LibWeb: Add Node.insertBefore(Node node, Node? child)

Libraries/LibWeb/DOM/Node.cpp

@@ -200,4 +200,16 @@ RefPtr<Node> Node::append_child(NonnullRefPtr<Node> node, bool notify)
     return node;
 }
 
+RefPtr<Node> Node::insert_before(NonnullRefPtr<Node> node, RefPtr<Node> child, bool notify)
+{
+    if (!child)
+        return append_child(move(node), notify);
+    if (child->parent_node() != this) {
+        dbg() << "FIXME: Trying to insert_before() a bogus child";
+        return nullptr;
+    }
+    TreeNode<Node>::insert_before(node, child, notify);
+    return node;
+}
+
 }

Libraries/LibWeb/DOM/Node.h

@@ -83,6 +83,7 @@ public:
     bool is_parent_node() const { return is_element() || is_document() || is_document_fragment(); }
 
     RefPtr<Node> append_child(NonnullRefPtr<Node>, bool notify = true);
+    RefPtr<Node> insert_before(NonnullRefPtr<Node> node, RefPtr<Node> child, bool notify = true);
 
     virtual RefPtr<LayoutNode> create_layout_node(const StyleProperties* parent_style) const;
 

Libraries/LibWeb/DOM/Node.idl

@@ -9,5 +9,7 @@ interface Node : EventTarget {
     readonly attribute Element? parentElement;
 
     Node appendChild(Node node);
+    Node insertBefore(Node node, Node? child);
+
 }
 

Libraries/LibWeb/TreeNode.h

@@ -110,6 +110,7 @@ public:
 
     void prepend_child(NonnullRefPtr<T> node);
     void append_child(NonnullRefPtr<T> node, bool notify = true);
+    void insert_before(NonnullRefPtr<T> node, RefPtr<T> child, bool notify = true);
     NonnullRefPtr<T> remove_child(NonnullRefPtr<T> node);
     void donate_all_children_to(T& node);
 
@@ -252,6 +253,33 @@ inline void TreeNode<T>::append_child(NonnullRefPtr<T> node, bool notify)
         static_cast<T*>(this)->children_changed();
 }
 
+template<typename T>
+inline void TreeNode<T>::insert_before(NonnullRefPtr<T> node, RefPtr<T> child, bool notify)
+{
+    if (!child)
+        return append_child(move(node), notify);
+
+    ASSERT(!node->m_parent);
+    ASSERT(child->parent() == this);
+
+    if (!static_cast<T*>(this)->is_child_allowed(*node))
+        return;
+
+    node->m_previous_sibling = child->m_previous_sibling;
+    node->m_next_sibling = child;
+
+    if (m_first_child == child)
+        m_first_child = node;
+
+    node->m_parent = static_cast<T*>(this);
+    if (notify)
+        node->inserted_into(static_cast<T&>(*this));
+    (void)node.leak_ref();
+
+    if (notify)
+        static_cast<T*>(this)->children_changed();
+}
+
 template<typename T>
 inline void TreeNode<T>::prepend_child(NonnullRefPtr<T> node)
 {