bug#50220: 27.2; follow.el: follow-recenter does not work correctly if invoked in a follow window before the middle follow window.

[Noah Evans]

In GNU Emacs 27.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, cairo version 1.16.0)

Windowing system distributor 'The X.Org Foundation', version 11.0.12013000

System Description: Arch Linux

In follow mode, 'follow-mode-recenter` with no argument should center

the middle window around point. It works fine if it is used in the

middle window or a window after it, but if it is used in a window before

middle the post-command-hook moves the window back.

Reproduce:

Find a long file.

Split the window vertically two or more times.

M-x follow-mode

Go to the leftmost window and do C-c . C-l

Patch to fix:

From 65c6ccae67a5b2744711c3bfae2ebff3e530c2c1 Mon Sep 17 00:00:00 2001

From: Noah Evans <noah@nevans.me>

Date: Thu, 26 Aug 2021 20:27:45 -0400

Subject: [PATCH] follow.el: Fix bug#XXXXX in follow-recenter.

When follow-recenter is called in a follow window before the middle

follow window, the post-command-hook undoes the recentering.

* list/follow.el (follow-recenter): Set

follow-internal-force-redisplay when dest point is before start of

middle window.

---

 lisp/follow.el | 7 +++++--

 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lisp/follow.el b/lisp/follow.el

index dde140d0fd5..b64f4cb7348 100644

--- a/lisp/follow.el

+++ b/lisp/follow.el

@@ -858,8 +858,11 @@ from the bottom."

           (windows (follow-all-followers))

           (win (nth (/ (- (length windows) 1) 2) windows)))

       (select-window win)

-      (goto-char dest)

-      (recenter))))

+      (let ((win-s (window-start)))

+        (goto-char dest)

+        (recenter)

+        (when (< dest win-s)

+          (setq follow-internal-force-redisplay t))))))

 

 

 (defun follow-redraw ()

--

2.33.0