Re: Equivalent of the gtk g_object_ref/unref functions in gtkmm?

[Murray Cumming <murrayc murrayc com>]

On Thu, 2007-03-22 at 16:49 +0100, Jef Driesen wrote:
> When I look at some gtk C code, I see everywhere pointers to widgets 
> (and other things). As i understand all gtk objects are reference 
> counted to keep the objects alive until the last pointer is released.
> 
> How does that work in gtkmm? At first sight, gtkmm widgets doesn't seem 
> to be reference counted, because something like this does not work 
> (because of the private copy constructor):
> 
> Gtk::Button a, b(a);
> 
> Do I need to use smart pointers (e.g. boost::shared_ptr) for that? Does 
> that means the underlying gtk reference counting mechanism is not used 
> in gtkmm?
> 
> I read in the gtkmm documentation there is a Glib::RefPtr, that uses the 
> internal gtk/gobject reference counting. If I understand that correctly, 
> I can use this smart pointer (instead of third party implementation like 
> boost)?
> 
> Glib::RefPtr<Gtk::Button> a(new Gtk::Button()), b(a);
> 
> But I've never seen that before, only with non-widgets objects like 
> pixbufs and treemodels.

RefPtr is not for use with widgets. Widgets (or other things that derive
from GtkObject rather than GObject) have different, more complicated
memory management than the reference-counted objects such as TreeModel. 

This page has an overview of gtkmm memory management:
http://www.gtkmm.org/docs/gtkmm-2.4/docs/tutorial/html/ch22.html

In summary, it's just regular C++ memory management so you can do what
you like, and we have some things to help you sometimes.

> One of the problems I'm trying to solve is I want to create a treeview 
> that will act as a sidebar pane in my application. And I would like to 
> store a reference to other widgets (which are in a notebook) in the 
> treemodel. When the user activates an item in the treeview, the 
> corresponding widget should be displayed in the main application pane 
> (by displaying the correct notebook page). How should this treemodel 
> look like in gtkmm? Is a smart pointer going to interfere with the 
> automatic memory management when I add the widget to the notebook? Do I 
> need smart pointers at all for all this?

You can use some other smartpointer, such as one from boost, or you can
use some parent-child relationship of your own.

-- 
Murray Cumming
murrayc murrayc com
www.murrayc.com
www.openismus.com