Fwd: RE: SUSPECT: Re: [gtkmm] RE: TreeView Model, SEGV on append - mor e info [erik_ohrnberger dme net]

[Martin Schulze <martin-ml hippogriff de>]

Am 2003.10.27 21:23 schrieb(en) "Ohrnberger, Erik":
Martin,
	Well, something must have changed as it's now working.  Wonder
what
I did.  Don't really like things like this that appear and then go away,
but
it appears to be working now.  Grrr.

	See below for additional comments interspersed.

	Erik.

> -----Original Message-----
> From: Martin Schulze [mailto:martin-ml hippogriff de]
> Sent: Monday, October 27, 2003 3:50 PM
> To: Ohrnberger, Erik
> Cc: 'gtkmm-list gnome org'
> Subject: SUSPECT: Re: [gtkmm] RE: TreeView Model, SEGV on
> append - more
> info
>
>
> Am 2003.10.27 19:32 schrieb(en) "Ohrnberger, Erik":
> > Everyone,
> > 	I have a little bit more information on this.
> >
> > 	In the class that uses the TreeView, I have the following
> > organization:
> >
> > Class is subclassed from Gtk::ScrolledWindow, and contains the
> > following
> > data members:
> > 	Gtk::TreeView					tvMoldList;
> > 	MoldListCols*					pCols;
> > 	Glib::RefPtr<Gtk::ListStore>			pMoldListModel;
> >
> > In the class CTOR, I create the column instance (pCols)
> with a new.  I
> > also
> > create the model:
> > 	pMoldListModel = ListStore::create( *pCols );
> >
> > Set the model to the treeview:
> > 	tvMoldList.set_model( pMoldListModel );
> >
> > and then append the columns to the treeview:
> > 	tvMoldList.append_column( "Icon", (*pCols).Icon );
> >
> > In the MoldListCols CTOR, I add it's columns:
> > 	add( Icon ); ....
> >
> > In one of the class's methods, I want to add a single line to the
> > model,
> > however, by then the data member pMoldListModel returns a NULL, like
> > it's
> > lost scope or something.  Well, once I create another
> model, load all
> > the
> > items that should be in there and append line item that I wanted
> > originally,
> > it appears to work just fine.
>
> The call
>      pMoldListModel = ListStore::create( *pCols );
> does indeed succeed and pMoldListModel is != 0 by then?

Yes.  In the class' CTOR, this succeeds.

> You do instantiate Gtk::Main before your ctor is executed?

Gtk::Main is declared inside of main(), and on the line below,
MainWindow is
declared.  This leads me to believe that Gtk::Main is instantiated
first.

> There is no other call pMoldListModel = ... in your code?

Nope.

> pMoldListModel isn't hidden by a local variable?

Nope.

> You always operate on the same instance of your class?

Yup.  It's declared as a data member of another class, which is higher
in
the GUI instance tree (if you think of how the widgets are all nested
within
each other).

> Have you tried to allocate the TreeView dynamically
> with Gtk::manage(new Gtk::TreeView) in your ctor?

Nope.

> What does tvMoldList.get_model() yield by the time
> pMoldListModel is 0?

It was NULL.  But now appears to have cleared up.

> > It strikes me as strange that the model data member (pMoldListModel)
> > would
> > loose it's value between method calls.  You would think
> that it would
> > maintain it's value so that you could manipulate the model for the
> > lifetime
> > of the object.
> >
> > What do you think?  Is this in fact the expected behavior of the
> > TreeView,
> > Gtk::ListStore classes?
>
> No, absolutely not. RefPtr<> aquires a reference on the ListStore.
> The ListStore will not be freed until the last reference has become
> out of scope. You could try to assign pMoldListModel to a global
> variable (so that two reference with a completely different scope
> refer to the same ListModel) and see if anything changes.
>
> I'm sorry, without a compilable example we can only do guesswork.
>
> Regards,
>
>    Martin

I understand about having a solid example for you making things easier,
however, I don't think that my employer would like it if I sent
proprietary
code out of the corporation.


I really appreciate you helping me out in the manner that you are.  It
is
proving itself to be useful.

   Thanks,
	Erik.