From 31aa97c7f0cc9bf7272f4e781192b1458ee98525 Mon Sep 17 00:00:00 2001
From: TEC <tec@tecosaur.com>
Date: Sun, 24 May 2020 23:35:33 +0800
Subject: [PATCH] Extend org-edit-special to editing LaTeX-fragments Defines a
 new function, `org-edit-latex-fragment' which is hooked into
 `org-edit-special', modifying `org-src--contents-area-modified' to recognise
 the element type.

---
 etc/ORG-NEWS    |  7 +++++++
 lisp/org-src.el | 45 +++++++++++++++++++++++++++++++++++++++++++++
 lisp/org.el     |  1 +
 3 files changed, 53 insertions(+)

diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
index 5183b58de..ea7ccb7c5 100644
--- a/etc/ORG-NEWS
+++ b/etc/ORG-NEWS
@@ -459,6 +459,13 @@ By default, Haskell blocks are interpreted. By adding =:compile yes=
 to a Haskell source block, it will be compiled, executed and the
 results will be displayed.
 
+*** Support for ~org-edit-special~ with LaTeX fragments.
+
+Calling ~org-edit-special~ on an inline LaTeX fragment calls a new
+function, ~org-edit-latex-fragment~. This functions in a comparable
+manner to editing inline source blocks, bringing up a minibuffer set
+to LaTeX mode. The math-mode deliminators are read only.
+
 * Version 9.3
 
 ** Incompatible changes
diff --git a/lisp/org-src.el b/lisp/org-src.el
index 1643607e4..43fb10fa5 100644
--- a/lisp/org-src.el
+++ b/lisp/org-src.el
@@ -363,6 +363,12 @@ where BEG and END are buffer positions and CONTENTS is a string."
 	     (end (progn (goto-char (org-element-property :end datum))
 			 (search-backward "}" (line-beginning-position) t))))
 	 (list beg end (buffer-substring-no-properties beg end))))
+      ((eq type 'latex-fragment)
+       (let ((beg (org-element-property :begin datum))
+	     (end (org-with-point-at (org-element-property :end datum)
+		    (skip-chars-backward " \t")
+		    (point))))
+	 (list beg end (buffer-substring-no-properties beg end))))
       ((org-element-property :contents-begin datum)
        (let ((beg (org-element-property :contents-begin datum))
 	     (end (org-element-property :contents-end datum)))
@@ -959,6 +965,45 @@ Throw an error when not at such a table."
     (table-recognize)
     t))
 
+(defun org-edit-latex-fragment ()
+  "Edit LaTeX fragment at point."
+  (interactive)
+  (let ((context (org-element-context)))
+    (unless (and (eq (org-element-type context) 'latex-fragment)
+		 (org-src--on-datum-p context))
+      (user-error "Not on a LaTeX fragment"))
+    (let*
+	;; Grab the LaTeX fragment for propertization.
+	((contents (buffer-substring-no-properties
+		    (org-element-property :begin context)
+		    (- (org-element-property :end context)
+		       (org-element-property :post-blank context))))
+	 (delim-length (if (string-match "\\`\\$[^$]" contents))
+		       1 2))
+      ;; Make the LaTeX deliminators read-only.
+      (add-text-properties
+       0 delim-length
+       '(read-only "Cannot edit LaTeX deliminator" front-sticky t rear-nonsticky t)
+       contents)
+      (add-text-properties
+       (- (length contents) delim-length)
+       (length contents)
+       '(read-only "Cannot edit LaTeX deliminator" front-sticky nil rear-nonsticky nil)
+       contents)
+      (org-src--edit-element
+       context
+       (org-src--construct-edit-buffer-name (buffer-name) "LaTeX fragment")
+       (org-src-get-lang-mode "latex")
+       (lambda ()
+	 ;; Blank lines break things, replace with a single newline.
+	 (while (re-search-forward "\n[ \t]*\n" nil t) (replace-match "\n"))
+	 ;; If within a table a newline would disrupt the structure, so remove newlines.
+	 (goto-char (point-min))
+	 (when (org-element-lineage context '(table-cell))
+	   (while (search-forward "\n" nil t) (replace-match " "))))
+       contents))
+    t))
+
 (defun org-edit-latex-environment ()
   "Edit LaTeX environment at point.
 \\<org-src-mode-map>
diff --git a/lisp/org.el b/lisp/org.el
index 40c3c46b9..0808fc210 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -17347,6 +17347,7 @@ Otherwise, return a user error."
 	 (pcase (org-element-type context)
 	   (`footnote-reference (org-edit-footnote-reference))
 	   (`inline-src-block (org-edit-inline-src-code))
+	   (`latex-fragment (org-edit-latex-fragment))
 	   (`timestamp (if (eq 'inactive (org-element-property :type context))
 			   (call-interactively #'org-time-stamp-inactive)
 			 (call-interactively #'org-time-stamp)))
-- 
2.26.2