module MouseMoveC (mouseMove) where

import Graphics.Rendering.OpenGL
import Graphics.UI.GLUT
import States
import Data.IORef 

------ passiveMotionCallbackに渡す関数
mouseMove :: (IORef CState) -> Position -> IO()
mouseMove cst position = do
		cst' <- readIORef cst
		let 	dCurPos = dCalcPos (cursorPos cst') (Just position)
			curPos = Just position
		cst $= (CState curPos dCurPos) 

------カーソルのPositionの変化量をmaxノルムで返す
dCalcPos :: Maybe Position -> Maybe Position -> GLint
dCalcPos Nothing _ = 0
dCalcPos _ Nothing = 0
dCalcPos (Just ( Position x1 y1)) (Just (Position x2 y2)) = max (abs (x1 - x2)) (abs (y1 - y2))