














	   X Logical Font Description Conventions

			Version 1.5

		   X Consortium Standard

		 X Version 11, Release 6.4






			Jim Flowers
	       Digital Equipment Corporation






	    Version 1.5 edited by Stephen Gildea
		     X Consortium, Inc.












































X Window System is a trademark of X Consortium, Inc.

Helvetica and Times are registered trademarks of Linotype Company.

ITC Avant Garde Gothic is a registered trademark of International Type-
face Corporation.

Times Roman is a registered trademark of Monotype Corporation.

Bitstream Amerigo is a registered trademark of Bitstream Inc.

Stone is a registered trademark of Adobe Systems Inc.

Copyright (C) 1988, 1994 X Consortium

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Soft-
ware"), to deal in the Software without restriction, including without
limitation the rights to use, copy, modify, merge, publish, distribute,
sublicense, and/or sell copies of the Software, and to permit persons to
whom the Software is furnished to do so, subject to the following condi-
tions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABIL-
ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT
SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABIL-
ITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
IN THE SOFTWARE.

Except as contained in this notice, the name of the X Consortium shall
not be used in advertising or otherwise to promote the sale, use or
other dealings in this Software without prior written authorization from
the X Consortium.

Copyright (C) 1988, 1989 Digital Equipment Corporation, Maynard MA.  All
rights reserved.

Permission to use, copy, modify, and distribute this documentation for
any purpose and without fee is hereby granted, provided that the above












copyright notice and this permission notice appear in all copies.  Digi-
tal Equipment Corporation makes no representations about the suitability
for any purpose of the information in this document.  This documentation
is provided as is without express or implied warranty.






























































1.  Introduction

It is a requirement that X client applications must be portable across
server implementations, with very different file systems, naming conven-
tions, and font libraries.  However, font access requests, as defined by
the X Window System Protocol, neither specify server-independent conven-
tions for font names nor provide adequate font properties for logically
describing typographic fonts.

X clients must be able to dynamically determine the fonts available on
any given server so that understandable information can be presented to
the user or so that intelligent font fallbacks can be chosen.  It is
desirable for the most common queries to be accomplished without the
overhead of opening each font and inspecting font properties, by means
of simple ListFonts requests.  For example, if a user selected a Hel-
vetica typeface family, a client application should be able to query the
server for all Helvetica fonts and present only those setwidths,
weights, slants, point sizes, and character sets available for that fam-
ily.

This document gives a standard logical font description (hereafter
referred to as XLFD) and the conventions to be used in the core protocol
so that clients can query and access screen type libraries in a consis-
tent manner across all X servers.  In addition to completely specifying
a given font by means of its FontName, the XLFD also provides for a
standard set of key FontProperties that describe the font in more
detail.

The XLFD provides an adequate set of typographic font properties, such
as CAP_HEIGHT, X_HEIGHT, and RELATIVE_SETWIDTH, for publishing and other
applications to do intelligent font matching or substitution when han-
dling documents created on some foreign server that use potentially
unknown fonts.	In addition, this information is required by certain
clients to position subscripts automatically and determine small capital
heights, recommended leading, word-space values, and so on.

2.  Requirements and Goals

The XLFD meets the short-term and long-term goals to have a standard
logical font description that:

o    Provides unique, descriptive font names that support simple pattern
     matching

o    Supports multiple font vendors, arbitrary character sets, and
     encodings

o    Supports naming and instancing of scalable and polymorphic fonts

o    Supports transformations and subsetting of fonts

o    Is independent of X server and operating or file system implementa-
     tions




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X Logical Font Description Conventions			X11, Release 6.4


o    Supports arbitrarily complex font matching or substitution

o    Is extensible

2.1.  Provide Unique and Descriptive Font Names

It should be possible to have font names that are long enough and
descriptive enough to have a reasonable probability of being unique
without inventing a new registration organization.  Resolution and size-
dependent font masters, multivendor font libraries, and so on must be
anticipated and handled by the font name alone.

