text: #ifndef MAINWINDOW_H
  #define MAINWINDOW_H
  
  #include <QMainWindow>
  
  #include "tree.h"
  #include "tree.cpp"
  #include "node.h"
  #include "node.cpp"
  
  QT_BEGIN_NAMESPACE
  namespace Ui { class MainWindow; }
  QT_END_NAMESPACE
  
  class MainWindow : public QMainWindow
  {
      Q_OBJECT
  
  public:
      MainWindow(QWidget *parent = nullptr);
      ~MainWindow();
      Ui::MainWindow *ui;
      //virtual void paintEvent(QPaintEvent* event);
  private slots:
  
      void on_add_node_clicked();
      void renderNodes(Node<int>* node);
      void on_show_clicked();
  private:
      //virtual void paintEvent(QPaintEvent *);
      Tree<int> *tree;
  };
  #endif // MAINWINDOW_H
  