TCountdownEvent = class(TSynchroObject)
class PASCALIMPLEMENTATION TCountdownEvent : public TSynchroObject
TCountdownEvent is a synchronization primitive that is signaled when its count reaches zero.
TCountdownEvent is a synchronization object that behaves similarly to a manual reset semaphore, only that it is signaled when the count is zero (0) instead of nonzero.
Note: Once the count reaches zero, the only way to unsignal the event is to call one of the Reset methods. AddCount can only be called if the current count is greater than zero. TryAddCount returns True if the count was greater than zero and it was added. If the count is already 0, it returns False.