LaTeX writer: include cancel package only if needed.

That is, only if there is math that contains `\cancel`,
`\bcancel`, or `\xcancel`.

2 files changed, 27 insertions, 0 deletions

diff --git a/src/Text/Pandoc/Writers/LaTeX.hs b/src/Text/Pandoc/Writers/LaTeX.hs
index 2c71e689a..fe549ad17 100644
--- a/src/Text/Pandoc/Writers/LaTeX.hs
+++ b/src/Text/Pandoc/Writers/LaTeX.hs
@@ -65,8 +65,11 @@ import Text.Pandoc.Writers.LaTeX.Util (stringToLaTeX, StringContext(..),
                                        wrapDiv, hypertarget, labelFor,
                                        getListingsLanguage, mbBraced)
 import Text.Pandoc.Writers.Shared
+import qualified Data.Attoparsec.Text as A
 import qualified Text.Pandoc.UTF8 as UTF8
 import qualified Text.Pandoc.Writers.AnnotatedTable as Ann
+import Data.Char (isLetter)
+import Control.Applicative ((<|>))
 
 -- Work around problems with notes inside emphasis (see #8982)
 isolateBigNotes :: ([Inline] -> Inline) -> [Inline] -> [Inline]
@@ -229,6 +232,7 @@ pandocToLaTeX options (Pandoc meta blocks) = do
                   defField "verbatim-in-note" (stVerbInNote st) $
                   defField "tables" (stTable st) $
                   defField "multirow" (stMultiRow st) $
+                  defField "cancel" (stCancel st) $
                   defField "strikeout" (stStrikeout st) $
                   defField "url" (stUrl st) $
                   defField "numbersections" (writerNumberSections options) $
@@ -1029,11 +1033,13 @@ inlineToLaTeX (Str str) = do
 inlineToLaTeX (Math _ str)
   | isMathEnv str -- see #9711
   = do setEmptyLine False
+       when (needsCancel str) $ modify $ \st -> st{ stCancel = True }
        pure $ literal str
 inlineToLaTeX (Math InlineMath str) = do
   setEmptyLine False
   inSoul <- gets stInSoulCommand
   let contents = literal (handleMathComment str)
+  when (needsCancel str) $ modify $ \st -> st{ stCancel = True }
   return $
     if inSoul -- #9597
        then "$" <> contents <> "$"
@@ -1042,6 +1048,7 @@ inlineToLaTeX (Math DisplayMath str) = do
   setEmptyLine False
   inSoul <- gets stInSoulCommand
   let contents = literal (handleMathComment str)
+  when (needsCancel str) $ modify $ \st -> st{ stCancel = True }
   return $
     if inSoul -- # 9597
        then "$$" <> contents <> "$$"
@@ -1339,3 +1346,21 @@ isMathEnv t =
       , "eqnarray"
       , "displaymath"
       ]
+
+-- True if the math needs the cancel package
+needsCancel :: Text -> Bool
+needsCancel t =
+  case A.parseOnly pCancel t of
+    Right True -> True
+    _ -> False
+ where
+  pCancel = (False <$ A.endOfInput) <|> do
+    c <- A.anyChar
+    case c of
+      '\\' -> do
+        x <- A.takeWhile isLetter
+        if x == "cancel" || x == "xcancel" || x == "bcancel"
+           then return True
+           else pCancel
+      _ -> pCancel
+
diff --git a/src/Text/Pandoc/Writers/LaTeX/Types.hs b/src/Text/Pandoc/Writers/LaTeX/Types.hs
index 2477c2fa7..1295d2d01 100644
--- a/src/Text/Pandoc/Writers/LaTeX/Types.hs
+++ b/src/Text/Pandoc/Writers/LaTeX/Types.hs
@@ -53,6 +53,7 @@ data WriterState =
   , stIsFirstInDefinition :: Bool    -- ^ first block in a defn list
   , stLang          :: Maybe Lang    -- ^ lang specified in metadata
   , stInSoulCommand :: Bool          -- ^ in a soul command like ul
+  , stCancel        :: Bool          -- ^ true if document uses \cancel
   }
 
 startingState :: WriterOptions -> WriterState
@@ -93,4 +94,5 @@ startingState options =
   , stIsFirstInDefinition = False
   , stLang = Nothing
   , stInSoulCommand = False
+  , stCancel = False
   }