Switch to new pandoc-types and use Text instead of String [API change].

PR #5884.

+ Use pandoc-types 1.20 and texmath 0.12.
+ Text is now used instead of String, with a few exceptions.
+ In the MediaBag module, some of the types using Strings
  were switched to use FilePath instead (not Text).
+ In the Parsing module, new parsers `manyChar`, `many1Char`,
  `manyTillChar`, `many1TillChar`, `many1Till`, `manyUntil`,
  `mantyUntilChar` have been added: these are like their
  unsuffixed counterparts but pack some or all of their output.
+ `glob` in Text.Pandoc.Class still takes String since it seems
  to be intended as an interface to Glob, which uses strings.
  It seems to be used only once in the package, in the EPUB writer,
  so that is not hard to change.

2 files changed, 174 insertions, 163 deletions

diff --git a/src/Text/Pandoc/Writers/Powerpoint/Output.hs b/src/Text/Pandoc/Writers/Powerpoint/Output.hs
index 58f230a9d..344a5564a 100644
--- a/src/Text/Pandoc/Writers/Powerpoint/Output.hs
+++ b/src/Text/Pandoc/Writers/Powerpoint/Output.hs
@@ -136,7 +136,7 @@ data MediaInfo = MediaInfo { mInfoFilePath :: FilePath
                            , mInfoLocalId  :: Int
                            , mInfoGlobalId :: Int
                            , mInfoMimeType :: Maybe MimeType
-                           , mInfoExt      :: Maybe String
+                           , mInfoExt      :: Maybe T.Text
                            , mInfoCaption  :: Bool
                            } deriving (Show, Eq)
 
@@ -159,16 +159,20 @@ runP env st p = evalStateT (runReaderT p env) st
 
 --------------------------------------------------------------------
 
-monospaceFont :: Monad m => P m String
+findAttrText :: QName -> Element -> Maybe T.Text
+findAttrText n = fmap T.pack . findAttr n
+
+monospaceFont :: Monad m => P m T.Text
 monospaceFont = do
   vars <- writerVariables <$> asks envOpts
   case lookupContext "monofont" vars of
-    Just s -> return (T.unpack s)
+    Just s -> return s
     Nothing -> return "Courier"
 
+-- Kept as string for XML.Light
 fontSizeAttributes :: Monad m => RunProps -> P m [(String, String)]
 fontSizeAttributes RunProps { rPropForceSize = Just sz } =
-  return [("sz", (show $ sz * 100))]
+  return [("sz", show $ sz * 100)]
 fontSizeAttributes _ = return []
 
 copyFileToArchive :: PandocMonad m => Archive -> FilePath -> P m Archive
@@ -177,7 +181,8 @@ copyFileToArchive arch fp = do
   distArchive <- asks envDistArchive
   case findEntryByPath fp refArchive `mplus` findEntryByPath fp distArchive of
     Nothing -> throwError $ PandocSomeError
-                          $ fp ++ " missing in reference file"
+                          $ T.pack
+                          $ fp <> " missing in reference file"
     Just e -> return $ addEntryToArchive e arch
 
 alwaysInheritedPatterns :: [Pattern]
@@ -196,7 +201,7 @@ alwaysInheritedPatterns =
 
 -- We only look for these under special conditions
 contingentInheritedPatterns :: Presentation -> [Pattern]
-contingentInheritedPatterns pres = [] ++
+contingentInheritedPatterns pres = [] <>
   if presHasSpeakerNotes pres
   then map compile [ "ppt/notesMasters/notesMaster*.xml"
                    , "ppt/notesMasters/_rels/notesMaster*.xml.rels"
@@ -207,7 +212,7 @@ contingentInheritedPatterns pres = [] ++
 
 inheritedPatterns :: Presentation -> [Pattern]
 inheritedPatterns pres =
-  alwaysInheritedPatterns ++ contingentInheritedPatterns pres
+  alwaysInheritedPatterns <> contingentInheritedPatterns pres
 
 patternToFilePaths :: PandocMonad m => Pattern -> P m [FilePath]
 patternToFilePaths pat = do
@@ -248,8 +253,8 @@ presentationToArchiveP p@(Presentation docProps slides) = do
   unless (null missingFiles)
     (throwError $
       PandocSomeError $
-      "The following required files are missing:\n" ++
-      (unlines $ map ("  " ++) missingFiles)
+      "The following required files are missing:\n" <>
+      (T.unlines $ map (T.pack . ("  " <>)) missingFiles)
     )
 
   newArch' <- foldM copyFileToArchive emptyArchive filePaths
@@ -276,11 +281,11 @@ presentationToArchiveP p@(Presentation docProps slides) = do
   contentTypesEntry <- presentationToContentTypes p >>= contentTypesToEntry
   -- fold everything into our inherited archive and return it.
   return $ foldr addEntryToArchive newArch' $
-    slideEntries ++
-    slideRelEntries ++
-    spkNotesEntries ++
-    spkNotesRelEntries ++
-    mediaEntries ++
+    slideEntries <>
+    slideRelEntries <>
+    spkNotesEntries <>
+    spkNotesRelEntries <>
+    mediaEntries <>
     [contentTypesEntry, docPropsEntry, docCustomPropsEntry, relsEntry,
      presEntry, presRelsEntry, viewPropsEntry]
 
@@ -352,11 +357,11 @@ getLayout layout = do
   distArchive <- asks envDistArchive
   parseXml refArchive distArchive layoutpath
 
-shapeHasId :: NameSpaces -> String -> Element -> Bool
+shapeHasId :: NameSpaces -> T.Text -> Element -> Bool
 shapeHasId ns ident element
   | Just nvSpPr <- findChild (elemName ns "p" "nvSpPr") element
   , Just cNvPr <- findChild (elemName ns "p" "cNvPr") nvSpPr
-  , Just nm <- findAttr (QName "id" Nothing Nothing) cNvPr =
+  , Just nm <- findAttrText (QName "id" Nothing Nothing) cNvPr =
       nm == ident
   | otherwise = False
 
@@ -397,7 +402,7 @@ getShapeDimensions ns element
   | otherwise = Nothing
 
 
-getMasterShapeDimensionsById :: String
+getMasterShapeDimensionsById :: T.Text
                              -> Element
                              -> Maybe ((Integer, Integer), (Integer, Integer))
 getMasterShapeDimensionsById ident master = do
@@ -422,7 +427,7 @@ getContentShapeSize ns layout master
         Nothing -> do let mbSz =
                             findChild (elemName ns "p" "nvSpPr") sp >>=
                             findChild (elemName ns "p" "cNvPr") >>=
-                            findAttr (QName "id" Nothing Nothing) >>=
+                            findAttrText (QName "id" Nothing Nothing) >>=
                             flip getMasterShapeDimensionsById master
                       case mbSz of
                         Just sz' -> return sz'
@@ -436,7 +441,7 @@ getContentShapeSize _ _ _ = throwError $
 buildSpTree :: NameSpaces -> Element -> [Element] -> Element
 buildSpTree ns spTreeElem newShapes =
   emptySpTreeElem { elContent = newContent }
-  where newContent = elContent emptySpTreeElem ++ map Elem newShapes
+  where newContent = elContent emptySpTreeElem <> map Elem newShapes
         emptySpTreeElem = spTreeElem { elContent = filter fn (elContent spTreeElem) }
         fn :: Content -> Bool
         fn (Elem e) = isElem ns "p" "nvGrpSpPr" e ||
@@ -506,8 +511,8 @@ registerMedia fp caption = do
         [] -> 0
         ids -> maximum ids
 
