What is it?
A high level wrapper round logind.
We are starting to use logind in numerous places; I need it in SDDM to track sessions. we have code in ksmserver to track Lock/Unlock signals, as well as in the kworkspace library to list sessions. It's coming into KWin for device hardware access as well as being used in solid.
The need for a library
Often we can simply automatically generate bindings at compile time using qdbusxml2cpp that turns DBus interface annotation into working code.
Unfortunately that doesn't work here for a few reasons.