Hi,

kdbusaddons is responsible for (re-)starting kdeinit5 (a daemon that 
speeds up startup of KDE applications by forking itself into a new 
process) when it is not running.  However, kdbusaddons is also a 
build dependency of kinit.

This patch adds a kinit-bootstrap package, makes it  an input of 
kdbusaddons, and embeds the store path of the kdeinit5 executable (an 
output of kinit-bootstrap) in the kdbusaddons source.  Without this 
patch, applications using kdbusaddons will always need a PATH 
environment variable in order to find kdeinit5.

Because kinit depends on kdbusaddons via a number of intermediate 
packages, I had to add kdbusaddons-bootstrap and a few other extra 
packages to avoid dependency cycles.  This patch would trigger a 
build of around ~30 packages.

A remaining issue with kdeinit is, that it needs to run in an 
environment with all the required environment variables (such as 
QT_PLUGIN_PATH and QML2_IMPORT_PATH) for all possible KDE 
applications it has to start (and any libraries they depend on), in 
order to find dependencies at runtime, such as plugins and Qml 
modules.  If a user wants to run a KDE application which relies on 
kdeinit, but kdeinit is already running without all the required 
environment vars, the application will not find all the plugins or 
Qml modules it needs.  (In a conventional system, kde applications 
just need to know one central directory where they will find all KDE 
plugins present on the system)

I don't know what would be a good solution.  A “kde-master” package, 
which has references to all packaged KDE applications (and some 
libraries which provide plugins) as inputs, and just adds the 
required paths to the user's profile (not very modular, but it could 
work)? Could a kdeinit service could help with this in GuixSD 
(haven't really looked at services yet)?

Thomas