hasHandoff abstract method
Declares a handoff buffer of slotBytes per slot - shared memory for
a value where only the newest copy matters, rather than a queue where
every record does.
Use has for a stream (commands, events, anything where dropping the third of five is a bug). Use this for a value that is completely replaced each time it is produced - a rendered frame being the case it exists for. See HandoffBuffer for why a ring is the wrong shape there.
Implementation
HandoffHandle hasHandoff({required int slotBytes});