The name itself should be structured to be amenable to simple pattern
matching and parsing, thus allowing X clients to restrict font queries
to some subset of all possible fonts in the server.

2.2.  Support Multiple Font Vendors and Character Sets

The font name and properties should distinguish between fonts that were
supplied by different font vendors but that possibly share the same
name.  We anticipate a highly competitive font market where users will
be able to buy fonts from many sources according to their particular
requirements.

A number of font vendors deliver each font with all glyphs designed for
that font, where charset mappings are defined by encoding vectors.  Some
server implementations may force these mappings to proprietary or stan-
dard charsets statically in the font data.  Others may desire to perform
the mapping dynamically in the server.	Provisions must be made in the
font name that allows a font request to specify or identify specific
charset mappings in server environments where multiple charsets are sup-
ported.

2.3.  Support Scalable and Polymorphic Fonts

If a font source can be scaled to an arbitrary size or varied in other
ways, it should be possible for an application to determine that fact
from the font name, and the application should be able to construct a
font name for any specific instance.

2.4.  Support Transformations and Subsetting of Fonts

Arbitrary two-dimensional linear transformations of fonts should be able
to be requested by applications.  Since such transformed fonts may be
used for special effects requiring a few characters from each of many
differently transformed fonts, it should be possible to request only a
few characters from a font for efficiency.

2.5.  Be Independent of X Server and Operating or File System Implemen-
tations

X client applications that require a particular font should be able to
use the descriptive name without knowledge of the file system or other
repository in use by the server.  However, it should be possible for



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X Logical Font Description Conventions			X11, Release 6.4


servers to translate a given font name into a file name syntax that it
knows how to deal with, without compromising the uniqueness of the font
name.  This algorithm should be reversible (exactly how this translation
is done is implementation dependent).

2.6.  Support Arbitrarily Complex Font Matching and Substitution

In addition to the font name, the XLFD should define a standard list of
descriptive font properties, with agreed-upon fallbacks for all fonts.
This allows client applications to derive font-specific formatting or
display data and to perform font matching or substitution when asked to
handle potentially unknown fonts, as required.

2.7.  Be Extensible

The XLFD must be extensible so that new and/or private descriptive font
properties can be added to conforming fonts without making existing X
client or server implementations obsolete.

3.  X Logical Font Description

XLFD is divided into two basic components: the FontName, which gives all
font information needed to uniquely identify a font in X protocol
requests (for example, OpenFont, ListFonts, and so on) and a variable
list of optional FontProperties, which describe a font in more detail.

The FontName is used in font queries and is returned as data in certain
X protocol requests.  It is also specified as the data value for the
FONT item in the X Consortium Character Bitmap Distribution Format Stan-
dard (BDF V2.1).

The FontProperties are supplied on a font-by-font basis and are returned
as data in certain X protocol requests as part of the XFontStruct data
structure.  The names and associated data values for each of the Font-
Properties may also appear as items of the STARTPROPERTIES...ENDPROPER-
TIES list in the BDF V2.1 specification.

3.1.  FontName

Each FontName is logically composed of two strings: a FontNameRegistry
prefix that is followed by a FontNameSuffix.  The FontName uses the ISO
8859-1 encoding.  The FontNameRegistry is an x-registered-name (a name
that has been registered with the X Consortium) that identifies the reg-
istration authority that owns the specified FontNameSuffix syntax and
semantics.

All font names that conform to this specification are to use a Font-
NameRegistry prefix, which is defined to be the string "-" (HYPHEN).
All FontNameRegistry prefixes of the form: +version-, where the speci-
fied version indicates some future XLFD specification, are reserved by
the X Consortium for future extensions to XLFD font names.  If required,
extensions to the current XLFD font name shall be constructed by append-
ing new fields to the current structure, each delimited by the existing
field delimiter.  The availability of other FontNameRegistry prefixes or



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X Logical Font Description Conventions			X11, Release 6.4


fonts that support other registries is server implementation dependent.