-  (imgBytes, mbMt) <- P.fetchItem fp
-  let imgExt = (mbMt >>= extensionFromMimeType >>= (\x -> return $ '.':x))
+  (imgBytes, mbMt) <- P.fetchItem $ T.pack fp
+  let imgExt = (mbMt >>= extensionFromMimeType >>= (\x -> return $ "." <> x))
                <|>
                case imageType imgBytes of
                  Just Png  -> Just ".png"
@@ -546,11 +551,11 @@ registerMedia fp caption = do
 makeMediaEntry :: PandocMonad m => MediaInfo -> P m Entry
 makeMediaEntry mInfo = do
   epochtime <- (floor . utcTimeToPOSIXSeconds) <$> asks envUTCTime
-  (imgBytes, _) <- P.fetchItem (mInfoFilePath mInfo)
+  (imgBytes, _) <- P.fetchItem (T.pack $ mInfoFilePath mInfo)
   let ext = case mInfoExt mInfo of
               Just e -> e
               Nothing -> ""
-  let fp = "ppt/media/image" ++ (show $ mInfoGlobalId mInfo) ++ ext
+  let fp = "ppt/media/image" <> (show $ mInfoGlobalId mInfo) <> T.unpack ext
   return $ toEntry fp epochtime $ BL.fromStrict imgBytes
 
 makeMediaEntries :: PandocMonad m => P m [Entry]
@@ -642,7 +647,7 @@ createCaption contentShapeDimensions paraElements = do
   elements <- mapM paragraphToElement [para]
   let ((x, y), (cx, cy)) = contentShapeDimensions
   let txBody = mknode "p:txBody" [] $
-               [mknode "a:bodyPr" [] (), mknode "a:lstStyle" [] ()] ++ elements
+               [mknode "a:bodyPr" [] (), mknode "a:lstStyle" [] ()] <> elements
   return $
     mknode "p:sp" [] [ mknode "p:nvSpPr" []
                        [ mknode "p:cNvPr" [("id","1"), ("name","TextBox 3")] ()
@@ -675,7 +680,7 @@ makePicElements layout picProps mInfo alt = do
   (pageWidth, pageHeight) <- asks envPresentationSize
   -- hasHeader <- asks envSlideHasHeader
   let hasCaption = mInfoCaption mInfo
-  (imgBytes, _) <- P.fetchItem (mInfoFilePath mInfo)
+  (imgBytes, _) <- P.fetchItem (T.pack $ mInfoFilePath mInfo)
   let (pxX, pxY) = case imageSize opts imgBytes of
         Right sz -> sizeInPixels $ sz
         Left _   -> sizeInPixels $ def
@@ -707,14 +712,14 @@ makePicElements layout picProps mInfo alt = do
   cNvPr <- case picPropLink picProps of
     Just link -> do idNum <- registerLink link
                     return $ mknode "p:cNvPr" cNvPrAttr $
-                      mknode "a:hlinkClick" [("r:id", "rId" ++ show idNum)] ()
+                      mknode "a:hlinkClick" [("r:id", "rId" <> show idNum)] ()
     Nothing   -> return $ mknode "p:cNvPr" cNvPrAttr ()
   let nvPicPr  = mknode "p:nvPicPr" []
                  [ cNvPr
                  , cNvPicPr
                  , mknode "p:nvPr" [] ()]
   let blipFill = mknode "p:blipFill" []
-                 [ mknode "a:blip" [("r:embed", "rId" ++ (show $ mInfoLocalId mInfo))] ()
+                 [ mknode "a:blip" [("r:embed", "rId" <> (show $ mInfoLocalId mInfo))] ()
                  , mknode "a:stretch" [] $
                    mknode "a:fillRect" [] () ]
   let xfrm =    mknode "a:xfrm" []
@@ -746,23 +751,23 @@ paraElemToElements :: PandocMonad m => ParaElem -> P m [Element]
 paraElemToElements Break = return [mknode "a:br" [] ()]
 paraElemToElements (Run rpr s) = do
   sizeAttrs <- fontSizeAttributes rpr
-  let attrs = sizeAttrs ++
-        (if rPropBold rpr then [("b", "1")] else []) ++
-        (if rPropItalics rpr then [("i", "1")] else []) ++
-        (if rPropUnderline rpr then [("u", "sng")] else []) ++
+  let attrs = sizeAttrs <>
+        (if rPropBold rpr then [("b", "1")] else []) <>
+        (if rPropItalics rpr then [("i", "1")] else []) <>
+        (if rPropUnderline rpr then [("u", "sng")] else []) <>
         (case rStrikethrough rpr of
             Just NoStrike     -> [("strike", "noStrike")]
             Just SingleStrike -> [("strike", "sngStrike")]
             Just DoubleStrike -> [("strike", "dblStrike")]
-            Nothing -> []) ++
+            Nothing -> []) <>
         (case rBaseline rpr of
             Just n -> [("baseline", show n)]
-            Nothing -> []) ++
+            Nothing -> []) <>
         (case rCap rpr of
             Just NoCapitals -> [("cap", "none")]
             Just SmallCapitals -> [("cap", "small")]
             Just AllCapitals -> [("cap", "all")]
-            Nothing -> []) ++
+            Nothing -> []) <>
         []
   linkProps <- case rLink rpr of
                  Just link -> do
@@ -773,14 +778,14 @@ paraElemToElements (Run rpr s) = do
                    return $ case link of
                      InternalTarget _ ->
                        let linkAttrs =
-                             [ ("r:id", "rId" ++ show idNum)
+                             [ ("r:id", "rId" <> show idNum)
                              , ("action", "ppaction://hlinksldjump")
                              ]
                        in [mknode "a:hlinkClick" linkAttrs ()]
                      -- external
                      ExternalTarget _ ->
                        let linkAttrs =
-                             [ ("r:id", "rId" ++ show idNum)
+                             [ ("r:id", "rId" <> show idNum)
                              ]
                        in [mknode "a:hlinkClick" linkAttrs ()]
                  Nothing -> return []
@@ -794,11 +799,11 @@ paraElemToElements (Run rpr s) = do
                         Nothing -> []
   codeFont <- monospaceFont
   let codeContents = if rPropCode rpr
-                     then [mknode "a:latin" [("typeface", codeFont)] ()]
+                     then [mknode "a:latin" [("typeface", T.unpack codeFont)] ()]
                      else []
-  let propContents = linkProps ++ colorContents ++ codeContents
+  let propContents = linkProps <> colorContents <> codeContents
   return [mknode "a:r" [] [ mknode "a:rPr" attrs $ propContents
-                          , mknode "a:t" [] s
+                          , mknode "a:t" [] $ T.unpack s
                           ]]
 paraElemToElements (MathElem mathType texStr) = do
   res <- convertMath writeOMML mathType (unTeXString texStr)
@@ -839,29 +844,29 @@ surroundWithMathAlternate element =
 paragraphToElement :: PandocMonad m => Paragraph -> P m Element
 paragraphToElement par = do
   let
-    attrs = [("lvl", show $ pPropLevel $ paraProps par)] ++
+    attrs = [("lvl", show $ pPropLevel $ paraProps par)] <>
             (case pPropMarginLeft (paraProps par) of
                Just px -> [("marL", show $ pixelsToEmu px)]
                Nothing -> []
-            ) ++
+            ) <>
             (case pPropIndent (paraProps par) of
                Just px -> [("indent", show $ pixelsToEmu px)]
                Nothing -> []
-            ) ++
+            ) <>
             (case pPropAlign (paraProps par) of
                Just AlgnLeft -> [("algn", "l")]
                Just AlgnRight -> [("algn", "r")]
                Just AlgnCenter -> [("algn", "ctr")]
                Nothing -> []
             )
-    props = [] ++
+    props = [] <>
             (case pPropSpaceBefore $ paraProps par of
                Just px -> [mknode "a:spcBef" [] [
                               mknode "a:spcPts" [("val", show $ 100 * px)] ()
                               ]
                           ]
                Nothing -> []
-            ) ++
+            ) <>
             (case pPropBullet $ paraProps par of
                Just Bullet -> []
                Just (AutoNumbering attrs') ->
@@ -869,7 +874,7 @@ paragraphToElement par = do
                Nothing -> [mknode "a:buNone" [] ()]
             )
   paras <- concat <$> mapM paraElemToElements (paraElems par)
-  return $ mknode "a:p" [] $ [mknode "a:pPr" attrs props] ++ paras
+  return $ mknode "a:p" [] $ [mknode "a:pPr" attrs props] <> paras
 
