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

[Eli Zaretskii <eliz@gnu.org>]

On October 17, 2017 5:44:51 AM GMT+03:00, Eli Zaretskii <eliz@gnu.org> wrote:
> > From: Paul Rankin <hello@paulwrankin.com>
> > Cc: Dmitry Gutov <dgutov@yandex.ru>, 28855@debbugs.gnu.org
> > Date: Tue, 17 Oct 2017 10:47:11 +1000
> > 
> > On Tue, 17 Oct 2017, at 02:05 AM, Eli Zaretskii wrote:
> > > Right, :align-to still counts from the window edge, even when line
> > > numbers are displayed, whereas you expected it to count from the
> end
> > > of the line-number display.
> > 
> > linum-mode.el (in 26.x) manages to display line numbers without
> interfering, so it’s really just about display-line-numbers-mode.
> 
> Yes, of course.  linum-mode displays the numbers in the display
> margin, and keeping off the margins was an explicit design goal of
> display-line-numbers-mode.
> 
> > > When this was briefly discussed during development, we decided not
> to
> > > change the reported window dimensions and geometry, including
> those of
> > > the text area, to account for the screen estate taken by the
> > > line-number display.  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?
> > 
> > Citing other discussions is not really relevant, if there’s a
> problem there’s a problem. User expectation is if a user writes codes
> following the Elisp manual, the expectation is that it should continue
> to work. In this case, using :align-to should align to its specified
> value.
> 
> :align-to does align to its value, it just doesn't currently update it
> to account for the space taken by line numbers.
> 
> It's clear that the change I have in mind will solve your specific
> problem, I just want to hear from others whether it could harm
> something.

Btw, in case it wasn't clear: a solution for this is already available --
use line-number-display-width when computing the value of :align-to.
Like tabulated-list-mode already does.

I'm just trying to establish if a more convenient solution could be possible.