bug#48095: 28.0.50; display-line-numbers-mode / display-line-numbers-width-start incorrect

[Eli Zaretskii <eliz@gnu.org>]

> From: Len Trigg <lenbok@gmail.com>
> Date: Fri, 30 Apr 2021 10:29:23 +1200
> Cc: 48095@debbugs.gnu.org
> 
> That seems to work perfectly for my goal (and I assume the intent of display-line-numbers-width-start) of
> having the width stay fixed unless content gets added to the buffer. It might help to add guidance in the docs
> that extra lines would typically be set to the maximum window height.

Thanks, I added that to the doc string.

> Or maybe that value could instead be
> automatically computed from the height of the tallest emacs frame at that time? I assume that's not too
> intensive to determine since it happens once when the mode is activated?

This would be over-engineering, IMO.  First, some people tend to have
lots of frames, so this might be expensive.  Second, what matters is
not the frame height but the window height, and we could have many
windows even if the number of frames is small.  Third, some frames and
windows could be dedicated to special displays, and thus not really
relevant (example: Speedbar frames), so we will no doubt be asked to
provide yet another defcustom, to let users control which frames are
exempt from accounting for their height.

So I think asking users to provide a value strikes a good balance
between functionality and complexity, at least unless we hear about
use cases where automatic adjustment would really make a lot of sense.

With that in mind, I installed the change on the master branch, and
I'm closing this bug report.