diff --git a/CHANGES b/CHANGES
--- a/CHANGES
+++ b/CHANGES
@@ -11,4 +11,5 @@
 0.6.0: 19 Dec 2011 
    * some bug fixes (temporary yet) related to automatic scrollbar disappearing. Check when new, open, annotate pdf if xournal file is not saved yet. 
  
- 
+0.6.1: 25 Dec 2011
+   * undo/redo support, double buffer rendering while scrolling
diff --git a/hxournal.cabal b/hxournal.cabal
--- a/hxournal.cabal
+++ b/hxournal.cabal
@@ -1,5 +1,5 @@
 Name:		hxournal
-Version:	0.6.0.1
+Version:	0.6.1
 Synopsis:	A pen notetaking program written in haskell 
 Description: 	notetaking program written in haskell and gtk2hs
 Homepage:       http://ianwookim.org/hxournal
@@ -19,12 +19,10 @@
   type: git
   location: http://www.github.com/wavewave/hxournal
 
-
 Flag Poppler
-  Description: Enable poppler support 
+  Description: Enable poppler support
   Default:     True
 
-
 Executable hxournal
   Main-is: hxournal.hs
   hs-source-dirs: exe
@@ -39,8 +37,8 @@
   hs-source-dirs: lib
   ghc-options: 	-Wall -O2 -threaded -funbox-strict-fields -fno-warn-unused-do-bind
   ghc-prof-options: -caf-all -auto-all
-  
-  if flag(poppler)
+
+  if flag(poppler) 
     Build-Depends:   base == 4.*, 
                      mtl == 2.*,
                      directory == 1.*,
@@ -50,9 +48,9 @@
                      cairo == 0.12.*,
                      monad-coroutine == 0.7.*, 
                      transformers == 0.2.*,
-                     xournal-types == 0.1.*,
+                     xournal-types == 0.2.*,
                      xournal-parser == 0.3.*,
-                     xournal-render == 0.3.0.*,
+                     xournal-render == 0.4.*,
                      xournal-builder == 0.1.*,
                      containers == 0.4.*,
                      template-haskell == 2.*,
@@ -72,9 +70,9 @@
                      cairo == 0.12.*,
                      monad-coroutine == 0.7.*, 
                      transformers == 0.2.*,
-                     xournal-types == 0.1.*,
+                     xournal-types == 0.2.*,
                      xournal-parser == 0.3.*,
-                     xournal-render == 0.3.0.*,
+                     xournal-render == 0.4.*,
                      xournal-builder == 0.1.*,
                      containers == 0.4.*,
                      template-haskell == 2.*,
@@ -96,6 +94,7 @@
                    Application.HXournal.Type.Coroutine
                    Application.HXournal.Type.XournalState
                    Application.HXournal.Type.Window
+                   Application.HXournal.Type.Undo 
                    Application.HXournal.ModelAction.Adjustment
                    Application.HXournal.ModelAction.Pen 
                    Application.HXournal.ModelAction.Page
@@ -103,7 +102,6 @@
                    Application.HXournal.ModelAction.Select
                    Application.HXournal.ModelAction.File
                    Application.HXournal.ModelAction.Window
-                   -- Application.HXournal.ModelAction.Common
                    Application.HXournal.Coroutine.Callback
                    Application.HXournal.GUI
                    Application.HXournal.GUI.Menu
@@ -128,7 +126,6 @@
                    Application.HXournal.Accessor
                    Application.HXournal.Config
 
-
   Other-Modules: 
                    Paths_hxournal
   c-sources: 
@@ -137,6 +134,6 @@
   install-includes: 
                    csrc/c_initdevice.h
                    csrc/template-hsc-gtk2hs.h
-  if flag(poppler) 
+
+  if flag(poppler)
     cpp-options: -DPOPPLER
-  
diff --git a/lib/Application/HXournal/Accessor.hs b/lib/Application/HXournal/Accessor.hs
--- a/lib/Application/HXournal/Accessor.hs
+++ b/lib/Application/HXournal/Accessor.hs
@@ -41,8 +41,8 @@
   let currCvsInfo  = getCurrentCanvasInfo xstate 
   let pagebbox = getPage currCvsInfo
       strs = do 
-        l <- gToList (glayers pagebbox)
-        s <- gstrokes l
+        l <- gToList (get g_layers pagebbox)
+        s <- get g_bstrokes l
         return s 
   return strs 
       
diff --git a/lib/Application/HXournal/Config.hs b/lib/Application/HXournal/Config.hs
--- a/lib/Application/HXournal/Config.hs
+++ b/lib/Application/HXournal/Config.hs
@@ -24,6 +24,9 @@
   config <- load [Required "$(HOME)/.hxournal"]
   return config
   
+getMaxUndo :: Config -> IO (Maybe Int)
+getMaxUndo c = C.lookup c "maxundo"
+
 getPenDevConfig :: Config -> IO (Maybe String, Maybe String,Maybe String) 
 getPenDevConfig c = do 
   mcore <- C.lookup c "core"
diff --git a/lib/Application/HXournal/Coroutine/Commit.hs b/lib/Application/HXournal/Coroutine/Commit.hs
--- a/lib/Application/HXournal/Coroutine/Commit.hs
+++ b/lib/Application/HXournal/Coroutine/Commit.hs
@@ -3,15 +3,66 @@
 import Application.HXournal.Type.XournalState 
 import Application.HXournal.Type.Coroutine
 import Application.HXournal.Type.Event
+import Application.HXournal.Type.Undo 
+
+import Application.HXournal.Coroutine.Draw 
 import Application.HXournal.ModelAction.File
+import Application.HXournal.ModelAction.Page
 
 import Data.Label
+-- import Control.Monad (liftM)
 import Control.Monad.Trans
 import Application.HXournal.Accessor
 
+import Graphics.Xournal.Render.BBoxMapPDF
+
 commit :: HXournalState -> Iteratee MyEvent XournalStateIO ()
 commit xstate = do 
   let ui = get gtkUIManager xstate
   liftIO $ toggleSave ui True
-  let xstate' = set isSaved False xstate
+  let xojstate = get xournalstate xstate
+      undotable = get undoTable xstate 
+      undotable' = addToUndo undotable xojstate
+      xstate' = set isSaved False 
+                . set undoTable undotable'
+                $ xstate
   putSt xstate' 
+
+undo :: Iteratee MyEvent XournalStateIO ()
+undo = do 
+    liftIO $ putStrLn "undo is called"
+    xstate <- getSt
+    let utable = get undoTable xstate
+    case getPrevUndo utable of 
+      Nothing -> liftIO $ putStrLn "no undo item yet"
+      Just (xojstate1,newtable) -> do 
+        xojstate <- liftIO $ resetXournalStateBuffers xojstate1 
+        let xstate' = set xournalstate xojstate
+                      . set undoTable newtable 
+                      . updatePageAll xojstate 
+                      $ xstate 
+      -- commit xstate' 
+        putSt xstate'
+        invalidateAll 
+      
+  
+redo :: Iteratee MyEvent XournalStateIO ()
+redo = do 
+    liftIO $ putStrLn "redo is called"
+    xstate <- getSt
+    let utable = get undoTable xstate
+    case getNextUndo utable of 
+      Nothing -> liftIO $ putStrLn "no redo item"
+      Just (xojstate1,newtable) -> do 
+        xojstate <- liftIO $ resetXournalStateBuffers xojstate1         
+        let xstate' = set xournalstate xojstate
+                      . set undoTable newtable 
+                      . updatePageAll xojstate 
+                      $ xstate 
+        putSt xstate'
+        invalidateAll 
+
+
+
+
+
diff --git a/lib/Application/HXournal/Coroutine/Default.hs b/lib/Application/HXournal/Coroutine/Default.hs
--- a/lib/Application/HXournal/Coroutine/Default.hs
+++ b/lib/Application/HXournal/Coroutine/Default.hs
@@ -12,6 +12,7 @@
 
 import Application.HXournal.GUI.Menu
 import Application.HXournal.Coroutine.Callback
+import Application.HXournal.Coroutine.Commit
 import Application.HXournal.Coroutine.Draw
 import Application.HXournal.Coroutine.Pen
 import Application.HXournal.Coroutine.Eraser
@@ -215,6 +216,8 @@
   changePage (const (totalnumofpages-1))
 menuEventProcess MenuNew  = askIfSave fileNew 
 menuEventProcess MenuAnnotatePDF = askIfSave fileAnnotatePDF
+menuEventProcess MenuUndo = undo 
+menuEventProcess MenuRedo = redo
 menuEventProcess MenuOpen = askIfSave fileOpen
 menuEventProcess MenuSave = fileSave 
 menuEventProcess MenuSaveAs = fileSaveAs
diff --git a/lib/Application/HXournal/Coroutine/Draw.hs b/lib/Application/HXournal/Coroutine/Draw.hs
--- a/lib/Application/HXournal/Coroutine/Draw.hs
+++ b/lib/Application/HXournal/Coroutine/Draw.hs
@@ -78,15 +78,49 @@
       keys = M.keys cinfoMap 
   invalidateGen (filter (/=currCvsId) keys) Nothing drawPageInBBox
 
