bug#47893: 27.1; `display-line-numbers-mode`, line numbers hidden with multiline overlays

bug#47893: 27.1; `display-line-numbers-mode`, line numbers hidden with multiline overlays

[Daniel Mendler]

When putting an overlay over multiple lines, the line numbers of
`display-line-numbers-mode` are hidden.

(defun bug ()
   (display-line-numbers-mode)
   (goto-char (point-min))
   (let ((ov (make-overlay (line-beginning-position)
                           (save-excursion (forward-line 4)
                                           (line-beginning-position)))))
     (overlay-put ov 'invisible t)
     (overlay-put ov 'before-string "line1\nline2\nline3\line3\nline4\n")))

I've also observed the issue with Emacs 28.

In GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.5, 
cairo version 1.16.0)
  of 2021-02-09, modified by Debian built on 3df710f593d9
Repository revision: b0229d4bbaea7fcddffced393512c650212830db
Repository branch: deb/emacs/d/sid/master
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian GNU/Linux 10 (buster)

bug#47893: 27.1; `display-line-numbers-mode`, line numbers hidden with multiline overlays

[Eli Zaretskii]

> From: Daniel Mendler <mail@daniel-mendler.de>
> Date: Mon, 19 Apr 2021 16:46:16 +0200
> 
> When putting an overlay over multiple lines, the line numbers of
> `display-line-numbers-mode` are hidden.
> 
> (defun bug ()
>    (display-line-numbers-mode)
>    (goto-char (point-min))
>    (let ((ov (make-overlay (line-beginning-position)
>                            (save-excursion (forward-line 4)
>                                            (line-beginning-position)))))
>      (overlay-put ov 'invisible t)
>      (overlay-put ov 'before-string "line1\nline2\nline3\line3\nline4\n")))

What do you mean by "hidden"?  With the above recipe, I see all the
line numbers starting from 5, as expected.  What is "hidden" here?

bug#47893: 27.1; `display-line-numbers-mode`, line numbers hidden with multiline overlays

[Daniel Mendler]

On 4/19/21 4:55 PM, Eli Zaretskii wrote:
> What do you mean by "hidden"?  With the above recipe, I see all the
> line numbers starting from 5, as expected.  What is "hidden" here?

When I have a buffer with the following content:

1 a
2 b
3 c
4 d
5 e
6 f
7 g
8 h
9 i

And run the given function, I see the following:

5 line1
   line2
   line3
   line4
   e
6 f
7 g
8 h
9 i

I suppose this is expected since the overlay hides all the lines in 
between? You can close this issue then as invalid, since the display 
line numbers don't reflect the visual lines but the lines in the buffer. 
Sorry for the noise!

bug#47893: 27.1; `display-line-numbers-mode`, line numbers hidden with multiline overlays

[Eli Zaretskii]

> Cc: 47893@debbugs.gnu.org
> From: Daniel Mendler <mail@daniel-mendler.de>
> Date: Mon, 19 Apr 2021 17:10:59 +0200
> 
> On 4/19/21 4:55 PM, Eli Zaretskii wrote:
> > What do you mean by "hidden"?  With the above recipe, I see all the
> > line numbers starting from 5, as expected.  What is "hidden" here?
> 
> When I have a buffer with the following content:
> 
> 1 a
> 2 b
> 3 c
> 4 d
> 5 e
> 6 f
> 7 g
> 8 h
> 9 i
> 
> And run the given function, I see the following:
> 
> 5 line1
>    line2
>    line3
>    line4
>    e
> 6 f
> 7 g
> 8 h
> 9 i

Right, and this is expected.

> I suppose this is expected since the overlay hides all the lines in 
> between?

Yes, exactly.  We only show the line numbers for lines that are
displayed.  Compare with, for example, Org buffers, where we don't
show line numbers for lines that are invisible.

> You can close this issue then as invalid, since the display line
> numbers don't reflect the visual lines but the lines in the buffer.

You can have the visual line numbers as well: just set the line-number
style to 'visual'.

Closing.