Re: gtk_object_sink in glade_palette_init

[tomas tuxteam de]

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On Tue, Nov 28, 2006 at 09:44:54AM +0100, Philippe Bertin wrote:
> Hello,
>
> [...] But what I actually meant to ask, is : what's the use of 
> first adding a reference, (because that's what's happening in my eyes), 
> for removing the reference /just the statement after/. Because that's 
> what's happening in my understanding.

Not quite...

[...]

> > > In glade_palette_init, there's this piece of code :
> > >
> > >    /* Add items tray (via a scrolled window) */
> > >    priv->tray = gtk_vbox_new (FALSE, 0);
> > >    g_object_ref (G_OBJECT (priv->tray));
> > >    gtk_object_sink (GTK_OBJECT (priv->tray));

AFAIU, after the _new() the box has a special reference to it: the ref
count is one, but it is marked as "floating"[1]. Now gtk_object_sink()
decrements the ref coung by one *only* if the object is marked as
floating and does nothing otherwise. So the net effect of this code is
to clear the floating flag. See for example

  <http://developer.gnome.org/doc/GGAD/z57.html>

for an explanation.

- ------------
[1] What this means in terms of practical consequences isn't quite clear
to me (perhaps some guru cares to give a pointer), but the idea is to
keep a ref to an yet-unused object you don't want to disappear from
under you before you've put it safely somewhere. Think of it as "half
referenced".

Note that putting the object in a container or whatever sinks() it and
that leads to quite natural code without ref leaks.

Regards
- -- tomÃs
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