I am re-factoring qgenericunixthemes.cpp, where QKdeTheme resides.
It contains some #ifdef’ry to cover the case that QKdeTheme is used w/o DBus, see here.
The question is: can that actually be the case? Should it be covered?
I think it is very unlikely that there is KDE Plasma session without D-Bus.
It is simply needed for too many things.
I guess the whole plugin could be made dependent of whether Qt is configured with or without D-Bus.
My only concern would be applications that bundle Qt and which could have been built without D-Bus (for whatever reason).
These would then lose even the integration bits that the current plugin can provide without the D-Bus sections.