[Panel-devel] Sensors and Meters in SK

[Vinay Khaitan]

Hello Everyone,

First of all, Sorry to [mX] for putting SK back in the scenario of plasma 
;-)

I saw the slides of Aaron's presentation about plasma. Looks like he has 
very nice and very well defined ideas about plasma. There are things which 
suits to our purposes too. As superkaramaba is going to be integrated to 
plasma, and some of the libs of SK may be useful to other plasma components, 
I think It would be very nice to make such libs of SK decoupled from SK 
design and make generic enough to be used by other extenders, applets. 
First thing, sensors.

Right now, sensors are integrated with SK as We can define in theme file, 
which sensor is shown by a meter.The purpose of sensor is just to provide 
data independent of how the data is being shown, So sensor has nothing to do 
with meter.
We can create a interface of the class sensor, which will be implemented by 
subclasses.The interface may consist of :-

type(), which says what type of data is returned by the sensor. it can be 
bool,int,QString,QMap<QString,QString> 
returnValue() which actually returns the value.
readOnly(), which tells if sensor is readOnly Or its properties can be 
changed. e.g., cpusensor is readonly. xmmssensor is read-write..
SIGNAL update(), which can be connected by a meter to know when it needs to 
be updated.
....and so on.

Sensors doesn't know anything about Meters at all. This way, sensors are 
useful for all the applets and extenders too. 
And one more useful feature is that, we can make sensor interface public and 
sensors can be created as plugins.

Now Meters:-
Meters actually acts as widgets but implemented as QObject, where they just 
paint over karambawidget. I think, this is inefficient as one repaint of 
karambawidget results in repaint of all the Meters(because karambawidget 
iterates over all the meters for painting). QWidgets are inherently 
optimized for painting. We should utilize this fact. Make all the Meters as 
real Widgets with karambaWidget as Parent widget.
The Meter Widgets would be very customizable. Take e.g. bars:- We should be 
able to set Mask, backgrounds etc. It may even be possible to make the each 
percent of bar as different picture. This way bars can be converted into a 
dial(through assigning different QPixmap for different percentage).

theme write are responsible to connect meters to sensors. For example, 
setBarValue(cpuload.returnValue()). then connecting sensors update SIGNALS 
to meters slots.

Now, As meters are very customizable, these meters can be used even by 
applets and extenders. 
meters would go into libplasma. Sensors would become plasma engine.

The SK parts part would be done by KarambaWidget. KarambaManager would 
load/unload theme. It creates KarambaWidget and And its childwidgets and all 
the language interface stuff, as we discussed.
So we should start making sensors free of meters. and meters, free of 
sensors in SK codebase.
Is this design looks good enough?

Vinay Khaitan
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