LaTeX template: define commands for zero width non-joiner character

Closes: #6639

The zero-width non-joiner character is used to avoid ligatures (e.g. in
German).

data/templates/default.latex

@@ -156,6 +156,25 @@ $if(CJKmainfont)$
   \fi
 $endif$
 \fi
+$if(zero-width-non-joiner)$
+%% Support for zero-width non-joiner characters.
+\makeatletter
+\def\zerowidthnonjoiner{%
+  % Prevent ligatures and adjust kerning, but still support hyphenating.
+  \texorpdfstring{%
+    \textormath{\nobreak\discretionary{-}{}{\kern.03em}%
+      \ifvmode\else\nobreak\hskip\z@skip\fi}{}%
+  }{}%
+}
+\makeatother
+\ifPDFTeX
+  \DeclareUnicodeCharacter{200C}{\zerowidthnonjoiner}
+\else
+  \catcode`^^^^200c=\active
+  \protected\def ^^^^200c{\zerowidthnonjoiner}
+\fi
+%% End of ZWNJ support
+$endif$
 $if(beamer)$
 $if(theme)$
 \usetheme[$for(themeoptions)$$themeoptions$$sep$,$endfor$]{$theme$}

src/Text/Pandoc/Writers/LaTeX.hs

@@ -173,6 +173,7 @@ pandocToLaTeX options (Pandoc meta blocks) = do
                   defField "has-chapters" (stHasChapters st) $
                   defField "has-frontmatter" (documentClass `elem` frontmatterClasses) $
                   defField "listings" (writerListings options || stLHS st) $
+                  defField "zero-width-non-joiner" (stZwnj st) $
                   defField "beamer" beamer $
                   (if stHighlighting st
                       then case writerHighlightStyle options of
@@ -1048,5 +1049,3 @@ extractInline _ _               = []
 -- Look up a key in an attribute and give a list of its values
 lookKey :: Text -> Attr -> [Text]
 lookKey key (_,_,kvs) =  maybe [] T.words $ lookup key kvs
-
-

src/Text/Pandoc/Writers/LaTeX/Types.hs

@@ -40,7 +40,7 @@ data WriterState =
   , stCsquotes      :: Bool          -- ^ true if document uses csquotes
   , stHighlighting  :: Bool          -- ^ true if document has highlighted code
   , stIncremental   :: Bool          -- ^ true if beamer lists should be
-                                     --   displayed bit by bit
+  , stZwnj          :: Bool          -- ^ true if document has a ZWNJ character
   , stInternalLinks :: [Text]        -- ^ list of internal link targets
   , stBeamer        :: Bool          -- ^ produce beamer
   , stEmptyLine     :: Bool          -- ^ true if no content on line
@@ -74,6 +74,7 @@ startingState options =
   , stCsquotes = False
   , stHighlighting = False
   , stIncremental = writerIncremental options
+  , stZwnj = False
   , stInternalLinks = []
   , stBeamer = False
   , stEmptyLine = True

src/Text/Pandoc/Writers/LaTeX/Util.hs

@@ -22,6 +22,7 @@ module Text.Pandoc.Writers.LaTeX.Util (
 where
 
 import Control.Applicative ((<|>))
+import Control.Monad (when)
 import Text.Pandoc.Class (PandocMonad, toLang)
 import Text.Pandoc.Options (WriterOptions(..), isEnabled)
 import Text.Pandoc.Writers.LaTeX.Types (LW, WriterState(..))
@@ -30,7 +31,7 @@ import Text.Pandoc.Highlighting (toListingsLanguage)
 import Text.DocLayout
 import Text.Pandoc.Definition
 import Text.Pandoc.ImageSize (showFl)
-import Control.Monad.State.Strict (gets)
+import Control.Monad.State.Strict (gets, modify)
 import Data.Text (Text)
 import qualified Data.Text as T
 import Text.Pandoc.Extensions (Extension(Ext_smart))
@@ -49,6 +50,8 @@ data StringContext = TextString
 stringToLaTeX :: PandocMonad m => StringContext -> Text -> LW m Text
 stringToLaTeX context zs = do
   opts <- gets stOptions
+  when ('\x200c' `elemText` zs) $
+    modify (\s -> s { stZwnj = True })
   return $ T.pack $
     foldr (go opts context) mempty $ T.unpack $
     if writerPreferAscii opts
@@ -270,5 +273,3 @@ mbBraced :: Text -> Text
 mbBraced x = if not (T.all isAlphaNum x)
                 then "{" <> x <> "}"
                 else x
-
-