Re: [Groff] Rules drawn with \D are rounded

[Tadziu Hoffmann]

> Well, it is justifiable, but it isn't documented correctly.

The only justification I can think of is that this way it is
not apparent when a closed curve isn't closed properly (in the
Postscript sense).  This shouldn't happen in a Postscript-aware
application, however.

> What exactly do you want to change?  By default, the corners
> are always rounded -- since this is a detail on the PS level
> I think it is just fair to use PS stuff to change that
> (with \X or with .device).

The PS prologue file contains "1 setlinecap 1 setlinejoin"
in the begin-page procedure BP, which means that your custom
settings will be overwritten on the beginning of a new page.
For myself, I've just changed this to "2 setlinecap 1 setlinejoin"
because I think rounded joins look quite okay in pic graphics,
but I prefer square-ended rules, particularly for the fraction
bars in equations.

(By the way, I've also added a line "DEFS /BPhook known { DEFS
begin BPhook end } if" to BP, which lets me define a custom
Postscript beginning-of-page function BPhook in the document
(with "ps: def") that gets executed before groff prints anything
on the page.  This is useful for watermarks or colored
backgrounds.)

> An unfilled polygon uses strokes to connect the points; those
> strokes obey the settings of PS functions `setlinecap' and
> `setlinejoin', which are both activated.  On the other hand, a
> filled polygon simply fills the area defined by straight lines
> which connect its corner coordinates.

Note that this means that a filled and an unfilled polygon have
a different size (unless maybe the line width is zero).