On Fri, Jun 17, 2016 at 10:21:01AM +0300, Eli Zaretskii wrote:
> Sorry, still not reproducible.  Maybe there's something else to be
> done?  Here's the complete recipe I used, after downloading
> smart-mode-line and rich-minority which it requires:
> 
>   emacs -Q
>   (add-to-list 'load-path "/path/to/smart-mode-line-master")
>   (load-library "smart-mode-line")
>   (sml/setup)
>   (dolist (sym '(mode-line mode-line-inactive))
>         (set-face-attribute
>          sym nil
>          :box `(:line-width 2 :color ,(face-attribute `,sym :background))))
> 
> I see no display problems in the mode line after the above.

I just tried this on the NS port and it leaves stuff behind. The line
number goes over into that left-hand section, which is fine since it's
not the fringe.

Aside from that, the digits seem to be placed wrongly. Sometimes
they're fine, other times they're all wonky. I've attached a
screenshot where it's displaying 404, but it looks like the 0 is too
far left, and the second 4 is cut off, and another screenshot after I
paged down and you can still see the left edge of the zero.

I don't see any other characters that are obviously displayed wrong.

I don't know how to tell what font it is, but I suspect it's
variable-width and Emacs doesn't notice when they change size. For
example, the misplaced 0 in 404 occurs after scrolling from a number
starting with 3, and the 3 appears to be narrower than the 4. The
second digit doesn't move right to compensate for the larger first
digit. When it finally does move, it leaves artifacts behind.

Changing line-width to 1 in your code fixes it.
-- 
Alan Third