questions about the NowListening applet and MPD support

Eric Deshayes edeshayes at
Wed May 20 20:27:52 CEST 2009

Thanks for the answers.

I have some new questions:

1. about the functionality
- shouldn't the nowplaying only monitor one music source at a time? 
- should the applet display the music played by all the running music sources? 
- does it make sense to give the user to select one and only one music source, 
either from the configuration ui or from the applet directly?

2. on the technical side
- regarding the addition of the MPD support, what should we consider as a data 
source for the nowplaying data engine:
the mpd datasource (and the host/port/password) is used when a service is 
any connection to a mpd server is a data source, ie you could have more than 
one mpd datasource, each of them being a different mpd server


----------  Forwarded Message  ----------

Subject: Re: questions about the NowListening applet and MPD support
Date: Monday 18 May 2009
From: "Aaron J. Seigo" <aseigo at>
To: plasma-devel at

On Sunday 17 May 2009, Eric Deshayes wrote:
> My first question is: is there a mailing-list for that applet and/or its
> data
> engine or is the general Plasma mailing list the right one?

this is the right list.

> Is there some documentation on Plasma (mainly about the data engines, the
> applets, the services) other than the Tutorial from or a
> mailing list to ask questions about the architecture?

you can ask here, or on #plasma in irc .. there's also a file on dataengines 
and services in kdebase/workspace/plasma/design/dataengines

> I kind of have figured out what are the data engine for but would that make
> sense to have parametrized datasource? In the case of a MPD data source,
> the parameters would be the server ip/port and the credentials. I have not
> found
> any data source with such a behaviour. Woud there be any other one?

there are several, such as the time, weather or twitter engines.

there are two common approaches:

a) put it all in the name of the source, and parse that out in the dataengine. 
this is how it is done in the time engine, where the name contains the 
timezone and whether or not to do things like the sun or moon calculations

b) name the source after the service destination (in the case of mpd that 
might consist of the hostname and port) and then use a Service retrieved using 
serviceForSource from the engine to add additional information such as the 
credentials. this is what the microblog engine does.

> Also, is anyone working in adding the support of MPD to the NowPlaying
> applet? I saw in the TODO that the support of MPD is to be done.

not that i know of, though people often are working on things quietly in the 
corners :)

Aaron J. Seigo
humru othro a kohnu se
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KDE core developer sponsored by Qt Software


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