In the X protocol specification, the FontName is required to be a
string; hence, numeric field values are represented in the name as
string equivalents.  All FontNameSuffix fields are also defined as Font-
Properties; numeric property values are represented as signed or
unsigned integers, as appropriate.

3.1.1.	FontName Syntax

The FontName is a structured, parsable string (of type STRING8) whose
Backus-Naur Form syntax description is as follows:

	  FontName ::=	 XFontNameRegistry XFontNameSuffix |
			 PrivFontNameRegistry PrivFontNameSuf-
			 fix
 XFontNameRegistry ::=	 XFNDelim | XFNExtPrefix Version XFN-
			 Delim
   XFontNameSuffix ::=	 FOUNDRY XFNDelim FAMILY_NAME XFNDelim
			 WEIGHT_NAME XFNDelim SLANT XFNDelim
			 SETWIDTH_NAME XFNDelim ADD_
			 STYLE_NAME XFNDelim PIXEL_SIZE XFNDe-
			 lim POINT_SIZE XFNDelim RESOLUTION_X
			 XFNDelim RESOLUTION_Y XFNDelim SPAC-
			 ING XFNDelim AVERAGE_WIDTH XFNDelim
			 CHARSET_REGISTRY XFNDelim
			 CHARSET_ENCODING
	   Version ::=	 STRING8 - the XLFD version that
			 defines an extension to the font name
			 syntax (for example, "1.4")
      XFNExtPrefix ::=	 OCTET - "+" (PLUS)
	  XFNDelim ::=	 OCTET - "-" (HYPHEN)
  PrivFontNameRegistry	 STRING8 - other than those strings
  ::=			 reserved by XLFD
PrivFontNameSuffix ::=	 STRING8


Field values are constructed as strings of ISO 8859-1 graphic charac-
ters, excluding the following:

o    "-" (HYPHEN), the XLFD font name delimiter character

o    "?" (QUESTION MARK) and "*" (ASTERISK), the X protocol font name
     wildcard characters

o    "," (COMMA), used by Xlib to separate XLFD font names in a font
     set.

o    """ (QUOTATION MARK), used by some commercial products to quote a
     font name.

Alphabetic case distinctions are allowed but are for human readability
concerns only.	Conforming X servers will perform matching on font name
query or open requests independent of case.  The entire font name string



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X Logical Font Description Conventions			X11, Release 6.4


must have no more than 255 characters.	It is recommended that clients
construct font name query patterns by explicitly including all field
delimiters to avoid unexpected results.  Note that SPACE is a valid
character of a FontName field; for example, the string "ITC Avant Garde
Gothic" might be a FAMILY_NAME.

3.1.2.	FontName Field Definitions

This section discusses the FontName:

o    FOUNDRY field

o    FAMILY_NAME field

o    WEIGHT_NAME field

o    SLANT field

o    SETWIDTH_NAME field

o    ADD_STYLE_NAME field

o    PIXEL_SIZE field

o    POINT_SIZE field

o    RESOLUTION_X and RESOLUTION_Y fields

o    SPACING field

o    AVERAGE_WIDTH field

o    CHARSET_REGISTRY and CHARSET_ENCODING fields

3.1.2.1.  FOUNDRY Field

FOUNDRY is an x-registered-name, the name or identifier of the digital
type foundry that digitized and supplied the font data, or if different,
the identifier of the organization that last modified the font shape or
metric information.

The reason this distinction is necessary is that a given font design may
be licensed from one source (for example, ITC) but digitized and sold by
any number of different type suppliers.  Each digital version of the
original design, in general, will be somewhat different in metrics and
shape from the idealized original font data, because each font foundry,
for better or for worse, has its own standards and practices for tweak-
ing a typeface for a particular generation of output technologies or has
its own perception of market needs.

