Fix mistake of calculating wrong size

Sine Striker

2023-12-07 f452b4a64bbef0d84518499a663dc527527d11b9

 examples/mainwindow/mainwindow.h

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

protected:
    void installWindowAgent();
};

#endif // MAINWINDOW_H