# [texhax] italic correction w/o italic [was ...anglbrackets...]

Uwe Lück uwe.lueck at web.de
Wed Mar 20 15:24:36 CET 2013

Am Mittwoch, den 20.03.2013, 12:01 +1000 schrieb David Crosswell:
> On 20/03/13 11:37, Reinhard Kotucha wrote:
> > On 2013-03-19 at 23:57:19 +0100, Uwe Lück wrote:
> >
> >  > while I still have not understood \/ entirely
> >  > ("provisional" for the case of \it?)
> >
> > It's mentioned in the index of The TeXbook.  AFAIK there is an
> > italics-correction entry for each glyph in the tfm files.
> >
> > If you want to investigate, the program tftopl is your friend:
> >
> >   tftopl --help
> >
> Not being able to recall the post that mentioned application of this,
> the only time I use \/ is to assist in separation of a font that
> interferes with itself on display, generally in regard to fi, ff, or fl
> combinations.

In this case, AFAIK f{}i, f{}f, f{}l are an alternative,
another issue that I have not understood completely
(what is better, and why it works -- The TeXbook once
confused me here).

> Is that the application here?

No, ...

According to The TeXbook (p. 14), the italic correction \/ is
appropriate when changing from a slanted (e.g., italic) to an
unslanted font, except before period or comma.

With LaTeX, you may not know about \/, \textit and \textsl insert
it automatically. There may be cases when the automatic behaviour
is wrong, then you can prevent it by \nocorr (if you know about
this feature).

What I wonder about is that I sometimes find other applications
of \/ in macros by very knowledgeable authors. I remember
applications after boldface. The recent example was

\def\<#1>{\leavevmode\hbox{$\langle$#1\/$\rangle$}}
% syntactic quantity

from Knuths manmac.tex for typesetting The TeXbook on top of
plain.tex. It is used to typeset TeX's Backus-Naur syntax rules.
The argument is typically typeset in \rm, I cannot remember
having seen anything else. I wondered what rationale differing
from what The TeXbook tells is behind such a use of \/ after
roman (or after upright boldface).

In the special recent example, I now guess: The italic correction
makes up for "ink" looking out of the character box to the right
(TeXbook p. 64). The ink of a closing bracket touches its left
box border even at its top, and it is from a different font than
what is at the left of it. Without the italic correction, there
is a real danger that the closing bracket touches the final
character.

You can search the texhax archives

http://tug.org/pipermail/texhax/

for "italic correction", you get 75 hits and a large thread
"cases for italic correction". Unfortunately, I have not
found a posting listed there dealing with its subject
(it was mainly about the "d" in math italic).

Cheers,

Uwe.