buff-menu and revert-buffer-restore-functions

buff-menu and revert-buffer-restore-functions

[Stefan Monnier]

In the recent

    commit a525cfb3af0c49c5c64e8af548ab23d086348fed
    Author: Juri Linkov <juri@linkov.net>
    Date:   Mon Jun 3 19:55:47 2024 +0300

    New variable 'revert-buffer-restore-functions' (bug#69511)
    
    * doc/lispref/backups.texi (Reverting):
    Add documentation for 'revert-buffer-restore-functions'.
    
    * lisp/files.el (revert-buffer-restore-functions): New variable.
    (revert-buffer-restore-read-only): New function.
    (revert-buffer): Use 'revert-buffer-restore-functions' with
    the default value 'revert-buffer-restore-read-only' (bug#69511).
    
    * lisp/buff-menu.el (Buffer-menu-mode): Add hook
    'revert-buffer-restore-functions' to restore
    outline-minor-mode highlighting.

Why is it the responsability of buff-menu to setup outline minor
mode's rehighlighting?  Wouldn't the same apply to several other modes
and should be handled directly by outline minor mode?
What's special about buff-menu in this respect?


        Stefan

Re: buff-menu and revert-buffer-restore-functions

[Juri Linkov]

> Why is it the responsability of buff-menu to setup outline minor
> mode's rehighlighting?  Wouldn't the same apply to several other modes
> and should be handled directly by outline minor mode?
> What's special about buff-menu in this respect?

I was unsure about the applicability of this outline rehighlighting
in the general case.  But now I see that the right place would be in
outline-minor-mode.  So this is fixed now.

Re: buff-menu and revert-buffer-restore-functions

[Juri Linkov]

>> Why is it the responsability of buff-menu to setup outline minor
>> mode's rehighlighting?  Wouldn't the same apply to several other modes
>> and should be handled directly by outline minor mode?
>> What's special about buff-menu in this respect?
>
> I was unsure about the applicability of this outline rehighlighting
> in the general case.  But now I see that the right place would be in
> outline-minor-mode.  So this is fixed now.

Then the right place to rehighlight hi-lock patterns would be
hi-lock-mode:

diff --git a/lisp/hi-lock.el b/lisp/hi-lock.el
index 516bee67dd0..8cbe3155b93 100644
--- a/lisp/hi-lock.el
+++ b/lisp/hi-lock.el
@@ -376,7 +376,9 @@ hi-lock-mode
 	(hi-lock-find-patterns)
         (add-hook 'font-lock-mode-hook 'hi-lock-font-lock-hook nil t)
         ;; Remove regexps from font-lock-keywords (bug#13891).
-	(add-hook 'change-major-mode-hook (lambda () (hi-lock-mode -1)) nil t))
+	(add-hook 'change-major-mode-hook (lambda () (hi-lock-mode -1)) nil t)
+	(add-hook 'revert-buffer-restore-functions
+		  #'hi-lock-revert-buffer-rehighlight nil t))
     ;; Turned off.
     (when (or hi-lock-interactive-patterns
 	      hi-lock-file-patterns)
@@ -390,7 +392,9 @@ hi-lock-mode
       (remove-overlays nil nil 'hi-lock-overlay t)
       (font-lock-flush))
     (define-key-after menu-bar-edit-menu [hi-lock] nil)
-    (remove-hook 'font-lock-mode-hook 'hi-lock-font-lock-hook t)))
+    (remove-hook 'font-lock-mode-hook 'hi-lock-font-lock-hook t)
+    (remove-hook 'revert-buffer-restore-functions
+		 #'hi-lock-revert-buffer-rehighlight t)))
 
 ;;;###autoload
 (define-globalized-minor-mode global-hi-lock-mode
@@ -859,6 +863,18 @@ hi-lock-font-lock-hook
     (font-lock-add-keywords nil hi-lock-file-patterns t)
     (font-lock-add-keywords nil hi-lock-interactive-patterns t)))
 
+(defun hi-lock-revert-buffer-rehighlight ()
+  "Rehighlight hi-lock patterns after `revert-buffer'.
+Apply the previous patterns after reverting the buffer."
+  (when-let ((patterns (or hi-lock-interactive-lighters
+                           hi-lock-interactive-patterns)))
+    (lambda ()
+      (setq hi-lock-interactive-lighters nil
+            hi-lock-interactive-patterns nil)
+      (let ((hi-lock-auto-select-face t))
+        (dolist (pattern (reverse patterns))
+          (highlight-regexp (car pattern) (hi-lock-read-face-name)))))))
+
 (defvar hi-lock--hashcons-hash
   (make-hash-table :test 'equal :weakness t)
   "Hash table used to hash cons regexps.")