Re: object_data -> qdata?

[Havoc Pennington <hp redhat com>]

Skip Montanaro <skip pobox com> writes:
> Where in 1.2 you have 
> 
>     &GTK_OBJECT (widget)->object_data
>

Yikes, you shouldn't be using this I don't think.

What are you trying to do, maybe we can give you what you should be
using in that context.
 
> Owen pointed me at some stuff on his website earlier today that helped, and
> the Changes-2.0.txt file looks like a goldmine.  Are there other places to
> read up on to get a nuts-n-bolts education on the Gtk type/class structure
> and the changes it's gone through recently?
> 

I have a half-done porting document, but it's fairly concise on this
matter, not going to be super-useful for language binding authors.

 <sect1 id="gobject">
    <title>GObject</title>

    <para>
The GTK+ type system and object system have been moved to GLib, as
"libgobject," and modified somewhat in
transit. <literal>GtkObject</literal> still exists for compatibility
reasons, but should not be used as a base class for new object
implementations.
    </para>

<para>
<literal>GObject</literal> differs from <literal>GtkObject</literal>
in two main application-programmer-visible respects. First, it is
strictly reference counted, with no "floating flag"; so when you
create a new <literal>GObject</literal>, you own a reference to it and
must always unref. With <literal>GtkObject</literal>, you don't own a
reference on a new object, there's only the owned-by-no-one floating
reference.  Second, there's no "destroy" signal. The "destroy" signal
on <literal>GtkObject</literal> was semantically broken, leading to a
lot of implementation difficulties; it means both "request that all
weak references drop their handle to this object to break cycles" and
"this object is about to be finalized." <literal>GObject</literal>
does not have a "please break cycles" signal, and notification of
finalization should be done with "weak references." Notification of
finalization is not done with a signal, because signal emission adds
references to an object and depends on the object being alive. It's
not possible to add references to an object that's already being
finalized.
</para>

<para>
GObject will be most visible to authors of custom widgets. 
The "correct way" to write a widget has changed a bit; 
look at some of the widgets new in GTK+ 2.0 to get an idea how
signals, object properties, and so on work with GObject.
</para>

Havoc