X logical font description

X logical font description (XLFD) is a font standard used by the X Window System. Modern X software typically relies on the newer Fontconfig system instead, but XLFDs are still supported in current X window implementations for compatibility with legacy software.

XLFD is intended to support:

unique, descriptive font names that support simple pattern matching

multiple font vendors, arbitrary character sets, and encodings

naming and instancing of scalable and polymorphic fonts

transformations and subsetting of fonts

independence of X server and operating or file system implementations

arbitrarily complex font matching or substitution

extensibility

One prominent XLFD convention is to refer to individual fonts including any variations using their unique FontName. It comprises a sequence of fourteen hyphen-prefixed, X-registered fields:

1. FOUNDRY: Type foundry - vendor or supplier of this font
2. FAMILY_NAME: Typeface family
3. WEIGHT_NAME: Weight of type
4. SLANT: Slant (upright, italic, oblique, reverse italic, reverse oblique, or "other")
5. SETWIDTH_NAME: Proportionate width (e.g. normal, condensed, narrow, expanded/double-wide)
6. ADD_STYLE_NAME: Additional style (e.g. (Sans) Serif, Informal, Decorated)
7. PIXEL_SIZE: Size of characters, in pixels; 0 (Zero) means a scalable font
8. POINT_SIZE: Size of characters, in tenths of points
9. RESOLUTION_X: Horizontal resolution in dots per inch (DPI), for which the font was designed
10. RESOLUTION_Y: Vertical resolution, in DPI
11. SPACING: monospaced, proportional, or "character cell"
12. AVERAGE_WIDTH: Average width of characters of this font; 0 means scalable font
13. CHARSET_REGISTRY: Registry defining this character set
14. CHARSET_ENCODING: Registry's character encoding scheme for this set

The following sample is for a 75-dpi, 12-point, Charter font:

-bitstream-charter-medium-r-normal--12-120-75-75-p-68-iso8859-1[65 70 80_90]

(which also tells the font source that the client is interested only in characters 65, 70, and 80-90.)