Implement `org-edit-latex-environment'

* lisp/org-src.el (org-edit-latex-environment): New function.
* lisp/org.el (org-edit-special): Use new function.

etc/ORG-NEWS

@@ -63,6 +63,12 @@ to the following
 list as their first argument.
 
 ** New features
+*** ~org-edit-special~ can edit LaTeX environments
+
+Using ~C-c '~ on a LaTeX environment opens a sub-editing buffer.  By
+default, major mode in that buffer is ~latex-mode~, but it can be
+changed by configuring ~org-src-lang-modes~.
+
 *** Agenda
 **** New variable : ~org-agenda-show-future-repeats~
 **** New variable : ~org-agenda-prefer-last-repeat~

lisp/org-src.el

@@ -332,7 +332,7 @@ where BEG and END are buffer positions and CONTENTS is a string."
 		    (skip-chars-backward " \r\t\n")
 		    (line-beginning-position 1))
 	     (org-element-property :value datum)))
-      ((memq type '(fixed-width table))
+      ((memq type '(fixed-width latex-environment table))
        (let ((beg (org-element-property :post-affiliated datum))
 	     (end (progn (goto-char (org-element-property :end datum))
 			 (skip-chars-backward " \r\t\n")
@@ -853,6 +853,28 @@ Throw an error when not at such a table."
     (table-recognize)
     t))
 
+(defun org-edit-latex-environment ()
+  "Edit LaTeX environment at point.
+\\<org-src-mode-map>
+The LaTeX environment is copied into a new buffer.  Major mode is
+set to the one associated to \"latex\" in `org-src-lang-modes',
+or to `latex-mode' if there is none.
+
+When done, exit with `\\[org-edit-src-exit]'.  The edited text \
+will then replace
+the LaTeX environment in the Org mode buffer."
+  (interactive)
+  (let ((element (org-element-at-point)))
+    (unless (and (eq (org-element-type element) 'latex-environment)
+		 (org-src--on-datum-p element))
+      (user-error "Not in a LaTeX environment"))
+    (org-src--edit-element
+     element
+     (org-src--construct-edit-buffer-name (buffer-name) "LaTeX environment")
+     (org-src--get-lang-mode "latex")
+     t)
+    t))
+
 (defun org-edit-export-block ()
   "Edit export block at point.
 \\<org-src-mode-map>

lisp/org.el

@@ -20920,6 +20920,7 @@ When at a table, call the formula editor with `org-table-edit-formulas'.
 When in a source code block, call `org-edit-src-code'.
 When in a fixed-width region, call `org-edit-fixed-width-region'.
 When in an export block, call `org-edit-export-block'.
+When in a LaTeX environment, call `org-edit-latex-environment'.
 When at an #+INCLUDE keyword, visit the included file.
 When at a footnote reference, call `org-edit-footnote-reference'
 On a link, call `ffap' to visit the link at point.
@@ -20964,6 +20965,7 @@ Otherwise, return a user error."
       (`example-block (org-edit-src-code))
       (`export-block (org-edit-export-block))
       (`fixed-width (org-edit-fixed-width-region))
+      (`latex-environment (org-edit-latex-environment))
       (_
        ;; No notable element at point.  Though, we may be at a link or
        ;; a footnote reference, which are objects.  Thus, scan deeper.