+-- | invalidate everything
+
 invalidate :: CanvasId -> Iteratee MyEvent XournalStateIO () 
-invalidate cid = invalidateSelSingle cid Nothing drawPageInBBox drawSelectionInBBox
+invalidate cid = invalidateSelSingle cid Nothing drawPageClearly drawPageSelClearly
+                 -- drawSelectionInBBox
+                 -- drawPageInBBox drawSelectionInBBox
 
+-- | Drawing objects only in BBox
+
 invalidateInBBox :: CanvasId -> BBox -> Iteratee MyEvent XournalStateIO ()
 invalidateInBBox cid bbox = invalidateSelSingle cid (Just bbox) drawPageInBBox drawSelectionInBBox
 
+-- | Drawing BBox
+
 invalidateDrawBBox :: CanvasId -> BBox -> Iteratee MyEvent XournalStateIO () 
 invalidateDrawBBox cid bbox = invalidateSelSingle cid (Just bbox) drawBBox drawBBoxSel
 
+
+{-
+-- | Drawing pen strokes as bbox
+
 invalidateBBoxOnly :: CanvasId -> Iteratee MyEvent XournalStateIO () 
-invalidateBBoxOnly cid = invalidateSelSingle cid Nothing drawBBoxOnly drawSelectionInBBoxOnly
+invalidateBBoxOnly cid = invalidateBBoxOnlyInBBox cid Nothing
+  -- invalidateSelSingle cid Nothing drawBBoxOnly drawSelectionInBBoxOnly
+
+invalidateBBoxOnlyInBBox :: CanvasId -> Maybe BBox -> Iteratee MyEvent XournalStateIO () 
+invalidateBBoxOnlyInBBox cid mbbox  = invalidateSelSingle cid mbbox drawBBoxOnly drawSelectionInBBoxOnly
+-}
+
+-- | Drawing using layer buffer
+
+invalidateWithBuf :: CanvasId -> Iteratee MyEvent XournalStateIO () 
+invalidateWithBuf = invalidateWithBufInBBox Nothing
+  
+  -- invalidateSelSingle cid Nothing drawBuf drawSelectionInBBox
+                        -- drawSelectionInBBoxOnly -- drawSelBuf -- temporarily
+
+
+-- | Drawing using layer buffer in BBox
+
+invalidateWithBufInBBox :: Maybe BBox -> CanvasId -> Iteratee MyEvent XournalStateIO () 
+invalidateWithBufInBBox mbbox cid = invalidateSelSingle cid mbbox drawBuf drawSelectionInBBox
+                                    
+                                   -- drawSelectionInBBoxOnly -- drawSelBuf  --temporarily
+
 
diff --git a/lib/Application/HXournal/Coroutine/Eraser.hs b/lib/Application/HXournal/Coroutine/Eraser.hs
--- a/lib/Application/HXournal/Coroutine/Eraser.hs
+++ b/lib/Application/HXournal/Coroutine/Eraser.hs
@@ -18,6 +18,8 @@
 import Data.Xournal.Map
 import Data.Xournal.BBox
 import Graphics.Xournal.Render.HitTest
+import Graphics.Xournal.Render.BBox
+import Graphics.Xournal.Render.BBoxMapPDF
 import Control.Monad.Coroutine.SuspensionFunctors
 import Control.Monad.Trans
 import qualified Control.Monad.State as St
@@ -67,22 +69,25 @@
                             Nothing -> error "something wrong in eraserProcess"
                             Just l -> l
               
-              (newstrokes,maybebbox) = St.runState (eraseHitted hitteststroke) Nothing
-              newlayerbbox = currlayer { gstrokes = newstrokes }    
-              newpagebbox = currpage { glayers = IM.adjust (const newlayerbbox) 0 (glayers currpage) } 
+              (newstrokes,maybebbox1) = St.runState (eraseHitted hitteststroke) Nothing
+              maybebbox = fmap (flip inflate 2.0) maybebbox1
+          newlayerbbox <- liftIO . updateLayerBuf maybebbox . set g_bstrokes newstrokes $ currlayer 
+          let newpagebbox = currpage { glayers = IM.adjust (const newlayerbbox) 0 (glayers currpage) } 
               newxojbbox = currxoj { gpages= IM.adjust (const newpagebbox) pgnum (gpages currxoj) }
               newxojstate = ViewAppendState newxojbbox
           commit . set xournalstate newxojstate 
                  . updatePageAll newxojstate $ xstate 
-          case maybebbox of 
-            Just bbox -> invalidateDrawBBox cid bbox
-            Nothing -> return ()
+          invalidateWithBufInBBox maybebbox cid 
+          {- case maybebbox of 
+            Just bbox -> -- invalidateWithBufInBBox m-- invalidateDrawBBox cid bbox
+            Nothing -> return () -}
           newstrs <- getAllStrokeBBoxInCurrentPage
           eraserProcess cid cpg connidup connidmove newstrs (x,y)
         else eraserProcess cid cpg connidmove connidup strs (x,y) 
     PenUp _cid' _pcoord -> do 
       disconnect connidmove 
       disconnect connidup 
+      
       invalidateAll
     _ -> return ()
     
diff --git a/lib/Application/HXournal/Coroutine/File.hs b/lib/Application/HXournal/Coroutine/File.hs
--- a/lib/Application/HXournal/Coroutine/File.hs
+++ b/lib/Application/HXournal/Coroutine/File.hs
@@ -58,8 +58,8 @@
       Just filename -> do     
         let xojstate = get xournalstate xstate
         let xoj = case xojstate of 
-              ViewAppendState xojmap -> Xournal <$> get g_title <*> gToList . fmap (toPage gToBackground) . get g_pages $ xojmap 
-              SelectState txoj -> Xournal <$> gselectTitle <*> gToList . fmap (toPage gToBackground) . gselectAll $ txoj 
+              ViewAppendState xojmap -> Xournal <$> get g_title <*> gToList . fmap (toPageFromBuf gToBackground) . get g_pages $ xojmap 
+              SelectState txoj -> Xournal <$> gselectTitle <*> gToList . fmap (toPageFromBuf gToBackground) . gselectAll $ txoj 
         liftIO . L.writeFile filename . builder $ xoj
         putSt . set isSaved True $ xstate 
         let ui = get gtkUIManager xstate
@@ -118,9 +118,9 @@
             let xoj = case xojstate of 
                   ViewAppendState xojmap -> Xournal 
                                             <$> get g_title 
-                                            <*> gToList . fmap (toPage gToBackground) . get g_pages 
+                                            <*> gToList . fmap (toPageFromBuf gToBackground) . get g_pages 
                                             $ xojmap 
-                  SelectState txoj -> Xournal <$> gselectTitle <*> gToList . fmap (toPage gToBackground) . gselectAll $ txoj 
+                  SelectState txoj -> Xournal <$> gselectTitle <*> gToList . fmap (toPageFromBuf gToBackground) . gselectAll $ txoj 
             liftIO . L.writeFile filename . builder $ xoj
             putSt . set isSaved True $ xstateNew    
             let ui = get gtkUIManager xstateNew
@@ -142,7 +142,7 @@
                                             FileChooserActionOpen 
                                             [ ("OK", ResponseOk) 
                                             , ("Cancel", ResponseCancel) ]
-    liftIO $ fileChooserSetCurrentFolder dialog cwd 
+    liftIO $ fileChooserSetCurrentFolder dialog cwd
     res <- liftIO $ dialogRun dialog
     case res of 
       ResponseDeleteEvent -> liftIO $ widgetDestroy dialog
diff --git a/lib/Application/HXournal/Coroutine/Mode.hs b/lib/Application/HXournal/Coroutine/Mode.hs
--- a/lib/Application/HXournal/Coroutine/Mode.hs
+++ b/lib/Application/HXournal/Coroutine/Mode.hs
@@ -5,6 +5,8 @@
 import Application.HXournal.Type.XournalState
 import Application.HXournal.Accessor
 
