Supporting Scalable Fonts in the XLFD
			      Public Review Draft
		   (Send comments to fonts@expo.lcs.mit.edu)

The following changes to the X Logical Font Description Conventions are to
support naming of scalable fonts and instances of scalable fonts.

DEFINITIONS

Font source: An object or set of objects from which fonts are realized.  A
	     font source might be a bitmap font, or it might be one or more
	     outlines together with zero or more hand-tuned bitmap fonts at
	     specific sizes and resolutions, or a programmatic description
	     together with zero or more bitmap fonts, or some other format.

Wildcards: The characters "*" and "?".

Well-formed XLFD pattern: A pattern containing 14 hyphens, one of which is the
		          the first character of the pattern.  Wildcards are
			  permitted.

Scalable fontname: A well-formed XLFD pattern containing no wildcards and
		   containing "0" in the PIXEL_SIZE, POINT_SIZE, and
		   AVERAGE_WIDTH fields.

Scalable fields: The XLFD fields PIXEL_SIZE, POINT_SIZE, RESOLUTION_X,
		 RESOLUTION_Y, and AVERAGE_WIDTH.

Derived instance: The result of replacing the scalable fields of a fontname
		  with values to yield a fontname that could actually be
		  produced from the font source.  A scaling engine is
		  permitted, but not required, to interpret the scalable
		  fields in fontnames to support anamorphic scaling.

Global list: The list of names that would be returned by a ListFonts on the
	     pattern "*" if there were no protocol restrictions on the total
	     number of names returned.

SEMANTICS

OpenFont on any pattern is equivalent to invoking ListFonts with that pattern
and using the first fontname returned.

OpenFont on a scalable fontname returns a font corresponding to an
implementation-dependent derived instance of that fontname.

The global list consists of fontnames derived from font sources.  If a single
font source can be used to generate multiple XLFD CharSets, each such CharSet
should be used to form a separate fontname (or set of fontnames) in the list.
For a nonscalable font source, the simple fontname (one for each CharSet) is
included in the global list.  For a scalable font source, the scalable
fontname is included in the list.  In addition to the scalable fontname,
specific derived instance names for the scalable font can also be included in
the list.  The relative order of derived instances with respect to the scalable
fontname is not constrained.  Finally, fontname aliases can also be included
in the list.  The relative order of aliases with respect to the "real" fontname
is not constrained.

The values of the RESOLUTION_X and RESOLUTION_Y fields of a scalable fontname
are implementation dependent, but to maximize backward compatibility they
should be reasonable non-zero values, e.g., a resolution close to that
provided by the screen (in a single-screen server).  To maximize backward
compatibility, server vendors are strongly encouraged in the near term to
provide a mechanism for including derived instances of scalable fonts in the
global list, since some existing applications rely on seeing a collection of
point/pixel sizes for reasonable operation.  For font sources that contain a
collection of hand-tuned bitmap fonts, including the names of these instances
in the global list is recommended and sufficient.

ListFonts on a pattern containing wildcards that is not a well-formed XLFD
pattern returns (a prefix of) the list obtained by performing a simple pattern
match against the global list.  Servers are permitted, but not required, to do
something more "intelligent".

ListFonts on a well-formed XLFD pattern returns the following.  Start with the
global list.  If the actual pattern argument has values containing no wildcards
in scalable fields, then substitute each such field into the corresponding
field in each scalable fontname in the list.  For each resulting fontname, if
the remaining scalable fields cannot be replaced with values to produce a
derived instance, remove the fontname from the list.  Now take the modified
list, and perform a simple pattern match against the pattern argument.
ListFonts returns the resulting list.