 shapeToElement :: PandocMonad m => Element -> Shape -> P m Element
 shapeToElement layout (TextBox paras)
@@ -879,7 +884,7 @@ shapeToElement layout (TextBox paras)
       sp <- getContentShape ns spTree
       elements <- mapM paragraphToElement paras
       let txBody = mknode "p:txBody" [] $
-                   [mknode "a:bodyPr" [] (), mknode "a:lstStyle" [] ()] ++ elements
+                   [mknode "a:bodyPr" [] (), mknode "a:lstStyle" [] ()] <> elements
           emptySpPr = mknode "p:spPr" [] ()
       return $
         surroundWithMathAlternate $
@@ -933,19 +938,19 @@ graphicFrameToElements layout tbls caption = do
           [ mknode "a:off" [("x", show $ 12700 * x), ("y", show $ 12700 * y)] ()
           , mknode "a:ext" [("cx", show $ 12700 * cx), ("cy", show $ 12700 * cy)] ()
           ]
-        ] ++ elements
+        ] <> elements
 
   if (not $ null caption)
     then do capElt <- createCaption ((x, y), (cx, cytmp)) caption
             return [graphicFrameElts, capElt]
     else return [graphicFrameElts]
 
-getDefaultTableStyle :: PandocMonad m => P m (Maybe String)
+getDefaultTableStyle :: PandocMonad m => P m (Maybe T.Text)
 getDefaultTableStyle = do
   refArchive <- asks envRefArchive
   distArchive <- asks envDistArchive
   tblStyleLst <- parseXml refArchive distArchive "ppt/tableStyles.xml"
-  return $ findAttr (QName "def" Nothing Nothing) tblStyleLst
+  return $ findAttrText (QName "def" Nothing Nothing) tblStyleLst
 
 graphicToElement :: PandocMonad m => Integer -> Graphic -> P m Element
 graphicToElement tableWidth (Tbl tblPr hdrCells rows) = do
@@ -970,7 +975,7 @@ graphicToElement tableWidth (Tbl tblPr hdrCells rows) = do
              [mknode "a:txBody" [] $
                ([ mknode "a:bodyPr" [] ()
                 , mknode "a:lstStyle" [] ()]
-                 ++ elements')]
+                 <> elements')]
   headers' <- mapM cellToOpenXML hdrCells
   rows' <- mapM (mapM cellToOpenXML) rows
   let borderProps = mknode "a:tcPr" [] ()
@@ -978,7 +983,7 @@ graphicToElement tableWidth (Tbl tblPr hdrCells rows) = do
   let mkcell border contents = mknode "a:tc" []
                             $ (if null contents
                                then emptyCell
-                               else contents) ++ [ borderProps | border ]
+                               else contents) <> [ borderProps | border ]
   let mkrow border cells = mknode "a:tr" [("h", "0")] $ map (mkcell border) cells
 
   let mkgridcol w = mknode "a:gridCol"
@@ -991,7 +996,7 @@ graphicToElement tableWidth (Tbl tblPr hdrCells rows) = do
                  , ("bandRow", if tblPrBandRow tblPr then "1" else "0")
                  ] (case mbDefTblStyle of
                       Nothing -> []
-                      Just sty -> [mknode "a:tableStyleId" [] sty])
+                      Just sty -> [mknode "a:tableStyleId" [] $ T.unpack sty])
 
   return $ mknode "a:graphic" [] $
     [mknode "a:graphicData" [("uri", "http://schemas.openxmlformats.org/drawingml/2006/table")] $
@@ -1001,7 +1006,7 @@ graphicToElement tableWidth (Tbl tblPr hdrCells rows) = do
                                then []
                                else map mkgridcol colWidths)
       ]
-      ++ [ mkrow True headers' | hasHeader ] ++ map (mkrow False) rows'
+      <> [ mkrow True headers' | hasHeader ] <> map (mkrow False) rows'
      ]
     ]
 
@@ -1009,7 +1014,7 @@ graphicToElement tableWidth (Tbl tblPr hdrCells rows) = do
 -- We get the shape by placeholder type. If there is NO type, it
 -- defaults to a content placeholder.
 
-data PHType = PHType String | ObjType
+data PHType = PHType T.Text | ObjType
   deriving (Show, Eq)
 
 findPHType :: NameSpaces -> Element -> PHType -> Bool
@@ -1024,7 +1029,7 @@ findPHType ns spElem phType
         -- if it's a named PHType, we want to check that the attribute
         -- value matches.
         Just phElem | (PHType tp) <- phType ->
-                        case findAttr (QName "type" Nothing Nothing) phElem of
+                        case findAttrText (QName "type" Nothing Nothing) phElem of
                           Just tp' -> tp == tp'
                           Nothing -> False
         -- if it's an ObjType, we want to check that there is NO
@@ -1063,7 +1068,7 @@ nonBodyTextToElement layout phTypes paraElements
       let hdrPara = Paragraph def paraElements
       element <- paragraphToElement hdrPara
       let txBody = mknode "p:txBody" [] $
-                   [mknode "a:bodyPr" [] (), mknode "a:lstStyle" [] ()] ++
+                   [mknode "a:bodyPr" [] (), mknode "a:lstStyle" [] ()] <>
                    [element]
       return $ replaceNamedChildren ns "p" "txBody" [txBody] sp
   -- XXX: TODO
@@ -1081,7 +1086,7 @@ contentToElement layout hdrShape shapes
       contentElements <- local
                          (\env -> env {envContentType = NormalContent})
                          (shapesToElements layout shapes)
-      return $ buildSpTree ns spTree (hdrShapeElements ++ contentElements)
+      return $ buildSpTree ns spTree (hdrShapeElements <> contentElements)
 contentToElement _ _ _ = return $ mknode "p:sp" [] ()
 
 twoColumnToElement :: PandocMonad m => Element -> [ParaElem] -> [Shape] -> [Shape] -> P m Element
@@ -1101,7 +1106,7 @@ twoColumnToElement layout hdrShape shapesL shapesR
                           (shapesToElements layout shapesR)
       -- let contentElementsL' = map (setIdx ns "1") contentElementsL
       --     contentElementsR' = map (setIdx ns "2") contentElementsR
-      return $ buildSpTree ns spTree (hdrShapeElements ++ contentElementsL ++ contentElementsR)
+      return $ buildSpTree ns spTree (hdrShapeElements <> contentElementsL <> contentElementsR)
 twoColumnToElement _ _ _ _= return $ mknode "p:sp" [] ()
 
