bug#28879: 26.0.90; Narrowed line numbers shown with display-line-numbers-widen

bug#28879: 26.0.90; Narrowed line numbers shown with display-line-numbers-widen

[Andy Moreton]

 From emacs -Q:
1) Open a lisp file
    (setq display-line-numbers-widen t)
    M-x display-line-numbers-mode
2) Move point inside a function
    M-x narrow-to-defun
3) M-x widen

After (2) the window shows line numbers relative to the start of
the buffer, as expected.

After (3), the window shows line numbers starting from 1 for the
narrowed region. After the next mouse or keyboard input, the line
numbers are displayed normally.

Thus it seems that when display-line-numbers-widen is non-nil the line
numbers are not recomputed after widen until then next input.

In GNU Emacs 26.0.90 (build 9, x86_64-w64-mingw32)
  of 2017-10-17 built on QUIETUS
Repository revision: 2e1b3522b8562f94a98fed07aeddb6b5ba0dbc6c

bug#28879: 26.0.90; Narrowed line numbers shown with display-line-numbers-widen

[Eli Zaretskii]

> From: Andy Moreton <andrewjmoreton@gmail.com>
> Date: Tue, 17 Oct 2017 21:40:16 +0100
> 
>  From emacs -Q:
> 1) Open a lisp file
>     (setq display-line-numbers-widen t)
>     M-x display-line-numbers-mode
> 2) Move point inside a function
>     M-x narrow-to-defun
> 3) M-x widen
> 
> After (2) the window shows line numbers relative to the start of
> the buffer, as expected.
> 
> After (3), the window shows line numbers starting from 1 for the
> narrowed region. After the next mouse or keyboard input, the line
> numbers are displayed normally.

Right.  And if your Emacs is built with --enable-checking (which is
something I advise for the first couple of pretest of a new release),
you might be able to trigger an assertion violation by repeating the
above recipe several times.

> Thus it seems that when display-line-numbers-widen is non-nil the line
> numbers are not recomputed after widen until then next input.

Actually, the numbers have been recomputed, as you see them change on
display.  They just were recomputed incorrectly: the logic related to
widening failed to catch the first redisplay cycle after 'widen',
which is special.  (In general, line numbers are computed as part of
displaying a window, so whenever you see redisplay, you know the line
numbers were recomputed, at least for some lines.)

Should be fixed now.  Thanks for reporting this.

bug#28879: 26.0.90; Narrowed line numbers shown with display-line-numbers-widen

[Andy Moreton]

On Wed 18 Oct 2017, Eli Zaretskii wrote:

>> From: Andy Moreton <andrewjmoreton@gmail.com>
>> Date: Tue, 17 Oct 2017 21:40:16 +0100
>> 
>>  From emacs -Q:
>> 1) Open a lisp file
>>     (setq display-line-numbers-widen t)
>>     M-x display-line-numbers-mode
>> 2) Move point inside a function
>>     M-x narrow-to-defun
>> 3) M-x widen
>> 
>> After (2) the window shows line numbers relative to the start of
>> the buffer, as expected.
>> 
>> After (3), the window shows line numbers starting from 1 for the
>> narrowed region. After the next mouse or keyboard input, the line
>> numbers are displayed normally.
>
> Right.  And if your Emacs is built with --enable-checking (which is
> something I advise for the first couple of pretest of a new release),
> you might be able to trigger an assertion violation by repeating the
> above recipe several times.

Good point - mine was built without it.

> Should be fixed now.  Thanks for reporting this.

Confirmed fixed.

bug#28879: 26.0.90; Narrowed line numbers shown with display-line-numbers-widen

[Eli Zaretskii]

> From: Andy Moreton <andrewjmoreton@gmail.com>
> Date: Wed, 18 Oct 2017 18:39:12 +0100
> 
> > Should be fixed now.  Thanks for reporting this.
> 
> Confirmed fixed.

Thanks, closing.