bug#27427: 26.0.50; Native line numbers lead to display error in company-mode popup

[Eli Zaretskii]

> From: Dmitry Gutov <dgutov@yandex.ru>
> Cc: alexanderm@web.de, 27427@debbugs.gnu.org
> Date: Fri, 14 Jul 2017 02:04:21 +0300
> 
> What doesn't work well is that the popup "background" gets displaced to 
> the left by the width of the numbers column, when rendered using the 
> popup overlay. Background meaning the contents of all the lines behind 
> the popup. And that happens because the line number glyphs are gone for 
> those specific lines, and we can't pad them without knowing the width of 
> the numbers column.

You could use the new function line-number-display-width to obtain
that information.

> Now, I've come upon this idea of a trivial patch. What do you think, 
> Eli? It seems to work perfectly, even though I'm struggling to 
> understand how this might happen under the covers. Is it brittle?

No, it isn't brittle.  What are you struggling to understand?  Maybe I
can help.