LibWeb: Add MathML Element presentational hints

Author: https://github.com/lpas
Commit: 96b34ea744
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6252
Reviewed-by: https://github.com/AtkinsSJ
Reviewed-by: https://github.com/gmta ✅

Libraries/LibWeb/MathML/MathMLMiElement.cpp

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2025, Lorenz Ackermann, <me@lorenzackermann.xyz>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/CSS/Parser/Parser.h>
+#include <LibWeb/CSS/StyleValues/KeywordStyleValue.h>
+#include <LibWeb/HTML/Parser/HTMLParser.h>
+#include <LibWeb/MathML/AttributeNames.h>
+#include <LibWeb/MathML/MathMLMiElement.h>
+
+namespace Web::MathML {
+
+GC_DEFINE_ALLOCATOR(MathMLMiElement);
+
+MathMLMiElement::MathMLMiElement(DOM::Document& document, DOM::QualifiedName qualified_name)
+    : MathMLElement(document, move(qualified_name))
+{
+}
+
+bool MathMLMiElement::is_presentational_hint(FlyString const& name) const
+{
+    if (Base::is_presentational_hint(name))
+        return true;
+    return first_is_one_of(name, AttributeNames::mathvariant);
+}
+
+void MathMLMiElement::apply_presentational_hints(GC::Ref<CSS::CascadedProperties> cascaded_properties) const
+{
+    Base::apply_presentational_hints(cascaded_properties);
+    // https://w3c.github.io/mathml-core/#dfn-mathvariant
+    // The mathvariant attribute, if present, must be an ASCII case-insensitive match of normal. In that case, the user
+    // agent is expected to treat the attribute as a presentational hint setting the element's text-transform property
+    // to none. Otherwise it has no effects.
+    if (auto mathvariant = attribute(AttributeNames::mathvariant); mathvariant.has_value() && mathvariant.value().equals_ignoring_ascii_case("normal"sv)) {
+        cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::TextTransform, CSS::KeywordStyleValue::create(CSS::Keyword::None));
+    }
+}
+
+}