+--import Data.Foldable
+import Data.Traversable
 import Data.Xournal.Map
 
 import Control.Monad.Trans
@@ -12,11 +14,13 @@
 import Control.Applicative
 import Control.Category
 import Data.Label
-import Prelude hiding ((.),id)
 
 import Data.Xournal.Generic
 import Graphics.Xournal.Render.BBoxMapPDF
 
+import Prelude hiding ((.),id, mapM_, mapM)
+
+
 modeChange :: MyEvent -> Iteratee MyEvent XournalStateIO ()
 modeChange ToViewAppendMode = do 
   xstate <- getSt
@@ -25,8 +29,10 @@
     ViewAppendState _ -> return () 
     SelectState txoj -> do 
       liftIO $ putStrLn "to view append mode"
+      let pages = get g_selectAll txoj 
+      newpages <- liftIO $ mapM resetPageBuffers pages 
       putSt 
-        . set xournalstate (ViewAppendState (GXournal (gselectTitle txoj) (gselectAll txoj)))
+        . set xournalstate (ViewAppendState (GXournal (get g_selectTitle txoj) newpages ))
         $ xstate  
 modeChange ToSelectMode = do 
   xstate <- getSt
diff --git a/lib/Application/HXournal/Coroutine/Page.hs b/lib/Application/HXournal/Coroutine/Page.hs
--- a/lib/Application/HXournal/Coroutine/Page.hs
+++ b/lib/Application/HXournal/Coroutine/Page.hs
@@ -7,8 +7,10 @@
 import Application.HXournal.Draw
 import Application.HXournal.Accessor
 import Application.HXournal.Coroutine.Draw
+import Application.HXournal.Coroutine.Commit
 import Application.HXournal.ModelAction.Adjustment
 import Graphics.Xournal.Render.Type 
+import Graphics.Xournal.Render.BBoxMapPDF
 import Data.Xournal.Generic
 import Data.Xournal.Map
 import Graphics.UI.Gtk hiding (get,set)
@@ -38,11 +40,11 @@
         (xstate',xoj',_pages',_totalnumofpages',newpage) <-
           if (modifyfn oldpage >= totalnumofpages) 
           then do 
-            let npage = lpage { glayers = IM.insert 0 (GLayer []) IM.empty } 
+            let npage = lpage { glayers = IM.insert 0 (GLayerBuf (LyBuf Nothing) []) IM.empty } 
                 npages = IM.insert totalnumofpages npage pgs 
                 newxoj = xoj { gpages = npages } 
                 xstate' = set xournalstate (ViewAppendState newxoj) xstate
-            putSt xstate'
+            commit xstate'
             return (xstate',newxoj,npages,totalnumofpages+1,totalnumofpages)
           else if modifyfn oldpage < 0 
                  then return (xstate,xoj,pgs,totalnumofpages,0)
@@ -58,7 +60,7 @@
             xstate'' = updatePageAll (ViewAppendState xoj')
                        . updateCanvasInfo currCvsInfo' 
                        $ xstate'
-        lift . St.put $ xstate'' 
+        putSt xstate'' 
         invalidate currCvsId 
       SelectState txoj -> do 
         let pgs = gselectAll txoj 
@@ -70,11 +72,11 @@
         (xstate',txoj',_pages',_totalnumofpages',newpage) <-
           if (modifyfn oldpage >= totalnumofpages) 
           then do 
-            let npage = lpage { glayers = IM.insert 0 (GLayer []) IM.empty } 
+            let npage = lpage { glayers = IM.insert 0 (GLayerBuf (LyBuf Nothing) []) IM.empty } 
                 npages = IM.insert totalnumofpages npage pgs 
                 newtxoj = txoj { gselectAll = npages } 
                 xstate' = set xournalstate (SelectState newtxoj) xstate
-            putSt xstate'
+            commit xstate'
             return (xstate',newtxoj,npages,totalnumofpages+1,totalnumofpages)
           else if modifyfn oldpage < 0 
                  then return (xstate,txoj,pgs,totalnumofpages,0)
@@ -90,7 +92,7 @@
             xstate'' = updatePageAll (SelectState txoj')
                        . updateCanvasInfo currCvsInfo' 
                        $ xstate'
-        lift . St.put $ xstate'' 
+        putSt xstate'' 
         invalidate currCvsId 
       
 canvasZoomUpdate :: Maybe ZoomMode -> CanvasId -> Iteratee MyEvent XournalStateIO ()
diff --git a/lib/Application/HXournal/Coroutine/Pen.hs b/lib/Application/HXournal/Coroutine/Pen.hs
--- a/lib/Application/HXournal/Coroutine/Pen.hs
+++ b/lib/Application/HXournal/Coroutine/Pen.hs
@@ -33,7 +33,6 @@
     let currxoj = unView . get xournalstate $ xstate        
         -- page = getPage cvsInfo 
         pagenum = get currentPageNum cvsInfo
-        -- (x0,y0) = get (viewPortOrigin.viewInfo) cvsInfo
         pinfo = get penInfo xstate
         zmode = get (zoomMode.viewInfo) cvsInfo
     geometry <- getCanvasGeometry cvsInfo 
@@ -41,8 +40,8 @@
     connidup   <- connectPenUp   cvsInfo 
     connidmove <- connectPenMove cvsInfo 
     pdraw <-penProcess cid geometry connidmove connidup (empty |> (x,y)) (x,y) 
-    let (newxoj,bbox) = addPDraw pinfo currxoj pagenum pdraw
-        bbox' = inflate bbox (get (penWidth.penInfo) xstate) 
+    (newxoj,bbox) <- liftIO $ addPDraw pinfo currxoj pagenum pdraw
+    let bbox' = inflate bbox (get (penWidth.penInfo) xstate) 
         xstate' = set xournalstate (ViewAppendState newxoj) 
                   . updatePageAll (ViewAppendState newxoj)
                   $ xstate
diff --git a/lib/Application/HXournal/Coroutine/Scroll.hs b/lib/Application/HXournal/Coroutine/Scroll.hs
--- a/lib/Application/HXournal/Coroutine/Scroll.hs
+++ b/lib/Application/HXournal/Coroutine/Scroll.hs
@@ -35,7 +35,8 @@
                         . set currentCanvas cid
                         $ xstate
           lift . St.put $ xstate'
-          invalidateBBoxOnly cid
+          -- invalidateBBoxOnly cid
+          invalidateWithBuf cid 
           vscrollMove cid 
     VScrollBarEnd cid' _v -> do 
       invalidate cid' 
diff --git a/lib/Application/HXournal/Coroutine/Select.hs b/lib/Application/HXournal/Coroutine/Select.hs
--- a/lib/Application/HXournal/Coroutine/Select.hs
+++ b/lib/Application/HXournal/Coroutine/Select.hs
@@ -30,7 +30,7 @@
 import Graphics.Xournal.Render.BBox
 
