[gtkada] Question wrt using the new paradigm for connecting handlers to signals

[Rob Groen]

Emmanuel,

Thanks for your explanation.

Is there a way to use the new paradigm without the conversion to/from a Gtype_Interface ?

> Not really.
> These new On_* subprograms are really simple wrappers around the old way, so mixing both
> in your application will definitely work, and there are no drawback.
> When they are generated, the type used for "Self" is that of the widget or interface that
> declares the signal. So if you are using a child type, you will have to convert the types in
> your callback. In practice, this conversion is safe (since otherwise you cannot call On_* in
> the first place), and well worth adding in exchange for some more static type checking that
> the compiler can do with the new approach (for the parameters other than Self).
Ok, I will continue with the mixed approach without mixed feelings
>
>> procedure Handler (Object : access gtk_combo_box_text_record’class);
>> type Cb_GObject_Void is not null access procedure (Self : access Glib.Object.GObject_Record'Class);
>>
>> I would have expected that the compiler complains about actual type of “Handler” not being (subtype) compatible / conformant to the formal type Cb_Gtk_Combo_Box_Void
> There is no notion of subtype compatibility here. The exact profile must be the same in Ada,
> so your Handler indeed needs to accept an access to GObject_Record'Class, and do a type
> conversion internally, as explained above.
>
>> I can’t find an obvious way to do a type conversion without running into accessibility level violations, and I guess that the type conversion isn’t even allowed.
> Accessibility level violations are unrelated to the errors you are seeing with the
> improper matching of types. You likely declare the Handler as a nested subprogram
> in your main procedure, I would guess. That's not the way real applications are structured
> in practice (the callbacks are always defined at library level in other packages), but for small
> demos you should use Handler'Unrestricted_Access rather than Handler'Access.
Agree
> regards
> Emmanuel
>
Regards
Rob

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