Character Sets and Fonts

An end user–defined character is always associated with a double-byte character set (DBCS) and a TrueType font. Applications identify the specified character by using the character's assigned DBCS character value, and the system uses this value to locate shape and style information in a corresponding TrueType font. The shape and style information specifies how the character is drawn on the screen or printed page.

The DBCS character values that can be assigned depend on the specified character set. Each set has at least one range of reserved values for use as end user–defined characters. The system or applications explicitly define these ranges by setting appropriate values under the EUDCCodeRange key in the registry. In the registry, each character set is identified by a unique code-page number.

To create an end user–defined character, the user chooses a character value that is within the specified range and adds the shape and style information to the TrueType font in the entry that corresponds to that character value. Users create the shape and style information using an EUDC editor or by purchasing end user–defined font packages from font vendors. Any DBCS TrueType font can contain end user–defined characters. The font is called a separate EUDC font if it contains only end user–defined characters. The font is an integrated EUDC font if it contains standard characters as well as end user–defined characters.

Separate EUDC fonts are said to be either font-aware or font-unaware. A font-unaware font is designed to be a general purpose font that can be used with fonts of different font styles and of different implementations, such as GDI raster, WIFE, device, and TrueType fonts. A font-aware font is designed for use with a specific TrueType font.

The system default EUDC font is a font-unaware font that the system automatically associates with all DBCS fonts except those TrueType fonts that have explicitly associated font-aware fonts. Applications set the system default EUDC font by setting the value of the SystemDefaultEUDCFont name under the EUDC key in the registry. Similarly, applications can associate font-aware fonts with corresponding TrueType fonts by specifying a font name and associated font file under the EUDC key. Separate EUDC fonts cannot be associated with integrated EUDC fonts.

The system hides the system default EUDC and font-aware fonts. This means applications cannot enumerate or otherwise examine these fonts using GDI functions. Applications, such as EUDC editors and Control Panel, must use the registry entries to add, modify, and delete EUDC fonts.

End user–defined characters can also be used in Unicode-enabled applications. The reserved ranges for each character set are mapped to corresponding values in the Unicode private use area (values 0xE000 and higher).