 
-
+import qualified Data.IntMap as IM
 import Data.Maybe
 
 -- | main mouse pointer click entrance in rectangular selection mode. 
@@ -95,10 +95,15 @@
           hittestbbox = mkHitTestInsideBBox bbox strs
           hittedstrs = concat . map unHitted . getB $ hittestbbox
       -- for the time being (until double buffer)
-      -- invalidateInBBox cid (inflate (fromJust (Just bbox `merge` Just prevbbox)) 2)
-      invalidateBBoxOnly cid 
-      invalidateDrawBBox cid bbox
-      mapM_ (invalidateDrawBBox cid . strokebbox_bbox) hittedstrs
+      
+      if not (isBBoxDeltaSmallerThan 1.0 geometry zmode bbox prevbbox) 
+         then do flip invalidateWithBufInBBox cid . Just $
+                   (inflate (fromJust (Just bbox `merge` Just prevbbox)) 5.0)
+                
+                 -- invalidateBBoxOnly cid 
+                 invalidateDrawBBox cid bbox
+                 mapM_ (invalidateDrawBBox cid . strokebbox_bbox) hittedstrs
+         else return ()
       newSelectRectangle cinfo geometry zmode connidmove connidup strs orig (x,y) 
     PenUp _cid' pcoord -> do 
       let (x,y) = device2pageCoord geometry zmode pcoord 
@@ -110,15 +115,24 @@
           selectstrs = fmapAL unNotHitted id hittestbbox
       xstate <- getSt    
       let SelectState txoj = get xournalstate xstate
-          newlayer = GLayer (TEitherAlterHitted (Right selectstrs))
+          
           newpage = case epage of 
                       Left pagebbox -> 
-                        let tpg = ttempPageSelectPDFFromTPageBBoxMapPDF pagebbox
+                        let currlayer = case IM.lookup 0 (get g_layers pagebbox) of
+                              Nothing -> error "something wrong in newSelectRectangle"
+                              Just l -> l
+                            newlayer = GLayerBuf (get g_buffer currlayer) (TEitherAlterHitted (Right selectstrs))
+                         
+                        
+                            tpg = gcast pagebbox
                             ls = glayers tpg 
-                        in  tpg { glayers = ls { gselectedlayer = newlayer}  }
+                        in  tpg { glayers = ls { gselectedlayerbuf = newlayer}  }
                       Right tpage -> 
                         let ls = glayers tpage 
-                        in  tpage { glayers = ls { gselectedlayer = newlayer } } 
+                            currlayer = gselectedlayerbuf ls
+                            newlayer = GLayerBuf (get g_buffer currlayer) (TEitherAlterHitted (Right selectstrs))
+
+                        in  tpage { glayers = ls { gselectedlayerbuf = newlayer } } 
           newtxoj = txoj { gselectSelected = Just (cpn,newpage) } 
       let ui = get gtkUIManager xstate
       liftIO $ toggleCutCopyDelete ui (isAnyHitted  selectstrs)
@@ -170,12 +184,13 @@
   xstate <- getSt
   let SelectState txoj = get xournalstate xstate 
       Just (n,tpage) = gselectSelected txoj
-  case unTEitherAlterHitted . gstrokes . gselectedlayer . glayers $ tpage of 
+      slayer = gselectedlayerbuf . glayers $ tpage
+  case unTEitherAlterHitted . get g_bstrokes $ slayer of 
     Left _ -> liftIO $ putStrLn "no stroke selection 2 "
     Right alist -> do 
       let newlayer = Left . concat . getA $ alist
           oldlayers = glayers tpage
-          newpage = tpage { glayers = oldlayers { gselectedlayer = GLayer (TEitherAlterHitted newlayer) } } 
+          newpage = tpage { glayers = oldlayers { gselectedlayerbuf = GLayerBuf (get g_buffer slayer) (TEitherAlterHitted newlayer) } } 
           newtxoj = updateTempXournalSelect txoj newpage n          
           newxstate = updatePageAll (SelectState newtxoj) 
                       . set xournalstate (SelectState newtxoj)
@@ -200,7 +215,8 @@
   case etpage of
     Left _ -> return ()
     Right tpage -> do 
-      case unTEitherAlterHitted . gstrokes . gselectedlayer . glayers $ tpage of 
+      let slayer =  gselectedlayerbuf . glayers $ tpage
+      case unTEitherAlterHitted . get g_bstrokes $ slayer of 
         Left _ -> return ()
         Right alist -> do 
           let strs = takeHittedStrokes alist 
@@ -225,18 +241,19 @@
       cinfo = getCurrentCanvasInfo xstate 
       pagenum = get currentPageNum cinfo 
       tpage = case get currentPage cinfo of 
-                Left pbbox -> ttempPageSelectPDFFromTPageBBoxMapPDF pbbox
+                Left pbbox -> (gcast pbbox :: TTempPageSelectPDFBuf)
                 Right tp -> tp 
-      layerselect = gselectedlayer . glayers $ tpage 
+      layerselect = gselectedlayerbuf . glayers $ tpage 
       ls  = glayers tpage
+      gbuf = get g_buffer layerselect
       newlayerselect = 
-        case unTEitherAlterHitted . gstrokes $ layerselect of 
-          Left strs -> (GLayer . TEitherAlterHitted . Right) (strs :- Hitted clipstrs :- Empty)
-          Right alist -> (GLayer . TEitherAlterHitted . Right) 
+        case unTEitherAlterHitted . get g_bstrokes $ layerselect of 
+          Left strs -> (GLayerBuf gbuf . TEitherAlterHitted . Right) (strs :- Hitted clipstrs :- Empty)
+          Right alist -> (GLayerBuf gbuf . TEitherAlterHitted . Right) 
                            (concat (interleave id unHitted alist) 
                             :- Hitted clipstrs 
                             :- Empty )
-      tpage' = tpage { glayers = ls { gselectedlayer = newlayerselect } } 
+      tpage' = tpage { glayers = ls { gselectedlayerbuf = newlayerselect } } 
       txoj' = updateTempXournalSelect txoj tpage' pagenum 
       xstate' = updatePageAll (SelectState txoj') 
                 . set xournalstate (SelectState txoj') 
@@ -252,14 +269,15 @@
   xstate <- getSt
   let SelectState txoj = get xournalstate xstate 
       Just (n,tpage) = gselectSelected txoj
-  case unTEitherAlterHitted . gstrokes . gselectedlayer . glayers $ tpage of 
+      slayer = gselectedlayerbuf . glayers $ tpage
+  case unTEitherAlterHitted . get g_bstrokes $ slayer of 
     Left _ -> liftIO $ putStrLn "no stroke selection 2 "
     Right alist -> do 
       let alist' = fmapAL id 
                      (Hitted . map (changeStrokeColor pcolor) . unHitted) alist
           newlayer = Right alist'
           ls = glayers tpage 
-          newpage = tpage { glayers = ls { gselectedlayer = GLayer (TEitherAlterHitted newlayer) }} 
+          newpage = tpage { glayers = ls { gselectedlayerbuf = GLayerBuf (get g_buffer slayer) (TEitherAlterHitted newlayer) }} 
           newtxoj = updateTempXournalSelect txoj newpage n
       commit . updatePageAll (SelectState newtxoj) 
              . set xournalstate (SelectState newtxoj) 
@@ -272,17 +290,22 @@
   xstate <- getSt
   let SelectState txoj = get xournalstate xstate 
       Just (n,tpage) = gselectSelected txoj
-  case unTEitherAlterHitted . gstrokes . gselectedlayer . glayers $ tpage of 
+      slayer = gselectedlayerbuf . get g_layers $ tpage
+  case unTEitherAlterHitted . get g_bstrokes $ slayer  of 
     Left _ -> liftIO $ putStrLn "no stroke selection 2 "
     Right alist -> do 
       let alist' = fmapAL id 
                      (Hitted . map (changeStrokeWidth pwidth) . unHitted) alist
           newlayer = Right alist'
-          ls = glayers tpage 
-          newpage = tpage { glayers = ls { gselectedlayer = GLayer (TEitherAlterHitted newlayer) }} 
+          ls = get g_layers tpage 
+          newpage = tpage { glayers = ls { gselectedlayerbuf = GLayerBuf (get g_buffer slayer) (TEitherAlterHitted newlayer) }} 
           newtxoj = updateTempXournalSelect txoj newpage n          
       commit . updatePageAll (SelectState newtxoj) 
              . set xournalstate (SelectState newtxoj)
              $ xstate 
       invalidateAll 
+
+
+
+
 
diff --git a/lib/Application/HXournal/Draw.hs b/lib/Application/HXournal/Draw.hs
--- a/lib/Application/HXournal/Draw.hs
+++ b/lib/Application/HXournal/Draw.hs
@@ -8,6 +8,7 @@
 import Data.Label
 import Prelude hiding ((.),id)
 
+import Data.Monoid
 import Data.Xournal.Simple
 import Data.Xournal.Generic
 import Data.Xournal.Map
@@ -33,10 +34,10 @@
                      }
   deriving (Show)  
 
-type PageDrawF = DrawingArea -> TPageBBoxMapPDF -> ViewInfo -> Maybe BBox 
+type PageDrawF = DrawingArea -> TPageBBoxMapPDFBuf -> ViewInfo -> Maybe BBox 
                  -> IO ()
 
-type PageDrawFSel = DrawingArea -> TTempPageSelectPDF -> ViewInfo -> Maybe BBox 
+type PageDrawFSel = DrawingArea -> TTempPageSelectPDFBuf -> ViewInfo -> Maybe BBox 
                     -> IO ()
 
 
@@ -57,6 +58,12 @@
                               (fromIntegral x0,fromIntegral y0)
                               (xorig, yorig)
 
+visibleViewPort :: CanvasPageGeometry -> ZoomMode -> BBox  
+visibleViewPort cpg@(CanvasPageGeometry (ws,hs) (w',h') (w,h) (x0,y0) (xorig,yorig)) zmode = 
+  let (xend,yend) = canvasToPageCoord cpg zmode (w',h')
+  in  BBox (xorig,yorig) (xend,yend)
+
+
 core2pageCoord :: CanvasPageGeometry -> ZoomMode 
                   -> (Double,Double) -> (Double,Double)
 core2pageCoord cpg@(CanvasPageGeometry (_ws,_hs) (_w',_h') (_w,_h) (_x0,_y0) (xorig,yorig))
@@ -96,7 +103,19 @@
       _    -> wacom2pageCoord cpg zmode (px,py)
 device2pageCoord _ _ NoPointerCoord = (-100,-100)
 
+pageToCanvasCoord :: CanvasPageGeometry -> ZoomMode -> (Double,Double) -> (Double,Double)
+pageToCanvasCoord cpg@(CanvasPageGeometry _ _ _ _ (xorig,yorig)) zmode (x,y) = 
+  let s = getRatioFromPageToCanvas cpg zmode
+      (xo,yo) = case zmode of 
+                  Original -> (xorig,yorig)
+                  FitWidth -> (0,yorig)
+                  FitHeight -> (xorig,0)
+                  _ -> error "not implemented yet in pageToScreenCoord"
+  in ((x-xo)*s,(y-yo)*s)
 
+canvasToPageCoord :: CanvasPageGeometry -> ZoomMode -> (Double,Double) -> (Double,Double) 
+canvasToPageCoord = core2pageCoord
+
 transformForPageCoord :: CanvasPageGeometry -> ZoomMode -> Render ()
 transformForPageCoord cpg zmode = do 
   let (xo,yo) = page_origin cpg
@@ -104,6 +123,7 @@
   scale s s
   translate (-xo) (-yo)      
   
+{-
 updateCanvas :: DrawingArea -> TXournalBBoxMapPDF -> Int -> ViewInfo -> IO ()
 updateCanvas canvas xoj pagenum vinfo = do 
   let zmode  = get zoomMode vinfo
@@ -113,12 +133,60 @@
                    Just  p -> p 
   geometry <- getCanvasPageGeometry canvas currpage origin
   win <- widgetGetDrawWindow canvas
+  let viewbbox = visibleViewPort geometry zmode
+      newmbbox = Just viewbbox
   renderWithDrawable win $ do
     transformForPageCoord geometry zmode
-    -- cairoDrawPage currpage
-    cairoRenderOption (DrawBuffer,DrawFull) currpage
+    -- cairoRenderOption (InBBoxOption newmbbox) (InBBox currpage)
+    cairoRenderOption (DrawBkgPDF,DrawFull)  currpage
   return ()
+-}
 