 
@@ -1133,7 +1138,7 @@ metadataToElement layout titleElems subtitleElems authorsElems dateElems
       dateShapeElements <- if null dateElems
                            then return []
                            else sequence [nonBodyTextToElement layout [PHType "dt"] dateElems]
-      return $ buildSpTree ns spTree (titleShapeElements ++ subtitleShapeElements ++ dateShapeElements)
+      return $ buildSpTree ns spTree (titleShapeElements <> subtitleShapeElements <> dateShapeElements)
 metadataToElement _ _ _ _ _ = return $ mknode "p:sp" [] ()
 
 slideToElement :: PandocMonad m => Slide -> P m Element
@@ -1186,7 +1191,7 @@ getNotesMaster = do
   distArchive <- asks envDistArchive
   parseXml refArchive distArchive "ppt/notesMasters/notesMaster1.xml"
 
-getSlideNumberFieldId :: PandocMonad m => Element -> P m String
+getSlideNumberFieldId :: PandocMonad m => Element -> P m T.Text
 getSlideNumberFieldId notesMaster
   | ns <- elemToNameSpaces notesMaster
   , Just cSld <- findChild (elemName ns "p" "cSld") notesMaster
@@ -1195,7 +1200,7 @@ getSlideNumberFieldId notesMaster
   , Just txBody <- findChild (elemName ns "p" "txBody") sp
   , Just p <- findChild (elemName ns "a" "p") txBody
   , Just fld <- findChild (elemName ns "a" "fld") p
-  , Just fldId <- findAttr (QName "id" Nothing Nothing) fld =
+  , Just fldId <- findAttrText (QName "id" Nothing Nothing) fld =
       return fldId
   | otherwise = throwError $
                 PandocSomeError $
@@ -1236,7 +1241,7 @@ speakerNotesBody :: PandocMonad m => [Paragraph] -> P m Element
 speakerNotesBody paras = do
   elements <- mapM paragraphToElement $ spaceParas $ map removeParaLinks paras
   let txBody = mknode "p:txBody" [] $
-               [mknode "a:bodyPr" [] (), mknode "a:lstStyle" [] ()] ++ elements
+               [mknode "a:bodyPr" [] (), mknode "a:lstStyle" [] ()] <> elements
   return $
     mknode "p:sp" [] $
     [ mknode "p:nvSpPr" [] $
@@ -1252,7 +1257,7 @@ speakerNotesBody paras = do
     , txBody
     ]
 
-speakerNotesSlideNumber :: Int -> String -> Element
+speakerNotesSlideNumber :: Int -> T.Text -> Element
 speakerNotesSlideNumber pgNum fieldId =
   mknode "p:sp" [] $
   [ mknode "p:nvSpPr" [] $
@@ -1273,7 +1278,7 @@ speakerNotesSlideNumber pgNum fieldId =
     [ mknode "a:bodyPr" [] ()
     , mknode "a:lstStyle" [] ()
     , mknode "a:p" [] $
-      [ mknode "a:fld" [ ("id", fieldId)
+      [ mknode "a:fld" [ ("id", T.unpack fieldId)
                        , ("type", "slidenum")
                        ]
         [ mknode "a:rPr" [("lang", "en-US")] ()
@@ -1329,24 +1334,24 @@ getSlideIdNum sldId = do
     Just n -> return n
     Nothing -> throwError $
                PandocShouldNeverHappenError $
-               "Slide Id " ++ (show sldId) ++ " not found."
+               "Slide Id " <> T.pack (show sldId) <> " not found."
 
 slideNum :: PandocMonad m => Slide -> P m Int
 slideNum slide = getSlideIdNum $ slideId slide
 
 idNumToFilePath :: Int -> FilePath
-idNumToFilePath idNum = "slide" ++ (show $ idNum) ++ ".xml"
+idNumToFilePath idNum = "slide" <> (show $ idNum) <> ".xml"
 
 slideToFilePath :: PandocMonad m => Slide -> P m FilePath
 slideToFilePath slide = do
   idNum <- slideNum slide
-  return $ "slide" ++ (show $ idNum) ++ ".xml"
+  return $ "slide" <> (show $ idNum) <> ".xml"
 
-slideToRelId :: PandocMonad m => Slide -> P m String
+slideToRelId :: PandocMonad m => Slide -> P m T.Text
 slideToRelId slide = do
   n <- slideNum slide
   offset <- asks envSlideIdOffset
-  return $ "rId" ++ (show $ n + offset)
+  return $ "rId" <> T.pack (show $ n + offset)
 
 
 data Relationship = Relationship { relId :: Int
@@ -1362,7 +1367,7 @@ elementToRel element
          num <- case reads numStr :: [(Int, String)] of
            (n, _) : _ -> Just n
            []         -> Nothing
-         type' <- findAttr (QName "Type" Nothing Nothing) element
+         type' <- findAttrText (QName "Type" Nothing Nothing) element
          target <- findAttr (QName "Target" Nothing Nothing) element
          return $ Relationship num type' target
   | otherwise = Nothing
@@ -1372,7 +1377,7 @@ slideToPresRel slide = do
   idNum <- slideNum slide
   n <- asks envSlideIdOffset
   let rId = idNum + n
-      fp = "slides/" ++ idNumToFilePath idNum
+      fp = "slides/" <> idNumToFilePath idNum
   return $ Relationship { relId = rId
                         , relType = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/slide"
                         , relTarget = fp
@@ -1397,7 +1402,7 @@ presentationToRels pres@(Presentation _ slides) = do
                            , relTarget = "notesMasters/notesMaster1.xml"
                            }]
         else []
-      insertedRels = mySlideRels ++ notesMasterRels
+      insertedRels = mySlideRels <> notesMasterRels
   rels <- getRels
   -- we remove the slide rels and the notesmaster (if it's
   -- there). We'll put these back in ourselves, if necessary.
@@ -1427,7 +1432,7 @@ presentationToRels pres@(Presentation _ slides) = do
 
       relsWeKeep' = map (\r -> r{relId = modifyRelNum $ relId r}) relsWeKeep
 
-  return $ insertedRels ++ relsWeKeep'
+  return $ insertedRels <> relsWeKeep'
 
