bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 18 Mar 2022 16:38:45 +0100
> From:  Ergus via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> emacs -Q
> (setq highlight-nonselected-windows t)
> 
> C-x 2
> C-x o
> C-x C-f /tmp/test
> (insert some text)
> C-a C-SPC C-f C-f C-f
> C-x o 
> 
> [at this point we should see a region highlighted over the 3 first
> letters of the inserted text in the other winfow buffer (test)]
> 
> then eval this several times:
> 
> (with-selected-window (get-buffer-window "test" 0)
>     (right-char))
> 
> This will move the point in the test window, but the region won't be
> updated.

Thanks.  Does the patch below solve the problem?

diff --git a/src/intervals.c b/src/intervals.c
index 687b237..cbcc100 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -44,6 +44,7 @@
 #include "lisp.h"
 #include "intervals.h"
 #include "buffer.h"
+#include "window.h"
 #include "puresize.h"
 #include "keymap.h"
 
@@ -1885,6 +1886,11 @@ set_point_both (ptrdiff_t charpos, ptrdiff_t bytepos)
       return;
     }
 
+  if (highlight_nonselected_windows
+      && !NILP (Vtransient_mark_mode)
+      && !NILP (BVAR (current_buffer, mark_active)))
+    bset_redisplay (current_buffer);
+
   /* Set TO to the interval containing the char after CHARPOS,
      and TOPREV to the interval containing the char before CHARPOS.
      Either one may be null.  They may be equal.  */