Eraser.hs

-----------------------------------------------------------------------------
-- |
-- Module      : Application.HXournal.ModelAction.Eraser 
-- Copyright   : (c) 2011, 2012 Ian-Woo Kim
--
-- License     : BSD3
-- Maintainer  : Ian-Woo Kim <ianwookim@gmail.com>
-- Stability   : experimental
-- Portability : GHC
--
-----------------------------------------------------------------------------

module Application.HXournal.ModelAction.Eraser where

import Control.Monad.State 
import Data.Xournal.BBox
import Graphics.Xournal.Render.Type 
import Graphics.Xournal.Render.HitTest

eraseHitted :: AlterList (NotHitted StrokeBBox) (AlterList (NotHitted StrokeBBox) (Hitted StrokeBBox)) 
               -> State (Maybe BBox) [StrokeBBox]
eraseHitted Empty = error "something wrong in eraseHitted"
eraseHitted (n :-Empty) = return (unNotHitted n)
eraseHitted (n:-h:-rest) = do 
  mid <- elimHitted h 
  return . (unNotHitted n ++) . (mid ++) =<< eraseHitted rest