Re: [Groff] rationale for italic correction mechanism?

[Denis M. Wilson]

On Mon, 11 Nov 2013 12:57:31 -0600
Dave Kemper <address@hidden> wrote:

> > There is no conflict to groff's `inability' to apply it
> > automatically. What you really want is a *macro package* which does
> > the job.
> 
> Well, having a macro package which does the job is certainly better
> than not having it.  And thanks to those who have pointed out macros
> which do the job: I can poach some of their code even if I'm not
> using that particular package.
> 
> > This is
> > exactly the same as with TeX and LaTeX: While TeX (the program)
> > doesn't apply italic correction automatically, there is LaTeX's
> > \emph command which does it.
> 
> I have complete ignorance of TeX/LaTeX implementation.  But using
> parallels in the groff world, it seems that groff handles most
> typographical issues at the character level (kerning, ligatures,
> etc.), whereas macro packages tend to take on issues at the layout
> level (margins, paragraphs, headers, page numbering, etc.).
> 
> To me, italic correction's closest kin is kerning: both are
> adjustments to the horizontal space between glyphs that are made to
> correspond to widespread practice in professional typesetting.  Yet
> groff handles them in fundamentally opposite ways: kerning is a
> global setting, done by the basic typesetting engine, and turned on
> by default; italic correction must be done case by case, can only be
> made global with use of a macro, and is not done by default.
> 
> In addition, while the problem *can* be solved with macros, it's a
> curious problem to *require* macros to solve, as it's the rare case
> indeed where one would want to leave the characters in question
> overlapping. In general, groff uses sensible defaults for typographic
> issues. Italic correction is a curious exception.
> 
> So perhaps a more accurate phrasing of my question is, why are two
> functions as similar as kerning and italic correction handled in such
> different ways?

Kerning applies to glyphs from the same face, but italic correction
applies to glyphs from different faces for which there are no tables.
Usually (but probably not always) the latter is between words and
punctuation, but the amount is an intelligent guess.

> 


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