Support exporting latex equation fragments

- ox-blackfriday.el updated to do the escaping using backslashes as suggested in https://gohugo.io/content-management/formats#solution > One solution is to simply escape each underscore in your math code by entering \_ instead of _. Org reference for latex fragments: http://orgmode.org/manual/LaTeX-fragments.html Add test.
kaushalmodi · 8da68a667657c2f0fc71f0eb2b17856ca5c6c5be · kaushalmodi committed Jul 31, 2017 · Jul 31, 2017 · 8da68a6
1 parent 5b966ad
commit 8da68a667657c2f0fc71f0eb2b17856ca5c6c5be
diff --git a/example-site/content-org/all-posts.org b/example-site/content-org/all-posts.org
@@ -684,6 +684,28 @@ This gets both categories =catA= and =catB=.
 :CUSTOM_ID: link-heading-2
 :END:
 - Link to [[#link-heading-1][Heading 1]]
+* Equations                                                       :equations:
+** Inline equations
+:PROPERTIES:
+:EXPORT_FILE_NAME: equation-latex-frag
+:EXPORT_DATE: 2017-07-31
+:END:
+Wrap the equations between =\(= and =\)=.
+
+For example, below in Org:
+#+BEGIN_SRC text
+LaTeX formatted equation: \( E = -J \sum_{i=1}^N s_i s_{i+1} \)
+#+END_SRC
+
+will look like this in Hugo rendered HTML (don't see this in Markdown,
+see what it looks after Hugo has processed it).
+
+LaTeX formatted equation: \( E = -J \sum_{i=1}^N s_i s_{i+1 }\)
+
+Here's another example similar to one in [[http://orgmode.org/manual/LaTeX-fragments.html][(org) LaTeX fragments]].
+
+If $a^2=b$ and \( b=2 \), then the solution must be either
+$a=+\sqrt{2}$ or \(a=-\sqrt{2}\).
 * TODO Pre-Draft State
 :PROPERTIES:
 :EXPORT_FILE_NAME: draft-state-todo
diff --git a/example-site/content/posts/equation-latex-frag.md b/example-site/content/posts/equation-latex-frag.md
@@ -0,0 +1,24 @@
++++
+title = "Inline equations"
+date = 2017-07-31
+tags = ["equations"]
+draft = false
++++
+
+Wrap the equations between `\(` and `\)`.
+
+For example, below in Org:
+
+```text
+LaTeX formatted equation: \( E = -J \sum_{i=1}^N s_i s_{i+1} \)
+```
+
+will look like this in Hugo rendered HTML (don't see this in Markdown,
+see what it looks after Hugo has processed it).
+
+LaTeX formatted equation: \\( E = -J \sum\_{i=1}^N s\_i s\_{i+1 }\\)
+
+Here's another example similar to one in [(org) LaTeX fragments](http://orgmode.org/manual/LaTeX-fragments.html).
+
+If \\(a^2=b\\) and \\( b=2 \\), then the solution must be either
+\\(a=+\sqrt{2}\\) or \\(a=-\sqrt{2}\\).
diff --git a/example-site/themes/bare_min/layouts/_default/baseof.html b/example-site/themes/bare_min/layouts/_default/baseof.html
@@ -11,11 +11,10 @@
             {{ .Title }} ❚ {{ .Site.Title }}
             {{ end }}
         </title>
+        {{ block "head" . }}{{ end }}
     </head>
 
     <body lang="en">
-
         {{ block "main" . }}{{ end }}
-
     </body>
 </html>
diff --git a/example-site/themes/bare_min/layouts/_default/single.html b/example-site/themes/bare_min/layouts/_default/single.html
@@ -1,3 +1,32 @@
+{{ define "head" }}
+
+<script type="text/x-mathjax-config">
+ MathJax.Hub.Config({
+     displayAlign: "center",
+     displayIndent: "0em",
+
+     "HTML-CSS": { scale: 100,
+                   linebreaks: { automatic: "false" },
+                   webFont: "TeX"
+     },
+     SVG: {scale: 100,
+           linebreaks: { automatic: "false" },
+           font: "TeX"},
+     NativeMML: {scale: 100},
+     TeX: { equationNumbers: {autoNumber: "AMS"},
+            MultLineWidth: "85%",
+            TagSide: "right",
+            TagIndent: ".8em"
+     }
+ });
+</script>
+<!-- https://gohugo.io/content-management/formats/#mathjax-with-hugo -->
+<script type="text/javascript"
+        src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS_HTML"></script>
+</head>
+
+{{ end }}
+
 {{ define "main" }}
 
