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 ✅
2025-12-08 06:09:58 +00:00 · 2025-09-20 22:54:45 +02:00 · 2025-09-20 22:54:45 +02:00 · 96b34ea744 · 2025-10-21 23:48:01 +00:00
commit 96b34ea744
parent f1571c4217
13 changed files with 380 additions and 2 deletions
--- a/Libraries/LibWeb/MathML/MathMLMspaceElement.cpp
+++ b/Libraries/LibWeb/MathML/MathMLMspaceElement.cpp
@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2025, Lorenz Ackermann, <me@lorenzackermann.xyz>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/CSS/Parser/Parser.h>
+#include <LibWeb/HTML/Parser/HTMLParser.h>
+#include <LibWeb/MathML/AttributeNames.h>
+#include <LibWeb/MathML/MathMLMspaceElement.h>
+
+namespace Web::MathML {
+
+GC_DEFINE_ALLOCATOR(MathMLMspaceElement);
+
+MathMLMspaceElement::MathMLMspaceElement(DOM::Document& document, DOM::QualifiedName qualified_name)
+    : MathMLElement(document, move(qualified_name))
+{
+}
+
+bool MathMLMspaceElement::is_presentational_hint(FlyString const& name) const
+{
+    if (Base::is_presentational_hint(name))
+        return true;
+    return first_is_one_of(name, AttributeNames::width, AttributeNames::height, AttributeNames::depth);
+}
+
+void MathMLMspaceElement::apply_presentational_hints(GC::Ref<CSS::CascadedProperties> cascaded_properties) const
+{
+    Base::apply_presentational_hints(cascaded_properties);
+    // https://w3c.github.io/mathml-core/#attribute-mspace-width
+    // The width, height, depth, if present, must have a value that is a valid <length-percentage>.
+    auto parse_non_percentage_value = [&](FlyString const& attribute_name) -> RefPtr<CSS::StyleValue const> {
+        if (auto attribute = this->attribute(attribute_name); attribute.has_value()) {
+            if (auto value = HTML::parse_dimension_value(attribute.value()); value && !value->is_percentage()) {
+                return value;
+            }
+        }
+        return nullptr;
+    };
+
+    // If the width attribute is present, valid and not a percentage then that attribute is used as a presentational hint
+    // setting the element's width property to the corresponding value.
+    if (auto width_value = parse_non_percentage_value(AttributeNames::width)) {
+        cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::Width, width_value.release_nonnull());
+    }
+
+    // https://w3c.github.io/mathml-core/#attribute-mspace-height
+    // If the height attribute is absent, invalid or a percentage then the requested line-ascent is 0. Otherwise the
+    // requested line-ascent is the resolved value of the height attribute, clamping negative values to 0.
+    auto height_value = parse_non_percentage_value(AttributeNames::height);
+    // FIXME set the line-ascent
+
+    // If both the height and depth attributes are present, valid and not a percentage then they are used as a
+    // presentational hint setting the element's height property to the concatenation of the
+    // strings "calc(", the height attribute value, " + ", the depth attribute value, and ")". If only one of these
+    // attributes is present, valid and not a percentage then it is treated as a presentational hint setting the
+    // element's height property to the corresponding value.
+    auto depth_value = parse_non_percentage_value(AttributeNames::depth);
+
+    if (height_value && depth_value) {
+        // FIXME set the presentational hint to calculate height + depth
+    } else if (height_value) {
+        cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::Height, height_value.release_nonnull());
+    } else if (depth_value) {
+        cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::Height, depth_value.release_nonnull());
+    }
+}
+
+}