Implemented Ext_implicit_figures.

* In markdown reader, add a '\1' character to the beginning
  of the title of an image that is alone in its paragraph,
  if implicit_figures extension is selected.
* In writers, check for Para [Image alt (src,'\1':tit)] and treat
  it as a figure if possible.
* Updated tests.

This is a bit of a hack, but it allows us to make implicit_figures
an extension of the markdown reader, rather than the writers.

src/Text/Pandoc/Readers/Markdown.hs

@@ -770,13 +770,23 @@ compactify'DL items =
 
 para :: MarkdownParser (F Blocks)
 para = try $ do
+  exts <- getOption readerExtensions
   result <- trimInlinesF . mconcat <$> many1 inline
-  option (B.plain <$> result) $ try $ do
-              newline
-              (blanklines >> return mempty)
-                <|> (guardDisabled Ext_blank_before_blockquote >> lookAhead blockQuote)
-                <|> (guardDisabled Ext_blank_before_header >> lookAhead header)
-              return $ B.para <$> result
+  option (B.plain <$> result)
+    $ try $ do
+            newline
+            (blanklines >> return mempty)
+              <|> (guardDisabled Ext_blank_before_blockquote >> lookAhead blockQuote)
+              <|> (guardDisabled Ext_blank_before_header >> lookAhead header)
+            return $ do
+              result' <- result
+              case B.toList result' of
+                   [Image alt (src,tit)]
+                     | Ext_implicit_figures `Set.member` exts ->
+                        -- the \1 at beginning of title indicates a figure
+                        return $ B.para $ B.singleton
+                               $ Image alt (src,'\1':tit)
+                   _ -> return $ B.para result'
 
 plain :: MarkdownParser (F Blocks)
 plain = fmap B.plain . trimInlinesF . mconcat <$> many1 inline <* spaces

src/Text/Pandoc/Writers/AsciiDoc.hs

@@ -116,6 +116,8 @@ blockToAsciiDoc _ Null = return empty
 blockToAsciiDoc opts (Plain inlines) = do
   contents <- inlineListToAsciiDoc opts inlines
   return $ contents <> cr
+blockToAsciiDoc opts (Para [Image alt (src,'\1':tit)]) =
+  blockToAsciiDoc opts (Para [Image alt (src,tit)])
 blockToAsciiDoc opts (Para inlines) = do
   contents <- inlineListToAsciiDoc opts inlines
   -- escape if para starts with ordered list marker

src/Text/Pandoc/Writers/ConTeXt.hs

@@ -131,7 +131,8 @@ blockToConTeXt :: Block
                -> State WriterState Doc
 blockToConTeXt Null = return empty
 blockToConTeXt (Plain lst) = inlineListToConTeXt lst
-blockToConTeXt (Para [Image txt (src,_)]) = do
+-- title beginning with \1 indicates that the image is a figure
+blockToConTeXt (Para [Image txt (src,'\1':_)]) = do
   capt <- inlineListToConTeXt txt
   return $ blankline $$ "\\placefigure[here,nonumber]" <> braces capt <>
            braces ("\\externalfigure" <> brackets (text src)) <> blankline

src/Text/Pandoc/Writers/Docbook.hs

@@ -144,7 +144,8 @@ blockToDocbook :: WriterOptions -> Block -> Doc
 blockToDocbook _ Null = empty
 blockToDocbook _ (Header _ _ _) = empty -- should not occur after hierarchicalize
 blockToDocbook opts (Plain lst) = inlinesToDocbook opts lst
-blockToDocbook opts (Para [Image txt (src,_)]) =
+-- title beginning with \1 indicates that the image is a figure
+blockToDocbook opts (Para [Image txt (src,'\1':_)]) =
   let alt  = inlinesToDocbook opts txt
       capt = if null txt
                 then empty

