it is done

core/src/mindustry/ui/layout/TreeLayout.java

@@ -0,0 +1,22 @@
+package mindustry.ui.layout;
+
+public interface TreeLayout{
+    void layout(TreeNode root);
+
+    class TreeNode<T extends TreeNode>{
+        public float width, height, x, y;
+
+        //should be initialized by user
+        public T[] children;
+        public T parent;
+
+        //internal stuff
+        public float mode, prelim, change, shift;
+        public int number = -1, leaves;
+        public TreeNode thread, ancestor;
+
+        public boolean isLeaf(){
+            return children == null || children.length == 0;
+        }
+    }
+}