+drawFuncGen :: (TPageBBoxMapPDFBuf -> Maybe BBox -> Render ()) -> PageDrawF 
+drawFuncGen render canvas page vinfo mbbox = do 
+  let zmode  = get zoomMode vinfo
+      origin = get viewPortOrigin vinfo
+  geometry <- getCanvasPageGeometry canvas page origin
+  win <- widgetGetDrawWindow canvas
+  let mbboxnew = adjustBBoxWithView geometry zmode mbbox
+  renderWithDrawable win $ do
+    transformForPageCoord geometry zmode
+    render page mbboxnew 
+    return ()
+  return ()
+  
+drawFuncSelGen :: (TTempPageSelectPDFBuf -> Maybe BBox -> Render ()) 
+                  -> (TTempPageSelectPDFBuf -> Maybe BBox -> Render ())
+                  -> PageDrawFSel  
+drawFuncSelGen rencont rensel canvas page vinfo mbbox = do 
+  let zmode  = get zoomMode vinfo
+      origin = get viewPortOrigin vinfo
+  geometry <- getCanvasPageGeometry canvas page origin
+  win <- widgetGetDrawWindow canvas
+  let mbboxnew = adjustBBoxWithView geometry zmode mbbox
+  renderWithDrawable win $ do
+    transformForPageCoord geometry zmode
+    rencont page mbboxnew 
+    rensel page mbboxnew 
+  return ()
+  
+
+
+drawPageClearly :: PageDrawF
+drawPageClearly = drawFuncGen $ \page _mbbox -> 
+                     cairoRenderOption (DrawBkgPDF,DrawFull) (gcast page :: TPageBBoxMapPDF)
+                     
+drawPageSelClearly :: PageDrawFSel                      
+drawPageSelClearly = drawFuncSelGen rendercontent renderselect 
+  where rendercontent tpg mbbox = do
+          let pg = (gcast tpg :: TPageBBoxMapPDFBuf)
+          cairoRenderOption (DrawBkgPDF,DrawFull) (gcast pg :: TPageBBoxMapPDF)
+        renderselect tpg mbbox = 
+          cairoHittedBoxDraw tpg mbbox
+
+
+
+
 drawBBoxOnly :: PageDrawF
 drawBBoxOnly canvas page vinfo _mbbox = do 
   let zmode  = get zoomMode vinfo
@@ -127,10 +195,17 @@
   win <- widgetGetDrawWindow canvas
   renderWithDrawable win $ do
     transformForPageCoord geometry zmode
-    -- cairoDrawPageBBoxOnly page
-    cairoRenderOption (DrawBuffer,DrawBoxOnly) page 
+    cairoRenderOption (DrawWhite,DrawBoxOnly) (gcast page :: TPageBBoxMapPDF)
+     --  tpageBBoxMapPDFFromTPageBBoxMapPDFBuf page )
   return ()
 
+adjustBBoxWithView :: CanvasPageGeometry -> ZoomMode -> Maybe BBox 
+                      -> Maybe BBox
+adjustBBoxWithView geometry zmode mbbox =   
+  let viewbbox = visibleViewPort geometry zmode
+  in  toMaybe $ (fromMaybe mbbox :: IntersectBBox)  
+                `mappend` 
+                (Intersect (Middle viewbbox))
 
 
 drawPageInBBox :: PageDrawF 
@@ -139,10 +214,10 @@
       origin = get viewPortOrigin vinfo
   geometry <- getCanvasPageGeometry canvas page origin
   win <- widgetGetDrawWindow canvas
+  let mbboxnew = adjustBBoxWithView geometry zmode mbbox
   renderWithDrawable win $ do
     transformForPageCoord geometry zmode
-    -- cairoDrawPageBBox mbbox page
-    cairoRenderOption (DrawBuffer,DrawFull) page
+    cairoRenderOption (InBBoxOption mbboxnew) (InBBox page) --  (InBBox (gcast page :: TPageBBoxMapPDF))
     return ()
   return ()
 
@@ -166,7 +241,7 @@
 drawBBoxSel :: PageDrawFSel 
 drawBBoxSel _ _ _ Nothing = return ()
 drawBBoxSel canvas tpg vinfo (Just bbox) = do 
-  let page = tpageBBoxMapPDFFromTTempPageSelectPDF tpg
+  let page = (gcast tpg :: TPageBBoxMapPDFBuf)
   let zmode  = get zoomMode vinfo
       origin = get viewPortOrigin vinfo
   geometry <- getCanvasPageGeometry canvas page origin
@@ -212,32 +287,6 @@
     lineTo x y
     stroke
   
-{- 
-showTXournalBBoxMapPDF :: DrawingArea -> TXournalBBoxMapPDF -> Int -> ViewInfo -> IO ()
-showTXournalBBoxMapPDF canvas xoj pagenum vinfo = do 
-  let zmode  = get zoomMode vinfo
-      origin = get viewPortOrigin vinfo
-  let currpagebbox = case ( M.lookup pagenum . gpages) xoj of 
-                       Nothing -> error "no such page in showTXournalBBoxMapPDF"
-                       Just p -> p 
-      currpage = pageFromPageBBox currpagebbox
-      strs = do 
-        l <- pagebbox_layers currpagebbox 
-        s <- layerbbox_strokes l
-        return s 
-  geometry <- getCanvasPageGeometry canvas currpage origin
-  win <- widgetGetDrawWindow canvas
-  renderWithDrawable win $ do
-    transformForPageCoord geometry zmode
-    setSourceRGBA 1.0 0 0 1.0 
-    setLineWidth  0.5 
-    let f str = do 
-          let BBox (ulx,uly) (lrx,lry) = strokebbox_bbox str 
-          rectangle ulx uly (lrx-ulx) (lry-uly)
-          stroke 
-    mapM_ f strs 
-  return ()
--}
 
 showBBox :: DrawingArea -> CanvasPageGeometry -> ZoomMode -> BBox -> IO ()
 showBBox canvas cpg zmode (BBox (ulx,uly) (lrx,lry)) = do 
@@ -260,34 +309,40 @@
 drawSelectionInBBox canvas tpg vinfo mbbox = do 
   let zmode  = get zoomMode vinfo
       origin = get viewPortOrigin vinfo
-      page = tpageBBoxMapPDFFromTTempPageSelectPDF tpg
+      page = (gcast tpg :: TPageBBoxMapPDFBuf)
   geometry <- getCanvasPageGeometry canvas page origin
   win <- widgetGetDrawWindow canvas
+  let mbboxnew = adjustBBoxWithView geometry zmode mbbox
   renderWithDrawable win $ do
     transformForPageCoord geometry zmode
-    cairoDrawPageBBoxPDF mbbox page
-    cairoHittedBoxDraw tpg mbbox  -- boxdrawaction 
---     boxdrawaction 
+    cairoRenderOption (InBBoxOption mbboxnew) (InBBox page)
+       -- (InBBox (gcast page :: TPageBBoxMapPDF))
+    cairoHittedBoxDraw tpg mbboxnew  
       
+{-
 drawSelectionInBBoxOnly :: PageDrawFSel 
 drawSelectionInBBoxOnly canvas tpg vinfo mbbox = do 
   let zmode  = get zoomMode vinfo
       origin = get viewPortOrigin vinfo
-      page = tpageBBoxMapPDFFromTTempPageSelectPDF tpg
+      page = (gcast tpg :: TPageBBoxMapPDFBuf)
   geometry <- getCanvasPageGeometry canvas page origin
-  win <- widgetGetDrawWindow canvas
+  win <- widgetGetDrawWindow canvas  
+  let mbboxnew = adjustBBoxWithView geometry zmode mbbox
   renderWithDrawable win $ do
     transformForPageCoord geometry zmode
-    cairoRenderOption (DrawBuffer,DrawBoxOnly) page
-    -- cairoDrawPageBBoxPDF mbbox page
-    cairoHittedBoxDraw tpg mbbox  -- boxdrawaction 
-
-
+    cairoRenderOption (InBBoxOption mbboxnew) (InBBox page)
+      -- (DrawWhite,DrawBoxOnly) (gcast page :: TPageBBoxMapPDF)
+      -- (DrawBuffer,DrawBoxOnly) (gcast page :: TPageBBoxMapPDF)
+    cairoHittedBoxDraw tpg mbbox 
+-}
   
-cairoHittedBoxDraw :: TTempPageSelectPDF -> Maybe BBox -> Render () 
+cairoHittedBoxDraw :: TTempPageSelectPDFBuf -> Maybe BBox -> Render () 
 cairoHittedBoxDraw tpg mbbox = do   
-  case unTEitherAlterHitted . gstrokes . gselectedlayer . glayers $ tpg of
+  let layers = get g_layers tpg 
+      slayer = gselectedlayerbuf layers 
+  case unTEitherAlterHitted . get g_bstrokes $ slayer of
     Right alist -> do 
+      clipBBox mbbox
       setSourceRGBA 0.0 0.0 1.0 1.0
       let hitstrs = concatMap unHitted (getB alist)
           oneboxdraw str = do 
@@ -299,25 +354,35 @@
                               else return () 
               Nothing -> drawbox 
       mapM_ oneboxdraw hitstrs                       
+      resetClip
     Left _ -> return ()  
 
