Subject: bug#55299: 29.0.50; Bug with the mode-line and pixel-scroll-precision-mode

From: Eli Zaretskii <[email-masked]>
Date: Sun, 08 May 2022 08:34:12 +0300

> Cc: [email-masked]
> Date: Sun, 08 May 2022 09:01:32 +0800
> From:  Po Lu via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <[email-masked]>
> 
> Konrad Podczeck <[email-masked]> writes:
> 
> > With this patch, I don’t get any error message, but If a frame has
> > only one window, I cannot scroll (using the mouse wheel) downwards
> > anymore, and after doing C-x 2, the same is true if I scroll in the
> > active pane, while when I scroll in the inactive pane, I always get
> > scrolling upwards, regardless of which direction I rotate the wheel.
> 
> Does this fix your problem?
> 
> diff --git a/src/window.c b/src/window.c
> index 15d6cf94b0..1e719c2598 100644
> --- a/src/window.c
> +++ b/src/window.c
> @@ -7980,6 +7980,8 @@ DEFUN ("set-window-vscroll", Fset_window_vscroll, Sset_window_vscroll,
>  
>  	  /* Prevent redisplay shortcuts.  */
>  	  XBUFFER (w->contents)->prevent_redisplay_optimizations_p = true;
> +
> +	  windows_or_buffers_changed = 1013;

I'm not surer we want this.  It will slow down redisplay, so we need a
good understanding why this is required.  And the problem happens only
on macOS, isn't that so?