It is up to the type supplier to register with the X Consortium a suit-
able name for this FontName field according to the registration proce-
dures defined by the Consortium.




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X Logical Font Description Conventions			X11, Release 6.4


The X Consortium shall define procedures for registering foundry and
other names and shall maintain and publish, as part of its public dis-
tribution, a registry of such registered names for use in XLFD font
names and properties.


3.1.2.2.  FAMILY_NAME Field

FAMILY_NAME is a string that identifies the range or family of typeface
designs that are all variations of one basic typographic style.  This
must be spelled out in full, with words separated by spaces, as
required.  This name must be human-understandable and suitable for pre-
sentation to a font user to identify the typeface family.

It is up to the type supplier to supply and maintain a suitable string
for this field and font property, to secure the proper legal title to a
given name, and to guard against the infringement of other's copyrights
or trademarks.	By convention, FAMILY_NAME is not translated.  FAM-
ILY_NAME may include an indication of design ownership if considered a
valid part of the typeface family name.

The following are examples of FAMILY_NAME:

o    Helvetica

o    ITC Avant Garde Gothic

o    Times

o    Times Roman

o    Bitstream Amerigo

o    Stone

3.1.2.3.  WEIGHT_NAME Field

WEIGHT_NAME is a string that identifies the font's typographic weight,
that is, the nominal blackness of the font, according to the FOUNDRY's
judgment.  This name must be human-understandable and suitable for pre-
sentation to a font user.  The value "0" is used to indicate a polymor-
phic font (see section 6).

The interpretation of this field is somewhat problematic because the
typographic judgment of weight has traditionally depended on the overall
design of the typeface family in question; that is, it is possible that
the DemiBold weight of one font could be almost equivalent in typo-
graphic feel to a Bold font from another family.

WEIGHT_NAME is captured as an arbitrary string because it is an impor-
tant part of a font's complete human-understandable name.  However, it
should not be used for font matching or substitution.  For this purpose,
X client applications should use the weight-related font properties
(RELATIVE_WEIGHT and WEIGHT) that give the coded relative weight and the



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X Logical Font Description Conventions			X11, Release 6.4


calculated weight, respectively.

3.1.2.4.  SLANT Field

SLANT is a code-string that indicates the overall posture of the type-
face design used in the font.  The encoding is as follows:

---------------------------------------------------------------------------
Code	  English Translation	Description
---------------------------------------------------------------------------
"R"	  Roman 		Upright design
"I"	  Italic		Italic design, slanted clockwise from the
				vertical
"O"	  Oblique		Obliqued upright design, slanted clockwise
				from the vertical
"RI"	  Reverse Italic	Italic design, slanted counterclockwise
				from the vertical
"RO"	  Reverse Oblique	Obliqued upright design, slanted counter-
				clockwise from the vertical
"OT"	  Other 		Other
numeric   Polymorphic		See section 6 on polymorphic font support.
---------------------------------------------------------------------------


The SLANT codes are for programming convenience only and usually are
converted into their equivalent human-understandable form before being
presented to a user.

3.1.2.5.  SETWIDTH_NAME Field

SETWIDTH_NAME is a string that gives the font's typographic proportion-
ate width, that is, the nominal width per horizontal unit of the font,
according to the FOUNDRY's judgment.  The value "0" is used to indicate
a polymorphic font (see section 6).

As with WEIGHT_NAME, the interpretation of this field or font property
is somewhat problematic, because the designer's judgment of setwidth has
traditionally depended on the overall design of the typeface family in
question.  For purposes of font matching or substitution, X client
applications should either use the RELATIVE_SETWIDTH font property that
gives the relative coded proportionate width or calculate the propor-
tionate width.

