public interface IMasterDetailSelectionProvider
A selection provider for master-detail views in which both the master
and the detail parts may provide a selection. The provider's selection
is the selection of either the master or the detail part, whichever is
currently active (usually meaning that it last had the input focus).
The detail provider can change as the master-detail UI creates/activates/destroys
different detail views, and there needs not always be a detail. Moreover,
the detail is free to provide different kind of selection (e.g., text vs. structured)
to the master.