-
+---- 
+    
+drawBuf :: PageDrawF 
+drawBuf canvas page vinfo mbbox = do 
+  let zmode  = get zoomMode vinfo
+      origin = get viewPortOrigin vinfo
+  geometry <- getCanvasPageGeometry canvas page origin
+  let mbboxnew = adjustBBoxWithView geometry zmode mbbox
+{-  let viewbbox = visibleViewPort geometry zmode
+      newmbbox = toMaybe $ (fromMaybe mbbox :: IntersectBBox)  `mappend` (Intersect (Middle viewbbox)) -}
+  win <- widgetGetDrawWindow canvas
+  renderWithDrawable win $ do
+    transformForPageCoord geometry zmode
+    cairoRenderOption (InBBoxOption mbboxnew) (InBBox page) 
+    return ()
+  return ()
 
 
-  {-
-  boxdrawaction <-  
-    case unTEitherAlterHitted . gstrokes . gselectedlayer . glayers $ tpg of
-      Right alist -> do 
-        return $ do 
-          setSourceRGBA 0.0 0.0 1.0 1.0
-          let hitstrs = concatMap unHitted (getB alist)
-              oneboxdraw str = do 
-                let bbox@(BBox (x1,y1) (x2,y2)) = strokebbox_bbox str
-                    drawbox = do { rectangle x1 y1 (x2-x1) (y2-y1); stroke }
-                case mbbox of 
-                  Just bboxarg -> if hitTestBBoxBBox bbox bboxarg 
-                                    then drawbox
-                                    else return () 
-                  Nothing -> drawbox 
-          mapM_ oneboxdraw hitstrs                       
-      Left _ -> return $ return ()  -}
+drawSelBuf :: PageDrawFSel 
+drawSelBuf canvas tpg vinfo mbbox = do 
+  let zmode  = get zoomMode vinfo
+      origin = get viewPortOrigin vinfo
+      page = (gcast tpg :: TPageBBoxMapPDFBuf)
+  geometry <- getCanvasPageGeometry canvas page origin
+  win <- widgetGetDrawWindow canvas
+  renderWithDrawable win $ do
+    transformForPageCoord geometry zmode
+    cairoRenderOption (InBBoxOption mbbox) (InBBox (gcast page :: TPageBBoxMapPDF))
+    cairoHittedBoxDraw tpg mbbox  
diff --git a/lib/Application/HXournal/GUI.hs b/lib/Application/HXournal/GUI.hs
--- a/lib/Application/HXournal/GUI.hs
+++ b/lib/Application/HXournal/GUI.hs
@@ -5,7 +5,7 @@
 import Application.HXournal.Type.XournalState 
 import Application.HXournal.Type.Event
 import Application.HXournal.Type.Canvas
-
+import Application.HXournal.Type.Undo 
 import qualified Data.IntMap as M
 
 import Application.HXournal.Coroutine.Callback
@@ -23,6 +23,7 @@
 import Control.Monad.Trans 
 
 import Data.IORef
+import Data.Maybe
 
 import Control.Category
 import Data.Label
@@ -37,8 +38,11 @@
   cfg <- loadConfigFile   
   devlst <- initDevice cfg 
   (tref,sref) <- initCoroutine devlst window
-  st1 <- readIORef sref 
-
+  st0 <- readIORef sref 
+  maxundo <- getMaxUndo cfg >>= 
+               \mmax -> maybe (return 50) (return . id) mmax
+  let st1 = set undoTable (emptyUndo maxundo) st0 
+            
   -- let st1 = set gtkUIManager ui st0
   st2 <- getFileContent mfname st1
   let ui = get gtkUIManager st2 
@@ -49,6 +53,7 @@
   
   setTitleFromFileName st2
   vbox <- vBoxNew False 0 
+  
   
   let st3 = set frameState wconf 
             . set rootWindow winCvsArea 
diff --git a/lib/Application/HXournal/GUI/Menu.hs b/lib/Application/HXournal/GUI/Menu.hs
--- a/lib/Application/HXournal/GUI/Menu.hs
+++ b/lib/Application/HXournal/GUI/Menu.hs
@@ -483,7 +483,7 @@
  
   let disabledActions = 
         [ recenta, printa, exporta
-        , undoa, redoa, cuta, copya, pastea, deletea
+        , {- undoa, redoa, -} cuta, copya, pastea, deletea
         , fscra,  zmina, zmouta, setzma
         , shwlayera, hidlayera
         , newpgba, newpgaa, newpgea, delpga, newlyra, dellyra, ppsizea, ppclra
@@ -491,7 +491,6 @@
         , shpreca, rulera 
         , erasropta, hiltropta, txtfnta, defpena, defersra, defhiltra, deftxta
         , setdefopta
-        {- , uxinputa -} 
         , dcrdcorea, ersrtipa, pressrsensa, pghilta, mltpgvwa
         , mltpga, btn2mapa, btn3mapa, antialiasbmpa, prgrsbkga, prntpprulea 
         , lfthndscrbra, shrtnmenua, autosaveprefa, saveprefa 
diff --git a/lib/Application/HXournal/ModelAction/File.hs b/lib/Application/HXournal/ModelAction/File.hs
--- a/lib/Application/HXournal/ModelAction/File.hs
+++ b/lib/Application/HXournal/ModelAction/File.hs
@@ -8,6 +8,7 @@
 import qualified Text.Xournal.Parse as P
 import qualified Data.IntMap as M
 
+import Control.Monad
 import Control.Category
 import Data.Label
 import Prelude hiding ((.),id)
@@ -27,7 +28,7 @@
 #ifdef POPPLER
 import qualified Graphics.UI.Gtk.Poppler.Document as Poppler
 import qualified Graphics.UI.Gtk.Poppler.Page as PopplerPage
-#endif 
+#endif
 
 -- | get file content from xournal file and update xournal state 
 
@@ -39,7 +40,8 @@
     nxstate <- constructNewHXournalStateFromXournal xojcontent xstate 
     return $ set currFileName (Just fname) nxstate 
 getFileContent Nothing xstate = do   
-    newxoj <- mkTXournalBBoxMapPDF defaultXournal 
+    newxoj <- mkTXournalBBoxMapPDFBufFromNoBuf <=< mkTXournalBBoxMapPDF 
+              $ defaultXournal 
     let newxojstate = ViewAppendState newxoj 
         xstate' = set currFileName Nothing 
                   . set xournalstate newxojstate
@@ -56,7 +58,7 @@
 constructNewHXournalStateFromXournal xoj xstate = do 
     let currcid = get currentCanvas xstate 
         cmap = get canvasInfoMap xstate 
-    xoj <- mkTXournalBBoxMapPDF xoj
+    xoj <- mkTXournalBBoxMapPDFBufFromNoBuf <=< mkTXournalBBoxMapPDF $ xoj
     let Dim width height = case M.lookup 0 (gpages xoj) of    
                              Nothing -> error "no first page in getFileContent" 
                              Just p -> gdimension p 
@@ -75,8 +77,8 @@
 
 makeNewXojWithPDF :: FilePath -> IO (Maybe Xournal)
 makeNewXojWithPDF fp = do 
-  let fname = C.pack fp 
 #ifdef POPPLER
+  let fname = C.pack fp 
   mdoc <- popplerGetDocFromFile fname
   case mdoc of 
     Nothing -> do 
@@ -94,8 +96,9 @@
       putStrLn $ "size = " ++ show (w,h)
       return (Just xoj)
 #else
-  error "makeNewXojWithPDF : this cannot be done without poppler lib." 
-#endif    
+  error "makeNewXojWithPDF should not be used without poppler lib"
+#endif
+      
       
 createPage :: Dimension -> B.ByteString -> Int -> Page
 createPage dim fn n 
diff --git a/lib/Application/HXournal/ModelAction/Page.hs b/lib/Application/HXournal/ModelAction/Page.hs
--- a/lib/Application/HXournal/ModelAction/Page.hs
+++ b/lib/Application/HXournal/ModelAction/Page.hs
@@ -16,21 +16,39 @@
 updatePageAll :: XournalState 
                  -> HXournalState 
                  -> HXournalState
-updatePageAll xst xstate = let cmap = get canvasInfoMap xstate
-                               cmap' = fmap (updatePage xst) cmap
-                           in  set canvasInfoMap cmap' xstate 
+updatePageAll xst xstate = 
+  let cmap = get canvasInfoMap xstate
+      cmap' = fmap (updatePage xst . adjustPage xst) cmap
+  in  set canvasInfoMap cmap' xstate 
 
+adjustPage :: XournalState -> CanvasInfo -> CanvasInfo
+adjustPage xojstate cinfo =
+    let cpn = get currentPageNum cinfo 
+        pagemap = case xojstate of 
+                    ViewAppendState xoj -> get g_pages xoj 
+                    SelectState txoj -> get g_selectAll txoj 
+    in  adjustwork cpn pagemap              
+  where adjustwork cpn pagemap = 
+         if M.notMember cpn pagemap  
+         then let (minp,_) = M.findMin pagemap 
+                  (maxp,_) = M.findMax pagemap 
+              in if cpn > maxp 
+                   then set currentPageNum maxp cinfo
+                   else set currentPageNum minp cinfo
+         else cinfo
+ 
 