The following are examples of SETWIDTH_NAME:

o    Normal

o    Condensed

o    Narrow

o    Double Wide





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X Logical Font Description Conventions			X11, Release 6.4


3.1.2.6.  ADD_STYLE_NAME Field

ADD_STYLE_NAME is a string that identifies additional typographic style
information that is not captured by other fields but is needed to iden-
tify the particular font.  The character "[" anywhere in the field is
used to indicate a polymorphic font (see section 6).

ADD_STYLE_NAME is not a typeface classification field and is only used
for uniqueness.  Its use, as such, is not limited to typographic style
distinctions.

The following are examples of ADD_STYLE_NAME:

o    Serif

o    Sans Serif

o    Informal

o    Decorated

3.1.2.7.  PIXEL_SIZE Field

PIXEL_SIZE gives the body size of the font at a particular POINT_SIZE
and RESOLUTION_Y.  PIXEL_SIZE is either an integer-string or a string
beginning with "[".  A string beginning with "[" represents a matrix
(see section 4).  PIXEL_SIZE usually incorporates additional vertical
spacing that is considered part of the font design.  (Note, however,
that this value is not necessarily equivalent to the height of the font
bounding box.)	Zero is used to indicate a scalable font (see section
5).

PIXEL_SIZE usually is used by X client applications that need to query
fonts according to device-dependent size, regardless of the point size
or vertical resolution for which the font was designed.

3.1.2.8.  POINT_SIZE Field

POINT_SIZE gives the body size for which the font was designed.
POINT_SIZE is either an integer-string or a string beginning with "[".
A string beginning with "[" represents a matrix (see section 4).  This
field usually incorporates additional vertical spacing that is consid-
ered part of the font design.  (Note, however, that POINT_SIZE is not
necessarily equivalent to the height of the font bounding box.)
POINT_SIZE is expressed in decipoints (where points are as defined in
the X protocol or 72.27 points equal 1 inch).  Zero is used to indicate
a scalable font (see section 5).

POINT_SIZE and RESOLUTION_Y are used by X clients to query fonts accord-
ing to device-independent size to maintain constant text size on the
display regardless of the PIXEL_SIZE used for the font.






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X Logical Font Description Conventions			X11, Release 6.4


3.1.2.9.  RESOLUTION_X and RESOLUTION_Y Fields

RESOLUTION_X and RESOLUTION_Y are unsigned integer-strings that give the
horizontal and vertical resolution, measured in pixels or dots per inch
(dpi), for which the font was designed.  Zero is used to indicate a
scalable font (see section 5).	Horizontal and vertical values are
required because a separate bitmap font must be designed for displays
with very different aspect ratios (for example, 1:1, 4:3, 2:1, and so
on).

The separation of pixel or point size and resolution is necessary
because X allows for servers with very different video characteristics
(for example, horizontal and vertical resolution, screen and pixel size,
pixel shape, and so on) to potentially access the same font library.
The font name, for example, must differentiate between a 14-point font
designed for 75 dpi (body size of about 14 pixels) or a 14-point font
designed for 150 dpi (body size of about 28 pixels).  Further, in
servers that implement some or all fonts as continuously scaled and
scan-converted outlines, POINT_SIZE and RESOLUTION_Y will help the
server to differentiate between potentially separate font masters for
text, title, and display sizes or for other typographic considerations.

3.1.2.10.  SPACING Field

SPACING is a code-string that indicates the escapement class of the
font, that is, monospace (fixed pitch), proportional (variable pitch),
or charcell (a special monospaced font that conforms to the traditional
data-processing character cell font model).  The encoding is as follows:

------------------------------------------------------------------
Code	English Translation   Description
------------------------------------------------------------------
"P"	Proportional	      A font whose logical character
			      widths vary for each glyph.  Note
			      that no other restrictions are
			      placed on the metrics of a propor-
			      tional font.
"M"	Monospaced	      A font whose logical character
			      widths are constant (that is, every
			      glyph in the font has the same log-
			      ical width).  No other restrictions
			      are placed on the metrics of a
			      monospaced font.














