From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) 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=3.4.6 Path: eternal-september.org!reader02.eternal-september.org!aioe.org!x6YkKUCkj2qHLwbKnVEeag.user.46.165.242.91.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: GtkAda callback and event Date: Sun, 5 Sep 2021 00:29:58 +0200 Organization: Aioe.org NNTP Server Message-ID: References: <6133e791$0$6461$426a74cc@news.free.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Info: gioia.aioe.org; logging-data="50500"; posting-host="x6YkKUCkj2qHLwbKnVEeag.user.gioia.aioe.org"; mail-complaints-to="abuse@aioe.org"; User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 X-Notice: Filtered by postfilter v. 0.9.2 Content-Language: en-US Xref: reader02.eternal-september.org comp.lang.ada:62631 List-Id: On 2021-09-04 23:39, DrPi wrote: > I use an event callback with user data. > > I first declare a package : >    package Handler_Motion_Notify is new > Gtk.Handlers.User_Return_Callback (Widget_Type => > Gtk.Text_View.Gtk_Text_View_Record, > >    Return_Type => Boolean, > >    User_Type   => t_Debug_Panel); > > The function callback is declared like this : >    function On_Motion_Notify (TextView : access > Gtk.Text_View.Gtk_Text_View_Record'Class; >                               DebugPanel : t_Debug_Panel) return Boolean; This is wrong. The motion-notify-event callback has the parameters: 1. Target 2. Gdk.Event.Gdk_Event_Motion 3. User data > The connection is done like this : >       Handler_Motion_Notify.Connect (Widget => Panel.TextView, >                                      Name   => > Gtk.Widget.Signal_Motion_Notify_Event, >                                      Cb     => On_Motion_Notify'Access, >                                      User_Data => t_Debug_Panel(Panel)); > > This works correctly. But... I need to have access to the event in the > callback function. Maybe it does not crash but it is incorrect. > How can I achieve this ? There is no shortcut Connect and Callback defined in User_Return_Callback. Therefore you have to use a general-case callback with the parameter list: function On_Motion_Notify ( Object : access Gtk_Text_View_Record'Class; Params : Glib.Values.GValues; Data : t_Debug_Panel ) return Boolean; connected as: Handler_Motion_Notify.Connect ( Panel.TextView, "motion-notify-event", -- = Signal_Motion_Notify_Event On_Motion_Notify'Access, t_Debug_Panel (Panel) ); The parameter is accessed using the function Nth or Gtk.Argument.Unchecked_To_Gdk_Event_Motion, e.g. Gtk.Argument.Unchecked_To_Gdk_Event_Motion (Params, 1) P.S. Since the target is practically never used in callbacks, you can instantiate Gtk.Handlers.User_Return_Callback with GObject_Record. This way you could use it with all types of widgets. That reduces the number of instantiations. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de