bug#28248: 26.0.50; display-line-numbers does not affect window-width / window-text-width

[Steve Purcell]

On 17 Oct 2017, at 15:34, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> That would be the actual amount of "screen estate used up for
>> line-number display".
>> 
>> Can I rely on the extra value always being 2?
> 
> As long as we don't change the implementation, yes.  Alternatively,
> you can call line-number-display-width with the optional argument and
> get the result in pixels, in which case it includes everything (you
> can divide by frame-char-width to get the result back in columns).


Thanks, this is helpful. I have some code which calculates the width of the 
buffer contents in characters, and calculating this pixelwise works nicely for 
me.

The odd thing is that there’s a one character discrepancy between graphical and 
terminal frames. It’s not related to the new line numbers support, since an 
adjustment for that discrepancy has always been necessary in the code, and the 
native line numbers are not present in the terminal anyway. Any idea where that 
one-column difference might be coming from?

https://github.com/purcell/page-break-lines/blob/610dbdc9d39a37912e2b8bfbd3e3d15c7e5d622f/page-break-lines.el#L128-L134