Програми для обліку

using Gtk;

class Program
{
    public static void Main()
    {
        Application.Init();
        new FirstWindow();
        Application.Run();
    }

    public static void Quit()
    {
        Application.Quit();
    }
}

using Gtk;

class FirstWindow : Window
{
    public FirstWindow() : base("Test")
    {
        SetDefaultSize(600, 350);
        SetPosition(WindowPosition.Center);

        DeleteEvent += delegate { Program.Quit(); };

        VBox vBox = new VBox();
        Add(vBox);

        HBox hBox = new HBox();
        vBox.PackStart(hBox, false, false, 5);

        Button bOpenCalendar = new Button("Відкрити календар");
        bOpenCalendar.Clicked += OnOpenCalendar;

        hBox.PackStart(bOpenCalendar, false, false, 5);

        ShowAll();
    }

    void OnOpenCalendar(object? sender, EventArgs args)
    {
        Popover popoverCalendar = new Popover((Widget)sender!) { BorderWidth = 5 };

        VBox vBox = new VBox();

        Calendar calendar = new Calendar() { Date = DateTime.Now };
        calendar.DaySelectedDoubleClick += (object? sender, EventArgs args) => { popoverCalendar.Hide(); };

        vBox.PackStart(calendar, false, false, 0);

        popoverCalendar.Add(vBox);
        popoverCalendar.ShowAll();
    }
}