[Panel-devel] applets and multiple dataengines

[Rüdiger Hacke]

Hi all,

I'm trying to write a little system monitor applet that should be able to 
display various information using more than one DataEngine.

Now with the current API the visualization gets its data via

    updated(QString sourceName, Plasma::DataEngine::Data data)

If I am not mistaken, with just that I have no easy means to tell which engine 
sent the data. If two engines happen to have sources with the same name, 
things would get complicated.

(say, one engine providing data about drive-throughput has a source 
named "hda" and an other one providing data about free/used space on disks 
also has a source named "hda")

I could check the keys to try to make a distinction. Or I could use some kind 
of proxy objects, one for each engine to connect its sources to.

But perhaps it is possible to add a third parameter to the above mentioned 
signal which indicates the DataEngine this is coming from. Either name or 
pointer. (I'd opt for pointer because getting the engine's name from the 
pointer is easy, the other way round is a little less efficient)

If I correctly understood the signals & slots mechanism, excess parameters of 
signals connected to a slot with a smaller signature are just ignored. So 
making such an addition shouldn't break existing stuff, right?

kind regards,
Rudi
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