Re: [Groff] color support in grotty

[Ruslan Ermilov]

On Wed, Oct 16, 2002 at 06:52:12PM +0300, Ruslan Ermilov wrote:
> On Thu, Feb 07, 2002 at 09:33:25AM +0100, Werner LEMBERG wrote:
> > 
> > Finally, here it is!
> > 
> > 
> > I've finished color support in grotty and committed it to the CVS.
> > SGR escape sequences will be the new default.  At the same time, I've
> > added two new options to nroff.
> > 
> OK, now that FreeBSD 5.0-CURRENT has Groff 1.18.1 in...
> 
> We have learned a few pitfalls with this new behavior of grotty(1).
> The biggest problem here is that grotty(1) emits ANSI SGR sequences
> to print bold and italic characters directly, but FreeBSD's default
> textual console terminal, cons25, renders "underscore" attribute the
> same as the "bold" attribute, as well as the Linux's one does.  On
> the other hand, classical nroff(1) filters like ul(1) and more(1)
> respect the TERM setting and pick up the correct escape sequences
> to enter the underscored mode (and fall back to using the "reverse"
> attribute if "underscore" is not available).  I mistakenly thought
> that adding the -r option to grotty(1) would solve this problem,
> but this turned out to worsen the output on terminals that support
> underlining, e.g. XFree86's "xterm".  So using -r generally is not
> allowed.
> 
> Another thing to remember is that nroff(1) is often used by man(1)
> to create preformatted manpages, catpages.  And these catpages
> should preferably be viewable on a wide variety of terminals all
> around.  As of this writing, FreeBSD runs nroff(1) with the -c
> option when creating catpages.  I am also interested in hearing
> what other operating system do with this.
> 
> On yet another hand, most nowadays terminals seem to support the
> ANSI SGR foreground/background color sequences, so I thought that
> it maybe worth separating the drawing of bold/italic fonts from
> the color output in grotty(1).  The attached patch modifies the
> -c option in such a way that if it is specified once, it causes
> grotty(1) to revert to the old drawing method for bold and italic
> characters (using the backspace), but the ANSI SGR color escapes
> are not disabled.  If specified more than once, it also disables
> the color output.  (The patch also fixes the nroff(1) "usage".)
> 
> As a side note, it would be great if troff(1) also provided the
> \n[.m] and \n[.M] read-only registers to represent the respective
> current colors.  This would be extremely useful when adding
> color support to groff_mdoc(7).
> 
Please don't apply the grotty -c patch yet.  I'm still trying
to find a right way, and am not so very sure that this way is
right.  I will follow up shortly.


Cheers,
-- 
Ruslan Ermilov          Sysadmin and DBA,
address@hidden          Sunbay Software AG,
address@hidden          FreeBSD committer,
+380.652.512.251        Simferopol, Ukraine

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