LibWeb: Add SVGList<T> and use it for SVGTransformList

The spec defines a generic list interfaces that we can reuse. Currently
we only have SVGTransformList, but we will need this to add
SVGNumberList as well.

Author: gmta

Libraries/LibWeb/CMakeLists.txt

@@ -932,6 +932,7 @@ set(SOURCES
     SVG/SVGLength.cpp
     SVG/SVGLinearGradientElement.cpp
     SVG/SVGLineElement.cpp
+    SVG/SVGList.cpp
     SVG/SVGMaskElement.cpp
     SVG/SVGMetadataElement.cpp
     SVG/SVGNumber.cpp

Libraries/LibWeb/SVG/SVGGraphicsElement.cpp

@@ -347,8 +347,8 @@ WebIDL::ExceptionOr<GC::Ref<Geometry::DOMRect>> SVGGraphicsElement::get_b_box(Op
 GC::Ref<SVGAnimatedTransformList> SVGGraphicsElement::transform() const
 {
     dbgln("(STUBBED) SVGGraphicsElement::transform(). Called on: {}", debug_description());
-    auto base_val = SVGTransformList::create(realm());
-    auto anim_val = SVGTransformList::create(realm());
+    auto base_val = SVGTransformList::create(realm(), ReadOnlyList::Yes);
+    auto anim_val = SVGTransformList::create(realm(), ReadOnlyList::Yes);
     return SVGAnimatedTransformList::create(realm(), base_val, anim_val);
 }
 

