From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on ip-172-31-74-118.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.5-pre1 Path: eternal-september.org!reader02.eternal-september.org!aioe.org!5WHqCw2XxjHb2npjM9GYbw.user.gioia.aioe.org.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: GtkAda : Trying to derive a widget Date: Fri, 9 Apr 2021 08:18:28 +0200 Organization: Aioe.org NNTP Server Message-ID: References: <606f5938$0$27421$426a74cc@news.free.fr> <606fe610$0$3717$426a74cc@news.free.fr> NNTP-Posting-Host: 5WHqCw2XxjHb2npjM9GYbw.user.gioia.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Complaints-To: abuse@aioe.org User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 Content-Language: en-US X-Notice: Filtered by postfilter v. 0.9.2 Xref: reader02.eternal-september.org comp.lang.ada:61764 List-Id: On 2021-04-09 07:28, DrPi wrote: > Le 09/04/2021 à 00:27, Dmitry A. Kazakov a écrit : >> On 2021-04-08 21:27, DrPi wrote: >> >>> I'm trying to create a GtkAda widget derived from a standard widget. >>> >>> -- debug_panel.ads >>> with Gtk.Scrolled_Window; use Gtk.Scrolled_Window; >>> with Gtk.Text_View;       use Gtk.Text_View; >>> >>> package Debug_Panel is >>> >>>    type Debug_Panel_Record is new Gtk_Scrolled_Window_Record with >>> private; >>>    type Debug_Panel is access all Debug_Panel_Record'Class; >>> >>> >>>    procedure Gtk_New (Panel : in out Debug_Panel); >>>    procedure Initialize (Panel : not null access >>> Debug_Panel_Record'Class); >>> >>> private >>> >>>    type Debug_Panel_Record is new Gtk_Scrolled_Window_Record with record >>>       Text       : Gtk_Text_View; >>>    end record; >>> >>> end Debug_Panel; >>> >>> >>> -- debug_panel.adb >>> package body Debug_Panel is >>> >>>    procedure Gtk_New (Panel : in out Debug_Panel) is >>>    begin >>>       Panel := new Debug_Panel_Record; >>>       Initialize (Panel); >> >>    Debug_Panel.Initialize (Panel); > I did try this notation and got this error : > debug_panel.adb:6:07: invalid prefix in selected component "Debug_Panel" > debug_panel.adb:6:18: prefixed call is only allowed for objects of a > tagged type > > I've just realized this is because the package and the access type have > the same name. You can disambiguate it so: Standard.Debug_Panel.Initialize (Panel) Standard.Debug_Panel - The package name Standard.Debug_Panel.Debug_Panel - The type name >> Another way would be to remove "use Gtk.Scrolled_Window" and declare as >> >>    type Debug_Panel_Record is >>       new Gtk.Scrolled_Window.Gtk_Scrolled_Window_Record with private; >> >> Without "use" Initialize is unambiguous. >> > That makes sense. > However, I don't understand why there is ambiguity when using "use". > Debug_Panel (the type) is of type Debug_Panel_Record, so Initialize > should resolve to the one using this type. Well, I guess I'm wrong. Debug_Panel belongs to both Debug_Panel_Record'Class and Gtk_Scrolled_Window_Record'Class (and many other classes), so the ambiguity. >> P.S. When you create new widget it is better to use a more general >> ancestor hiding insufficient details, e.g. >> >>    type Debug_Panel_Record is >>       new Gtk.Widget.Gtk_Widget_Record with private; >>    ... >> private >>    type Debug_Panel_Record is >>       new Gtk.Scrolled_Window.Gtk_Scrolled_Window_Record with >>    record >>       ... >>    end record; > > I'm surprized this is possible to write such a thing in Ada. > What does the compiler do with this ? The public view is Gtk_Widget_Record [with no record members], the full view is Gtk_Scrolled_Window_Record [with record members you specified]. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de