The ownership for virtual desktops is moved from Workspace into a new
VirtualDesktopManager. The manager is responsible for providing the count
of virtual desktops and keeping track of the currently used virtual
desktop.
All methods related to moving between desktops are also moved from
Workspace to the new manager, though all methods related to Clients on
Virtual Desktops remain in Workspace for the time being. This is to have
the new manager as independent from KWin core as possible.
An rather important change for the handling of virtual desktops is that
the count and the id of a desktop is now an unsinged integer instead of
an integer. The reason for that is that we cannot have a negative count
of desktops as well as it is not possible to be on a desktop with a
negative identifier.
In that regard it is important to remember that a Client can be on a
desktop with a negative identifier. The special value for a Client being
on all desktops is handled by using -1 as a desktop. For the time being
this is not adjusted but instead of comparing the virtual desktop ids one
should prefer to use the convenient methods like isOnDesktop and
isOnAllDesktops. This would allow in future to internally change the
representation for on all desktops.
