Add explicit layer datatype

src/Dodge/Picture/Layer.hs

@@ -6,7 +6,6 @@ module Dodge.Picture.Layer
 --    , levLayer
 --    , Layer (..)
     ) where
-import Dodge.Picture.Layer.Data
 import Picture
 {- | Uses a layer to set the depth.  -}
 --onLayer :: Layer -> Picture -> Picture

src/Dodge/Picture/SizeInvariant.hs

@@ -14,7 +14,7 @@ fixedSizePicAt
     -> World
     -> Picture
 fixedSizePicAt pic p w 
-    = setLayer 4 
+    = setLayer TopLayer 
     . setDepth 50 
     . translate x y 
     . scale theScale theScale 
@@ -34,7 +34,7 @@ fixedSizePicClamp
     -> World
     -> Picture
 fixedSizePicClamp xbord ybord pic p cfig w
-    = setLayer 4 
+    = setLayer TopLayer 
 --    . setDepth 50 
     . translate x y 
     . scale theScale theScale 
@@ -59,8 +59,8 @@ fixedSizePicClampArrow
     -> World
     -> Picture
 fixedSizePicClampArrow xbord ybord pic p cfig w = pictures 
-    [ setLayer 4 . translate x y . scale theScale theScale $ pic 
-    , setLayer 4 . color white . setDepth 20 $ arrowPic
+    [ setLayer TopLayer . translate x y . scale theScale theScale $ pic 
+    , setLayer TopLayer . color white . setDepth 20 $ arrowPic
     ]
   where
     winps = screenPolygon cfig w