Most efficient way of getting position of visual-line?

[Thomas F. K. Jorna]

Hello!

For a package I'm developing I need to insert an overlay every n visual 
lines. The fastest way of obtaining the positions of those lines I found 
is something like

 (let ((vl-list '(0))
        (n 10))
  (save-excursion
    (goto-line (point-min))
    (dotimes (line (/ (count-screen-lines) n))
      (vertical-motion n)
      (setq vl-list (append vl-list (list (point))))))


Perhaps not the most elegant written, but I've found no faster way than 
simply scrolling somewhere using vertical-motion

I had hoped that compute-motion could help me, but that does not seem to 
work well with word-wrapping, as that causes the width of the lines to 
change.

Ideally I would use something like what display-line-numbers-mode uses 
for its 'visual setting, but I have to admit that reading the source 
code is still a bit beyond me, in addition to the fact that those 
methods do not seem accessible from outsidedisplay-line-numbers-mode.

Anyone have any better ways of solving this? Thank you for your time!

- Thomas F. K. Jorna