Re: Reference counting

["Tristan Van Berkom" <tvb gnome org>]

On Dec 23, 2007 1:20 AM, Alwin Leerling <leerling xtra co nz> wrote:

Hi,

I'm slightly overwhelmed as to the whole reference counting issue. Could
someone explain the though process or logic behind the reference
counting or direct me to some information where I can find the correct
use. For example, in my code I set up my combo boxes on startup using
gtk_list_store_newv and gtk_combo_box_set_model. (Do I need to unref the
list_store pointer at this stage?)

This is a question of how you interpret your application, think, do you
want to give the ownership of your data model to your view widget ?

Will you be having multiple list stores that you might want to keep
around and alternate the view ?

If you unref your list store (passing ownership to the combo box), then
destroying (freeing) the combo box will take care of finalizing (freeing)
the list store.
 

At a later stage I am ready to put
some data in the combo box, so I get the store (with
gtk_combo_box_get_model) and add some entries to the sore. Do I need to
unref the aquired pointer?

No. in general gtk_[widget]_get_[parameter]() functions never duplicate
strings or add references (strings are easier because they are always
const return values if they are not duplicated).

Usually a returned value that has a reference will note in the docs that
it must be unreffed (strings from g_object_get() are dupped and objects
refcount incremented for instance).

To make matters more confusing, I also have a
couple of combo's with filters. I wrote a little stub to acquire the store:

GtkTreeModel * gtk_combo_get_filter_model( GktComboBox * combo )
{
    return gtk_tree_model_filter_get_model( GTK_TREE_MODEL_FILTER(
gtk_combo_box_get_model( combo ) ) );
}

Do I leak a reference here?

No.

Also read the description portion of:
   http://library.gnome.org/devel/gtk/unstable/GtkObject.html

Cheers,
                 -Tristan