From d8870a3dede52045518dc24a53143295df899943 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <jp@neverwas.me>
Date: Thu, 21 Sep 2023 06:54:27 -0700
Subject: [PATCH 3/3] [5.6] Add command to refill buffer with
 erc-fill-wrap-mode

* lisp/erc/erc-fill.el (erc-fill--wrap-rejigger-last-message):
New internal variable.
(erc-fill--wrap-rejigger-region,
erc-fill-wrap-refill-buffer): New command and helper function.
(Bug#60936)
---
 lisp/erc/erc-fill.el | 51 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/lisp/erc/erc-fill.el b/lisp/erc/erc-fill.el
index d323682476d..b419fb57bd4 100644
--- a/lisp/erc/erc-fill.el
+++ b/lisp/erc/erc-fill.el
@@ -552,6 +552,57 @@ erc-fill-wrap
                                `((space :width (- erc-fill--wrap-value ,len))
                                  (space :width erc-fill--wrap-value))))))
 
+(defvar erc-fill--wrap-rejigger-last-message nil
+  "Temporary working instance of `erc-fill--wrap-last-msg'.")
+
+(defun erc-fill--wrap-rejigger-region (start finish on-next)
+  "Recalculate `line-prefix' from START to FINISH.
+After refilling each message, call ON-NEXT with no args.  But
+stash and restore `erc-fill--wrap-last-msg' before doing so, in
+case this module's insert hooks run by way of the process filter."
+  (goto-char start)
+  (cl-assert (null erc-fill--wrap-rejigger-last-message))
+  (let (erc-fill--wrap-rejigger-last-message)
+    (while-let
+        (((< (point) finish))
+         (beg (if (get-text-property (point) 'line-prefix)
+                  (point)
+                (next-single-property-change (point) 'line-prefix)))
+         (val (get-text-property beg 'line-prefix))
+         (end (text-property-not-all beg finish 'line-prefix val)))
+      ;; If this is a left-side stamp on its own line.
+      (remove-text-properties beg (1+ end) '(line-prefix nil wrap-prefix nil))
+      (save-restriction
+        (narrow-to-region beg (1+ end))
+        (if-let (((eq 'erc-timestamp (field-at-pos beg)))
+                 ((eq 'date-left (get-text-property beg 'erc-stamp-type))))
+            (progn
+              (goto-char (field-end beg))
+              (erc-fill--wrap-stamp-insert-prefixed-date))
+          (let ((erc-fill--wrap-last-msg erc-fill--wrap-rejigger-last-message))
+            (erc-fill-wrap)
+            (setq erc-fill--wrap-rejigger-last-message
+                  erc-fill--wrap-last-msg))))
+      (when on-next
+        (funcall on-next))
+      (goto-char end))))
+
+(defun erc-fill-wrap-refill-buffer ()
+  "Recalculate all `fill-wrap' prefixes in the current buffer."
+  (interactive)
+  (unless erc-fill-wrap-mode
+    (user-error "Module `fill-wrap' not active in current buffer."))
+  (save-excursion
+    (with-silent-modifications
+      (let* ((rep (make-progress-reporter
+                   "Rewrap" 0 (line-number-at-pos erc-insert-marker) 1))
+             (seen 0)
+             (callback (lambda ()
+                         (progress-reporter-update rep (cl-incf seen))
+                         (accept-process-output nil 0.000001))))
+        (erc-fill--wrap-rejigger-region (point-min) erc-insert-marker callback)
+        (progress-reporter-done rep)))))
+
 ;; FIXME use own text property to avoid false positives.
 (defun erc-fill--wrap-merged-button-p (point)
   (equal "" (get-text-property point 'display)))
-- 
2.41.0