 -- We make this ourselves, in case there's a thumbnail in the one from
 -- the template.
@@ -1455,8 +1460,8 @@ topLevelRelsEntry :: PandocMonad m => P m Entry
 topLevelRelsEntry = elemToEntry "_rels/.rels" $ relsToElement topLevelRels
 
 relToElement :: Relationship -> Element
-relToElement rel = mknode "Relationship" [ ("Id", "rId" ++ (show $ relId rel))
-                                         , ("Type", relType rel)
+relToElement rel = mknode "Relationship" [ ("Id", "rId" <> (show $ relId rel))
+                                         , ("Type", T.unpack $ relType rel)
                                          , ("Target", relTarget rel) ] ()
 
 relsToElement :: [Relationship] -> Element
@@ -1479,7 +1484,7 @@ slideToEntry slide = do
   idNum <- slideNum slide
   local (\env -> env{envCurSlideId = idNum}) $ do
     element <- slideToElement slide
-    elemToEntry ("ppt/slides/" ++ idNumToFilePath idNum) element
+    elemToEntry ("ppt/slides/" <> idNumToFilePath idNum) element
 
 slideToSpeakerNotesEntry :: PandocMonad m => Slide -> P m (Maybe Entry)
 slideToSpeakerNotesEntry slide = do
@@ -1492,7 +1497,7 @@ slideToSpeakerNotesEntry slide = do
       Just element | Just notesIdNum <- mbNotesIdNum ->
                        Just <$>
                        elemToEntry
-                       ("ppt/notesSlides/notesSlide" ++ show notesIdNum ++ ".xml")
+                       ("ppt/notesSlides/notesSlide" <> show notesIdNum <> ".xml")
                        element
       _ -> return Nothing
 
@@ -1505,7 +1510,7 @@ slideToSpeakerNotesRelElement slide@(Slide _ _ _) = do
     [("xmlns", "http://schemas.openxmlformats.org/package/2006/relationships")]
     [ mknode "Relationship" [ ("Id", "rId2")
                             , ("Type", "http://schemas.openxmlformats.org/officeDocument/2006/relationships/slide")
-                            , ("Target", "../slides/slide" ++ show idNum ++ ".xml")
+                            , ("Target", "../slides/slide" <> show idNum <> ".xml")
                             ] ()
     , mknode "Relationship" [ ("Id", "rId1")
                             , ("Type", "http://schemas.openxmlformats.org/officeDocument/2006/relationships/notesMaster")
@@ -1524,7 +1529,7 @@ slideToSpeakerNotesRelEntry slide = do
     Just element | Just notesIdNum <- mbNotesIdNum ->
       Just <$>
       elemToEntry
-      ("ppt/notesSlides/_rels/notesSlide" ++ show notesIdNum ++ ".xml.rels")
+      ("ppt/notesSlides/_rels/notesSlide" <> show notesIdNum <> ".xml.rels")
       element
     _ -> return Nothing
 
@@ -1532,21 +1537,21 @@ slideToSlideRelEntry :: PandocMonad m => Slide -> P m Entry
 slideToSlideRelEntry slide = do
   idNum <- slideNum slide
   element <- slideToSlideRelElement slide
-  elemToEntry ("ppt/slides/_rels/" ++ idNumToFilePath idNum ++ ".rels") element
+  elemToEntry ("ppt/slides/_rels/" <> idNumToFilePath idNum <> ".rels") element
 
 linkRelElement :: PandocMonad m => Int -> LinkTarget -> P m Element
 linkRelElement rIdNum (InternalTarget targetId) = do
   targetIdNum <- getSlideIdNum targetId
   return $
-    mknode "Relationship" [ ("Id", "rId" ++ show rIdNum)
+    mknode "Relationship" [ ("Id", "rId" <> show rIdNum)
                           , ("Type", "http://schemas.openxmlformats.org/officeDocument/2006/relationships/slide")
-                          , ("Target", "slide" ++ show targetIdNum ++ ".xml")
+                          , ("Target", "slide" <> show targetIdNum <> ".xml")
                           ] ()
 linkRelElement rIdNum (ExternalTarget (url, _)) = do
   return $
-    mknode "Relationship" [ ("Id", "rId" ++ show rIdNum)
+    mknode "Relationship" [ ("Id", "rId" <> show rIdNum)
                           , ("Type", "http://schemas.openxmlformats.org/officeDocument/2006/relationships/hyperlink")
-                          , ("Target", url)
+                          , ("Target", T.unpack url)
                           , ("TargetMode", "External")
                           ] ()
 
@@ -1559,9 +1564,9 @@ mediaRelElement mInfo =
               Just e -> e
               Nothing -> ""
   in
-    mknode "Relationship" [ ("Id", "rId" ++ (show $ mInfoLocalId mInfo))
+    mknode "Relationship" [ ("Id", "rId" <> (show $ mInfoLocalId mInfo))
                           , ("Type", "http://schemas.openxmlformats.org/officeDocument/2006/relationships/image")
-                          , ("Target", "../media/image" ++ (show $ mInfoGlobalId mInfo) ++ ext)
+                          , ("Target", "../media/image" <> (show $ mInfoGlobalId mInfo) <> T.unpack ext)
                           ] ()
 
 speakerNotesSlideRelElement :: PandocMonad m => Slide -> P m (Maybe Element)
@@ -1571,7 +1576,7 @@ speakerNotesSlideRelElement slide = do
   return $ case M.lookup idNum mp of
     Nothing -> Nothing
     Just n ->
-      let target = "../notesSlides/notesSlide" ++ show n ++ ".xml"
+      let target = "../notesSlides/notesSlide" <> show n <> ".xml"
       in Just $
          mknode "Relationship" [ ("Id", "rId2")
                                , ("Type", "http://schemas.openxmlformats.org/officeDocument/2006/relationships/notesSlide")
@@ -1605,14 +1610,14 @@ slideToSlideRelElement slide = do
     ([mknode "Relationship" [ ("Id", "rId1")
                            , ("Type", "http://schemas.openxmlformats.org/officeDocument/2006/relationships/slideLayout")
                            , ("Target", target)] ()
-    ] ++ speakerNotesRels ++ linkRels ++ mediaRels)
+    ] <> speakerNotesRels <> linkRels <> mediaRels)
 
 slideToSldIdElement :: PandocMonad m => Slide -> P m Element
 slideToSldIdElement slide = do
   n <- slideNum slide
   let id' = show $ n + 255
   rId <- slideToRelId slide
-  return $ mknode "p:sldId" [("id", id'), ("r:id", rId)] ()
+  return $ mknode "p:sldId" [("id", id'), ("r:id", T.unpack rId)] ()
 
 presentationToSldIdLst :: PandocMonad m => Presentation -> P m Element
 presentationToSldIdLst (Presentation _ slides) = do
@@ -1637,7 +1642,7 @@ presentationToPresentationElement pres@(Presentation _ slds) = do
       notesMasterElem =  mknode "p:notesMasterIdLst" []
                          [ mknode
                            "p:NotesMasterId"
-                           [("r:id", "rId" ++ show notesMasterRId)]
+                           [("r:id", "rId" <> show notesMasterRId)]
                            ()
                          ]
 
