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From: Shark8 <onewingedshark@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Properties
Date: Wed, 1 Dec 2010 11:36:57 -0800 (PST)
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Date: 2010-12-01T11:36:57-08:00
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>> Agreed, but I don't believe we're stuck with that solution.
>> All you need is procedure'Access for the callback.
>
>No, because events have parameters and those must be typed.
>The standard solution is that you instantiate a generic (and
>there is one for each number of parameters and the results).
>That is extremely boring.

Er, why not use OO/tagged-records for the events themselves and let
the base-handler have that as a parameter?

i.e. the handler would be an access to something like this:
Procedure On_Event( Object : in out : GUI_Object; --'Class?
                    Event  : In Base_Event'Class );

The Root for GUI-objects can say "On_Event(...) is null*" and allow
overriding for the components that DO use it. *A Null-body, not null-
access.

Further some mouse-event can extend the base-record with items such as
the position of the mouse.

Or is there something I'm missing?