Mercurial > gui
annotate clock.ur @ 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 | 2947170fcfd6 |
| rev | line source |
|---|---|
| adam@10 | 1 (** Reactive view of the current time *) |
| adam@10 | 2 |
| adam@11 | 3 type t = { |
| adam@11 | 4 Source : source time, (* Server time as of last tick event *) |
| adam@11 | 5 Skew : source int, (* How many seconds do we add to the local clock to match the server clock? *) |
| adam@11 | 6 Period : int (* How many milliseconds between ticks? *) |
| adam@11 | 7 } |
| adam@10 | 8 |
| adam@10 | 9 fun create ms = |
| adam@10 | 10 tm <- now; |
| adam@10 | 11 t <- source tm; |
| adam@11 | 12 sk <- source 0; |
| adam@11 | 13 return {Source = t, Skew = sk, Period = ms} |
| adam@10 | 14 |
| adam@10 | 15 fun start t = |
| adam@10 | 16 let |
| adam@10 | 17 fun loop () = |
| adam@10 | 18 sleep t.Period; |
| adam@10 | 19 tm <- now; |
| adam@11 | 20 sk <- get t.Skew; |
| adam@11 | 21 set t.Source (addSeconds tm sk); |
| adam@10 | 22 loop () |
| adam@11 | 23 |
| adam@11 | 24 fun serverTime () = now |
| adam@10 | 25 in |
| adam@11 | 26 spawn (server <- rpc (serverTime ()); |
| adam@11 | 27 local <- now; |
| adam@11 | 28 set t.Skew (diffInSeconds server local)); |
| adam@10 | 29 spawn (loop ()) |
| adam@10 | 30 end |
| adam@10 | 31 |
| adam@10 | 32 fun signal t = Basis.signal t.Source |