static int
compare_foo (const Gtk::TreeModel::iterator& a, const Gtk::TreeModel::iterator& b)
{
    std::tr1::shared_ptr<Foo> l1, l2;
    l1 = a->get_value (COLUMN_FOO);
    l2 = b->get_value (COLUMN_FOO);

    if (!l1)
        return -1;

    if (!l2)
        return 1;

    return l1->get_id () - l2->get_id ();
}

Can you spot the error? Running it under valgrind indicated that I was reading data from *before* the start of the array that was being sorted. In fact, the following lines of code in g_qsort_with_data() were causing tmp_ptr to be decreased back past the start of the array:

        while ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr, user_data) < 0)
          tmp_ptr -= size;

Hmm. Why is there no guard to prevent tmp_ptr from being decreased past the start? Then I noticed the following comment up a few lines:

    /* Find smallest element in first threshold and place it at the
       array's beginning.  This is the smallest array element,
       and the operation speeds up insertion sort's inner loop. */

So at this point, the code is assuming that the very first element of the array is the smallest, so compare_func should always return >= 0 when it reaches the start of the array. Aha! So the problem is my compare_func. It turns out I forgot to handle the single case of both values being NULL.

    l1 = a->get_value (COLUMN_FOO);
    l2 = b->get_value (COLUMN_FOO);
+
+   if (!l1 && !l2)
+       return 0;

    if (!l1)
        return -1;

So there’s not really a big lesson to be learned here, but if you ever hit strange segfaults deep inside glib’s qsort while sorting a treemodel, do yourself a favor and double-check that your sort function is sane first. Also, do yourself a favor and run it under valgrind as soon as you get a strange segfault. Knowing the exact point of the invalid read is infinitely more helpful than waiting until that invalid read causes a segfault.

The Toy Dogs today are bred solely as pets. They have no other purpose in life except to give pleasure, especially to ladies.

Also, I’ll be attending GUADEC for the first time this year, and I’m looking forward to a good time in Istanbul and finally meeting a lot of people in person that I’ve known online for a while.

WebKit work is going quite well. I’ve mostly been focusing on bug fixing so far, though I’ve added some new features as well (CSS text shadows are now supported in the Qt port, for instance). Overall I’ve been really impressed with how clean and well-organized WebKit is for such a large and complex project. I’ve also started playing around with ‘webkitmm’ in my spare time as well. Nothing much to show at the moment, I’m afraid, but I don’t expect it to take too much effort before it’s relatively usable.

I’ve also spent some time in the past week adding a marginally useful feature to nemiver: highlighting memory values when they’ve changed since the last time the debugger stopped. Adding this functionality required some significant modifications to the shared GtkHex widget that we use, so it’s not checked into svn yet, but hopefully will be soon. I’m not sure how people did significant refactorings and API additions before tools like git-svn were available. It’s so nice to be able to try out different things and make changes locally with full version control support instead of trying to maintain a mega-patch or committing half-baked ideas to the central repository.

I also released a new version of cairomm to coincide with the 1.6 release of cairo.

Since then it seems like I’ve been sick most of the time. Instead of doing something useful, I’ve taken to fidding on a re-write of my Agave colorscheme designer, and I’ve made a decent amount of progress. It still lacks a lot of features of the original, but it benefits from my vastly better grasp of gtkmm and related technologies. I still don’t know if I’ll ever actually get around to releasing it. It’s currently serving as a way for me to relax and take breaks from my other projects. It’s become sort of a playground for me to try out new technologies, and I think I’ve succeeded in making it nearly impossible for normal users to build as it requires quite a few very new or unreleased libraries (goocanvasmm, giomm, glibmm-utils, etc).

Here’s a little screencast of what I’ve done so far:

I’ve set up a repository on github for anybody that’s interested in playing around with it.

Also, I’ll be taking over some glibmm maintainer duties from murray after the 2.16.0 release.

Now if we could just get a replacement for gnome_help_display() into GTK+, we’d be able to knock off a lot of other extra dependencies as well.

Update: It appears that in the time it took me to write this post, several others have expressed this sentiment more eloquently than I could have.

In the past, I’ve used GNOME applications for web browsing, checking email, viewing images, listening to music, and all of my other day-to-day computer activities. But I’ve never really had any GNOME tools that I’ve been able to use for development. It feels like we’re finally making progress on some good basic development tools for GNOME, which makes me really happy. In addition to the ones I mentioned, there’s also some really great stuff happening in the new versions of glade3, and there seems to be some good stuff happening in Anjuta as well (though I don’t personally use an IDE). All in all, I’m pretty positive about the future of developer tools in GNOME.

In other news, Ruby is still the-cutest-baby-ever™ and doing really well. We’re even getting some decent sleep (though decent is pretty relative I suppose).

Keep in mind that this is just at an experimental stage at the moment, so I may just throw it away if I decide that it doesn’t work well. I do think it gives a better sense of how the colors are related, though.

In any case, it’s been fun playing around a little bit with cairomm for once. In the end though, I’d probably want to implement this using some sort of canvas library, but I haven’t done enough research on the options that are currently available.

Since it may be a while before we get to a nice restaurant, we went out for a meal at Vincent in downtown Minneapolis for Valentines day. I don’t think I’ve ever enjoyed food as much in my life. It was absolutely phenomenal. I didn’t even regret the small fortune we paid for the meal.

I just pushed out a new minor release of Agave and I’ve also recently added support for enabling and disabling breakpoints in Nemiver.