Re: how to tell if a widget is still "alive" ?

[Gregory Hosler <ghosler redhat com>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 06/17/2010 03:38 PM, David NeÄas wrote:
> On Thu, Jun 17, 2010 at 09:07:46AM +0800, Gregory Hosler wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > Hi all,
> >
> > I have an application where I'm making use of animated gifs on a GtkTextBuffer.
> > I set a timer (g_timeout_add()) to remove the animated character after a small
> > period of time (10 secs in this case).
> >
> > The argument to the timer callback includes a pointer to the text buffer
> > GtkTextChildAnchor in front of where I inserted my animation. The idea is that
> > inside the timeout, I insert a static copy of the gif, and do a
> > gtk_text_buffer_delete() of the iter's before and after the animation.
> >
> > This works about 99.999% of the time.
> >
> > In some rare circumstances, by the time that the timer callback is called, the
> > GtkTextChildAnchor has been deleted.
> >
> > To guard against this, I tested the GtkTextChildAnchor with
> > GTK_IS_TEXT_CHILD_ANCHOR(), but on occassion, I will get a segfault on the
> > GTK_IS_TEXT_CHILD_ANCHOR() (the address of the GtkTextChildAnchor is still a
> > valid address).
> >
> > I'm thinking that the GtkTextChildAnchor has been deleted, the memory used for
> > something else, and the GTK_IS_TEXT_CHILD_ANCHOR() is seg faulting as a result.
> >
> > Question: how might I avoid this seg fault situation ? Will "GTK_IS_WIDGET()"
> > help to determine if the GtkTextChildAnchor is still alive before testing it
> > with GTK_IS_TEXT_CHILD_ANCHOR() ? or is there a better way of doing this ?
>
> The standard rule is: if you permanently use an object take a reference
> with g_object_ref().  Then it can't be finalized unless you release
> the reference.

<slaps head>

ah, yes! of course!

In my earlier days of gtk+ usage I didn't understand the significance of the
ref. I do now (and have for some time), but somehow missed this obvious soln!

Thanks a lot!

- -Greg

> See also the description of gtk_text_child_anchor_get_deleted().
>
> You can get notified when an object is finalized, but this is not a case
> where you should do it.
>
> Yeti


- -- 
+---------------------------------------------------------------------+

Please also check the log file at "/dev/null" for additional information.
                (from /var/log/Xorg.setup.log)

| Greg Hosler                                   ghosler redhat com    |
+---------------------------------------------------------------------+
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.10 (GNU/Linux)
Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/

iEYEARECAAYFAkwZ03UACgkQ404fl/0CV/SZfwCgwcyRO4l0zLAxZYGYAZenV62z
4jMAoIDLVaz0owZWz4DZuBwOsGit1l+b
=ZJnK
-----END PGP SIGNATURE-----