 <div class="post">
diff --git a/ox-blackfriday.el b/ox-blackfriday.el
@@ -69,6 +69,7 @@
               (if a (org-blackfriday-export-to-markdown t s v)
                 (org-open-file (org-blackfriday-export-to-markdown nil s v)))))))
   :translate-alist '((inner-template . org-blackfriday-inner-template)
+                     (latex-fragment . org-blackfriday-latex-fragment)
                      (paragraph . org-blackfriday-paragraph)
                      (strike-through . org-blackfriday-strike-through)
                      (src-block . org-blackfriday-src-block)
@@ -81,6 +82,43 @@
 
 ;;; Transcode Functions
 
+;;;; Inner Template
+(defun org-blackfriday-inner-template (contents info)
+  "Return body of document after converting it to Markdown syntax.
+CONTENTS is the transcoded contents string.  INFO is a plist
+holding export options."
+  (let* ((depth (plist-get info :with-toc))
+         (headlines (and depth (org-export-collect-headlines info depth)))
+         (toc-tail (if headlines "\n\n" ""))
+         (toc-string ""))
+
+    (when headlines
+      (dolist (headline headlines)
+        (setq toc-string (concat toc-string
+                                 (org-blackfriday-format-toc headline info)
+                                 "\n"))))
+    (org-trim (concat toc-string toc-tail contents "\n" (org-blackfriday-footnote-section info)))))
+
+;;;; Latex Fragment
+(defun org-blackfriday-latex-fragment (latex-fragment _contents info)
+  "Transcode a LATEX-FRAGMENT object from Org to Blackfriday Markdown.
+INFO is a plist holding contextual information."
+  (let ((latex-frag (org-element-property :value latex-fragment))
+	(processing-type (plist-get info :with-latex)))
+    (cond
+     ((memq processing-type '(t mathjax))
+      (let* ((frag (org-html-format-latex latex-frag 'mathjax info))
+             ;; https://gohugo.io/content-management/formats#solution
+             (frag (replace-regexp-in-string "\\(\\\\[()]\\)" "\\\\\\1" frag)) ;\( -> \\(, \) -> \\)
+             (frag (replace-regexp-in-string "_" "\\\\_" frag))) ;_ -> \_
+        frag))
+     ((assq processing-type org-preview-latex-process-alist)
+      (let ((formula-link
+	     (org-html-format-latex latex-frag processing-type info)))
+	(when (and formula-link (string-match "file:\\([^]]*\\)" formula-link))
+	  (org-html--format-image (match-string 1 formula-link) nil info))))
+     (t latex-frag))))
+
 ;;;; Paragraph
 (defun org-blackfriday-paragraph (paragraph contents info)
   "Transcode PARAGRAPH element into Blackfriday Markdown format.
@@ -314,24 +352,7 @@ INFO is a plist used as a communication channel."
          fn-alist
          "\n"))))))
 
-;;;; Template
-(defun org-blackfriday-inner-template (contents info)
-  "Return body of document after converting it to Markdown syntax.
-CONTENTS is the transcoded contents string.  INFO is a plist
-holding export options."
-  (let* ((depth (plist-get info :with-toc))
-         (headlines (and depth (org-export-collect-headlines info depth)))
-         (toc-tail (if headlines "\n\n" ""))
-         (toc-string ""))
-
-    (when headlines
-      (dolist (headline headlines)
-        (setq toc-string (concat toc-string
-                                 (org-blackfriday-format-toc headline info)
-                                 "\n"))))
-    (org-trim (concat toc-string toc-tail contents "\n" (org-blackfriday-footnote-section info)))))
-
-
+
 ;;; Interactive functions
 
 ;;;###autoload