-getPageFromXojBBoxMapPDF :: Int -> TXournalBBoxMapPDF -> TPageBBoxMapPDF
-getPageFromXojBBoxMapPDF pagenum xoj  = 
-  case M.lookup pagenum (gpages xoj) of 
-    Nothing -> error "something wrong in updatePage"
+
+getPageFromGXournalMap :: Int -> GXournal M.IntMap a -> a
+getPageFromGXournalMap pagenum xoj  = 
+  case M.lookup pagenum (get g_pages xoj) of 
+    Nothing -> error "something wrong in getPageFromGXournalMap"
     Just p -> p
 
 updatePage :: XournalState -> CanvasInfo -> CanvasInfo 
 updatePage (ViewAppendState xojbbox) cinfo = 
   let pagenum = get currentPageNum cinfo 
-      pg = getPageFromXojBBoxMapPDF pagenum xojbbox 
+      pg = getPageFromGXournalMap pagenum xojbbox 
       Dim w h = gdimension pg
   in  set currentPageNum pagenum 
       . set (pageDimension.viewInfo) (w,h)       
@@ -56,7 +74,9 @@
   
 setPage :: XournalState -> Int -> CanvasInfo -> CanvasInfo
 setPage (ViewAppendState xojbbox) pagenum cinfo = 
-  let pg = getPageFromXojBBoxMapPDF pagenum xojbbox 
+  let pg = getPageFromGXournalMap pagenum xojbbox
+        -- getPageFromXojBBoxMapPDF pagenum xojbbox 
+       
       Dim w h = gdimension pg
   in  set currentPageNum pagenum 
       . set (viewPortOrigin.viewInfo) (0,0) 
@@ -65,7 +85,6 @@
       $ cinfo 
 setPage (SelectState txoj) pagenum cinfo = 
   let mspage = gselectSelected  txoj 
-               -- tx_selectpage 
       pageFromArg = case M.lookup pagenum (gselectAll txoj) of 
                       Nothing -> error "no such page in setPage"
                       Just p -> p
@@ -82,11 +101,11 @@
      . set currentPage newpage
      $ cinfo 
                             
-getPage :: CanvasInfo -> TPageBBoxMapPDF
-getPage cinfo = case get currentPage cinfo of 
-                  Right tpgs -> tpageBBoxMapPDFFromTTempPageSelectPDF tpgs
-                    
-                    -- pageBBoxMapFromTempPageSelect tpgs
-                  Left pg -> pg 
+getPage :: CanvasInfo -> TPageBBoxMapPDFBuf
+getPage cinfo = 
+  case get currentPage cinfo of 
+    Right tpgs -> gcast tpgs :: TPageBBoxMapPDFBuf 
+             -- tpageBBoxMapPDFBufFromTTempPageSelectPDFBuf tpgs
+    Left pg -> pg 
                   
 
diff --git a/lib/Application/HXournal/ModelAction/Pen.hs b/lib/Application/HXournal/ModelAction/Pen.hs
--- a/lib/Application/HXournal/ModelAction/Pen.hs
+++ b/lib/Application/HXournal/ModelAction/Pen.hs
@@ -23,14 +23,14 @@
 import Data.Xournal.Map
 
 
-addPDraw :: PenInfo -> TXournalBBoxMapPDF -> Int -> Seq (Double,Double) 
-            -> (TXournalBBoxMapPDF,BBox)
-addPDraw pinfo xoj pgnum pdraw = 
+addPDraw :: PenInfo -> TXournalBBoxMapPDFBuf -> Int -> Seq (Double,Double) 
+            -> IO (TXournalBBoxMapPDFBuf,BBox)
+addPDraw pinfo xoj pgnum pdraw = do 
   let pcolor = get penColor pinfo
       pcolname = fromJust (M.lookup pcolor penColorNameMap)
       pwidth = get penWidth pinfo
-      currpage = getPageFromXojBBoxMapPDF  pgnum xoj
-      currlayer = case IM.lookup 0 (glayers currpage) of
+      currpage = getPageFromGXournalMap pgnum xoj
+      currlayer = case IM.lookup 0 (get g_layers currpage) of
                     Nothing -> error "something wrong in addPDraw"
                     Just l -> l
       newstroke = Stroke { stroke_tool = "pen" 
@@ -39,10 +39,14 @@
                          , stroke_data = map (uncurry (:!:)) . toList $ pdraw
                          } 
       newstrokebbox = mkStrokeBBoxFromStroke newstroke
-      newlayerbbox =  set g_strokes (get g_strokes currlayer ++ [newstrokebbox]) currlayer
-      newpagebbox = set g_layers (IM.adjust (const newlayerbbox) 0 (get g_layers currpage)) currpage 
+      bbox = strokebbox_bbox newstrokebbox
+      
+  newlayerbbox <- updateLayerBuf (Just bbox)
+                   . set g_bstrokes (get g_bstrokes currlayer ++ [newstrokebbox]) 
+                   $ currlayer
+  let newpagebbox = set g_layers (IM.adjust (const newlayerbbox) 0 (get g_layers currpage)) currpage 
       newxojbbox = set g_pages (IM.adjust (const newpagebbox) pgnum (get g_pages xoj) ) xoj 
       
-  in  (newxojbbox,strokebbox_bbox newstrokebbox)
+  return (newxojbbox,strokebbox_bbox newstrokebbox)
 
 
diff --git a/lib/Application/HXournal/ModelAction/Select.hs b/lib/Application/HXournal/ModelAction/Select.hs
--- a/lib/Application/HXournal/ModelAction/Select.hs
+++ b/lib/Application/HXournal/ModelAction/Select.hs
@@ -1,6 +1,8 @@
 module Application.HXournal.ModelAction.Select where
 
 import Application.HXournal.Type.Enum
+import Application.HXournal.Type.Canvas
+import Application.HXournal.Draw
 
 import Data.Xournal.Simple
 import Data.Xournal.Generic
@@ -19,6 +21,19 @@
 import Data.Label
 import Prelude hiding ((.),id)
 
+                  
+isBBoxDeltaSmallerThan :: Double ->CanvasPageGeometry -> ZoomMode 
+                          -> BBox -> BBox -> Bool 
+isBBoxDeltaSmallerThan delta cpg zmode 
+                       (BBox (x11,y11) (x12,y12)) (BBox (x21,y21) (x22,y22)) = 
+  let (x11',y11') = pageToCanvasCoord cpg zmode (x11,y11)
+      (x12',y12') = pageToCanvasCoord cpg zmode (x12,y12)
+      (x21',y21') = pageToCanvasCoord cpg zmode (x21,y21)
+      (x22',y22') = pageToCanvasCoord cpg zmode (x22,y22)
+  in (x11'-x21' > (-delta) && x11'-x21' < delta) 
+     && (y11'-y21' > (-delta) && y11'-y21' < delta)  
+     && (x12'-x22' > (-delta) && x12'-x22' < delta)
+     && (y11'-y21' > (-delta) && y12'-y22' < delta)
 
 changeStrokeByOffset :: (Double,Double) -> StrokeBBox -> StrokeBBox 
 changeStrokeByOffset (offx,offy) (StrokeBBox t c w ds bbox) = 
@@ -28,25 +43,29 @@
       newbbox = BBox (x1+offx,y1+offy) (x2+offx,y2+offy)
   in  StrokeBBox t c w newds newbbox
 
-changeSelectionByOffset :: TTempPageSelectPDF -> (Double,Double) -> TTempPageSelectPDF
+changeSelectionByOffset :: TTempPageSelectPDFBuf -> (Double,Double) 
+                           -> TTempPageSelectPDFBuf
 changeSelectionByOffset tpage off = 
   let ls = glayers tpage
-      activelayer = unTEitherAlterHitted . gstrokes . gselectedlayer $ ls
+      slayer = gselectedlayerbuf ls
+      buf = get g_buffer slayer 
+      activelayer = unTEitherAlterHitted . get g_bstrokes $ slayer 
   in case activelayer of 
        Left _ -> tpage 
        Right alist -> 
          let alist' =fmapAL id 
                             (Hitted . map (changeStrokeByOffset off) . unHitted) 
                             alist 
-             layer' = GLayer . TEitherAlterHitted . Right $ alist'
-         in tpage { glayers = ls { gselectedlayer = layer' }}
+             layer' = GLayerBuf buf . TEitherAlterHitted . Right $ alist'
+         in tpage { glayers = ls { gselectedlayerbuf = layer' }}
 
-updateTempXournalSelect :: TTempXournalSelectPDF -> TTempPageSelectPDF -> Int 
-                           -> TTempXournalSelectPDF
+updateTempXournalSelect :: TTempXournalSelectPDFBuf 
+                           -> TTempPageSelectPDFBuf
+                           -> Int 
+                           -> TTempXournalSelectPDFBuf
 updateTempXournalSelect txoj tpage pagenum =                
   let pgs = gselectAll txoj 
-      pgs' = M.adjust (const (tpageBBoxMapPDFFromTTempPageSelectPDF tpage))
-                        pagenum pgs
+      pgs' = M.adjust (const (gcast tpage)) pagenum pgs
   in set g_selectAll pgs' 
      . set g_selectSelected (Just (pagenum,tpage))
      $ txoj 
@@ -54,9 +73,9 @@
 
     
     
