time management

src/Main.hs

@@ -19,6 +19,7 @@ import Options.Applicative
 import Control.Monad
 import Control.Monad.Loops
 
+import Control.Concurrent (threadDelay)
 import Control.Concurrent.MVar
 
 import qualified Data.Text as T
@@ -31,6 +32,8 @@ import Data.Maybe
 
 import Data.Time.Clock
 
+import Data.Word (Word32(..))
+
 import System.Exit (exitFailure)
 
 import Foreign.C.String
@@ -98,13 +101,14 @@ main = do
   vebo <- initGL
   program <- GU.simpleShaderProgramBS vertexShader fragmentShader
   verb opts "Initializing state"
-  time <- getCurrentTime
+  time <- SDL.ticks
   state <- newMVar (
     State 
       1
       (optFile opts)
       (last $ map fst wins)
       time
+      time
       wins
       program
       vebo
@@ -121,6 +125,12 @@ main = do
       draw state ident
       SDL.glSwapWindow window
       ) wins
+    st <- readMVar state
+    now <- SDL.ticks
+    -- let dt = now - (stLastTime st)
+    -- verb opts ("dt: " ++ show dt)
+    -- threadDelay (fromIntegral $ (max 0 ((1000 `div` 30) - dt)))
+    modifyMVar_ state (\st -> return st { stLastTime = now })
     )
   verb opts "Deleting context"
   SDL.glDeleteContext context

src/Types.hs

@@ -8,6 +8,8 @@ import qualified Graphics.GLUtil as GU
 
 import qualified Data.Text as T
 
+import Data.Word (Word32)
+
 import Data.Time.Clock
 
 data Options = Options
@@ -22,7 +24,8 @@ data State = State
   { stCurrentPage :: Word
   , stFilename :: T.Text
   , stPresentationWindow :: Word
-  , stStartTime :: UTCTime
+  , stStartTime :: Word32
+  , stLastTime :: Word32
   , stWindows :: [(Word, SDL.Window)]
   , stProgram :: GU.ShaderProgram
   , stVEBO :: GLvebo