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List: gtk-devel
Subject: Re: GTK+ canvas?
From: Damon Chaplin <damon () karuna ! uklinux ! net>
Date: 2006-08-31 13:16:58
Message-ID: 1157030218.2497.25.camel () localhost ! localdomain
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On Thu, 2006-08-31 at 13:03 +0200, Marco Pesenti Gritti wrote:
> Goocanvas has a view/model split at item level too. There is an
> ItemModel and and ItemView, and the Item interface has a create_view
> method. IHMO this introduce needless complexity, especially in the
> event handling.
>
> Mouse events are signals on the ItemView, so you have two options to
> listen for item events:
>
> 1 Subclass Item and ItemView and handle signals in ItemView
> 2 Handle events from the CanvasView (which therefore needs to know
> about his Model internals)
>
> None of these is really acceptable.
I don't see the problem with (1) for large applications. That is
standard model/view stuff.
For simple apps you can connect signal handlers to the item views. This
isn't that hard (it is easier in the latest release).
> I can see the usefullness of model/view split at item level in a
> widget system (Swing for example) where logic and presentation are
> clearly separated. But in goocanvas Model is totally about
> presentation (stroke-color, fill-color, line-width to cite some of the
> SimpleItem properties).
>
The simple items are all basic shapes, but for real-world use
applications would use their document objects as the model.
I agree that the model/view split does complicate it a bit. But it can
also help a lot for larger apps.
Damon
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