src/Text/Pandoc/Writers/Docx.hs

@@ -347,9 +347,10 @@ blockToOpenXML opts (Header lev (ident,_,_) lst) = do
   let bookmarkEnd = mknode "w:bookmarkEnd" [("w:id", id')] ()
   return $ [bookmarkStart] ++ contents ++ [bookmarkEnd]
 blockToOpenXML opts (Plain lst) = blockToOpenXML opts (Para lst)
-blockToOpenXML opts (Para x@[Image alt _]) = do
+-- title beginning with \1 indicates that the image is a figure
+blockToOpenXML opts (Para [Image alt (src,'\1':tit)]) = do
   paraProps <- getParaProps
-  contents <- inlinesToOpenXML opts x
+  contents <- inlinesToOpenXML opts [Image alt (src,tit)]
   captionNode <- withParaProp (pStyle "ImageCaption")
                  $ blockToOpenXML opts (Para alt)
   return $ mknode "w:p" [] (paraProps ++ contents) : captionNode

src/Text/Pandoc/Writers/FB2.hs

@@ -316,7 +316,9 @@ linkID i = "l" ++ (show i)
 blockToXml :: Block -> FBM [Content]
 blockToXml (Plain ss) = cMapM toXml ss  -- FIXME: can lead to malformed FB2
 blockToXml (Para [Math DisplayMath formula]) = insertMath NormalImage formula
-blockToXml (Para [img@(Image _ _)]) = insertImage NormalImage img
+-- title beginning with \1 indicates that the image is a figure
+blockToXml (Para [Image alt (src,'\1':tit)]) =
+  insertImage NormalImage (Image alt (src,tit))
 blockToXml (Para ss) = liftM (list . el "p") $ cMapM toXml ss
 blockToXml (CodeBlock _ s) = return . spaceBeforeAfter .
                              map (el "p" . el "code") . lines $ s

src/Text/Pandoc/Writers/HTML.hs

@@ -392,7 +392,8 @@ treatAsImage fp =
 blockToHtml :: WriterOptions -> Block -> State WriterState Html
 blockToHtml _ Null = return mempty
 blockToHtml opts (Plain lst) = inlineListToHtml opts lst
-blockToHtml opts (Para [Image txt (s,tit)]) = do
+-- title beginning with \1 indicates that the image is a figure
+blockToHtml opts (Para [Image txt (s,'\1':tit)]) = do
   img <- inlineToHtml opts (Image txt (s,tit))
   let tocapt = if writerHtml5 opts
                   then H5.figcaption

src/Text/Pandoc/Writers/LaTeX.hs

@@ -277,7 +277,8 @@ blockToLaTeX :: Block     -- ^ Block to convert
              -> State WriterState Doc
 blockToLaTeX Null = return empty
 blockToLaTeX (Plain lst) = inlineListToLaTeX lst
-blockToLaTeX (Para [Image txt (src,tit)]) = do
+-- title beginning with \1 indicates that the image is a figure
+blockToLaTeX (Para [Image txt (src,'\1':tit)]) = do
   capt <- if null txt
              then return empty
              else (\c -> "\\caption" <> braces c) `fmap` inlineListToLaTeX txt

src/Text/Pandoc/Writers/Markdown.hs

@@ -246,6 +246,9 @@ blockToMarkdown _ Null = return empty
 blockToMarkdown opts (Plain inlines) = do
   contents <- inlineListToMarkdown opts inlines
   return $ contents <> cr
+-- title beginning with \1 indicates figure
+blockToMarkdown opts (Para [Image alt (src,'\1':tit)]) =
+  blockToMarkdown opts (Para [Image alt (src,tit)])
 blockToMarkdown opts (Para inlines) = do
   contents <- inlineListToMarkdown opts inlines
   -- escape if para starts with ordered list marker

src/Text/Pandoc/Writers/MediaWiki.hs

@@ -81,7 +81,8 @@ blockToMediaWiki _ Null = return ""
 blockToMediaWiki opts (Plain inlines) =
   inlineListToMediaWiki opts inlines
 
