : m_realm(const_cast<JS::Realm&>(document.realm()))
     , m_document(&document)
     , m_url(document.url())
+    , m_mode(mode)
 {
 }
 
-ParsingContext::ParsingContext(DOM::ParentNode& parent_node)
+ParsingContext::ParsingContext(DOM::ParentNode& parent_node, Mode mode)
     : m_realm(parent_node.realm())
     , m_document(&parent_node.document())
     , m_url(parent_node.document().url())
+    , m_mode(mode)
 {
 }
 

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

@@ -14,10 +14,18 @@ namespace Web::CSS::Parser {
 
 class ParsingContext {
 public:
-    explicit ParsingContext(JS::Realm&);
-    explicit ParsingContext(DOM::Document const&);
-    explicit ParsingContext(DOM::Document const&, AK::URL);
-    explicit ParsingContext(DOM::ParentNode&);
+    enum class Mode {
+        Normal,
+        SVGPresentationAttribute, // See https://svgwg.org/svg2-draft/types.html#presentation-attribute-css-value
+    };
+
+    explicit ParsingContext(JS::Realm&, Mode = Mode::Normal);
+    explicit ParsingContext(DOM::Document const&, Mode = Mode::Normal);
+    explicit ParsingContext(DOM::Document const&, AK::URL, Mode = Mode::Normal);
+    explicit ParsingContext(DOM::ParentNode&, Mode = Mode::Normal);
+
+    Mode mode() const { return m_mode; }
+    bool is_parsing_svg_presentation_attribute() const { return m_mode == Mode::SVGPresentationAttribute; }
 
     bool in_quirks_mode() const;
     DOM::Document const* document() const { return m_document; }
@@ -34,6 +42,7 @@ private:
     JS::GCPtr<DOM::Document const> m_document;
     PropertyID m_current_property_id { PropertyID::Invalid };
     AK::URL m_url;
+    Mode m_mode { Mode::Normal };
 };
 
 }