Libraries/LibWeb/SVG/SVGList.cpp

@@ -0,0 +1,208 @@
+/*
+ * Copyright (c) 2025, Jelle Raaijmakers <jelle@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/SVG/SVGList.h>
+#include <LibWeb/SVG/SVGTransform.h>
+
+namespace Web::SVG {
+
+template<typename T>
+SVGList<T>::SVGList(JS::Realm& realm, Vector<T> items, ReadOnlyList read_only)
+    : m_realm(realm)
+    , m_items(move(items))
+    , m_read_only(read_only)
+{
+}
+
+template<typename T>
+SVGList<T>::SVGList(JS::Realm& realm, ReadOnlyList read_only)
+    : m_realm(realm)
+    , m_read_only(read_only)
+{
+}
+
+template<typename T>
+void SVGList<T>::visit_edges(GC::Cell::Visitor& visitor)
+{
+    visitor.visit(m_realm);
+    visitor.visit(m_items);
+}
+
+// https://www.w3.org/TR/SVG2/types.html#__svg__SVGNameList__length
+template<typename T>
+WebIDL::UnsignedLong SVGList<T>::length() const
+{
+    // The length and numberOfItems IDL attributes represents the length of the list, and on getting simply return the
+    // length of the list.
+    return m_items.size();
+}
+
+// https://www.w3.org/TR/SVG2/types.html#__svg__SVGNameList__clear
+template<typename T>
+WebIDL::ExceptionOr<void> SVGList<T>::clear()
+{
+    // 1. If the list is read only, then throw a NoModificationAllowedError.
+    if (m_read_only == ReadOnlyList::Yes)
+        return WebIDL::NoModificationAllowedError::create(m_realm, "Cannot modify a read-only list"_utf16);
+
+    // 2. Detach and then remove all elements in the list.
+    // FIXME: Detach items.
+    m_items.clear();
+
+    // FIXME: 3. If the list reflects an attribute, or represents the base value of an object that reflects an attribute, then
+    //    reserialize the reflected attribute.
+
+    return {};
+}
+
+// https://www.w3.org/TR/SVG2/types.html#__svg__SVGNameList__initialize
+template<typename T>
+WebIDL::ExceptionOr<T> SVGList<T>::initialize_(T new_item)
+{
+    // 1. If the list is read only, then throw a NoModificationAllowedError.
+    if (m_read_only == ReadOnlyList::Yes)
+        return WebIDL::NoModificationAllowedError::create(m_realm, "Cannot modify a read-only list"_utf16);
+
+    // 2. Detach and then remove all elements in the list.
+    // FIXME: Detach items.
+    m_items.clear();
+
+    // FIXME: 3. If newItem is an object type, and newItem is not a detached object, then set newItem to be a newly created
+    //    object of the same type as newItem and which has the same (number or length) value.
+
+    // FIXME: 4. Attach newItem to the list interface object.
+
+    // 5. Append newItem to this list.
+    m_items.append(new_item);
+
+    // FIXME: 6. If the list reflects an attribute, or represents the base value of an object that reflects an attribute, then
+    //    reserialize the reflected attribute.
+
+    // 7. Return newItem.
+    return new_item;
+}
+
+// https://www.w3.org/TR/SVG2/types.html#__svg__SVGNameList__getItem
+template<typename T>
+WebIDL::ExceptionOr<T> SVGList<T>::get_item(WebIDL::UnsignedLong index)
+{
+    // 1. If index is greater than or equal to the length of the list, then throw an IndexSizeError.
+    if (index >= m_items.size())
+        return WebIDL::IndexSizeError::create(m_realm, "List index out of bounds"_utf16);
+
+    // 2. Return the element in the list at position index.
+    return m_items[index];
+}
+
+// https://www.w3.org/TR/SVG2/types.html#__svg__SVGNameList__insertItemBefore
+template<typename T>
+WebIDL::ExceptionOr<T> SVGList<T>::insert_item_before(T new_item, WebIDL::UnsignedLong index)
+{
+    // 1. If the list is read only, then throw a NoModificationAllowedError.
+    if (m_read_only == ReadOnlyList::Yes)
+        return WebIDL::NoModificationAllowedError::create(m_realm, "Cannot modify a read-only list"_utf16);
+
+    // FIXME: 2. If newItem is an object type, and newItem is not a detached object, then set newItem to be a newly created
+    //    object of the same type as newItem and which has the same (number or length) value.
+
+    // 3. If index is greater than the length of the list, then set index to be the list length.
+    if (index > m_items.size())
+        index = m_items.size();
+
+    // 4. Insert newItem into the list at index index.
+    m_items.insert(index, new_item);
+
+    // FIXME: 5. Attach newItem to the list interface object.
+
+    // FIXME: 6. If the list reflects an attribute, or represents the base value of an object that reflects an attribute, then
+    //    reserialize the reflected attribute.
+
+    // 7. Return newItem.
+    return new_item;
+}
+
+// https://www.w3.org/TR/SVG2/types.html#__svg__SVGNameList__replaceItem
+template<typename T>
+WebIDL::ExceptionOr<T> SVGList<T>::replace_item(T new_item, WebIDL::UnsignedLong index)
+{
+    // 1. If the list is read only, then throw a NoModificationAllowedError.
+    if (m_read_only == ReadOnlyList::Yes)
+        return WebIDL::NoModificationAllowedError::create(m_realm, "Cannot modify a read-only list"_utf16);
+
+    // 2. If index is greater than or equal to the length of the list, then throw an IndexSizeError.
+    if (index >= m_items.size())
+        return WebIDL::IndexSizeError::create(m_realm, "List index out of bounds"_utf16);
+
+    // FIXME: 3. If newItem is an object type, and newItem is not a detached object, then set newItem to be a newly created
+    //    object of the same type as newItem and which has the same (number or length) value.
+
+    // FIXME: 4. Detach the element in the list at index index.
+
+    // 5. Replace the element in the list at index index with newItem.
+    m_items[index] = new_item;
+
+    // FIXME: 6. Attach newItem to the list interface object.
+
+    // FIXNE: 7. If the list reflects an attribute, or represents the base value of an object that reflects an attribute, then
+    //    reserialize the reflected attribute.
+
+    // 8. Return newItem.
+    return new_item;
+}
+
+// https://www.w3.org/TR/SVG2/types.html#__svg__SVGNameList__removeItem
+template<typename T>
+WebIDL::ExceptionOr<T> SVGList<T>::remove_item(WebIDL::UnsignedLong index)
+{
+    // 1. If the list is read only, then throw a NoModificationAllowedError.
+    if (m_read_only == ReadOnlyList::Yes)
+        return WebIDL::NoModificationAllowedError::create(m_realm, "Cannot modify a read-only list"_utf16);
+
+    // 2. If index is greater than or equal to the length of the list, then throw an IndexSizeError with code.
+    if (index >= m_items.size())
+        return WebIDL::IndexSizeError::create(m_realm, "List index out of bounds"_utf16);
+
+    // 3. Let item be the list element at index index.
+    auto item = m_items[index];
+
+    // FIXME: 4. Detach item.
+
+    // 5. Remove the list element at index index.
+    m_items.remove(index);
+
+    // 6. Return item.
+    return item;
+}
+
+// https://www.w3.org/TR/SVG2/types.html#__svg__SVGNameList__appendItem
+template<typename T>
+WebIDL::ExceptionOr<T> SVGList<T>::append_item(T new_item)
+{
+    // 1. If the list is read only, then throw a NoModificationAllowedError.
+    if (m_read_only == ReadOnlyList::Yes)
+        return WebIDL::NoModificationAllowedError::create(m_realm, "Cannot modify a read-only list"_utf16);
+
+    // FIXME: 2. If newItem is an object type, and newItem is not a detached object, then set newItem to be a newly created
+    //    object of the same type as newItem and which has the same (number or length) value.
+
+    // 3. Let index be the length of the list.
+    // AD-HOC: No, this is unused.
+
+    // 4. Append newItem to the end of the list.
+    m_items.append(new_item);
+
+    // FIXME: 5. Attach newItem to the list interface object.
+
+    // FIXME: 6. If the list reflects an attribute, or represents the base value of an object that reflects an attribute, then
+    //    reserialize the reflected attribute.
+
+    // 7. Return newItem.
+    return new_item;
+}
+
+template class SVGList<GC::Ref<SVGTransform>>;
+
+}

