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Date: Wed, 27 Apr 2016 00:47:00 -0700 (PDT)
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Subject: Re: Where do I get my Cairo context from (in GTK3)?
From: briot.emmanuel@gmail.com
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Xref: news.eternal-september.org comp.lang.ada:30299
Date: 2016-04-27T00:47:00-07:00
List-Id: <comp.lang.ada>

> I would use On_* procedures if I didn't need user data. Until now no 
> success.

Are you sure you really need that user data ? In my experience, it is often
better to extend the widget type in your application, store whatever information
is needed in that child type, and then use the On_* procedure passing a Slot
object (so that the callback receives your widget type, rather than the widget
on which the action occurred). This works in 95% of the cases.

The GNAT Development Studio (GPS), which is about 500_000 lines of code
has almost no use of user data, and those that remain are mostly because
that part of the code hasn't been updated yet.