In many cases, there is a need to periodically execute some code. While you can create and manage threads to achieve the same effect, there are already functions to factilitate just that:

MapGameTimeRepeat(name, interval, func) : Declares a repeating function func which will be called every interval milliseconds of GameTime while there is a map loaded.

MapRealTimeRepeat(name, interval, func) : Declares a repeating function func which will be called every interval milliseconds of RealTime while there is a map loaded.

The function func receives as parameter the time from the previous invocation. On the first invocation it receives nil as parameter.

func can return a value which will be used (one time only) as sleep time before the next invocation instead of the interval provided.

!!! WARNING If interval is zero or a negative number func will be called in a loop without any delay. In that case it must sleep otherwise it will freeze the entire game.

Since func runs in its own thread it can sleep or wait for wakeup or wait for messages. You can easily wakeup a repeat function:

WakeupPeriodicRepeatThread(name, ...) : Wakes up the thread of the periodic repeat with name. To have an effect, the repeat function func should have called WaitWakeup().

Repeats have several advantages:

• after lua reload, the new func is called instead of the old one
• after loading a savegame created with an old repeat func the new func gets called instead
• when loading a savegame created before the repeat was introduced in the code, the repeat is started
• the repeat is started on entering a map and stopped it when exiting the map

Update the daily quest once a day. In this case, we know the map starts at 6am, so we use the first invocation when interval is nil to sleep 6 more hours and then call UpdateDailyQuest() exactly at 12h every day thereafter.

MapRealTimeRepeat("", const.HourDuration * 24, function (interval)
	if not interval then
		return const.HourDuration * 6 -- sleep 6h on the first invocation
	end
	UpdateDailyQuest()
end)

If updating the UI is slow, it can be done in a thread after UpdateUI is called but no more often than once every 100ms:

MapVar("UIUpdatePending", false)
MapRealTimeRepeat("UpdateUI", 100, function (interval)
	if not UIUpdatePending then WaitWakeup() end
	UIUpdatePending = false
	UpdateUIForReal()
end)

function UpdateUI()
	UIUpdatePending = true
	WakeupPeriodicRepeatThread("UpdateUI")
end

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