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X Logical Font Description Conventions			X11, Release 6.4


------------------------------------------------------------------
Code	English Translation   Description
------------------------------------------------------------------
"C"	CharCell	      A monospaced font that follows the
			      standard typewriter character cell
			      model (that is, the glyphs of the
			      font can be modeled by X clients as
			      "boxes" of the same width and
			      height that are imaged side-by-side
			      to form text strings or top-to-bot-
			      tom to form text lines).	By defi-
			      nition, all glyphs have the same
			      logical character width, and no
			      glyphs have "ink" outside of the
			      character cell.  There is no kern-
			      ing (that is, on a per-character
			      basis with positive metrics: 0 <=
			      left-bearing <= right-bearing <=
			      width; with negative metrics: width
			      <= left-bearing <= right-bearing <=
			      zero).  Also, the vertical extents
			      of the font do not exceed the ver-
			      tical spacing (that is, on a per-
			      character basis: ascent <= font-
			      ascent and descent <= font-
			      descent).  The cell height = font-
			      descent + font-ascent, and the
			      width = AVERAGE_WIDTH.
------------------------------------------------------------------


3.1.2.11.  AVERAGE_WIDTH Field

AVERAGE_WIDTH is an integer-string typographic metric value that gives
the unweighted arithmetic mean of the absolute value of the width of
each glyph in the font (measured in tenths of pixels), multiplied by -1
if the dominant writing direction for the font is right-to-left.  A
leading "~" (TILDE) indicates a negative value.  For monospaced and
character cell fonts, this is the width of all glyphs in the font.  Zero
is used to indicate a scalable font (see section 5).

3.1.2.12.  CHARSET_REGISTRY and CHARSET_ENCODING Fields

The character set used to encode the glyphs of the font (and implicitly
the font's glyph repertoire), as maintained by the X Consortium charac-
ter set registry.  CHARSET_REGISTRY is an x-registered-name that identi-
fies the registration authority that owns the specified encoding.
CHARSET_ENCODING is a registered name that identifies the coded charac-
ter set as defined by that registration authority and, optionally, a
subsetting hint.

Although the X protocol does not explicitly have any knowledge about
character set encodings, it is expected that server implementors will
prefer to embed knowledge of certain proprietary or standard charsets



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X Logical Font Description Conventions			X11, Release 6.4


into their font library for reasons of performance and convenience.  The
CHARSET_REGISTRY and CHARSET_ENCODING fields or properties allow an X
client font request to specify a specific charset mapping in server
environments where multiple charsets are supported.  The availability of
any particular character set is font and server implementation depen-
dent.

To prevent collisions when defining character set names, it is recom-
mended that CHARSET_REGISTRY and CHARSET_ENCODING name pairs be con-
structed according to the following conventions:

	CharsetRegistry ::=   StdCharsetRegistryName | PrivCharsetReg-
			      istryName
	CharsetEncoding ::=   StdCharsetEncodingName | PrivCharsetEn-
			      codingName
 StdCharsetRegistryName ::=   StdOrganizationId StdNumber | StdOrgani-
			      zationId StdNumber Dot Year
PrivCharsetRegistryName ::=   OrganizationId STRING8
 StdCharsetEncodingName ::=   STRING8-numeric part number of refer-
			      enced standard
PrivCharsetEncodingName ::=   STRING8
      StdOrganizationId ::=   STRING8-the registered name or acronym
			      of the referenced standard organization
	      StdNumber ::=   STRING8-referenced standard number
	 OrganizationId ::=   STRING8-the registered name or acronym
			      of the organization
		    Dot ::=   OCTET-"." (FULL STOP)
		   Year ::=   STRING8-numeric year (for example, 1989)


The X Consortium shall maintain and publish a registry of such character
set names for use in X protocol font names and properties as specified
in XLFD.

