blob: c44c5ebf83fa7a4316fe496231999bbfb52f8966 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
|
{-# LANGUAGE OverloadedRecordDot, DuplicateRecordFields #-}
-- |
-- Module : Foobar.Services.Coalescing
-- Description: Coalesce multiple events using a timeout.
module Foobar.Services.Coalescing
( EventScheduler
, mkEventScheduler
, scheduleEvent
) where
import Data.IORef (IORef, newIORef, readIORef, writeIORef)
import Data.Word (Word32)
import qualified GI.GLib as GLib
-- | Management structure for coalescing events.
data EventScheduler
= EventScheduler { delay :: !Int
, sourceId :: !(IORef (Maybe Word32)) }
-- | Create a new event scheduler for coalescing events.
mkEventScheduler
:: Int -- ^ Delay for scheduling events in milliseconds.
-> IO EventScheduler -- ^ The event scheduler structure.
mkEventScheduler delay' = EventScheduler delay' <$> newIORef Nothing
-- | Schedule an event.
--
-- If there is already an event scheduled, the two are coalesced.
scheduleEvent
:: EventScheduler -- ^ The event scheduler.
-> IO () -- ^ The event to be scheduled.
-> IO ()
scheduleEvent s event = do
existingId <- readIORef s.sourceId
let sourceFunc :: GLib.SourceFunc
sourceFunc = do
event
writeIORef s.sourceId Nothing
pure GLib.SOURCE_REMOVE
case existingId of
Just _ -> pure ()
Nothing -> do newId <- GLib.timeoutAdd GLib.PRIORITY_DEFAULT (fromIntegral s.delay) sourceFunc
writeIORef s.sourceId (Just newId)
|
