LibHTML: Add LayoutNode::first_ancestor_of_type<T>()

Libraries/LibHTML/Layout/LayoutNode.h

@@ -67,6 +67,7 @@ public:
 
     const StyleProperties& style() const;
 
+    LayoutNodeWithStyle* parent();
     const LayoutNodeWithStyle* parent() const;
 
     void inserted_into(LayoutNode&) {}
@@ -97,6 +98,12 @@ public:
     template<typename T>
     T* first_child_of_type();
 
+    template<typename T>
+    const T* first_ancestor_of_type() const;
+
+    template<typename T>
+    T* first_ancestor_of_type();
+
 protected:
     explicit LayoutNode(const Node*);
 
@@ -157,6 +164,11 @@ inline const LayoutNodeWithStyle* LayoutNode::parent() const
     return static_cast<const LayoutNodeWithStyle*>(TreeNode<LayoutNode>::parent());
 }
 
+inline LayoutNodeWithStyle* LayoutNode::parent()
+{
+    return static_cast<LayoutNodeWithStyle*>(TreeNode<LayoutNode>::parent());
+}
+
 template<typename T>
 inline bool is(const LayoutNode&)
 {
@@ -248,3 +260,23 @@ inline T* LayoutNode::first_child_of_type()
     }
     return nullptr;
 }
+
+template<typename T>
+inline const T* LayoutNode::first_ancestor_of_type() const
+{
+    for (auto* ancestor = parent(); ancestor; ancestor = ancestor->parent()) {
+        if (is<T>(*ancestor))
+            return &to<T>(*ancestor);
+    }
+    return nullptr;
+}
+
+template<typename T>
+inline T* LayoutNode::first_ancestor_of_type()
+{
+    for (auto* ancestor = parent(); ancestor; ancestor = ancestor->parent()) {
+        if (is<T>(*ancestor))
+            return &to<T>(*ancestor);
+    }
+    return nullptr;
+}