Fix #5: Verse typesetting

Thanks to the pandoc-discussion thread at
<https://groups.google.com/forum/#!topic/pandoc-discuss/_JnTJnsSK3k>,
line breaks in verse have been converted to <span class="line">s,
which enables the CSS to style them with hanging indents, given
a too-small viewport.  This commit also includes a makefile edit to
reflect this change, and the Haskell source and executable of the
pandoc filter.

4 files changed, 15 insertions, 0 deletions

@@ -0,0 +1,15 @@
+import Text.Pandoc.JSON
+import Data.List.Split
+
+main :: IO ()
+main = toJSONFilter transformVerseParas
+
+transformVerseParas :: Block -> Block
+transformVerseParas (Para xs)
+    | LineBreak `elem` xs = Para (addLineSpans xs)
+    | otherwise = Para xs
+transformVerseParas x = x
+
+addLineSpans :: [Inline] -> [Inline]
+addLineSpans = map encloseInSpan . splitWhen (== LineBreak)
+    where encloseInSpan = Span("", ["line"], [])