Mercurial > gui
changeset 11:ccd0a169e827
Clock corrects for skew, so that it matches server time (if an RPC round-trips fast enough)
author | Adam Chlipala <adam@chlipala.net> |
---|---|
date | Sun, 24 Jul 2011 14:51:16 -0400 |
parents | 0337f88f2efc |
children | bbdedfde154e |
files | clock.ur |
diffstat | 1 files changed, 14 insertions(+), 4 deletions(-) [+] |
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--- a/clock.ur Fri Jul 22 15:40:03 2011 -0400 +++ b/clock.ur Sun Jul 24 14:51:16 2011 -0400 @@ -1,21 +1,31 @@ (** Reactive view of the current time *) -type t = { Source : source time, - Period : int } +type t = { + Source : source time, (* Server time as of last tick event *) + Skew : source int, (* How many seconds do we add to the local clock to match the server clock? *) + Period : int (* How many milliseconds between ticks? *) +} fun create ms = tm <- now; t <- source tm; - return {Source = t, Period = ms} + sk <- source 0; + return {Source = t, Skew = sk, Period = ms} fun start t = let fun loop () = sleep t.Period; tm <- now; - set t.Source tm; + sk <- get t.Skew; + set t.Source (addSeconds tm sk); loop () + + fun serverTime () = now in + spawn (server <- rpc (serverTime ()); + local <- now; + set t.Skew (diffInSeconds server local)); spawn (loop ()) end