Re: Bug: org-src-font-lock-fontify-block should be wrapped with save-match-data [9.3.7 (9.3.7-4-gba6ca7-elpaplus @ mixed installation! /mnt/c/Users/toz/Weiterbildung/Soft/Emacs/ and /mnt/c/Users/toz/.emacs.d/elpa/org-plus-contrib-20200615/)

[Timothy <tecosaur@gmail.com>]

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Hi Tobias,

Thanks for your efforts. I have prepared a patch accordingly that wraps
org-src-font-lock-fontify-block’s body with save-match-data (attached).

If I don’t hear anything bad about it in the next few days, I’ll push it :)
Please let me know if my commit message agrees with your understanding of the
issue.

All the best,
Timothy

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From c435fd41428b6eb4f9f7971e73ca0a422006461b Mon Sep 17 00:00:00 2001
From: TEC <tec@tecosaur.com>
Date: Mon, 23 Aug 2021 15:09:24 +0800
Subject: [PATCH] org-src: Save match data when fontifying src block

* lisp/org-src.el (org-src-font-lock-fontify-block): Since
`org-src-font-lock-fontify-block' modifies match data during
fontification, when called in `org-fontify-meta-lines-and-blocks-1' by
`font-lock-fontify-region' the text property font-lock-multiline is
applied to text from the beginning to the last match.  Since there is a
difference in buffer sizes, the match data is invalid and problematic.
This issue can drastically slow down editing operations in large source
blocks.  This can be avoided simply by wrapping `save-match-data' around
`org-src-font-lock-fontify-block'.

Reported by: "Tobias Zawada" <i_inbox@tn-home.de>
<https://lists.gnu.org/archive/html/emacs-orgmode/2021-08/msg00307.html>
---
 lisp/org-src.el | 69 +++++++++++++++++++++++++------------------------
 1 file changed, 35 insertions(+), 34 deletions(-)

diff --git a/lisp/org-src.el b/lisp/org-src.el
index 4698c6dd2..ce33e1f54 100644
--- a/lisp/org-src.el
+++ b/lisp/org-src.el
@@ -586,40 +586,41 @@ (defun org-src-font-lock-fontify-block (lang start end)
   "Fontify code block.
 This function is called by emacs automatic fontification, as long
 as `org-src-fontify-natively' is non-nil."
-  (let ((lang-mode (org-src-get-lang-mode lang)))
-    (when (fboundp lang-mode)
-      (let ((string (buffer-substring-no-properties start end))
-	    (modified (buffer-modified-p))
-	    (org-buffer (current-buffer)))
-	(remove-text-properties start end '(face nil))
-	(with-current-buffer
-	    (get-buffer-create
-	     (format " *org-src-fontification:%s*" lang-mode))
-	  (let ((inhibit-modification-hooks nil))
-	    (erase-buffer)
-	    ;; Add string and a final space to ensure property change.
-	    (insert string " "))
-	  (unless (eq major-mode lang-mode) (funcall lang-mode))
-	  (org-font-lock-ensure)
-	  (let ((pos (point-min)) next)
-	    (while (setq next (next-property-change pos))
-	      ;; Handle additional properties from font-lock, so as to
-	      ;; preserve, e.g., composition.
-	      (dolist (prop (cons 'face font-lock-extra-managed-props))
-		(let ((new-prop (get-text-property pos prop)))
-		  (put-text-property
-		   (+ start (1- pos)) (1- (+ start next)) prop new-prop
-		   org-buffer)))
-	      (setq pos next))))
-	;; Add Org faces.
-	(let ((src-face (nth 1 (assoc-string lang org-src-block-faces t))))
-          (when (or (facep src-face) (listp src-face))
-            (font-lock-append-text-property start end 'face src-face))
-	  (font-lock-append-text-property start end 'face 'org-block))
-	(add-text-properties
-	 start end
-	 '(font-lock-fontified t fontified t font-lock-multiline t))
-	(set-buffer-modified-p modified)))))
+  (save-match-data
+    (let ((lang-mode (org-src-get-lang-mode lang)))
+      (when (fboundp lang-mode)
+	(let ((string (buffer-substring-no-properties start end))
+	      (modified (buffer-modified-p))
+	      (org-buffer (current-buffer)))
+	  (remove-text-properties start end '(face nil))
+	  (with-current-buffer
+	      (get-buffer-create
+	       (format " *org-src-fontification:%s*" lang-mode))
+	    (let ((inhibit-modification-hooks nil))
+	      (erase-buffer)
+	      ;; Add string and a final space to ensure property change.
+	      (insert string " "))
+	    (unless (eq major-mode lang-mode) (funcall lang-mode))
+	    (org-font-lock-ensure)
+	    (let ((pos (point-min)) next)
+	      (while (setq next (next-property-change pos))
+		;; Handle additional properties from font-lock, so as to
+		;; preserve, e.g., composition.
+		(dolist (prop (cons 'face font-lock-extra-managed-props))
+		  (let ((new-prop (get-text-property pos prop)))
+		    (put-text-property
+		     (+ start (1- pos)) (1- (+ start next)) prop new-prop
+		     org-buffer)))
+		(setq pos next))))
+	  ;; Add Org faces.
+	  (let ((src-face (nth 1 (assoc-string lang org-src-block-faces t))))
+	    (when (or (facep src-face) (listp src-face))
+	      (font-lock-append-text-property start end 'face src-face))
+	    (font-lock-append-text-property start end 'face 'org-block))
+	  (add-text-properties
+	   start end
+	   '(font-lock-fontified t fontified t font-lock-multiline t))
+	  (set-buffer-modified-p modified))))))
 
 \f
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