A couple of days ago, I released version 0.2.1 of Bustle, someone's favourite D-Bus profiler. As the version number suggests, there aren't really any big new features; most of the changes just make it a bit nicer to use, like showing you all the bus names a service owns, ellipsizing strings, a slightly less spartan UI, etc. Having finally gotten around to cutting a release, I've started wondering what to work on next. There are various small things I have in mind, such as searching, filtering, integrating the various statistic tools (bustle-time and friends) into the UI, and so on, but it'd be nice to have a larger goal to work towards.

One recurring feature request is the ability to see messages' arguments. This isn't currently possible because the simple plain-text logs produced by the monitor (which is a variation on the theme of dbus-monitor --profile) only includes the message header. I've thought for a while that the right thing to do would be to log the raw dbus messages, together with a timestamp, but wasn't sure what the files would look like. (Maybe shove the timestamps into the message headers?) Rob had a nice idea: why not log to pcap files? This avoids inventing a new format—the UI would just use libpcap and feed each message through the dbus parser—and would also let you look at the logs in WireShark, if you're into that kind of thing. I'm hoping to find some time to give this a shot soon. (Maybe on a cold Christmas evening, in front of a fire?)

In the meantime, have a peek at what your D-Bus-using applications are up to, and let me know what's missing!

Jason's hands were tired after typing two days of excellent notes on sessions at the Gnome Summit, so I took over writing up the Telepathy BOF (which was largely about Telepathy integration in Gnome Games).

Gnome Games's tubes code is broken because of Empathy moving to Mission Control 5, which broke the contact chooser they were using (which used Mission Control 4). A Canonical person (your scribe did not catch who it was) has written a contact selector in C which just uses telepathy-glib, which Gnome Games will use and then start working again. This widget could form the basis of the long-anticipated telepathy-gtk.

Rob pointed out that it's currently a bit of pain to request a channel for yourself: you can't just call one D-Bus method and get a channel back, you also have to implement a Client.Handler object on which MC will call the HandleChannels() method. Sjoerd noted that Empathy has helper code for doing this in simple cases, which could be moved to tp-glib (it's under the LGPL).

Jason wants a way to share high scores with your contacts. (Digression about a gnome-games high score server on gnome.org ensued, the notes of which your scribe lost in a kernel panic. One main point is that global high scores end up just featuring incredibly good scores and people setting their name to obscenities.) Jason wonders if g-g could publish your high scores to your contacts in the background?

• Rob and Will suggested that in principle this could use PEP on XMPP, which allows you to publish a blob of information to your XMPP server and be notified when your contacts' blobs change. (This is how Geolocation works in Empathy, for instance.) Unfortunately Google's server doesn't support PEP, so most people wouldn't be able to use this; plus, it would need an extension in Gabble.
• Another way to do it would be to initiate file transfers behind the scenes.
• Rob suggested using tubes. Gnome Games would come with a tiny daemon that handles tubes for the "org.gnome.games.highscores" service, serving up your high scores to anyone who asks. Then, when you open a high scores table, it would use ContactCapabilities to discover which of your online contacts support that service, and then ask them for their latest high scores (with a cache and a rate limit, obviously). It could show a throbber while it's doing this. Jason thinks this sounds like a good idea. Prerequisites: you need the latest MC and Gabble 0.9 in order for ContactCapabilities to work, but that's it.

J5 wondered if any g-g people are documenting how they're using tubes, because he was always confused by them, and he reckons this is a very important thing for app developers. Rob suggested pushing this into tp-book, and Sjoerd noted that Danielle has a helper which lets you say "give me a stream to this person" and get a GIOChannel back branch with methods to convert between telepathy address GValues and GSocketAddresses, which could conceivably be extended to set up a socket automatically. J5 thinks that if patterns for using tubes were really well documented, people would jump on the chance to use them.

Jason mentioned that people were discussing having a help option which jumps you to #gnome-games-$lang. J5 said that Ximian tried that, but found that people would just end up in empty chatrooms or paste goatse at each other. Integration with DevHelp would be nice to let people post examples etc.

J5 suggested that another good way to improve documentation is to make writing it a requirement for SoC. Rob noted that Telepathy hackers know that you need to use, eg., a Handler and a Tube, but it's hard for people really immersed in the stack to remember which prerequisites people need to learn in order to understand that stuff. Sandy said they'd been discussing documenting requirements and standards for SoC students, and thinks it's a great idea to ask students to blog stream-of-consciousness "this is what i did" updates. People have to make sure that they do this as they go along, because you forget the learning process after a few weeks.

Advantage of peer-to-peer high scores: you don't get the problem of one incredibly good person dominating. ajaxxx suggested that you could make high scores decay over time, or once you reach a particular level, to address this problem.

Tetrinet is latency-sensitive: will that be a problem with Telepathy, particularly using MUC tubes? Rob said just try it and if it's too slow it'll get faster as the implementation of Tubes improves. Sjoerd noted that for tetrinet you probably want to just export the Tetrinet server over a multi-user stream tube, rather than using d-tubes.

Telepathy should use UPnP to make FT and tubes fast in more cases. This is on the TODO list.

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!

An oft-requested feature in Empathy and Telepathy is support for OTR (Off The Record) encryption of messages, interoperating with the OTR plugin for Pidgin and other popular IM clients. We've been resisting implementing it so far, mainly because we think there are better ways to do end-to-end encryption of messages and audio and video calls over XMPP, which we hope to implement in the not too distant future.

However, a nice aspect of OTR as compared to other encryption solutions is that it allows you to plausibly deny having taken part in a conversation. We believe this to be an example of a wider trend towards deniability on the internet, a position which is backed up by the growing popularity of Tor, and by several modern browsers allowing you to cover your browsing tracks out of the box.

As a result, we've been working hard to help secure your privacy while you're using Empathy. We've had to do this quietly for various legal reasons, but we're proud to announce Empathy's new Private Mode. When enabled, your contact list will be anonymized, as will your entry on your contacts'. Thus, you can conduct conversations with anyone without fear of repercussions from their discovering your identity, or of anyone else knowing the conversation took place:

It's not obvious how to bring these privacy benefits to Jingle video calls. We came up with a technique we refer to as Kitten Secrecy (patents pending in all relevant countries), and managed to integrate it with Empathy with the help of our friends at Collabora Multimedia, who constructed a fantastic GStreamer element using only two leaky queues!

We think the results speak for themselves. The source is not quite ready for release yet, but (lawyers permitting) we hope it'll be public by the end of the month. Hope you can wait until then!

— the Telepathy and Empathy teams

If you're about to leave an angry comment:

At the Boston Gnome summit, Robert McQueen, Sjoerd Simons and I sketched out a plan for the API for end-to-end encryption of communications (implemented using XTLS, OTR or anything else) and how we'd implement this API for OTR. Work's just started on a challenge-response authentication API, which is a prerequisite. Stay tuned; or, jump onto the Telepathy list or #telepathy on Freenode if you're interested in helping out!

(Hi, I'm at LCA 2009!)

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:

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 willthompson.co.uk/bustle.

In what onlookers are already calling “potentially unwise”, our robot overlord ordered various toys from ThinkGeek.

Today — being as it is Friday, always the most productive of all days — they arrived! Apparently appropriate tools to control the missile launchers are not yet packaged for Debian. :(