Boston Gnome Summit and Maemo Summit

I’m just getting ready to fly away to Boston for the Gnome Summit. I’m looking forward to meeting people and seeing MIT, as well as getting the chance to spend more than a few hours in Boston (unlike every other time I’ve been there).

Inevitably, I haven’t been organised enough to propose a Telepathy- or Empathy-related session, but Rob McQueen, Sjoerd Simons, Andres Salomon, Dafydd Harries, Shaun McCance (when he’s not busy running a pair of interesting-sounding documentation sessions!) and myself will be around if people are interested; maybe something will coalesce. If window manager theming is more your kind of bag, Thomas Thurman‘s running a session on CSS in Metacity/Mutter. It’d be great to talk about integrating IM with the Gnome Shell; Moblin’s people panel and many parts of Maemo make interesting use of Telepathy, and it’d be nice to have something similar on the desktop.

Speaking of Maemo, going to Boston means I’m not at the Maemo Summit in Amsterdam, which is a real shame: I’d love to meet more of the Maemo community, hear what people have up their sleeves for the N900, and discuss how Telepathy could help. Happily, Marco Barisione‘s giving a talk about how Telepathy’s used on Maemo, and how you can use it too; relatedly, Travis Reitter and Mathias Hasselmann will speak about the address book, one of the heaviest users of Telepathy. Also, Marc Ordinas i Llopis is hosting a BoF on extending the (frankly stunning) Hildon desktop, and Ian Monroe is giving a talk with Sergiy Dubovik about preparing Qt4 applications for Fremantle and Harmattan. I hear Philippe Kalaf is also floating around somewhere. ☺

See you in (the wrong) Cambridge!

GCDS, D-Bus, Telepathy, and other items

Hello, internet! I’m at the Gran Canaria Desktop Summit. I’m a big fan of this “conference beside a beach” concept: interesting people, talks and projects, in the sun beside the Atlantic. There are a *lot* of Collabora people here; the head-count on the roof of the hotel last night exceeded 20, with still more people arriving today (and others stuck in Madrid). As ever, it’s good to catch up with colleagues and others!

Bringing GUADEC and aKademy together seems to have been a partial success. It’s interesting to learn about projects from the other side of the fence, and I’ve had some productive conversations about the state of using Telepathy in KDE. That said, it’s a bit sad that so much of the cross-desktop schedule seemed to be a talk about a GNOME implementation of a concept, followed by a KDE implementation of the same idea. Maybe putting the duplicated effort in people’s faces could help improve matters, but that seems unlikely.

Earlier today I gave a talk about profiling and optimizing D-Bus APIs (grab the slides!), including Bustle, a D-Bus visualization and profiling tool I’ve written to help visualize bus activity and find issues. I think it went quite well, and it lead to some interesting questions and discussions afterwards. In the talk, I mentioned a few examples of sub-ideal API design in other frameworks, but largely focused on the problems we’ve found in the Telepathy API, and how we’ve gone about fixing them. A couple of people mentioned that this might have reinforced the impression that Telepathy is really hard to use, which was not what I intended at all! On the contrary, the improvements I talked about have made Telepathy a lot more developer-friendly than it was when I first got involved: both the D-Bus API (if you ignore the deprecated bits) and the higher-level client-side convenience libraries (telepathy-glib and telepathy-qt4) have become significantly easier to use. It’s telling that a lot of the changes that have made developers’ lives easier have also made the D-Bus API more efficient, sane, and correct.

Of course, there’s still room for improvement. As I mentioned, contact lists are quite awkward to work with, which is a shame because most Telepathy UIs would like to use contact lists. :-) libempathy-gtk has a couple of contact list widgets you could reuse, some of which I’d like to see in a smaller, API-stable libtelepathy-gtk; I hear that there’s talk to extract the Python contact list widget that’s being written for GNOME Games to a library that other Pythonic Telepathy applications (such as pyhallebard for which I can’t find a website right now — thanks Anonymous!) could use.

In other news, Tracker 0.7 sounds (among other things) like a potential solution to the silly unfortunate situation where every music player uses its own library database, and thus your DAAP server either needs a separate database or to be built into your music player. Mojito looks pretty interesting; I’d love to see a UI for it on my desktop. It annoys me that I have to check so many disjoint sources at the moment. It might be nice if it could show me blog post titles from my LiveJournal or Facebook contacts; I suppose I should start hacking. :)

Bustle: a D-Bus activity charting tool

When working on Telepathy, I’ve often wanted to be see which D-Bus methods are being called on whom, when signals are emitted, and so on. Timing information is also handy: I’d like to figure out why cold-starting Empathy takes 12 seconds, and it’d be much easier if I could look at a diagram rather than staring at the unreadable output of dbus-monitor.

Previously, Alban wrote a tool that used a patched version of mscgen, and produced appropriate input with a dbus-monitor-like Python script. I wanted some more D-Bus-specific diagrams, and ended up reimplementing both the monitoring component (by forking dbus-monitor, as its --profile output did not contain quite enough information) and the diagram-drawing component (using Cairo). I’m happy to present an initial release of Bustle:

Screenshot of Bustle 0.1

There’s a Telepathy-specific hack in the tool to shorten object paths, but it shouldn’t make the tool any less useful for looking at other D-Bus traffic.

I haven’t made binary packages yet, I’m afraid, so you’ll need to grab the source tarball and build it if you want to try it out. In Debian-land, the dependencies are libdbus-1-dev libglib2.0-dev libghc6-mtl-dev libghc6-cairo-dev libghc6-gtk-dev libghc6-parsec-dev; see README in the source tree for how to build and use it.

The astute among you may have noticed from the dependencies that the diagram-building component is implemented in Haskell, using the excellent bindings to Gtk+ and Cairo. I got a prototype going within a few hours, and the strong correctness guarantees that the type system provides meant that I could refactor it mercilessly with confidence. I’m sure that I would have spent many frustrating hours chasing type bugs had I written it in Python, which is a more conventional high-level language for prototyping and writing tools like this. Next time you’re frustrated by such bugs, you should give Haskell a try. :-)

Edit: Bustle now lives at

The near-impossibility of teaching programming to a subset of students

The camel has two humps[pdf] was an interesting read; a bit wooly, but believable. One of my favourite paragraphs, tangential to the paper’s findings, concerned IDEs:

Programmers, who on the whole like to point and click,
often expect that if you make programming point-and-click, then novices will find it easier. The
entire field can be summarised as saying “no, they don’t”.