From 194c28aaf22979d46f22cc424ba8f1bc78db27b3 Mon Sep 17 00:00:00 2001
From: Paul Hsin-ti McClelland <PaulHMcClelland@protonmail.com>
Date: Wed, 22 Apr 2026 23:49:09 -0400
Subject: [PATCH] Add outline-search-from-regexp generic helper

Add outline-search-from-regexp generic helper (bug#80887)

Minor modes and third-party packages that customize 'outline-regexp'
typically need an 'outline-search-function' implementation that
searches for 'outline-regexp' anchored at beginning of line.  Without
a generic helper, each such user reinvents the function locally.
Add it to outline.el.

This pattern has been in production use as a default value of
'outline-search-function' (set via 'setq-default') without issues.

* lisp/outline.el (outline-search-from-regexp): New function.
* etc/NEWS: Announce it.
---
 etc/NEWS        |  9 +++++++++
 lisp/outline.el | 20 ++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/etc/NEWS b/etc/NEWS
index b60d1788e91..b76b18cdc8c 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -117,6 +117,15 @@ obsolete.
 It is bound to 'C-e' and reveals the current entry
 with its parent hierarchy.
 
+---
+*** New function 'outline-search-from-regexp'.
+A generic 'outline-search-function' implementation driven by
+'outline-regexp', suitable for modes or minor modes that customize
+'outline-regexp' but do not need a custom search strategy.
+Install it with:
+
+  (setq-local outline-search-function #'outline-search-from-regexp)
+
 
 * New Modes and Packages in Emacs 32.1
 
diff --git a/lisp/outline.el b/lisp/outline.el
index 79bb8982e4e..3eb354a22ce 100644
--- a/lisp/outline.el
+++ b/lisp/outline.el
@@ -1550,6 +1550,26 @@ The rest of arguments are described in `outline-search-function'."
         (when move (goto-char (or bound (if backward (point-min) (point-max)))))
         nil))))
 
+
+;;; Search regexp for outline headings
+
+;;;###autoload
+(defun outline-search-from-regexp (&optional bound move backward looking-at)
+  "Search for the next heading matching `outline-regexp'.
+The arguments BOUND, MOVE, BACKWARD, and LOOKING-AT are described
+in `outline-search-function'.  This function is intended to be
+used in `outline-search-function' by modes and minor modes that
+customize `outline-regexp' but do not need a custom search strategy.
+Install it with
+
+  (setq-local outline-search-function #\\='outline-search-from-regexp)"
+  (if looking-at
+      (looking-at outline-regexp)
+    (funcall (if backward #'re-search-backward #'re-search-forward)
+             (concat "^\\(?:" outline-regexp "\\)")
+             bound
+             (if move 'move t))))
+
 
 (defun outline-headers-as-kill (beg end)
   "Save the visible outline headers between BEG and END to the kill ring.