Re: Emacs26: Quick thoughts on display-line-numbers-mode

[Eli Zaretskii <eliz@gnu.org>]

> From: Matthew Plant <maplant95@gmail.com>
> Cc: emacs-devel@gnu.org
> Date: Thu, 05 Oct 2017 20:09:39 -0700
> 
> > There's a technical problem with doing that, for which I didn't have
> > a
> > solution at the time and still don't.  Such an option would also slow
> > redisplay, albeit in minor ways.
> > 
> For now, you can go to src/xdisp.c:20996 and change the line:
>     strcat (lnum_buf, " ");
> to  
>    strcat (lnum_buf, "|");

The problem with this is that in R2L paragraphs the glyph should
_precede_ the number, i.e. be to the left of the number.  And when the
number is generated for the first line to be redrawn, the paragraph
direction was not yet computed.  This is the technical problem to
which I alluded.  Until I find a way to solve it, such solutions
cannot be accepted, sorry.

> Although I think I like the pipe character better than the space.

That definitely depends on the font you are using.  Some fonts have an
extremely ugly pipe glyphs.  So this will have to be another
customization option, not just a hard-coded character.