-blockToMediaWiki opts (Para [Image txt (src,tit)]) = do
+-- title beginning with \1 indicates that the image is a figure
+blockToMediaWiki opts (Para [Image txt (src,'\1':tit)]) = do
   capt <- if null txt
              then return ""
              else ("|caption " ++) `fmap` inlineListToMediaWiki opts txt

src/Text/Pandoc/Writers/Org.hs

@@ -114,7 +114,8 @@ blockToOrg :: Block         -- ^ Block element
            -> State WriterState Doc
 blockToOrg Null = return empty
 blockToOrg (Plain inlines) = inlineListToOrg inlines
-blockToOrg (Para [Image txt (src,tit)]) = do
+-- title beginning with \1 indicates that the image is a figure
+blockToOrg (Para [Image txt (src,'\1':tit)]) = do
   capt <- if null txt
              then return empty
              else (\c -> "#+CAPTION: " <> c <> blankline) `fmap`

src/Text/Pandoc/Writers/RST.hs

@@ -148,7 +148,8 @@ blockToRST :: Block         -- ^ Block element
            -> State WriterState Doc
 blockToRST Null = return empty
 blockToRST (Plain inlines) = inlineListToRST inlines
-blockToRST (Para [Image txt (src,tit)]) = do
+-- title beginning with \1 indicates that the image is a figure
+blockToRST (Para [Image txt (src,'\1':tit)]) = do
   capt <- inlineListToRST txt
   let fig = "figure:: " <> text src
   let alt = ":alt: " <> if null tit then capt else text tit

src/Text/Pandoc/Writers/Texinfo.hs

@@ -126,7 +126,8 @@ blockToTexinfo Null = return empty
 blockToTexinfo (Plain lst) =
   inlineListToTexinfo lst
 
-blockToTexinfo (Para [Image txt (src,tit)]) = do
+-- title beginning with \1 indicates that the image is a figure
+blockToTexinfo (Para [Image txt (src,'\1':tit)]) = do
   capt <- if null txt
              then return empty
              else (\c -> text "@caption" <> braces c) `fmap`

src/Text/Pandoc/Writers/Textile.hs

@@ -101,7 +101,8 @@ blockToTextile _ Null = return ""
 blockToTextile opts (Plain inlines) =
   inlineListToTextile opts inlines
 
-blockToTextile opts (Para [Image txt (src,tit)]) = do
+-- title beginning with \1 indicates that the image is a figure
+blockToTextile opts (Para [Image txt (src,'\1':tit)]) = do
   capt <- blockToTextile opts (Para txt)
   im <- inlineToTextile opts (Image txt (src,tit))
   return $ im ++ "\n" ++ capt

tests/testsuite.native

@@ -384,7 +384,7 @@ Pandoc (Meta {docTitle = [Str "Pandoc",Space,Str "Test",Space,Str "Suite"], docA
 ,HorizontalRule
 ,Header 1 ("images",[],[]) [Str "Images"]
 ,Para [Str "From",Space,Quoted DoubleQuote [Str "Voyage",Space,Str "dans",Space,Str "la",Space,Str "Lune"],Space,Str "by",Space,Str "Georges",Space,Str "Melies",Space,Str "(1902):"]
-,Para [Image [Str "lalune"] ("lalune.jpg","Voyage dans la Lune")]
+,Para [Image [Str "lalune"] ("lalune.jpg","\SOHVoyage dans la Lune")]
 ,Para [Str "Here",Space,Str "is",Space,Str "a",Space,Str "movie",Space,Image [Str "movie"] ("movie.jpg",""),Space,Str "icon."]
 ,HorizontalRule
 ,Header 1 ("footnotes",[],[]) [Str "Footnotes"]

tests/writer.native

@@ -384,7 +384,7 @@ Pandoc (Meta {docTitle = [Str "Pandoc",Space,Str "Test",Space,Str "Suite"], docA
 ,HorizontalRule
 ,Header 1 ("images",[],[]) [Str "Images"]
 ,Para [Str "From",Space,Quoted DoubleQuote [Str "Voyage",Space,Str "dans",Space,Str "la",Space,Str "Lune"],Space,Str "by",Space,Str "Georges",Space,Str "Melies",Space,Str "(1902):"]
-,Para [Image [Str "lalune"] ("lalune.jpg","Voyage dans la Lune")]
+,Para [Image [Str "lalune"] ("lalune.jpg","\SOHVoyage dans la Lune")]
 ,Para [Str "Here",Space,Str "is",Space,Str "a",Space,Str "movie",Space,Image [Str "movie"] ("movie.jpg",""),Space,Str "icon."]
 ,HorizontalRule
 ,Header 1 ("footnotes",[],[]) [Str "Footnotes"]