About Fonts
Fonts share the following attributes across all script systems:
• Single fonts, although belonging to a single script, may contain
characters from multiple scripts (typically Roman plus the font's
native script). A script system may substitute a Roman font for some of
the character encodings, typically the 128 ASCII low-order codes. In
this case, the font routines that return information, such as the ascent
or descent, have been modified to return the proper information,
usually the maximum of the corresponding values for the two fonts.
• Fonts may have zero-width characters. These are usually overlapping
diacritical marks, which typically follow the base character in
memory (also called backing-store order). With double-byte
characters, all but the first (high- order, low-address) byte are
measured as zero width (for example, with the MeasureText procedure).
• Since the script systems are built on top of the Toolbox graphics
routines, all of the normal QuickDraw font features are usually
available on the screen and when printing, including styles (bold,
italic, and so on), variable sizes (12 point, 18 point, and so on), and
multiple font families. Certain styles may be disabled in some scripts.