bug#56682: locked narrowing (was: bug#56682: Fix the long lines font locking related slowdowns)

[Gregory Heytings]

Another comment:

> diff --git a/nlinum.el b/nlinum.el
> index 4f0e02fef1..3feaaca5c3 100644
> --- a/nlinum.el
> +++ b/nlinum.el
> @@ -312,7 +312,7 @@ Only works right if point is at BOL."
>   (if nlinum-widen
>       (save-excursion
>         (save-restriction
> -          (widen)
> +          (REALLY-widen)
>           (forward-line 0)              ;In case (point-min) was not at BOL.
>           (let ((nlinum-widen nil))
>             (nlinum--line-number-at-pos))))

FWIW, that's not a good example, because it's a bad idea to calculate line 
numbers in buffers with long lines or with too many lines: it takes too 
much time.