Using kqmlgraphplugin in Plasma Next

[Sebastian Gottfried]

Hi
> Currently I am working on a QML Canvas based SignalPlotter, to replace
> the old Plasma1SignalPlotter which is KSignalPlotter and
> QGraphicWidget based. My SignalPlotter is in bshah/plotter-qml branch
> of plasma-framework
> (src/declarativeimports/plasmaextracomponents/SignalPlotter.qml)
Conceptually charts and signal plotters are pretty different. A plotter tracks 
a value of a fixed amount of time (set by the available horizontal space) and 
cuts earlier values off. Charts on the contrary display whatever they are told 
to do. Both are useful and should IMO coexist.

> 
> Meanwhile I was notified by apol that something like this already
> exist, which is QML, So basically my plan is to port kqmlgraphplugin
> to KDE Frameworks 5 and use it to plot data in Plasma Next.
> 
> I am interested in porting it to KDE Frameworks 5. Is someone already
> working on that? If yes can I help with that? Otherwise I will start
> to port it. :)
Sure, go for it.

It needs to be investigated what the best porting strategy is. Three ways come 
to mind.

The easy way: use QPaintedItem. Very straightforward, but virtually no gain in 
comparison to the Qt Quick 1 version since the continued use of software 
rendering.

Canvas based: I have no experience with that but I guess performance is should 
be better than with QPaintedItem, since it directly renders to a GPU 
framebuffer and painting can be done in an separate thread.

Shader based: Perform the actual rendering in a fragment shader. Definitely 
the most ambitious and complicated solution, but also the only with pure GPU 
rendering. I don't know if it's really worth the effort.

Best regards,

Sebastian