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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Gtkada: attach signals to menus
Date: Sun, 19 Jun 2016 20:33:34 +0200
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Date: 2016-06-19T20:33:34+02:00
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On 2016-06-19 17:02, Stephen Leake wrote:
> Basic menus work, but I can't figure out how to compute the submenu on the fly.
>
> Here's my attempt:

[...]

> If I use "On_Activate" for On_Menu_Table, the submenu is not shown. So I tried "On_Select"; still no submenu, and it crashes with

This is because you do not "show" submenu you create.

> (menu_demo.exe:5884): Gtk-WARNING **: GtkWindow 001915B0 is mapped but visible child GtkMenu 08B2C468 is not mapped

This is because you do it each time new. Looks like a GTK bug to me, but 
the usage is not intended.

> I know how to compute a dynamic submenu in Emacs and Win32; there must be a way to do this in Gtk.

Here I changed your signal handler:

procedure On_Menu_Table (Self : access
Gtk.Menu_Item.Gtk_Menu_Item_Record'Class)
is
    use Gtk.Menu_Item;
    use Gtk.Widget;
    Table_Item : constant Gtk_Menu_Item := Gtk_Menu_Item (Self);
begin
    if Table_Item.Get_Submenu = null then -- Do it only once
       declare
          Menu : constant Gtk.Menu.Gtk_Menu := Gtk.Menu.Gtk_Menu_New;
          Item : Gtk_Menu_Item;
       begin
          Item := Gtk_Menu_Item_New_With_Mnemonic ("_Add");
          Menu.Append (Item);
          Item := Gtk_Menu_Item_New_With_Mnemonic ("_Edit");
          Menu.Append (Item);
          Item := Gtk_Menu_Item_New_With_Mnemonic ("_Delete");
          Menu.Append (Item);
          Menu.Show_All; -- Make it visible
          Table_Item.Set_Submenu (Menu);
       end;
    end if;
end On_Menu_Table;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de