Background
TrueType GX fonts contain advanced tables exploiting the typographic power of of QuickDraw GX, Apple's advanced model for printing, typography and graphics.GX fonts (which are not necessarily TrueType) make fine typography much easier. Previously, one had to use multiple "expert" fonts, and position characters manually to obtain the typographic quality demanded by fine books and magazines. Now a single GX font may contain:
- Automatic common ligatures without affecting the semantic characters in the text, i.e. spell-checking and text searching still work.
- Rare ligatures for particular fonts, such as "RA" in Avant Garde.
- Alternate glyphs, allowing Univers to be shipped with both its original, classical ampersand and the lineale version designed for the American market.
- Automatic substitution of small caps.
- Lining and non-lining numerals.
- Typographically correct fractions,
- Mathematical and Pi symbols.
- Characters for multiple foreign languages.
- Font variations.
This behaviour depends on the declaration of intelligent font features in the font (such as swashes, ligatures, alternate glyphs), along with the contexts that in which they may appear (beginning of line, replacing the sequence "ffl", etc.).
TrueType GX fonts can also contain font variations similar in concept to Adobe multiple masters. (In fact multiple masters can be used in GX more easily than on other platforms.) Font variations, defined in the GX 'fvar' table, depend on consistent point numbering on the glyph variations, so that smooth "in-between" glyphs may be interpolated.
GX Tools
Apple have made available a suite of tools for editing GX fonts (and normal TrueType fonts) - for free. These do a variety of things to fonts, such as GX-ifying normal fonts so that their ligatures become automatic in GX. Download them from Apple's font site.
TrueType GX on the Web
- Apple's GX site
... has a GX typography section and a full description of the GX-specific tables. There is a large section on font quality. - Comparing GX Line Layout and OpenType layout
Dave Opstad performs a surprisingly fair-minded comparison of Steve's (GX) and Bill's (OpenType) typographic futures. - How GX does justification
Another article by Dave Opstad. - Inside Macintosh: Typography
This is the GX Typography section of Apple's online reference series. - The GX Fan Club
Kenneth Trueman runs the fan club, which includes sections on GX Typography, currently available GX fonts, a GX-ready application list and a useful developer's corner. Sign up here with the GX mailing lists. - Lawrence d'Oliveiro's GX site
Lawrence's site is an antipodean alternative for GX developers. It includes conversations with some of the designers of GX at Apple, including Dave Opstad on type, and Cary Clark. - Inside QuickDraw GX Fonts
A MacWorld article by Erfert Fenton, October 1994. - TrueType GX
from the Comp.fonts FAQ. - QuickDraw GX Guide
by Simon Lawson at Lari Software's site.