LibWeb/CSS: Implement CSSMathSum

Author: https://github.com/AtkinsSJ
Commit: e17052a343
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5955
Reviewed-by: https://github.com/trflynn89

Libraries/LibWeb/CSS/CSSMathSum.cpp

@@ -0,0 +1,140 @@
+/*
+ * Copyright (c) 2025, Sam Atkins <sam@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "CSSMathSum.h"
+#include <LibWeb/Bindings/CSSMathSumPrototype.h>
+#include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/CSS/CSSNumericArray.h>
+#include <LibWeb/WebIDL/DOMException.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
+
+namespace Web::CSS {
+
+GC_DEFINE_ALLOCATOR(CSSMathSum);
+
+GC::Ref<CSSMathSum> CSSMathSum::create(JS::Realm& realm, NumericType type, GC::Ref<CSSNumericArray> values)
+{
+    return realm.create<CSSMathSum>(realm, move(type), move(values));
+}
+
+// https://drafts.css-houdini.org/css-typed-om-1/#dom-cssmathsum-cssmathsum
+WebIDL::ExceptionOr<GC::Ref<CSSMathSum>> CSSMathSum::construct_impl(JS::Realm& realm, Vector<CSSNumberish> values)
+{
+    // The CSSMathSum(...args) constructor must, when called, perform the following steps:
+
+    // 1. Replace each item of args with the result of rectifying a numberish value for the item.
+    GC::RootVector<GC::Ref<CSSNumericValue>> converted_values { realm.heap() };
+    converted_values.ensure_capacity(values.size());
+    for (auto const& value : values) {
+        converted_values.append(rectify_a_numberish_value(realm, value));
+    }
+
+    // 2. If args is empty, throw a SyntaxError.
+    if (converted_values.is_empty())
+        return WebIDL::SyntaxError::create(realm, "Cannot create an empty CSSMathSum"_utf16);
+
+    // 3. Let type be the result of adding the types of all the items of args. If type is failure, throw a TypeError.
+    auto type = converted_values.first()->type();
+    bool first = true;
+    for (auto const& value : converted_values) {
+        if (first) {
+            first = false;
+            continue;
+        }
+        if (auto added_types = type.added_to(value->type()); added_types.has_value()) {
+            type = added_types.release_value();
+        } else {
+            return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Cannot create a CSSMathSum with values of incompatible types"sv };
+        }
+    }
+
+    // 4. Return a new CSSMathSum whose values internal slot is set to args.
+    auto values_array = CSSNumericArray::create(realm, { converted_values });
+    return CSSMathSum::create(realm, move(type), move(values_array));
+}
+
+CSSMathSum::CSSMathSum(JS::Realm& realm, NumericType type, GC::Ref<CSSNumericArray> values)
+    : CSSMathValue(realm, Bindings::CSSMathOperator::Sum, move(type))
+    , m_values(move(values))
+{
+}
+
+CSSMathSum::~CSSMathSum() = default;
+
+void CSSMathSum::initialize(JS::Realm& realm)
+{
+    WEB_SET_PROTOTYPE_FOR_INTERFACE(CSSMathSum);
+    Base::initialize(realm);
+}
+
+void CSSMathSum::visit_edges(Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_values);
+}
+
+// https://drafts.css-houdini.org/css-typed-om-1/#serialize-a-cssmathvalue
+String CSSMathSum::serialize_math_value(Nested nested, Parens parens) const
+{
+    // NB: Only steps 1 and 3 apply here.
+    // 1. Let s initially be the empty string.
+    StringBuilder s;
+
+    // 3. Otherwise, if this is a CSSMathSum:
+    {
+        // 1. If paren-less is true, continue to the next step; otherwise, if nested is true, append "(" to s;
+        //    otherwise, append "calc(" to s.
+        if (parens == Parens::With) {
+            if (nested == Nested::Yes) {
+                s.append("("sv);
+            } else {
+                s.append("calc("sv);
+            }
+        }
+
+        // 2. Serialize the first item in this’s values internal slot with nested set to true, and append the result
+        //    to s.
+        s.append(m_values->values().first()->to_string({ .nested = true }));
+
+        // 3. For each arg in this’s values internal slot beyond the first:
+        bool first = true;
+        for (auto const& arg : m_values->values()) {
+            if (first) {
+                first = false;
+                continue;
+            }
+
+            // 1. If arg is a CSSMathNegate, append " - " to s, then serialize arg’s value internal slot with nested
+            //    set to true, and append the result to s.
+            // FIXME: Detect CSSMathNegate once that's implemented.
+            if (false) {
+                s.append(" - "sv);
+                s.append(arg->to_string({ .nested = true }));
+            }
+
+            // 2. Otherwise, append " + " to s, then serialize arg with nested set to true, and append the result to s.
+            else {
+                s.append(" + "sv);
+                s.append(arg->to_string({ .nested = true }));
+            }
+        }
+
+        // 4. If paren-less is false, append ")" to s,
+        if (parens == Parens::With)
+            s.append(")"sv);
+
+        // 5. Return s.
+        return s.to_string_without_validation();
+    }
+}
+
+// https://drafts.css-houdini.org/css-typed-om-1/#dom-cssmathsum-values
+GC::Ref<CSSNumericArray> CSSMathSum::values() const
+{
+    return m_values;
+}
+
+}