port some more code (for os < win10)

Yuhang Zhao

2023-12-05 9b1599d82e86d2d0463b60fe6fa61f94be50f983

 examples/mainwindow/mainwindow.h

@@ -7,6 +7,9 @@
public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

protected:
    void installWindowAgent();
};

#endif // MAINWINDOW_H