> > I just need triangles [...]
> I have made filled triangles in gpic by a simple kludge of
> automating the removal of one corner of a filled rectangle.
> [...]
How about something crude as
.PS
define triangle { box invis "$4\v'$3'\D'P $1 -$2 $1 $2'" }
triangle(1c,1.8c,1c,\M[green]) "Hello" ""; arrow; box "world"
.PE
or maybe even
.PS
define triangle { box invis "$4\v'$3'\D'P $1 -$2 $1 $2'" $5 "" }
triangle(1c,1.8c,1c,\M[green],"Hello"); arrow; box "world"
.PE
?
It doesn't follow the syntax of other objects and it's missing
configurability analogous to boxwid and boxht and arrows don't
extend to the edges etc., but it's still kinda workable...