From ba7868765acae0071f684797771d83f9cc31b402 Mon Sep 17 00:00:00 2001
From: John MacFarlane <jgm@berkeley.edu>
Date: Wed, 22 Jun 2016 11:45:45 -0700
Subject: HTML writer:  Better support for raw LaTeX environments.

Previously we just passed all raw TeX through when MathJax
was used for HTML math.  This passed through too much.
With this patch, only raw LaTeX environments that MathJax
can handle get passed through.

This patch also causes raw LaTeX environments to be treated
as math, when possible, with MathML and WebTeX output.

Closes #2758.
---
 src/Text/Pandoc/Writers/HTML.hs | 53 +++++++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 12 deletions(-)

(limited to 'src/Text/Pandoc/Writers/HTML.hs')

diff --git a/src/Text/Pandoc/Writers/HTML.hs b/src/Text/Pandoc/Writers/HTML.hs
index d8b8384e7..433e28bf2 100644
--- a/src/Text/Pandoc/Writers/HTML.hs
+++ b/src/Text/Pandoc/Writers/HTML.hs
@@ -483,11 +483,9 @@ blockToHtml opts (Div attr@(ident, classes, kvs) bs) = do
         else addAttrs opts (ident, classes', kvs) $ divtag $ contents'
 blockToHtml opts (RawBlock f str)
   | f == Format "html" = return $ preEscapedString str
-  | f == Format "latex" =
-      case writerHTMLMathMethod opts of
-           MathJax _  -> do modify (\st -> st{ stMath = True })
-                            return $ toHtml str
-           _          -> return mempty
+  | (f == Format "latex" || f == Format "tex") &&
+     allowsMathEnvironments (writerHTMLMathMethod opts) &&
+     isMathEnvironment str = blockToHtml opts $ Plain [Math DisplayMath str]
   | otherwise          = return mempty
 blockToHtml opts (HorizontalRule) = return $ if writerHtml5 opts then H5.hr else H.hr
 blockToHtml opts (CodeBlock (id',classes,keyvals) rawCode) = do
@@ -811,13 +809,6 @@ inlineToHtml opts inline =
                          InlineMath  -> m
                          DisplayMath -> brtag >> m >> brtag 
     (RawInline f str)
-      | f == Format "latex" ->
-                          case writerHTMLMathMethod opts of
-                               LaTeXMathML _ -> do modify (\st -> st {stMath = True})
-                                                   return $ toHtml str
-                               MathJax _     -> do modify (\st -> st {stMath = True})
-                                                   return $ toHtml str
-                               _             -> return mempty
       | f == Format "html" -> return $ preEscapedString str
       | otherwise          -> return mempty
     (Link attr txt (s,_)) | "mailto:" `isPrefixOf` s -> do
@@ -915,3 +906,41 @@ renderKaTeX = unlines [
   , " katex.render(texText.data, mathElements[i])"
   , "}}"
   ]
+
+isMathEnvironment :: String -> Bool
+isMathEnvironment s = "\\begin{" `isPrefixOf` s &&
+                         envName `elem` mathmlenvs
+  where envName = takeWhile (/= '}') (drop 7 s)
+        mathmlenvs = [ "align"
+                     , "align*"
+                     , "alignat"
+                     , "alignat*"
+                     , "aligned"
+                     , "alignedat"
+                     , "array"
+                     , "Bmatrix"
+                     , "bmatrix"
+                     , "cases"
+                     , "CD"
+                     , "eqnarray"
+                     , "eqnarray*"
+                     , "equation"
+                     , "equation*"
+                     , "gather"
+                     , "gather*"
+                     , "gathered"
+                     , "matrix"
+                     , "multline"
+                     , "multline*"
+                     , "pmatrix"
+                     , "smallmatrix"
+                     , "split"
+                     , "subarray"
+                     , "Vmatrix"
+                     , "vmatrix" ]
+
+allowsMathEnvironments :: HTMLMathMethod -> Bool
+allowsMathEnvironments (MathJax _) = True
+allowsMathEnvironments (MathML _)  = True
+allowsMathEnvironments (WebTeX _)  = True
+allowsMathEnvironments _           = False
-- 
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