-hitInSelection :: TTempPageSelectPDF -> (Double,Double) -> Bool 
+hitInSelection :: TTempPageSelectPDFBuf -> (Double,Double) -> Bool 
 hitInSelection tpage point = 
-  let activelayer = unTEitherAlterHitted . gstrokes .  gselectedlayer . glayers $ tpage
+  let activelayer = unTEitherAlterHitted . get g_bstrokes .  gselectedlayerbuf . glayers $ tpage
   in case activelayer of 
        Left _ -> False   
        Right alist -> 
diff --git a/lib/Application/HXournal/Type/Canvas.hs b/lib/Application/HXournal/Type/Canvas.hs
--- a/lib/Application/HXournal/Type/Canvas.hs
+++ b/lib/Application/HXournal/Type/Canvas.hs
@@ -9,7 +9,6 @@
 import Prelude hiding ((.), id)
 import Graphics.Xournal.Render.BBoxMapPDF
 import Data.Xournal.Map
--- import Data.Xournal.Select
 import Graphics.UI.Gtk hiding (get,set)
 
 type CanvasId = Int 
@@ -38,7 +37,7 @@
                              , _scrolledWindow :: ScrolledWindow
                              , _viewInfo :: ViewInfo 
                              , _currentPageNum :: Int
-                             , _currentPage :: Either TPageBBoxMapPDF TTempPageSelectPDF 
+                             , _currentPage :: Either TPageBBoxMapPDFBuf TTempPageSelectPDFBuf 
                              , _horizAdjustment :: Adjustment
                              , _vertAdjustment :: Adjustment 
                              }
diff --git a/lib/Application/HXournal/Type/Undo.hs b/lib/Application/HXournal/Type/Undo.hs
new file mode 100644
--- /dev/null
+++ b/lib/Application/HXournal/Type/Undo.hs
@@ -0,0 +1,84 @@
+module Application.HXournal.Type.Undo where
+
+import Data.Sequence
+import Control.Monad
+
+type SeqZipper a = (a, (Seq a,Seq a))
+
+data UndoTable a = UndoTable { undo_allowednum :: Int
+                             , undo_totalnum :: Int 
+                             , undo_zipper :: Maybe (SeqZipper a)
+                             }
+                 
+
+singletonSZ :: a -> SeqZipper a  
+singletonSZ x = (x, (empty,empty))
+
+appendGoLast :: SeqZipper a -> a -> SeqZipper a
+appendGoLast (y,(y1s,y2s)) x = (x, ((y1s |> y) >< y2s, empty))
+
+chopFirst :: SeqZipper a -> Maybe (SeqZipper a)
+chopFirst (y,(y1s,y2s)) = 
+  case viewl y1s of
+    EmptyL -> case viewl y2s of 
+                EmptyL -> Nothing 
+                z :< zs -> Just (z,(empty,zs))
+    z :< zs -> Just (y,(zs,y2s))
+    
+moveLeft :: SeqZipper a -> Maybe (SeqZipper a)
+moveLeft (x,(x1s,x2s)) = 
+  case viewr x1s of
+    EmptyR -> Nothing 
+    zs :> z -> Just (z,(zs,x<|x2s))
+
+moveRight :: SeqZipper a -> Maybe (SeqZipper a) 
+moveRight (x,(x1s,x2s)) = 
+  case viewl x2s of 
+    EmptyL -> Nothing
+    z :< zs -> Just (z,(x1s|>x,zs)) 
+
+
+current :: SeqZipper a -> a 
+current (x,(_,_)) = x
+
+prev :: SeqZipper a -> Maybe a 
+prev = fmap current . moveLeft
+
+next :: SeqZipper a -> Maybe a 
+next = fmap current . moveRight
+
+ 
+emptyUndo :: Int -> UndoTable a
+emptyUndo n | n > 0 = UndoTable n 0 Nothing
+            | otherwise = error "undo table must be larger than 0" 
+
+singletonUndo :: Int -> a -> UndoTable a 
+singletonUndo n e = addToUndo (emptyUndo n) e
+
+addToUndo :: UndoTable a -> a -> UndoTable a 
+addToUndo utable e = 
+  let tn = undo_totalnum utable 
+      an = undo_allowednum utable 
+      mzs = undo_zipper utable 
+  in case mzs of  
+       Nothing -> UndoTable an 1 . Just . singletonSZ $ e
+       Just zs -> 
+         if tn < an
+           then UndoTable an (tn+1) . Just . appendGoLast zs $ e
+           else UndoTable an an . chopFirst . appendGoLast zs $ e
+
+getCurrentUndoItem :: UndoTable a -> Maybe a
+getCurrentUndoItem = fmap current . undo_zipper
+
+getPrevUndo :: UndoTable a -> Maybe (a, UndoTable a)
+getPrevUndo t = do 
+  newzs <- moveLeft =<< undo_zipper t 
+  return (current newzs, t {undo_zipper = Just newzs})
+  
+getNextUndo :: UndoTable a -> Maybe (a, UndoTable a)
+getNextUndo t = do 
+  newzs <- moveRight =<< undo_zipper t 
+  return (current newzs, t {undo_zipper = Just newzs})
+
+numOfUndo :: UndoTable a -> Int 
+numOfUndo = undo_totalnum 
diff --git a/lib/Application/HXournal/Type/XournalState.hs b/lib/Application/HXournal/Type/XournalState.hs
--- a/lib/Application/HXournal/Type/XournalState.hs
+++ b/lib/Application/HXournal/Type/XournalState.hs
@@ -8,12 +8,12 @@
 import Application.HXournal.Type.Canvas
 import Application.HXournal.Type.Clipboard
 import Application.HXournal.Type.Window 
-
--- import Graphics.Xournal.Render.Select
+import Application.HXournal.Type.Undo
 import Data.Xournal.Map
 
 import Graphics.Xournal.Render.BBoxMapPDF
 
+import Control.Category
 import Control.Monad.State
 import Data.Xournal.Simple
 import Data.Xournal.Predefined 
@@ -24,26 +24,28 @@
 
 type XournalStateIO = StateT HXournalState IO 
 
-data XournalState = ViewAppendState { unView :: TXournalBBoxMapPDF }
-                  | SelectState { tempSelect :: TTempXournalSelectPDF }
+data XournalState = ViewAppendState { unView :: TXournalBBoxMapPDFBuf }
+                  | SelectState { tempSelect :: TTempXournalSelectPDFBuf }
 
-data HXournalState = HXournalState { _xournalstate :: XournalState
-                                   , _currFileName :: Maybe FilePath
-                                   , _canvasInfoMap :: CanvasInfoMap 
-                                   , _currentCanvas :: Int
-                                   , _frameState :: WindowConfig 
-                                   , _rootWindow :: Widget
-                                   , _rootContainer :: Box
-                                   , _rootOfRootWindow :: Window
-                                   , _currentPenDraw :: PenDraw
-                                   , _clipboard :: Clipboard
-                                   , _callBack ::  MyEvent -> IO ()
-                                   , _deviceList :: DeviceList
-                                   , _penInfo :: PenInfo
-                                   , _selectInfo :: SelectInfo 
-                                   , _gtkUIManager :: UIManager 
-                                   , _isSaved :: Bool 
-                                   } 
+data HXournalState = 
+  HXournalState { _xournalstate :: XournalState
+                , _currFileName :: Maybe FilePath
+                , _canvasInfoMap :: CanvasInfoMap 
+                , _currentCanvas :: Int
+                , _frameState :: WindowConfig 
+                , _rootWindow :: Widget
+                , _rootContainer :: Box
+                , _rootOfRootWindow :: Window
+                , _currentPenDraw :: PenDraw
+                , _clipboard :: Clipboard
+                , _callBack ::  MyEvent -> IO ()
+                , _deviceList :: DeviceList
+                , _penInfo :: PenInfo
+                , _selectInfo :: SelectInfo 
+                , _gtkUIManager :: UIManager 
+                , _isSaved :: Bool 
+                , _undoTable :: UndoTable XournalState
+                } 
 
 
 $(mkLabels [''HXournalState]) 
@@ -51,8 +53,7 @@
 emptyHXournalState :: HXournalState 
 emptyHXournalState = 
   HXournalState  
-  { _xournalstate = ViewAppendState emptyTXournalBBoxMapPDF
-                    -- (mkXournalBBoxMapFromXournal emptyXournal)
+  { _xournalstate = ViewAppendState emptyGXournalMap
   , _currFileName = Nothing 
   , _canvasInfoMap = error "emptyHXournalState.canvasInfoMap"
   , _currentCanvas = error "emtpyHxournalState.currentCanvas"
@@ -68,6 +69,12 @@
   , _selectInfo = SelectInfo SelectRectangleWork 
   , _gtkUIManager = error "emptyHXournalState.gtkUIManager"
   , _isSaved = False 
+  , _undoTable = emptyUndo 1 
   }
 
-  
+resetXournalStateBuffers :: XournalState -> IO XournalState 
+resetXournalStateBuffers xojstate1 = 
+  case xojstate1 of 
+    ViewAppendState xoj -> liftIO . liftM ViewAppendState . resetXournalBuffers $ xoj
+    _ -> return xojstate1
+