SingletonRef was only invented because lib::Depend (or lib::Singleton at that time)
offered only on-demand initialisation, but could not attach to an external service.
But this is required for calling out at the implementation side of a
Lumiera Interface into the actual service implementation.
The recently created DependInject::ServiceInstance now fulfils this task way better
and is seamlessly integrated into the lib::Depend front-end
This change was caused by investigation of UI event loop dispatch;
since the GTK UI is designed to run single threaded, any invocation
from other threads need to be diepatched explicitly.
A possible way to achieve this is to use Glib::Dispatcher, which
in turn requires that the current thread (which is in this case the UI thread)
already holds a Glib::MainContext
This prompted me to create a tight link between the external facade interfaces
of the UI and the event loop itself. What remains to be settled is how
to hand over arguments to the action in the main loop
to make them stand out more prominently, some entity comments
where started with a line of starts. Unfortunately, doxygen
(and javadoc) only recogise comments which are started exactly
with /**
This caused quite some comments to be ignored by doxygen.
Credits to Hendrik Boom for spotting this problem!
A workaround is to end the line of stars with *//**
DisplayService is intended to implement the Display facade and additionally
manage N display output sinks (DisplayerSlot). Now the playback-controller
contains just the bare controller logic, all services like tick generation
or signal dispatching have been factored out... makes me feel better :-)
