Juri,

You could set `display-line-numbers' to 'absolute and run code below every
time the window is scrolled up/down (e.g. with a hook):

(save-excursion
  (move-to-window-line 0)
  (setq display-line-numbers-offset
           (* -1
              (line-number-at-pos))))

Notice that if `display-line-numbers' is 'absolute and narrowing is
enabled, you already get your desired behaviour.


On Tue, Dec 6, 2022 at 10:28 AM Juri Linkov <juri@linkov.net> wrote:

> I wonder why ‘display-line-numbers’ doesn't provide an option
> to display line numbers relative to the window-start?
> IMHO, one of the most reasonable excuses to sacrifice the screen space
> for line numbers is to display only these short numbers that could be
> used to jump to a line visible on the screen.  For that the quickest
> key sequence is e.g. 'M-5 M-r'.
>
> Then all possibilities will be covered by these options of
> ‘display-line-numbers’:
>
> - absolute line numbers can be used by 'M-g M-g' (goto-line);
> - relative line numbers - by 'C-u N C-n' and 'C-u N C-p';
> - window line numbers - by 'M-r'.
>
>

-- 
João Paulo L. de Carvalho
Ph.D Computer Science |  IC-UNICAMP | Campinas , SP - Brazil
Postdoctoral Research Fellow | University of Alberta | Edmonton, AB - Canada
joao.carvalho@ic.unicamp.br
joao.carvalho@ualberta.ca