Subject: Re: bug#28855: 26.0.90; display-line-numbers-mode does not respect (line|wrap)-prefix '(space :align-to N) text property

From: Eli Zaretskii <[email-masked]>
Date: Wed, 18 Oct 2017 19:47:31 +0300

> Cc: [email-masked]
> From: Dmitry Gutov <[email-masked]>
> Date: Wed, 18 Oct 2017 12:29:08 +0300
> 
> FTR, I'd have preferred for the line numbers to be considered outside of 
> the window edge, together with fringes and margins. And I still don't 
> see any downside to it (except it might be harder to implement).

Well, "harder to implement" is very relevant here ;-)

Also, "outside of the window edge" has implications besides text
layout, and I trust Martin's judgment (which happens to match mine)
that we should try letting those sleeping dogs lie.

In any case, this opinion of yours probably means that having
:align-to automatically update its offsets to account for the line
numbers is in the direction you wanted Emacs to go, albeit not all the
way, right?  I mean, it does make Emacs behave as if line numbers were
not part of the text area in this case.

> As it is now, third-party code has to adapt instead, by handling the 
> line numbers specially.

Yes.  But this is nothing new, it happens with almost every
display-related feature.

> > But maybe :align-to should be an exception, when
> > used to align buffer text (as opposed to header-line or mode-line)?
> > Though I'm bothered whether some users of :align-to may not want this
> > automatic offset.  :align-to is a very popular feature; does anyone
> > know or imagine why a Lisp program would NOT like such an offset?
> > 
> > What do people think?  Dmitry, what about company-mode popups, for
> > example?
> 
> Not sure. What about them? We don't use align-to in the popups (though 
> we could, for space-only offsets, now that I've read about this spec; 
> not sure if the change will be worth it, performance or memory-wise).
> 
> And as for align-to's used in the buffer text, we probably don't support 
> them very well, but the proposed change shouldn't make it any worse, I 
> think.

OK, thanks.

Martin, any comments or thoughts about this, before I go out and make
the code changes to implement this?

Anybody else?  Stefan? John?

TIA