.

[evilC]

If you need timers more accurate than the minimum granularity of the system timer (~10ms) then you can use MicroTimer.

[SKAN]

I tried the script and I noticed that it always fires few houndreds milliseconds late, which means it can be as late as 999 milliseconds, which means it can be late almost a full second. Is it impossible to do using A_TickCount or other functions and NOT checking time constantly?

You don't have to check time constantly for the whole period of wait... just for a few 10s of ms.
Try this.

Code: Select all

T := A_Now
T += 1, Seconds
T .= ".500"
MsgBox % SleepTill( T )


SleepTill( Timestamp ) {
Local OTC := TC := A_TickCount, V := StrSplit( TimeStamp ".0", "." ), SleepMS := V.1     
  SleepMS -= A_Now, Seconds
  SleepMS := ( SleepMS * 1000 + V.2 )
  TC :=  TC + SleepMS
  Sleep, %SleepMS%
  While ( A_Tickcount < TC )
    Sleep -1
Return ( A_Tickcount - OTC ) / 1000
}

You could call it like.. for eg.

Code: Select all

SleepTill( 20170818054334.500 )
SetTimer, Alarm, -1

Should be precise to the nearest 32ms.
SleepTill() function can be be precise to 1ms if query performance counters are used. See AccuSleep()

[just me]

I noticed that it always fires few houndreds milliseconds late, which means it can be as late as 999 milliseconds, which means it can be late almost a full second.

The problem isn't the accuracy of Sleep/SetTimer, it's the calculation of DelayInMilliseconds/Period.

Code: Select all

TargetTime  := 20170818000010
CurrentTime := 20170818000000 ; replaces A_Now
TimeToWait := TargetTime
TimeToWait -= CurrentTime, Seconds
TimeToWait *= 1000 ; convert to milliseconds
MsgBox, %TimeToWait%

will always retrieve 10000 ignoring the milliseconds at calculation time.

If calculated at CurrentTime + 0 ms it will expire about TargetTime + 0 ms which is the wanted behaviour. But if calculated at CurrentTime + 999 ms it will expire about TargetTime + 999 ms which is correct but unwanted. You have to subtract the current milliseconds in a 'milliseconds until' calculation:

Code: Select all

TimeToWait *= 1000 ; convert to milliseconds
TimeToWait -= CurrentMSec ; subtract current milliseconds

[BoBo]

You have to subtract the current milliseconds in a 'milliseconds until' calculation

Kinda A_TickCount/QueryPerformanceCounter scenario ?!

https://autohotkey.com/board/topic/1090 ... r-example/
https://autohotkey.com/board/topic/4806 ... cecounter/