SDL.hs

-- |
-- Copyright  : (c) Ivan Perez & Henrik Nilsson, 2014.
-- License    : See LICENSE file.
-- Maintainer : Ivan Perez <ivan.perez@keera.co.uk>
--
-- Auxiliary functions related to Graphics.UI.SDL.
module Graphics.UI.Extra.SDL where

-- External imports
import Data.IORef
import Graphics.UI.SDL as SDL

-- Auxiliary SDL stuff
isEmptyEvent :: Event -> Bool
isEmptyEvent NoEvent = True
isEmptyEvent _       = False

initializeTimeRef :: IO (IORef Int)
initializeTimeRef = do
  -- Weird shit I have to do to get accurate time!
  timeRef <- newIORef (0 :: Int)
  _       <- senseTimeRef timeRef
  _       <- senseTimeRef timeRef
  _       <- senseTimeRef timeRef
  _       <- senseTimeRef timeRef

  return timeRef

senseTimeRef :: IORef Int -> IO Int
senseTimeRef timeRef = do
  -- Get time passed since SDL init
  newTime <- fmap fromIntegral SDL.getTicks

  -- Obtain time difference
  dt <- updateTime timeRef newTime
  return dt

-- | Updates the time in an IO Ref and returns the time difference
updateTime :: IORef Int -> Int -> IO Int
updateTime timeRef newTime = do
  previousTime <- readIORef timeRef
  writeIORef timeRef newTime
  return (newTime - previousTime)

milisecsToSecs :: Int -> Double
milisecsToSecs m = fromIntegral m / 1000