Flushes the notification event queue.
This method flushes the notification event queue synchronously, blocking until all pending Notification Events have been fired. The Notifications Events themselves are still fired asynchronously, as always. If successful, this method returns true; otherwise, it returns false.
This method only flushes the Notification Events that are present in the queue when it starts executing; new Notification Events can be enqueued while this method executes, but it won't wait for them.
Error Handling (C++)
This method returns a Boolean value; after it returns, call the GetLastErrorCode() method to obtain its result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.