EPUB writer: stylesheet changes. Closes #2040.

* Allow `--css` to be used to specify stylesheets.
* Deprecated `--epub-stylesheet` and made it a synoynym of
  `--css`.
* If a code block with class "css" is given as contents of the
  `stylesheet` metadata field, use its literal code as contents of
  the epub stylesheet.  Otherwise, treat it as a filename and
  read the file.
* Note: `--css` and `stylesheet` in metadata are not compatible.
  `stylesheet` takes precedence.

3 files changed, 32 insertions, 20 deletions

diff --git a/README b/README
index fa93bf8e5..10097f4b7 100644
--- a/README
+++ b/README
@@ -646,6 +646,8 @@ Options affecting specific writers
     is specified, pandoc will look for a file `epub.css` in the
     user data directory (see `--data-dir`).  If it is not
     found there, sensible defaults will be used.
+    (*Deprecated:* use `--css` or the `stylesheet` metadata field
+    instead.)
 
 `--epub-cover-image=`*FILE*
 
diff --git a/pandoc.hs b/pandoc.hs
index 9023b2625..45e5de5f2 100644
--- a/pandoc.hs
+++ b/pandoc.hs
@@ -689,8 +689,10 @@ options =
     , Option "" ["epub-stylesheet"]
                  (ReqArg
                   (\arg opt -> do
-                     text <- UTF8.readFile arg
-                     return opt { optEpubStylesheet = Just text })
+                     warn "--epub-stylesheet is deprecated. Use --css or stylesheet in metadata."
+                     let newvars = optVariables opt ++ [("css",arg)]
+                     return opt { optVariables = newvars,
+                                  optStandalone = True })
                   "FILENAME")
                  "" -- "Path of epub.css"
 
diff --git a/src/Text/Pandoc/Writers/EPUB.hs b/src/Text/Pandoc/Writers/EPUB.hs
index 37c285dc2..f35d2d245 100644
--- a/src/Text/Pandoc/Writers/EPUB.hs
+++ b/src/Text/Pandoc/Writers/EPUB.hs
@@ -99,7 +99,7 @@ data EPUBMetadata = EPUBMetadata{
   , epubPageDirection      :: Maybe ProgressionDirection
   } deriving Show
 
-data Stylesheet = StylesheetPath FilePath
+data Stylesheet = StylesheetPaths [FilePath]
                 | StylesheetContents String
                 deriving Show
 
@@ -323,8 +323,14 @@ metadataFromMeta opts meta = EPUBMetadata{
         coverImage = lookup "epub-cover-image" (writerVariables opts) `mplus`
              (metaValueToString <$> lookupMeta "cover-image" meta)
         stylesheet = (StylesheetContents <$> writerEpubStylesheet opts) `mplus`
-                     ((StylesheetPath . metaValueToString) <$>
-                       lookupMeta "stylesheet" meta)
+                     (case lookupMeta "stylesheet" meta of
+                         Just (MetaBlocks [CodeBlock (_,["css"],_) code])
+                                -> Just (StylesheetContents code)
+                         Just x -> Just (StylesheetPaths [metaValueToString x])
+                         Nothing -> Nothing) `mplus`
+                     (case [x | ("css", x) <- writerVariables opts] of
+                           []   -> Nothing
+                           xs   -> Just (StylesheetPaths xs))
         pageDirection = case map toLower . metaValueToString <$>
                              lookupMeta "page-progression-direction" meta of
                               Just "ltr" -> Just LTR
@@ -340,20 +346,21 @@ writeEPUB opts doc@(Pandoc meta _) = do
   let epub3 = version == EPUB3
   epochtime <- floor `fmap` getPOSIXTime
   let mkEntry path content = toEntry path epochtime content
-  let vars = ("epub3", if epub3 then "true" else "false")
-           : ("css", "stylesheet.css")
-           : writerVariables opts
-  let opts' = opts{ writerEmailObfuscation = NoObfuscation
-                  , writerStandalone = True
-                  , writerSectionDivs = True
-                  , writerHtml5 = epub3
-                  , writerVariables = vars
-                  , writerHTMLMathMethod =
-                       if epub3
-                          then MathML Nothing
-                          else writerHTMLMathMethod opts
-                  , writerWrapText = True }
-  metadata <- getEPUBMetadata opts' meta
+  let vars = ("epub3", if epub3 then "true" else "false") :
+             writerVariables opts
+  let opts'' = opts{ writerEmailObfuscation = NoObfuscation
+                   , writerStandalone = True
+                   , writerSectionDivs = True
+                   , writerHtml5 = epub3
+                   , writerVariables = vars
+                   , writerHTMLMathMethod =
+                        if epub3
+                           then MathML Nothing
+                           else writerHTMLMathMethod opts
+                   , writerWrapText = True }
+  metadata <- getEPUBMetadata opts'' meta
+  let opts' = opts''{ writerVariables = ("css", "stylesheet.css") :
+                      filter (\(x,_) -> x /= "css") vars }
 
   -- cover page
   (cpgEntry, cpicEntry) <-
@@ -675,7 +682,8 @@ writeEPUB opts doc@(Pandoc meta _) = do
 
   -- stylesheet
   stylesheet <- case epubStylesheet metadata of
-                   Just (StylesheetPath fp)    -> UTF8.readFile fp
+                   Just (StylesheetPaths fp)   -> concat <$>
+                                                  mapM UTF8.readFile fp
                    Just (StylesheetContents s) -> return s
                    Nothing -> UTF8.toString `fmap`
                               readDataFile (writerUserDataDir opts) "epub.css"