GNotificationPriority

the default priority, to be used for the majority of notifications (for example email messages, software updates, completed download/sync operations)

for notifications that do not require immediate attention - typically used for contextual background information, such as contact birthdays or local weather

for events that require more attention, usually because responses are time-sensitive (for example chat and SMS messages or alarms)

for urgent notifications, or notifications that require a response in a short space of time (for example phone calls or emergency warnings)