[Gtk-sharp-list] SubWidget problems

Alex Graveley alex@beatniksoftware.com
Wed, 15 Dec 2004 21:07:08 -0800


How is Gtk# 2.0 fixing this?


On Wed, 2004-12-15 at 10:48 -0500, Dan Winship wrote:
> On Tue, 2004-12-14 at 19:41 -0600, Sergio Duran wrote:
> > I created a Widget (DBMenu) that inherits from Gtk.Menu, it works ok,
> > but sometimes it ends up reading an empty instance of itself, I set
> > some variables in the ctor, and I end up dealing with an instance with
> > those variables unitialized, I found some stuff that said one should
> > add a ctor(IntPtr x) but then it instantiates the class when it
> > shouldnt be doing it, apparently randomly so get some weird crashes.
> > 
> > I found some links that said that it is related to gtk and c#'s
> > garbage collection.
> The issue is that for every Gtk# object, there are actually two
> different "objects" created; the underlying C-based GObject, and the
> C#/managed object that wraps it.
> The problem is that when you add your DBMenu to a C-based container
> widget, the container only keeps track of the GObject part, not the
> managed part. So if there are no other references to the managed object,
> it will get garbage collected, even though the C-based object is still
> there.
> So then if Gtk# finds a reference to the C-based object later, it needs
> to create a new managed wrapper for it. This is what the IntPtr ctor is
> for. However, as you've discovered, it's only safe to have an IntPtr
> ctor if you can completely reconstruct the wrapper object's state from
> the C-based object.
> If you can't do that, the easiest thing to do is to make sure that
> something somewhere in managed code keeps a reference to the DBMenu
> object so that it won't be garbage collected.
> The good news is that this problem will be fixed in Gtk# 2.0
> -- Dan
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