[gtkada] Signal handler

[Dmitry A. Kazakov]

On Wed, 03 Aug 2011 11:28:07 +0200, you wrote:

> I encourage people who want to fix widgets in GtkAda to look into modifying 
> directly the python scripts in contrib/ to do the automatic binding of the 
> widgets. This is work in progress on our side, the goal is to make transition to 
> more recent versions of gtk+ easier in the future.

If you are about to change GtkAda, why not to consider making handlers
type-safe? The existing schema only appears safe, it adds Ada types, but
does not ensure them matching the actual types of the signal or that signal
names are correct.

A type-/event-safe schema might be based on Ada 2005 interfaces. E.g.

package Gtk.Button is
   ...
-- Signal handlers:
   -- Clicked event
   type Clicked_Handler is limited interface;
   procedure Connect
                  (   Button : not null access Gtk_Button_Record;
                      Handler : in out Clicked_Handler'Class
                  );
   procedure Connect
                  (   Button : not null access Gtk_Button_Record;
                      Handler : in out Clicked_Handler'Class;
                      ID : out Handler_Id
                  );
   procedure Handle
                  (  Handler : in out Clicked_Handler;
                     Button : not null access Gtk_Button_Record'Class
                  )  is abstract;

   -- Released event
   type Released_Handler is limited interface;
   procedure Connect
                  (   Button : not null access Gtk_Button_Record;
                      Handler : in out Released_Handler'Class;
                      ID : out Handler_Id
                  );
   procedure Connect
                  (   Button : not null access Gtk_Button_Record;
                      Handler : in out Released_Handler'Class
                  );
   procedure Handle
                  (  Handler : in out Released_Handler;
                     Button : not null access Gtk_Button_Record'Class
                  )  is abstract;
   ... etc

This schema can be implemented on top of the existing one.

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