I'm trying to implement the idea of @davidedmundson from this https://phabricator.kde.org/T10172 with my limited knowledge of C++/Qt/KDE/programming. This is the start of a new class so it could lack many things but it's usable.
- It allows clients to set the available screen rect/region from outside through dbus.
- The final available screen rect/region would be the intersection of all set values.
- When a client dies, its values would be removed automatically.