void OnGUI() { EditorGUILayout.BeginHorizontal(); { if (GUILayout.Button("Change")) { _changeAction.Invoke(_treeView.GetSelectObject()); _window.Close(); return; } if (GUILayout.Button("Quit")) { _window.Close(); return; } } var lastRect = GUILayoutUtility.GetLastRect(); _treeView.OnGUI(new Rect(0, lastRect.y + lastRect.height, position.width, position.height)); }