Libraries/LibWeb/SVG/SVGList.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2025, Jelle Raaijmakers <jelle@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Vector.h>
+#include <LibGC/Cell.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
+#include <LibWeb/WebIDL/Types.h>
+
+namespace Web::SVG {
+
+// https://www.w3.org/TR/SVG2/types.html#ReadOnlyList
+enum class ReadOnlyList : u8 {
+    Yes,
+    No,
+};
+
+// https://www.w3.org/TR/SVG2/types.html#TermListInterface
+template<typename T>
+class SVGList {
+public:
+    // https://www.w3.org/TR/SVG2/types.html#__svg__SVGNameList__length
+    WebIDL::UnsignedLong length() const;
+    WebIDL::UnsignedLong number_of_items() const { return length(); }
+
+    WebIDL::ExceptionOr<void> clear();
+    WebIDL::ExceptionOr<T> initialize_(T);
+    WebIDL::ExceptionOr<T> get_item(WebIDL::UnsignedLong);
+    WebIDL::ExceptionOr<T> insert_item_before(T, WebIDL::UnsignedLong);
+    WebIDL::ExceptionOr<T> replace_item(T, WebIDL::UnsignedLong);
+    WebIDL::ExceptionOr<T> remove_item(WebIDL::UnsignedLong);
+    WebIDL::ExceptionOr<T> append_item(T);
+
+    ReadonlySpan<T> items() { return m_items; }
+
+protected:
+    SVGList(JS::Realm&, Vector<T>, ReadOnlyList);
+    SVGList(JS::Realm&, ReadOnlyList);
+
+    void visit_edges(GC::Cell::Visitor& visitor);
+
+    ReadOnlyList read_only() const { return m_read_only; }
+
+private:
+    GC::Ref<JS::Realm> m_realm;
+    Vector<T> m_items;
+
+    // https://www.w3.org/TR/SVG2/types.html#ReadOnlyList
+    ReadOnlyList m_read_only;
+};
+
+}

