Merge pull request #26 from lixinchin/master

Ensure LaTeX equation environments are processed by pandoc.

ox-pandoc.el

@@ -211,7 +211,8 @@
  :type 'list)
 
 (org-export-define-derived-backend 'pandoc 'org
- :translate-alist '((link . org-pandoc-link)
+ :translate-alist '((latex-environment . org-pandoc-latex-environ)
+ (link . org-pandoc-link)
  (template . org-pandoc-template)
  (paragraph . org-pandoc-identity))
  ;; :export-block "PANDOC"
@@ -1247,12 +1248,54 @@ t means output to buffer."
  (concat (make-temp-name ".tmp") ".org") s)
  a s v b e (lambda (f) (org-pandoc-run-to-buffer-or-file f format s buf-or-open))))
 
-(defun org-pandoc-link (link contents info)
+(defun org-pandoc-latex-environ (blob contents _info)
+ "Transcode a latex environment for export with pandoc.
+Works around a bug in
+pandoc (https://github.com/jgm/pandoc/issues/1764, present in at
+least up-to and including pandoc 1.18) to surround an AMSMath
+latex environment in BLOB with plain TeX equation block
+delimiters, '$$ .. $$' in order for pandoc to properly recognise
+the maths environment as a latex equation. Also adds surrounding
+line-breaks so that pandoc treats the math environment as its own
+paragraph. This avoids having text before or after the math
+environment ending up on the same line as the equation.
+CONTENTS is its contents, as a string or nil. INFO is ignored."
+ (let ((raw-value (org-export-expand blob contents t)))
+ ;; If we're exporting to a TeX-based format, there's no need for
+ ;; this hack
+ (if (member org-pandoc-format '(beamer beamer-pdf latex latex-pdf))
+ raw-value
+ ;; Otherwise, add '$$' elements before and after the block to
+ ;; get pandoc to process it.
+ (let* ((post-blank (org-element-property :post-blank blob))
+ (case-fold-search t)
+ (preface
+ (replace-regexp-in-string
+ (rx (group-n 1 "\\begin{"
+ (or "align" "alignat" "eqnarray" "equation" "flalign" "gather" "multline")
+ (zero-or-one "*" ) "}"))
+ "\n$$\\1"
+ raw-value))
+ (output
+ (replace-regexp-in-string
+ (rx (group-n 1 "\\end{"
+ (or "align" "alignat" "eqnarray" "equation" "flalign" "gather" "multline")
+ (zero-or-one "*" ) "}"))
+ "\\1$$"
+ preface)))
+ ;; If we've added the '$$' delimiters, then also set the
+ ;; :post-blank property to add a blank line after this current
+ ;; latex equation environment
+ (unless (or (>= post-blank 1)
+ (string-equal raw-value output))
+ (org-element-put-property blob :post-blank 1))
+ output))))
+
+(defun org-pandoc-link (link contents _info)
  "Transcode LINK object using the registered formatter for the
-'pandoc backend. If none exists, transcode using the registered
-formatter for the 'org export backend. CONTENTS is the
-description of the link, as a string, or nil. INFO is a plist
-containing current export state."
+'pandoc backend. If none exists, transcode using the registered
+formatter for the 'org export backend. CONTENTS is the
+description of the link, as a string, or nil. INFO is ignored."
  (or (org-export-custom-protocol-maybe link contents 'pandoc)
  (org-export-custom-protocol-maybe link contents 'org)
  (org-element-link-interpreter link contents)))
@@ -1308,12 +1351,11 @@ Option table is created in this stage."
  (funcall org-template contents info)
  contents)))
 
-(defun org-pandoc-identity (blob contents info)
+(defun org-pandoc-identity (blob contents _info)
  "Transcode BLOB element or object back into Org syntax.
-CONTENTS is its contents, as a string or nil. INFO is ignored.
+CONTENTS is its contents, as a string or nil.  INFO is ignored.
 Like `org-org-identity', but also preserves #+ATTR_* tags in the
 output."
- (ignore info)
  (org-export-expand blob contents t))
 
 (defun org-pandoc-put-options (options)