@@ -1683,7 +1688,7 @@ docPropsElement :: PandocMonad m => DocProps -> P m Element
 docPropsElement docProps = do
   utctime <- asks envUTCTime
   let keywords = case dcKeywords docProps of
-        Just xs -> intercalate ", " xs
+        Just xs -> T.intercalate ", " xs
         Nothing -> ""
   return $
     mknode "cp:coreProperties"
@@ -1692,16 +1697,16 @@ docPropsElement docProps = do
     ,("xmlns:dcterms","http://purl.org/dc/terms/")
     ,("xmlns:dcmitype","http://purl.org/dc/dcmitype/")
     ,("xmlns:xsi","http://www.w3.org/2001/XMLSchema-instance")]
-    $ (mknode "dc:title" [] $ fromMaybe "" $ dcTitle docProps)
-    : (mknode "dc:creator" [] $ fromMaybe "" $ dcCreator docProps)
-    : (mknode "cp:keywords" [] keywords)
+    $ (mknode "dc:title" [] $ maybe "" T.unpack $ dcTitle docProps)
+    : (mknode "dc:creator" [] $ maybe "" T.unpack $ dcCreator docProps)
+    : (mknode "cp:keywords" [] $ T.unpack keywords)
     : (if isNothing (dcSubject docProps) then [] else
-           [mknode "dc:subject" [] $ fromMaybe "" $ dcSubject docProps])
-    ++ (if isNothing (dcDescription docProps) then [] else
-           [mknode "dc:description" [] $ fromMaybe "" $ dcDescription docProps])
-    ++ (if isNothing (cpCategory docProps) then [] else
-           [mknode "cp:category" [] $ fromMaybe "" $ cpCategory docProps])
-    ++ (\x -> [ mknode "dcterms:created" [("xsi:type","dcterms:W3CDTF")] x
+           [mknode "dc:subject" [] $ maybe "" T.unpack $ dcSubject docProps])
+    <> (if isNothing (dcDescription docProps) then [] else
+           [mknode "dc:description" [] $ maybe "" T.unpack $ dcDescription docProps])
+    <> (if isNothing (cpCategory docProps) then [] else
+           [mknode "cp:category" [] $ maybe "" T.unpack $ cpCategory docProps])
+    <> (\x -> [ mknode "dcterms:created" [("xsi:type","dcterms:W3CDTF")] x
              , mknode "dcterms:modified" [("xsi:type","dcterms:W3CDTF")] x
              ]) (formatTime defaultTimeLocale "%FT%XZ" utctime)
 
@@ -1715,7 +1720,7 @@ docCustomPropsElement docProps = do
   let mkCustomProp (k, v) pid = mknode "property"
          [("fmtid","{D5CDD505-2E9C-101B-9397-08002B2CF9AE}")
          ,("pid", show pid)
-         ,("name", k)] $ mknode "vt:lpwstr" [] v
+         ,("name", T.unpack k)] $ mknode "vt:lpwstr" [] (T.unpack v)
   return $ mknode "Properties"
           [("xmlns","http://schemas.openxmlformats.org/officeDocument/2006/custom-properties")
           ,("xmlns:vt","http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes")
@@ -1745,15 +1750,15 @@ makeViewPropsEntry = viewPropsElement >>= elemToEntry "ppt/viewProps.xml"
 defaultContentTypeToElem :: DefaultContentType -> Element
 defaultContentTypeToElem dct =
   mknode "Default"
-  [("Extension", defContentTypesExt dct),
-    ("ContentType", defContentTypesType dct)]
+  [("Extension", T.unpack $ defContentTypesExt dct),
+    ("ContentType", T.unpack $ defContentTypesType dct)]
   ()
 
 overrideContentTypeToElem :: OverrideContentType -> Element
 overrideContentTypeToElem oct =
   mknode "Override"
   [("PartName", overrideContentTypesPart oct),
-    ("ContentType", overrideContentTypesType oct)]
+    ("ContentType", T.unpack $ overrideContentTypesType oct)]
   ()
 
 contentTypesToElement :: ContentTypes -> Element
@@ -1761,11 +1766,11 @@ contentTypesToElement ct =
   let ns = "http://schemas.openxmlformats.org/package/2006/content-types"
   in
     mknode "Types" [("xmlns", ns)] $
-    (map defaultContentTypeToElem $ contentTypesDefaults ct) ++
+    (map defaultContentTypeToElem $ contentTypesDefaults ct) <>
     (map overrideContentTypeToElem $ contentTypesOverrides ct)
 
 data DefaultContentType = DefaultContentType
-                           { defContentTypesExt :: String
+                           { defContentTypesExt :: T.Text
                            , defContentTypesType:: MimeType
                            }
                          deriving (Show, Eq)
@@ -1785,12 +1790,12 @@ contentTypesToEntry :: PandocMonad m => ContentTypes -> P m Entry
 contentTypesToEntry ct = elemToEntry "[Content_Types].xml" $ contentTypesToElement ct
 
 pathToOverride :: FilePath -> Maybe OverrideContentType
-pathToOverride fp = OverrideContentType ("/" ++ fp) <$> (getContentType fp)
+pathToOverride fp = OverrideContentType ("/" <> fp) <$> (getContentType fp)
 
 mediaFileContentType :: FilePath -> Maybe DefaultContentType
 mediaFileContentType fp = case takeExtension fp of
   '.' : ext -> Just $
-               DefaultContentType { defContentTypesExt = ext
+               DefaultContentType { defContentTypesExt = T.pack ext
                                   , defContentTypesType =
                                       case getMimeType fp of
                                         Just mt -> mt
@@ -1800,7 +1805,8 @@ mediaFileContentType fp = case takeExtension fp of
 
 mediaContentType :: MediaInfo -> Maybe DefaultContentType
 mediaContentType mInfo
-  | Just ('.' : ext) <- mInfoExt mInfo =
+  | Just t <- mInfoExt mInfo
+  , Just ('.', ext) <- T.uncons t =
       Just $ DefaultContentType { defContentTypesExt = ext
                                 , defContentTypesType =
                                     case mInfoMimeType mInfo of
@@ -1813,7 +1819,7 @@ getSpeakerNotesFilePaths :: PandocMonad m => P m [FilePath]
 getSpeakerNotesFilePaths = do
   mp <- asks envSpeakerNotesIdMap
   let notesIdNums = M.elems mp
-  return $ map (\n -> "ppt/notesSlides/notesSlide" ++ show n ++ ".xml") notesIdNums
+  return $ map (\n -> "ppt/notesSlides/notesSlide" <> show n <> ".xml") notesIdNums
 
 presentationToContentTypes :: PandocMonad m => Presentation -> P m ContentTypes
 presentationToContentTypes p@(Presentation _ slides) = do
@@ -1824,7 +1830,7 @@ presentationToContentTypes p@(Presentation _ slides) = do
                  , DefaultContentType "rels" "application/vnd.openxmlformats-package.relationships+xml"
                  ]
       mediaDefaults = nub $
-                      (mapMaybe mediaContentType $ mediaInfos) ++
+                      (mapMaybe mediaContentType $ mediaInfos) <>
                       (mapMaybe mediaFileContentType $ mediaFps)
 
       inheritedOverrides = mapMaybe pathToOverride filePaths
@@ -1835,55 +1841,56 @@ presentationToContentTypes p@(Presentation _ slides) = do
                                                  ]
   relativePaths <- mapM slideToFilePath slides
   let slideOverrides = mapMaybe
-                       (\fp -> pathToOverride $ "ppt/slides/" ++ fp)
+                       (\fp -> pathToOverride $ "ppt/slides/" <> fp)
                        relativePaths
   speakerNotesOverrides <- (mapMaybe pathToOverride) <$> getSpeakerNotesFilePaths
   return $ ContentTypes
-    (defaults ++ mediaDefaults)
-    (inheritedOverrides ++ createdOverrides ++ slideOverrides ++ speakerNotesOverrides)
+    (defaults <> mediaDefaults)
+    (inheritedOverrides <> createdOverrides <> slideOverrides <> speakerNotesOverrides)
 
