Proposal and RFC: Introducing DAL, the "Desktop Abstraction Layer"

Ikke eikke at
Thu Jan 13 16:31:21 EET 2005

> > ...
> I don't know if DAL is the right name for it but it seems like a worthy
> goal.  I would think the major goal of a project like this would be to
> identify common integration points and define a spec that defines a set
> of standard interfaces (signals and methods) classes of applications
> should implement.  Perhaps the Common Desktop Interface would describe
> it better.
> --
> J5

thanks for your reply.
As far as I understand you're proposing an application should send out
events/information/... using some strict well-known interface. I was
rather thinking of some other method:

application -> (some IPC method: Unix socket, DBUS,...) -> DAL daemon ->
(DBUS session bus) -> Listening applications.

Like this a developer of (e.g.) XMMS is not forced to get DBUS in his
software, he should just deliver a plugin for DAL able to listen on the
existing socket and pass a struct to the DAL core, which in turn
generates and broadcasts some DBUS message. In this way it's far less
intrusive in the code of existing applications. I'm particularly
thinking of KDE applications (where DBUS isn't very "common" yet
afaik?), or Evolution 2.1 series which have DBUS support etc. They still
can use the IPC method they're used to, which also implies applications
that use this existing method will still work.

Its more like HAL: one central daemon (session-wide here) that takes
information from several "agents" (plugins that know how to listen to
specific events of specific applications) and sends out DBUS messages
representing these events using some well-sprcified interface.

If you'd want the application sending out events itself, it'll limit the
possibilities. As an example, the xscreensaver developer won't ever be
willing to add such a feature [1], and listening for XEvents isn't
really "easy to do" for most desktop apps. Which is where DAL could be
usefull: one place that listens to information, and broadcasts it to
everyone who is interested.

Regarding the name: DAL is just a "working title", a better name can be
found :-)

Regards, Ikke


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