Re: Potential bug in sv geometry

On Fri, Nov 21, 2025 at 08:28:49PM +0100, onf wrote:
> Hi all,
> 
> there seems to be an off by one bug in sv's geometry in groff.
> 
> Given the input,
>   .de x
>   . br
>   ..
>   .wh 2v x
>   Lorem
>   .br
>   .sv 1v
>   ipsum
>   .br
>   dolor
> 
> groff gives the output
>   Lorem
>   ipsum
>   dolor
> 
> whereas both Heirloom troff and Plan 9 troff give
>   Lorem
> 
>   ipsum
>   dolor
> 
> Groff gives the same output when the wh line is
> changed to
>   .wh 2v+1u x
> 
> (in troff mode; in nroff mode, +1v is needed due to lower resolution)
> 
> Cheers,
> onf
> 
  The bug in the 'sv' request is in the heirloom's and plan9's version.

  A text baseline lands exactly on the next baseline after a 1v long jump.

  See "Troff User's Manual" (https://troff.org/54.pdf).