-presML :: String
+presML :: T.Text
 presML = "application/vnd.openxmlformats-officedocument.presentationml"
 
-noPresML :: String
+noPresML :: T.Text
 noPresML = "application/vnd.openxmlformats-officedocument"
 
 getContentType :: FilePath -> Maybe MimeType
 getContentType fp
-  | fp == "ppt/presentation.xml" = Just $ presML ++ ".presentation.main+xml"
-  | fp == "ppt/presProps.xml" = Just $ presML ++ ".presProps+xml"
-  | fp == "ppt/viewProps.xml" = Just $ presML ++ ".viewProps+xml"
-  | fp == "ppt/tableStyles.xml" = Just $ presML ++ ".tableStyles+xml"
+  | fp == "ppt/presentation.xml" = Just $ presML <> ".presentation.main+xml"
+  | fp == "ppt/presProps.xml" = Just $ presML <> ".presProps+xml"
+  | fp == "ppt/viewProps.xml" = Just $ presML <> ".viewProps+xml"
+  | fp == "ppt/tableStyles.xml" = Just $ presML <> ".tableStyles+xml"
   | fp == "docProps/core.xml" = Just $ "application/vnd.openxmlformats-package.core-properties+xml"
   | fp == "docProps/custom.xml" = Just $ "application/vnd.openxmlformats-officedocument.custom-properties+xml"
-  | fp == "docProps/app.xml" = Just $ noPresML ++ ".extended-properties+xml"
+  | fp == "docProps/app.xml" = Just $ noPresML <> ".extended-properties+xml"
   | "ppt" : "slideMasters" : f : [] <- splitDirectories fp
   , (_, ".xml") <- splitExtension f =
-      Just $ presML ++ ".slideMaster+xml"
+      Just $ presML <> ".slideMaster+xml"
   | "ppt" : "slides" : f : [] <- splitDirectories fp
   , (_, ".xml") <- splitExtension f =
-      Just $ presML ++ ".slide+xml"
+      Just $ presML <> ".slide+xml"
   | "ppt" : "notesMasters"  : f : [] <- splitDirectories fp
   , (_, ".xml") <- splitExtension f =
-      Just $ presML ++ ".notesMaster+xml"
+      Just $ presML <> ".notesMaster+xml"
   | "ppt" : "notesSlides"  : f : [] <- splitDirectories fp
   , (_, ".xml") <- splitExtension f =
-      Just $ presML ++ ".notesSlide+xml"
+      Just $ presML <> ".notesSlide+xml"
   | "ppt" : "theme" : f : [] <- splitDirectories fp
   , (_, ".xml") <- splitExtension f =
-      Just $ noPresML ++ ".theme+xml"
+      Just $ noPresML <> ".theme+xml"
   | "ppt" : "slideLayouts" : _ : [] <- splitDirectories fp=
-      Just $ presML ++ ".slideLayout+xml"
+      Just $ presML <> ".slideLayout+xml"
   | otherwise = Nothing
 
+-- Kept as String for XML.Light
 autoNumAttrs :: ListAttributes -> [(String, String)]
 autoNumAttrs (startNum, numStyle, numDelim) =
-  numAttr ++ typeAttr
+  numAttr <> typeAttr
   where
     numAttr = if startNum == 1
               then []
               else [("startAt", show startNum)]
-    typeAttr = [("type", typeString ++ delimString)]
+    typeAttr = [("type", typeString <> delimString)]
     typeString = case numStyle of
       Decimal -> "arabic"
       UpperAlpha -> "alphaUc"
diff --git a/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs b/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs
index 8667c79f4..75ce0dd4e 100644
--- a/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs
+++ b/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs
@@ -1,5 +1,7 @@
 {-# LANGUAGE NoImplicitPrelude          #-}
+{-# LANGUAGE OverloadedStrings          #-}
 {-# LANGUAGE PatternGuards              #-}
+{-# LANGUAGE ViewPatterns               #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {- |
    Module      : Text.Pandoc.Writers.Powerpoint.Presentation
@@ -54,6 +56,7 @@ import Text.Pandoc.Logging
 import Text.Pandoc.Walk
 import Data.Time (UTCTime)
 import qualified Text.Pandoc.Shared as Shared -- so we don't overlap "Element"
+import Text.Pandoc.Shared (tshow)
 import Text.Pandoc.Writers.Shared (lookupMetaInlines, lookupMetaBlocks
                                  , lookupMetaString, toTableOfContents)
 import qualified Data.Map as M
@@ -93,7 +96,7 @@ instance Default WriterEnv where
 
 data WriterState = WriterState { stNoteIds :: M.Map Int [Block]
                                -- associate anchors with slide id
-                               , stAnchorMap :: M.Map String SlideId
+                               , stAnchorMap :: M.Map T.Text SlideId
                                , stSlideIdSet :: S.Set SlideId
                                , stLog :: [LogMessage]
                                , stSpeakerNotes :: SpeakerNotes
@@ -123,17 +126,17 @@ reservedSlideIds = S.fromList [ metadataSlideId
                               , endNotesSlideId
                               ]
 
-uniqueSlideId' :: Integer -> S.Set SlideId -> String -> SlideId
+uniqueSlideId' :: Integer -> S.Set SlideId -> T.Text -> SlideId
 uniqueSlideId' n idSet s =
-  let s' = if n == 0 then s else s ++ "-" ++ show n
+  let s' = if n == 0 then s else s <> "-" <> tshow n
   in if SlideId s' `S.member` idSet
      then uniqueSlideId' (n+1) idSet s
      else SlideId s'
 
-uniqueSlideId :: S.Set SlideId -> String -> SlideId
+uniqueSlideId :: S.Set SlideId -> T.Text -> SlideId
 uniqueSlideId = uniqueSlideId' 0
 
-runUniqueSlideId :: String -> Pres SlideId
+runUniqueSlideId :: T.Text -> Pres SlideId
 runUniqueSlideId s = do
   idSet <- gets stSlideIdSet
   let sldId = uniqueSlideId idSet s
@@ -159,14 +162,14 @@ type Pixels = Integer
 data Presentation = Presentation DocProps [Slide]
   deriving (Show)
 
-data DocProps = DocProps { dcTitle :: Maybe String
-                         , dcSubject :: Maybe String
-                         , dcCreator :: Maybe String
-                         , dcKeywords :: Maybe [String]
-                         , dcDescription :: Maybe String
-                         , cpCategory :: Maybe String
+data DocProps = DocProps { dcTitle :: Maybe T.Text
+                         , dcSubject :: Maybe T.Text
+                         , dcCreator :: Maybe T.Text
+                         , dcKeywords :: Maybe [T.Text]
+                         , dcDescription :: Maybe T.Text
+                         , cpCategory :: Maybe T.Text
                          , dcCreated :: Maybe UTCTime
-                         , customProperties :: Maybe [(String, String)]
+                         , customProperties :: Maybe [(T.Text, T.Text)]
                          } deriving (Show, Eq)
 
 
@@ -175,7 +178,7 @@ data Slide = Slide { slideId :: SlideId
                    , slideSpeakerNotes :: SpeakerNotes
                    } deriving (Show, Eq)
 
-newtype SlideId = SlideId String
+newtype SlideId = SlideId T.Text
   deriving (Show, Eq, Ord)
 
