added range loop based layout nodes traversal

engine/layout.h

@@ -168,4 +168,37 @@ public:
     void load(const char* path);
     void load_internal(const tinyxml2::XMLElement* x_node);
     void reload();
+
+    class iterator
+    {
+        std::stack<Node*> m_nodes;
+        Node* m_current;
+    public:
+        iterator(Node* root)
+        {
+            m_current = root;
+            if (root)
+                m_nodes.push(root);
+        }
+        iterator& operator++() 
+        { 
+            m_nodes.pop();
+            for (auto& c : m_current->children)
+                m_nodes.push(&c);
+            m_current = m_nodes.size() ? m_nodes.top() : nullptr;
+            return *this;
+        }
+        Node& operator*() { return *m_current; }
+        Node* operator->() { return m_current; }
+        bool operator==(const iterator& rhs) { return m_current == rhs.m_current; }
+        bool operator!=(const iterator& rhs) { return m_current != rhs.m_current; }
+    };
+    iterator begin()
+    {
+        return this;
+    }
+    iterator end()
+    {
+        return nullptr;
+    }
 };