> This [disagreement in position of a drawn baseline] > seems like a bug in Heirloom Doctools troff to me, but given that > code base's provenance, it's easily possible that it's better aligned > with AT&T troff behavior. (Does someone know?)
I don't know absolutely, but it's very likely that both groff and heirloom agree with one "AT&T troff'' or another. Ossanna's original did not have drawing capability, so it created horizontal lines as a row of underscores. The vertical position and thickness of such a line is determined by the current font. Later, in ditroff, Kernighan introduced \D drawing capability. Then the position and thickness of the line became the baseline and the current point size. Doug
