Re: Italic display in less

[Rhialto <rhialto%falu.nl@localhost>]

On Sun 29 Mar 2009 at 21:58:34 +0000, Valeriy E. Ushakov wrote:
> Rhialto <rhialto%falu.nl@localhost> wrote:
> 
> > On Fri 27 Mar 2009 at 06:22:45 +0000, Valeriy E. Ushakov wrote:
> >> It's not italic, it's underline.
> > 
> > Yes, but underline is already a substitute for italic. (The postscript
> > output will show it properly)
> 
> Which postscript output are you talking about?

The postscript output of the man pages:

$ cd /usr/share/man/man1
$ groff -mandoc -Tps groff.1 >/tmp/groff.ps
$ gv /tmp/groff.ps      # that's ghostview

> $ echo -e '\033[4mANSI udnerline\033[m'

The replacement of italics by underline stems from the time of line
printers, which could do overprinting (you make underlines with
underscore, backspace, letter, and bold with letter, backspace, letter).
ANSI (née VT100) codes for underlining are much later.

The specific order (underscore, backspace, letter) was chosen so that it
also works on glass terminals that don't overprint but just replace: you
see the letter when it is printed last (in the other order you'd only
see the underscore which is far less useful).

Even later, less(1) was taught to replace the overprint sequences with
terminal codes so that you'd see the intended effect even on
non-printing terminals.

Apparently, wscons can't do underline, so it uses a different colour.

-Olaf.
-- 
___ Olaf 'Rhialto' Seibert    -- You author it, and I'll reader it.
\X/ rhialto/at/xs4all.nl      -- Cetero censeo "authored" delendum esse.