[Fontinst] On the proper look of the \AA

[Lars Hellström]

At 14.55 +0100 2004-01-16, Vladimir Volovich wrote:
>
>Some arguments for the special look of Aring (which I share):
>
>1) D.Knuth defined a special command for \AA, which puts ring close to
>   A instead of using \accent
>
>2) the same approach is used in LaTeX in ot1enc.def and ot4enc.def,
>   and LaTeX has in mind not only the CM fonts, but any font families,
>   so these definitions are meant to be applied not only to CM fonts.
>
>3) The fontinst package contains some code to put the ring close to A
>   (the glyph ringfitted defined in latin.mtx, and used in ot1.etx).
>   (and this package is meant to be used for installation of "arbitrary"
>   fonts)

This is mostly because the (implicit) definition of the OT1 encoding made
in ot1enc.def, since the definition of the OT1 \r{A} (\AA is obsolete
notation in LaTeX) assumes that the width of the ring glyph is equal to
that of the A glyph. In other words, this is effect, not cause.

>4) the article http://en.wikipedia.org/wiki/%C5 in the Online
>   Encyclopedia states that:
>
>  The letter "\r{A}" is often perceived as an "A" with a ring,
>  interpreting the ring as a diacritic mark. However, the ring is not a
>  diacritic. Rather, the letter developed as a form of semi-ligature of
>  two consecutive "A"s.
>
>   so this gives some basis to think that ring might be located not as
>   plain accent, but closer to A.

I don't think this historical aspect is particularly relevant. It is true
that the ring in \r{a} isn't linguistically a diacritical mark, but neither
are (in Swedish) the dots in \"{a} and \"{o}. \r{a}, \"{a}, and \"{o} are
three last letters in the Swedish alphabet, not mere variations on a and o.

Trivia information: The Swedish alphabet has 28 letters (V and W are
considered equivalent, so A-Z are 25 letters), 9 of which are vowels (a, o,
u, \r{a} are classified as "hard", e, i, y, \"{a}, \"{o} are classified as
"soft"). We really need that many vowels too, because there are 18 distinct
vowel sounds in Swedish.

>5) my memories about the look of the Angstrom sign in the books
>   suggest that it should be written as plain TeX does it.
>
>Arguments against the close placement of the ring (from Alexander
>Lebedev and Lars Engebretsen) state that from aesthetic reasons the
>ring should be put on the same height as other accents.

This might actually be the reason to _make_ it touch the A. Recall that
accents over capitals are usually quite close to the letter (closer than in
the case of lower case letters). Also note that the height of the ring in
many fonts is significantly larger than that of the dieresis. Vertically
centering them both on the same axis may well result in the ring touching
the A.

>E.g., the
>Bitstream specification for developers of new fonts contains an
>example of Aring on page 5 and an example of accents on page 4:
>http://www.bitstream.com/categories/products/nfc/NFCSubmissions.pdf
>
>I have some questions to experts:
>
>1) what was the rationale to use the special definition of \AA - why
>   not just use the \accent to put the ring over A?

Within the TeX world, the reason is that Knuth did it this way. I would
look in Computers and Typesetting Vol. A (TeXbook) or Vol. E (CM typefaces)
for the rationale.

>2) is this rationale only a design decision of the Computer Modern
>   fonts, or it can be applied to other font families? I.e., shall the
>   ring in the Aring glyph be put with a gap of the same widths as all
>   other accents, or it is preferred to use "gap-less" Aring?

This is probably nothing CM-specific.

>3) should the glyphs for the LATIN CAPITAL LETTER A WITH RING ABOVE
>   and the ANGSTROM SIGN be the same in respect of the placement of
>   the ring above A? (I.e., maybe the ring over A in U+00C5 should be
>   put as an accent; but the preferred placement of the ring over A in
>   the angstrom sign U+212B is without the gap).

I see no reason for making them different in this respect. The ANGSTROM
sign is, after all, simply the first letter in the last name of Anders
Jonas \r{A}ngstr\"{o}m (see http://www.angstrom.uu.se/andersknut.html).

Lars Hellström