The STIX folks (Scientific and Technical Information eXchange) folks have a beta version of their math font. There are more math characters in the STIX fonts than in Cambria Math. The primary typeface is Times Roman. This post describes how you can examine the fonts and gives some reasons why they aren’t quite ready to use with Word 2007 and RichEdit 6. To get the fonts, go to http://www.stixfonts.org/ and follow the download instructions.

On Windows, you can use Asmus Freytag’s nifty Unibook program to look at the fonts. Unibook is the program that typesets the Unicode Standard’s code charts and it’s also great for checking out character properties. Here are Asmus’s instructions on how to use it to see the fonts and where the characters are located:

1) download Stix fonts, unpack, and drag/copy to Windows/Fonts folder to install

2) download Unibook (beta) from http://www.unicode.org/unibook

3) create a StixBeta.cfl file (see below)

4) run Unibook, open that cfl file using File / Open,

5) Select Index View in View/Show As..

6) Check "Show Private Use Area" in the View / Show As.. dialog

StixBeta.cfl is a text file with these lines

STIXIntegralsDisplay,22

STIXSize1Symbols,22

STIXVariants,22

STIXNonUnicode,22

STIXGeneral,22

STIXGeneral,22,I

STIXGeneral,22,B

STIXGeneral,22,BI

Let’s examine the font STIXGeneral.otf. It has a math table, so Word 2007 does recognize it as a math font. But as soon as you type an English letter in a math zone, Word 2007 switches to Cambria Math because STIXGeneral.otf doesn’t have any math italic characters. If you don’t load the cfl file above (which shows all the characters), Unibook reveals that STIXGeneralItalic.otf *does* have math italic, but not math bold italic, or math bold.

The Unicode Technical Committee added the math alphanumerics primarily because without them plain text can destroy the semantics of mathematical expressions. The Hamiltonian example appearing in Sec. 2.2 of Unicode Technical Report #25 illustrates that plain text without math alphanumerics converts the Hamiltonian into an integral equation. For plain text to display such characters faithfully, they must all be in the same font, since plain text ignores rich-text attributes like bold and italic. Accordingly, Office 2007 software assumes all the math alphanumerics belong to a single font. So the first thing to fix is to put all the math alphanumerics into STIXGeneral.otf.

In addition, the various size glyph variants need to be accessible in this font. There are some little errors, such as U+2145..U+2149 (including the differential d U+2146) have upright glyphs in STIXGeneral.otf. This error is probably related to the choice of putting all italic into an italic font, upright into an upright font, etc., which doesn’t agree with the Unicode Standard for math characters.

For nonmathematical text, such a separation is standard practice and the italic, bold, and bold-italic fonts are needed for such text. But these fonts shouldn’t have any math alphanumerics, since the latter belong in the math font.

Needless to say, we’re all very excited to see this excellent font family running with our software. It’d be great to have a choice of two math fonts and the STIX fonts have many less common math operators that are missing in Cambria Math.