[gtkada] simple.adb (again)

[Vinicius F Arcaro]

Dear list member,

On a previous message about the simple.adb procedure Joel Brobecker
wrote:

> Remember that callback packages must be instantiated at library
> level, so in this example, you'll have to create a separate package
> (simple is just a procedure).

What does it means to instantiate at library level? Why do I need a
separate package? What is wrong with the following version of
simple.adb?

Thank you,
Vinicius

with
Gtk.Window,
Gtk.Widget,
Gtk.Handlers,
Gtk.Main;

procedure Test00 is

   Window : Gtk.Window.Gtk_Window;

   -- Callback
   procedure Destroy (Widget : access
Gtk.Widget.Gtk_Widget_Record'Class) is

   begin
      Gtk.Main.Main_Quit;
   end Destroy;

   package Handlers is new Gtk.Handlers.Callback
(Gtk.Widget.Gtk_Widget_Record);

begin
   --  This is called in all GtkAda applications. Arguments are parsed
   --  from the command line and are returned to the application.
   Gtk.Main.Init;

   --  Create a new window.
   Gtk.Window.Gtk_New (Window);

   --  Change the title of the window.
   Gtk.Window.Set_Title (Window,"Test00");

   --  Specify a minimal size for the window.
   Gtk.Window.Set_Default_Size (Window,300,200);

   --  Connect the "destroy" event to a signal handler.
   --  This event occurs when we call Gtk.Widget.Destroy on the window.
   Handlers.Connect (Window, "destroy", Handlers.To_Marshaller
(Destroy'Access));

   --  Display the newly created window.
   Gtk.Window.Show (Window);

   --  All GtkAda applications must have a Main. Control ends here
   --  and waits for an event to occur (like a key press or
   --  mouse event).
   Gtk.Main.Main;
end Test00;