The ids of the shown features that have an event state, by state: what putEventState and
user interactions have put, and cleanEventState(s) hasn't taken off yet.
Remarks
A state no feature has is absent rather than an empty array. The ids are those
ByIdOrIndex takes, so each can go straight back into putEventState or cleanEventState.
The ids of the shown features that have an event state, by state: what
putEventStateand user interactions have put, andcleanEventState(s)hasn't taken off yet.