Timer function using gtk2hs - haskell

Question

I'm trying to make a Timer in Haskell using gtk2hs.
I found an example on this website wiki.haskell Tutorial Threaded GUI
which I could successfully implement in my project. The only problem I'm facing is creating a restart button for the timer.
My goal is that when people pres the "New game" button, that a new game starts and that the timer resets.
If a want to just restart a game I can use this line of code
onClicked button1 (startNewGame table window)
, which works. The problem is I can't find a way to bind a the start timer function to a button.
I tried doing this:
onClicked button1 (do (startTimer box) (startNewGame table window))
Which does not work, also this does not work:
onClicked button1 (startTimer box)
How am I suppose to restart a thread correctly?
When I run this code:
onClicked button1 (startTimer box)
I get this error:
gui.hs:29:25:
Couldn't match type `ThreadId' with `()'
Expected type: IO ()
Actual type: IO ThreadId
In the return type of a call of `startTimer'
In the second argument of `onClicked', namely `(startTimer box)'
In a stmt of a 'do' block: onClicked button1 (startTimer box)
How can I bind the (startTimer box) function to a button?
Source code:
import Graphics.UI.Gtk
import SetTest
import qualified Data.Set as Set
import qualified Data.Map.Strict as Map
import Control.Monad.Trans(liftIO)
import Debug.Trace
import Control.Concurrent
import Control.Concurrent.MVar
import System.Exit
main :: IO ()
main = do
initGUI
window <- windowNew
set window [windowTitle := "Minesweeper",
windowDefaultWidth := 450, windowDefaultHeight := 200]
box <- vBoxNew False 0
containerAdd window box
button1 <- buttonNewWithLabel "New game"
boxPackStart box button1 PackGrow 0
widgetShowAll window
table <- tableNew 5 5 True
--onClicked button1 (do (startTimer box) (startNewGame table window))
--onClicked button1 (startTimer box)
onClicked button1 (startNewGame table window)
startTimer box
containerAdd window table
startNewGame table window
boxPackStart box table PackNatural 0
widgetShowAll window
onDestroy window mainQuit
mainGUI
startTimer :: BoxClass self => self -> IO ThreadId
startTimer box = do
timeLabel <- labelNew Nothing
boxPackStart box timeLabel PackNatural 0
forkIO $ do
let
printTime t = do{
threadDelay 1000000;
postGUIAsync $ labelSetText timeLabel (show t);
printTime (t+1)}
printTime 0
startNewGame:: (WidgetClass self, TableClass self1) => self1 -> self -> IO ()
startNewGame table window = let board = (SetTest.initialize 5 (5,5) (1,1)) :: MyBoard
in checkStatusGame table board window
:: (WidgetClass self, TableClass self1) =>
self1 -> MyBoard -> self -> IO ()
checkStatusGame table board window
| won board = do
cleanAndGenerateTable board table window True
(dialogMessage "hurray hurray hurray" "Gratz, you won!!!")
| lost board = do
(dialogMessage "Baby rage window" "Soz, you lost...")
cleanAndGenerateTable board table window True
| otherwise = (cleanAndGenerateTable board table window False)
cleanAndGenerateTable :: (WidgetClass self, TableClass self1) =>
MyBoard -> self1 -> self -> Bool -> IO ()
cleanAndGenerateTable board table window finished = do
let fieldList = [(x,y) | x <- [0 .. (height board)] , y <- [0 .. (width board)] ]
children <- containerGetChildren table
mapM_ (\child -> containerRemove table child >> widgetDestroy child) children
if finished
then mapM_(generateTableFinished board table window) fieldList
else mapM_ (generateTable board table window) fieldList
widgetShowAll window
generateTable board table window (x,y)
| Set.member (x,y) (flaggedCells board) = createButton "flag.jpg" (x,y) table board window
| Map.member (x,y) (clickedCells board) = createClickedButton (show (Map.findWithDefault (-1) (x,y) (clickedCells board))) (x,y) table
| otherwise = createButton "masked.png" (x,y) table board window
generateTableFinished board table window (x,y)
| Set.member (x,y) (bombs board) = createButtonNoAction "bomb.jpg" (x,y) table board window
| Map.member (x,y) (clickedCells board) = createClickedButton (show (Map.findWithDefault (-1) (x,y) (clickedCells board))) (x,y) table
| otherwise = createClickedButton (show (Map.findWithDefault (-1) (x,y) (maskedCells board))) (x,y) table
createButtonNoAction pth (x,y) table board window = do
button <- buttonNew
box <- hBoxNew False 0
image <- imageNewFromFile pth
boxPackStart box image PackRepel 0
containerAdd button box
tableAttachDefaults table button x (x+1) y (y+1)
createClickedButton lbl (x,y) table = do
button <- buttonNew
box <- hBoxNew False 0
label <- labelNew (Just lbl)
boxPackStart box label PackRepel 0
containerAdd button box
tableAttachDefaults table button x (x+1) y (y+1)
createButton pth (x,y) table board window = do
button <- buttonNew
box <- hBoxNew False 0
image <- imageNewFromFile pth
boxPackStart box image PackRepel 0
containerAdd button box
tableAttachDefaults table button x (x+1) y (y+1)
on button buttonReleaseEvent $ do
click <- eventButton
liftIO $ case click of { LeftButton -> (checkStatusGame table (SetTest.click (x,y) board) window); RightButton -> (checkStatusGame table (SetTest.flag (x,y) board) window) }
return False
return ()
dialogMessage title msg = do dialog <- messageDialogNew Nothing [] MessageOther ButtonsOk msg
set dialog [windowTitle := title]
widgetShowAll dialog
dialogRun dialog
widgetDestroy dialog

Answer 1

If you want to communicate with your timer thread, you will need to hand it a communication channel. An MVar seems appropriate here.
startTimer :: BoxClass self => self -> MVar Integer -> IO ThreadId
startTimer box timer = do
timeLabel <- labelNew Nothing
boxPackStart box timeLabel PackNatural 0
forkIO . forever $ do
threadDelay 1000000
t <- takeMVar timer
putMVar timer (t+1)
postGUIAsync $ labelSetText timeLabel (show t)
At the top of main, you can now create a fresh MVar with timer <- newMVar 0, and pass this to startTimer. In your button callback, you can takeMVar timer >> putMVar timer 0 to reset the timer.