From 832580989619d3343f06cd9a9eeed9f22ddad376 Mon Sep 17 00:00:00 2001
From: Manuel Giraud <manuel@ledu-giraud.fr>
Date: Fri, 6 Feb 2026 20:20:49 +0100
Subject: [PATCH] Fix selected group sort with topics (bug#80341)

* lisp/gnus/gnus-topic.el (gnus-group-sort-selected-topic): New
function to sort selected groups into topic.
(gnus-topic-mode): Use it as sort selected function in topic
mode.
* etc/NEWS: Announce the change.
---
 etc/NEWS                |  3 +++
 lisp/gnus/gnus-topic.el | 28 ++++++++++++++++++++++++++--
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index 88235ce0de6..fb78b3f7b5e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1787,6 +1787,9 @@ It is believed to no longer be useful as a method to fight spam.  The
 The symbolic prefix is another kind of universal prefix that is used in
 Gnus, see "(gnus) Symbolic Prefixes" in the Gnus manual.
 
+---
+*** Sorting selected groups is now possible with 'gnus-topic-mode'.
+
 ** Sieve
 
 +++
diff --git a/lisp/gnus/gnus-topic.el b/lisp/gnus/gnus-topic.el
index 315f1a018c9..4fb796105e2 100644
--- a/lisp/gnus/gnus-topic.el
+++ b/lisp/gnus/gnus-topic.el
@@ -1158,7 +1158,8 @@ articles in the topic and its subtopics."
                   #'gnus-topic-group-indentation)
       (setq-local gnus-group-update-group-function
 	          #'gnus-topic-update-topics-containing-group)
-      (setq-local gnus-group-sort-alist-function #'gnus-group-sort-topic)
+      (setq-local gnus-group-sort-alist-function #'gnus-group-sort-topic
+                  gnus-group-sort-selected-function #'gnus-group-sort-selected-topic)
       (setq gnus-group-change-level-function #'gnus-topic-change-level)
       (setq gnus-goto-missing-group-function #'gnus-topic-goto-missing-group)
       (add-hook 'gnus-check-bogus-groups-hook #'gnus-topic-clean-alist
@@ -1173,7 +1174,8 @@ articles in the topic and its subtopics."
       (setq gnus-group-change-level-function nil)
       (remove-hook 'gnus-check-bogus-groups-hook #'gnus-topic-clean-alist)
       (setq gnus-group-prepare-function #'gnus-group-prepare-flat)
-      (setq gnus-group-sort-alist-function #'gnus-group-sort-flat))
+      (setq gnus-group-sort-alist-function #'gnus-group-sort-flat
+            gnus-group-sort-selected-function #'gnus-group-sort-selected-flat))
     (when (called-interactively-p 'any)
       (gnus-group-list-groups))))
 
@@ -1651,6 +1653,28 @@ If performed on a topic, edit the topic parameters instead."
       (setcar alist (delete "dummy.group" (car alist)))
       (gnus-topic-sort-topic (pop alist) func reverse))))
 
+(defun gnus-group-sort-selected-topic (groups func reverse)
+  "Sort selected GROUPS in the topics according to FUNC and REVERSE."
+  (let ((alist gnus-topic-alist))
+    (while alist
+      ;; !!!Sometimes nil elements sneak into the alist,
+      ;; for some reason or other.
+      (setcar alist (delq nil (car alist)))
+      (setcar alist (delete "dummy.group" (car alist)))
+      (let* ((topic (pop alist))
+             (inter (seq-intersection groups (cdr topic))))
+        ;; Do something only if there are some selected groups in this
+        ;; topic.
+        (when inter
+          (let ((sorted (mapcar #'gnus-info-group
+                                (sort (mapcar #'gnus-get-info inter) func))))
+            ;; Do the reversal, if necessary.
+            (when reverse
+              (setq sorted (nreverse (cdr sorted))))
+            ;; Set the topic contents as the union of the sorted
+            ;; selected groups and its previous contents.
+            (setcdr topic (seq-union sorted (cdr topic)))))))))
+
 (defun gnus-topic-sort-topic (topic func reverse)
   ;; Each topic only lists the name of the group, while
   ;; the sort predicates expect group infos as inputs.