Libraries/LibWeb/SVG/SVGTransformList.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2024, MacDue <macdue@dueutil.tech>
+ * Copyright (c) 2025, Jelle Raaijmakers <jelle@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -13,48 +14,26 @@ namespace Web::SVG {
 
 GC_DEFINE_ALLOCATOR(SVGTransformList);
 
-GC::Ref<SVGTransformList> SVGTransformList::create(JS::Realm& realm)
+GC::Ref<SVGTransformList> SVGTransformList::create(JS::Realm& realm, Vector<GC::Ref<SVGTransform>> items, ReadOnlyList read_only)
 {
-    return realm.create<SVGTransformList>(realm);
+    return realm.create<SVGTransformList>(realm, move(items), read_only);
 }
 
-SVGTransformList::~SVGTransformList() = default;
-
-SVGTransformList::SVGTransformList(JS::Realm& realm)
-    : PlatformObject(realm)
-{
-}
-
-// https://svgwg.org/svg2-draft/single-page.html#types-__svg__SVGNameList__length
-WebIDL::UnsignedLong SVGTransformList::length()
-{
-    // The length and numberOfItems IDL attributes represents the length of the list, and on getting simply return the length of the list.
-    return m_transforms.size();
-}
-
-// https://svgwg.org/svg2-draft/single-page.html#types-__svg__SVGNameList__numberOfItems
-WebIDL::UnsignedLong SVGTransformList::number_of_items()
+GC::Ref<SVGTransformList> SVGTransformList::create(JS::Realm& realm, ReadOnlyList read_only)
 {
-    // The length and numberOfItems IDL attributes represents the length of the list, and on getting simply return the length of the list.
-    return m_transforms.size();
+    return realm.create<SVGTransformList>(realm, read_only);
 }
 
-// https://svgwg.org/svg2-draft/single-page.html#types-__svg__SVGNameList__getItem
-WebIDL::ExceptionOr<GC::Ref<SVGTransform>> SVGTransformList::get_item(WebIDL::UnsignedLong index)
+SVGTransformList::SVGTransformList(JS::Realm& realm, Vector<GC::Ref<SVGTransform>> items, ReadOnlyList read_only)
+    : Bindings::PlatformObject(realm)
+    , SVGList(realm, move(items), read_only)
 {
-    // 1. If index is greater than or equal to the length of the list, then throw an IndexSizeError.
-    if (index >= m_transforms.size())
-        return WebIDL::IndexSizeError::create(realm(), "SVGTransformList index out of bounds"_utf16);
-    // 2. Return the element in the list at position index.
-    return m_transforms.at(index);
 }
 
-// https://svgwg.org/svg2-draft/single-page.html#types-__svg__SVGNameList__appendItem
-GC::Ref<SVGTransform> SVGTransformList::append_item(GC::Ref<SVGTransform> new_item)
+SVGTransformList::SVGTransformList(JS::Realm& realm, ReadOnlyList read_only)
+    : Bindings::PlatformObject(realm)
+    , SVGList(realm, read_only)
 {
-    // FIXME: This does not implement the steps from the specification.
-    m_transforms.append(new_item);
-    return new_item;
 }
 
 void SVGTransformList::initialize(JS::Realm& realm)
@@ -63,11 +42,10 @@ void SVGTransformList::initialize(JS::Realm& realm)
     Base::initialize(realm);
 }
 
-void SVGTransformList::visit_edges(Cell::Visitor& visitor)
+void SVGTransformList::visit_edges(Visitor& visitor)
 {
     Base::visit_edges(visitor);
-    for (auto transform : m_transforms)
-        transform->visit_edges(visitor);
+    SVGList::visit_edges(visitor);
 }
 
 }