[Yes, I know that I'm replying to a two-years-old thread...]

On Sun, Jul 16, 2017 at 12:03 AM Yuri D'Elia <wavexx@thregr.org> wrote:

> Is there a way to customize the face on a line basis, like
> `linum-format' allows?
>
> I currently highlight every 5th line using a different face in order to
> make the line numbers a little prettier ;)

Performance-wise, the new line numbers are fantastic. Great job, Eli.

But I miss the ability to call a function to return the "number"
string, as I did in linum.

(The image shows both my customized linum.el numbers and the new
native line numbers, for comparison.)

To be clear, I'm not *asking* for it to be implemented. I can imagine
the performance hit, and the added complexity for a feature that
almost nobody (except, apparently, Yuri D'Elia and I) would find
useful.