Re: [Groff] The \D request in nroff and troff modes

[Ralph Corderoy]

Hi Werner,

>       0     1     2
>    +-----+-----+-----+  ...
>    0     24    48    72 ...
> 
> It's obvious that the values 0..23 are somehow `assigned' to character
> cell 0, and for orthogonality we have to assign position 24 already to
> character cell 1.
> 
> Another complication is that everything which specifies a length is
> rounded internally to be multiples of either \n[.H] or \n[.V].  In
> nroff mode this means that a horizontal length of 12u is still one
> character cell, but 13u is rounded up to be two character cells.

That seems odd.  If this were pixel computer graphics then 13u may be
rounded up to 24u but that would be a 24 pixel-long line occupying
pixels 0 to 23 inclusive;  clearly just a single character cell.

I can see the issue with spotting intersections, but is the vertical
line conceptually going down the left, middle, or right of the cell?
Perhaps both left and right so it spots intersections on either side?

Cheers,
Ralph.