Re: destroying an unparented widget

[Olivier Sessink <oliviersessink gmail com>]

On 05/05/2011 09:37 PM, Allin Cottrell wrote:
> There's one thing I've never quite understood: the correct
> mechanism for destroying a gtk widget that is never parented or
> shown.
>
> The context is that I'm creating a temporary widget with
> gtk_label_new(), just for the purpose of getting hold of its
> PangoContext so I can figure something out about the font in use
> (whether it supports the UTF-8 minus sign, 0x2212). Once I've got
> that info I'm using gtk_widget_destroy on the label. And valgrind
> is showing me a leak, which I take to mean that I haven't managed
> to destroy the widget. If I try using g_object_unref() instead I
> get an error message from GTK saying I can't do that on an object
> which has only a floating reference.
>
> Would the correct sequence be
>
> label = gtk_label_new("");
> g_object_ref_sink(G_OBJECT(label));
> /* do pango stuff */
> g_object_unref(G_OBJECT(label));
>
> ? And if so, is there an equivalent in GLib<  2.10? Thanks.

I think this is the correct way yes. a widget is created with a floating 
reference. With ref_sink() you now own the reference, and after the 
unref the reference count should be 0.

you can debug this with the LD_PRELOAD GObject lifetime debugging tool, 
see 
http://blogs.gnome.org/danni/2011/02/17/ld_preload-gobject-lifetime-debugging-tool/

Olivier