Start adapting the code to make use of the new PDF.Box class type

reveal.cabal

@@ -24,7 +24,9 @@ executable reveal
   build-depends:       base >=4.9.1 && <4.13
                      , bytestring
                      , containers
+                     , mtl
                      , Hufflepdf >= 0.2.0
                      , zlib
   hs-source-dirs:      src
+  ghc-options:         -Wall
   default-language:    Haskell2010

src/Main.hs

@@ -3,6 +3,7 @@
 module Main where
 
 import Codec.Compression.Zlib (compress, decompress)
+import Control.Monad.State (execState)
 import Data.ByteString.Char8 (ByteString)
 import qualified Data.ByteString.Char8 as BS (
     length, readFile
@@ -11,8 +12,10 @@ import qualified Data.ByteString.Lazy.Char8 as Lazy (
     fromStrict, intercalate, split, toStrict, writeFile
   )
 import qualified Data.Map as Map (insert, lookup)
-import PDF (Document(..), parseDocument, render)
-import PDF.Object (Content(..), DirectObject(..), Object(..), Name(..), Number(..))
+import PDF (Document(..), UnifiedLayers(..), parseDocument, render)
+import PDF.Box ((.@), modifyAt)
+import PDF.Layer (AllObjects(..))
+import PDF.Object (DirectObject(..), Object(..), Name(..), Number(..))
 import PDF.TextRendering (TextRendering(..), update)
 import Prelude hiding (lines, unlines)
 import System.Environment (getArgs)
@@ -40,15 +43,9 @@ revealObject obj@(Stream {header, streamContent}) =
     _ -> obj
 revealObject obj = obj
 
-revealContent :: Content -> Content
-revealContent content = content {
-    objects = revealObject <$> (objects content)
-  }
-
 reveal :: Document -> Document
-reveal document = document {
-    updates = revealContent <$> (updates document)
-  }
+reveal = execState $ do
+  modifyAt (UnifiedLayers .@ AllObjects) (return . fmap revealObject)
 
 main :: IO ()
 main = do