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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: GTK key-press-event
Date: Wed, 2 Nov 2016 10:45:21 +0100
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Date: 2016-11-02T10:45:21+01:00
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On 02/11/2016 10:19, hreba wrote:

> I am trying to write a key press handler with user data. I know how to
> connect the handler and that its type is
>
> type Handler is access procedure
>     Widget    : access Widget_Type'Class;
>         Params    : Glib.Values.GValues;
>     User_Data : User_Type);

There is a typed marshaller for handing this type of events:

    type Handler is access function
         (  Widget    : access Gtk_Widget_Record'Class;
            Event     : Gdk_Event;
            User_Data : User_Type
         )  return Boolean;

> What I don't know is how to get the key which was pressed.

The event parameter contains input event type and if that was a keyboard 
event, the key pressed/released:

    case Get_Event_Type (Event) is
       when Key_Press => -- This a key-press event
          case Get_Key_Val (Event) is
             when GDK_Insert => -- This is INSERT key
                ...

> A few months ago I had a similar problem where I needed a Cairo Graphics
> context, and I got it from the parameter list "Params" , selecting the
> first component with Glib.Values.Nth(), and converting that with
> Cairo.Get_Context.

You could use Nth () but there is no reason doing that. And for this 
type of event there is a return value.

Note that key press events must be unmasked to be emitted. Then some 
widgets never emit these events anyway. They must be wrapped into an 
"event-box" which itself is invisible but emits the events.

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