[Groff] Re: SGR implementation in groff

[Markus Kuhn]

On Mon, 15 Oct 2001, Thomas E. Dickey wrote:

> On Sun, 14 Oct 2001, Werner LEMBERG wrote:
> > > >   . I intend to handle SGR escapes similar to the handling of
> > > >     character set changes in Emacs.  This means that at the end of a
> > > >     line, the state is always reset to the default.  BTW, `less'

That sounds very good to me, like all your other suggestions!

> newline shouldn't reset video attributes (not if you're pretending to make
> it ISO-compatible).

I think that is not what he meant. I think we are talking about the
following:

The groff output will reset any SGR state changes that it makes in a line
*before* the LF at the end of the line. So if an entire paragraph is in
green or italic, then every line of the paragraph will start with the SGR
sequence for green or italic, but the LF at the end of each line will
always be sent to the terminal back in the default mode. This is fully ISO
compatible. Nobody proposes here to change the meaning of a line feed, if
that is what you understood.

Groff will just never send out a green or italic LF. This will not only
work around "less" definiencies, it also will keep classic Unix tools such
as grep, head, tail, sort, etc. operational without modifications. All
this is old and well-established practice in the EUC world for code set
changes.

The only attribute where this principle might be problematic visually is
the background colour, which groff probabaly should not touch for that
reason. Background colour changes would not affect the space between
the last graphic character of a line and the right margin.

With SGR man, it would also be very nice to have italic support in xterm.
The fonts are already there and emacs can do it already.

Markus

-- 
Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at acm.org,  WWW: <http://www.cl.cam.ac.uk/~mgk25/>