 -- In theory you could have anything on a notes slide but it seems
@@ -197,7 +200,7 @@ data Layout = MetadataSlide [ParaElem] [ParaElem] [[ParaElem]] [ParaElem]
 data Shape = Pic PicProps FilePath [ParaElem]
            | GraphicFrame [Graphic] [ParaElem]
            | TextBox [Paragraph]
-           | RawOOXMLShape String
+           | RawOOXMLShape T.Text
   deriving (Show, Eq)
 
 type Cell = [Paragraph]
@@ -240,17 +243,17 @@ instance Default ParaProps where
                   , pPropIndent = Just 0
                   }
 
-newtype TeXString = TeXString {unTeXString :: String}
+newtype TeXString = TeXString {unTeXString :: T.Text}
   deriving (Eq, Show)
 
 data ParaElem = Break
-              | Run RunProps String
+              | Run RunProps T.Text
               -- It would be more elegant to have native TeXMath
               -- Expressions here, but this allows us to use
               -- `convertmath` from T.P.Writers.Math. Will perhaps
               -- revisit in the future.
               | MathElem MathType TeXString
-              | RawOOXMLParaElem String
+              | RawOOXMLParaElem T.Text
               deriving (Show, Eq)
 
 data Strikethrough = NoStrike | SingleStrike | DoubleStrike
@@ -259,9 +262,9 @@ data Strikethrough = NoStrike | SingleStrike | DoubleStrike
 data Capitals = NoCapitals | SmallCapitals | AllCapitals
   deriving (Show, Eq)
 
-type URL = String
+type URL = T.Text
 
-data LinkTarget = ExternalTarget (URL, String)
+data LinkTarget = ExternalTarget (URL, T.Text)
                 | InternalTarget SlideId
                 deriving (Show, Eq)
 
@@ -360,7 +363,7 @@ inlineToParElems (Note blks) = do
         curNoteId = maxNoteId + 1
     modify $ \st -> st { stNoteIds = M.insert curNoteId blks notes }
     local (\env -> env{envRunProps = (envRunProps env){rLink = Just $ InternalTarget endNotesSlideId}}) $
-      inlineToParElems $ Superscript [Str $ show curNoteId]
+      inlineToParElems $ Superscript [Str $ tshow curNoteId]
 inlineToParElems (Span (_, ["underline"], _) ils) =
   local (\r -> r{envRunProps = (envRunProps r){rPropUnderline=True}}) $
   inlinesToParElems ils
@@ -389,11 +392,11 @@ isListType (BulletList _) = True
 isListType (DefinitionList _) = True
 isListType _ = False
 
-registerAnchorId :: String -> Pres ()
+registerAnchorId :: T.Text -> Pres ()
 registerAnchorId anchor = do
   anchorMap <- gets stAnchorMap
   sldId <- asks envCurSlideId
-  unless (null anchor) $
+  unless (T.null anchor) $
     modify $ \st -> st {stAnchorMap = M.insert anchor sldId anchorMap}
 
 -- Currently hardcoded, until I figure out how to make it dynamic.
@@ -531,11 +534,11 @@ withAttr _ sp = sp
 blockToShape :: Block -> Pres Shape
 blockToShape (Plain ils) = blockToShape (Para ils)
 blockToShape (Para (il:_))  | Image attr ils (url, _) <- il =
-      (withAttr attr . Pic def url) <$> inlinesToParElems ils
+      (withAttr attr . Pic def (T.unpack url)) <$> inlinesToParElems ils
 blockToShape (Para (il:_))  | Link _ (il':_) target <- il
                             , Image attr ils (url, _) <- il' =
-      (withAttr attr . Pic def{picPropLink = Just $ ExternalTarget target} url) <$>
-      inlinesToParElems ils
+      (withAttr attr . Pic def{picPropLink = Just $ ExternalTarget target} (T.unpack url))
+      <$> inlinesToParElems ils
 blockToShape (Table caption algn _ hdrCells rows) = do
   caption' <- inlinesToParElems caption
   hdrCells' <- rowToParagraphs algn hdrCells
@@ -711,7 +714,7 @@ blocksToSlide blks = do
 
 makeNoteEntry :: Int -> [Block] -> [Block]
 makeNoteEntry n blks =
-  let enum = Str (show n ++ ".")
+  let enum = Str (tshow n <> ".")
   in
     case blks of
       (Para ils : blks') -> (Para $ enum : Space : ils) : blks'
@@ -786,7 +789,7 @@ combineParaElems' (Just pElem') (pElem : pElems)
   | Run rPr' s' <- pElem'
   , Run rPr s <- pElem
   , rPr == rPr' =
-    combineParaElems' (Just $ Run rPr' $ s' ++ s) pElems
+    combineParaElems' (Just $ Run rPr' $ s' <> s) pElems
   | otherwise =
     pElem' : combineParaElems' (Just pElem) pElems
 
@@ -831,7 +834,8 @@ applyToSlide f slide = do
 
 replaceAnchor :: ParaElem -> Pres ParaElem
 replaceAnchor (Run rProps s)
-  | Just (ExternalTarget ('#':anchor, _)) <- rLink rProps = do
+  | Just (ExternalTarget (T.uncons -> Just ('#', anchor), _)) <- rLink rProps
+  = do
       anchorMap <- gets stAnchorMap
       -- If the anchor is not in the anchormap, we just remove the
       -- link.
@@ -843,9 +847,9 @@ replaceAnchor pe = return pe
 
 emptyParaElem :: ParaElem -> Bool
 emptyParaElem (Run _ s) =
-  null $ Shared.trim s
+  T.null $ Shared.trim s
 emptyParaElem (MathElem _ ts) =
-  null $ Shared.trim $ unTeXString ts
+  T.null $ Shared.trim $ unTeXString ts
 emptyParaElem _ = False
 
 emptyParagraph :: Paragraph -> Bool
@@ -900,7 +904,7 @@ blocksToPresentationSlides blks = do
   -- slide later
   blksLst <- splitBlocks blks'
   bodySlideIds <- mapM
-                  (\n -> runUniqueSlideId $ "BodySlide" ++ show n)
+                  (\n -> runUniqueSlideId $ "BodySlide" <> tshow n)
                   (take (length blksLst) [1..] :: [Integer])
   bodyslides <- mapM
                 (\(bs, ident) ->
@@ -935,11 +939,11 @@ metaToDocProps meta =
 
       authors = case map Shared.stringify $ docAuthors meta of
                   [] -> Nothing
-                  ss -> Just $ intercalate "; " ss
+                  ss -> Just $ T.intercalate "; " ss
 
       description = case map Shared.stringify $ lookupMetaBlocks "description" meta of
                   [] -> Nothing
-                  ss -> Just $ intercalate "_x000d_\n" ss
+                  ss -> Just $ T.intercalate "_x000d_\n" ss
 
       customProperties' = case [(k, lookupMetaString k meta) | k <- M.keys (unMeta meta)
                                , k `notElem` (["title", "author", "keywords", "description"
@@ -987,7 +991,7 @@ formatToken sty (tokType, txt) =
         Just tokSty -> applyTokStyToRunProps tokSty rProps
         Nothing     -> rProps
   in
-    Run rProps' $ T.unpack txt
+    Run rProps' txt
 
 formatSourceLine :: Style -> FormatOptions -> SourceLine -> [ParaElem]
 formatSourceLine sty _ srcLn = map (formatToken sty) srcLn