[Accessibility] D-Bus AT-SPI - The way forward

Mark Doffman mark.doffman at codethink.co.uk
Wed Dec 5 08:56:57 PST 2007

Hello all,

Available at http://live.gnome.org/GAP/AtSpiDbusInvestigation is the
results of an investigation into a move of the AT-SPI interface to a
D-Bus transport. The investigation mainly looks at the relative
performance of ORBit and D-Bus, but also details some architectural
issues and a preliminary task list.

In brief:


GOK and Orca were profiled to get a good idea of the type of traffic on
the AT-SPI interface. Using this information the performance of some of
the most common method calls were tested in D-Bus and ORBit.

D-Bus is undoubtedly slower at most of the common method calls, 5-6x
slower when making a call that passes one int as an argument. When
passing more data per call this speed difference decreases. ORBit takes
a long time to pass an Object reference, making D-Bus up to 1.5x faster
at these method calls.

Although D-Bus is the slower transport, looking at the calls made by
Orca and GOK, we feel it will be possible to provide sensible caching
that should mitigate this effect.


For a switchover to D-Bus a number of core libraries will need to have
the transport mechanism changed: cspi, pyatspi, GAIL. There will also
need to be a new Java accessibility back end. Some core D-Bus work is
also needed, in the areas of interface specification, bindings and
possibly optimisation.

If you are interested please go and take a look at the wiki page. We'd
really like to get every ones opinion on what the way forward for AT-SPI
is in terms of its transport mechanism.



Mark Doffman, Codethink Ltd. - http://codethink.co.uk

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