Re: How to determine if a GObject is "contained"?

[Tristan Van Berkom <tvb gnome org>]

Hans Oesterholt-Dijkema wrote:
[...]
> Normally when a GObject is "handed" to another GObject, the
> reference count is increased, so, after taking ownership and handing over,
> the GObject will have a reference count of 2.  Then, when the proxy to
> the GObject is finalized, the reference count will drop to 1. No problems
> here.

This isn't exactly true, passing ownership works like this:

 bar = my_bar_new();     // create an object
 foo_add_bar (foo, bar); // foo now "has bar in its inventory"
 g_object_unref (bar);   // give ownership of bar to foo.

ownership is the deciding reference count that will eventually
result in finalization if unreffed, all other references are
temporary.

GtkObject / GtkContainer is a special convenience case to avoid
the redundant g_object_unref () code (as stated above), note that
the initial gtk_container_add() call will not increse the reference
count on the child GtkObject (and *because* the reference is not
incremented ownership is passed).

> However, not with the case of the GdkPixbuf of GtkImage. It returns
> a GObject with reference count=1. mzgtk2 takes ownership of the GObject,
> resulting in a situation that two Objects "think" they own the GObject.
> When the proxy of mzgtk2 is finalized by the Garbage Collector, the
> reference count of the GdkPixmap drops to 0, and it is prematurly
> finalized.

When object 'foo' is created as a delagate of another object 'bar',
object foo "belongs to bar" and will be finalized by bar.

Why would a garbage collector be in any way interested in a resource
that was not explicitly allocated by the calling application code ?

I flipped through your previously referenced document... and
found this "Code sample 3", I really wonder what is the logic
behind this, is the goal of this excersize just to have a single
clean extra reference to every GObject ?
===========================================
 if (GTK_IS_OBJECT(g)) {
   if (GTK_OBJECT_FLOATING(g)) {
      g_object_ref(g);
      gtk_object_sink(g);
   }
   else {
      g_object_ref(g);
   }
 }
 else if (gobject_ref_count(g)>1) {
   g_object_ref(g);
 }
===========================================

May I ask why you aren't referencing objects that
have a ref_count of "1" and why you are not adding
a reference to floating GtkObjects ?

I obviously dont know enough about your project to solve
your problem, but I hope this was helpfull anyway.

Cheers,
                        -Tristan