The ISO Latin-1 character set shall be registered by the X Consortium as
the CHARSET_REGISTRY-CHARSET_ENCODING value pair: "ISO8859-1".

If the CHARSET_ENCODING contains a "[" (LEFT SQUARE BRACKET), the "["
and the characters after it up to a "]" (RIGHT SQUARE BRACKET) are a
subsetting hint telling the font source that the client is interested
only in a subset of the characters of the font.  The font source can,
optionally, return a font that contains only those characters or any
superset of those characters.  The client can expect to obtain valid
glyphs and metrics only for those characters, and not for any other
characters in the font.  The font properties may optionally be calcu-
lated by considering only the characters in the subset.

The BNF for the subsetting hint is

      Subset ::=   LeftBracket RangeList RightBracket
   RangeList ::=   Range | Range Space RangeList
       Range ::=   Number | Number Underscore Number
      Number ::=   "0x" HexNumber | DecNumber




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X Logical Font Description Conventions			X11, Release 6.4


   HexNumber ::=   HexDigit | HexDigit HexNumber
   DecNumber ::=   DecDigit | DecDigit DecNumber
    DecDigit ::=   "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
    HexDigit ::=   DecDigit | "a" | "b" | "c" | "d" | "e" | "f"
 LeftBracket ::=   "[" (LEFT SQUARE BRACKET)
RightBracket ::=   "]" (RIGHT SQUARE BRACKET)
       Space ::=   " " (SPACE)
  Underscore ::=   "_" (LOW LINE)


Each Range specifies characters that are to be part of the subset
included in the font.  A Range containing two Numbers specifies the
first and last character, inclusively, of a range of characters.  A
Range that is a single Number specifies a single character to be
included in the font.  A HexNumber is interpreted as a hexadecimal num-
ber.  A DecNumber is interpreted as a decimal number.  The font consists
of the union of all the Ranges in the RangeList.

For example,
     -misc-fixed-medium-r-normal--0-0-0-0-c-0-iso8859-1[65 70 80_90]
tells the font source that the client is interested only in characters
65, 70, and 80-90.

3.1.3.	Examples

The following examples of font names are derived from the screen fonts
shipped with the X Consortium distribution.

------------------------------------------------------------------------------
Font		 X FontName
------------------------------------------------------------------------------
75-dpi Fonts
Charter 12 pt	 -Bitstream-Charter-Medium-R-Nor-
		 mal--12-120-75-75-P-68-ISO8859-1
Charter Bold	 -Bitstream-Charter-Bold-R-Nor-
12 pt		 mal--12-120-75-75-P-76-ISO8859-1
Charter Bold	 -Bitstream-Charter-Bold-I-Nor-
Italic 12 pt	 mal--12-120-75-75-P-75-ISO8859-1
Charter Italic	 -Bitstream-Charter-Medium-I-Nor-
12 pt		 mal--12-120-75-75-P-66-ISO8859-1
Courier 8 pt	 -Adobe-Courier-Medium-R-Normal--8-80-75-75-M-50-ISO8859-1
Courier 10 pt	 -Adobe-Courier-Medium-R-Normal--10-100-75-75-M-60-ISO8859-1
Courier 12 pt	 -Adobe-Courier-Medium-R-Normal--12-120-75-75-M-70-ISO8859-1
Courier 24 pt	 -Adobe-Courier-Medium-R-Normal--24-240-75-75-M-150-ISO8859-1
Courier Bold	 -Adobe-Courier-Bold-R-Normal--10-100-75-75-M-60-ISO8859-1
10 pt
Courier Bold	 -Adobe-Courier-Bold-O-Normal--10-100-75-75-M-60-ISO8859-1
Oblique 10 pt
Courier 	 -Adobe-Courier-Medium-O-Normal--10-100-75-75-M-60-ISO8859-1
Oblique 10 pt
100-dpi Fonts
Symbol 10 pt	 -Adobe-Symbol-Medium-R-Normal--14-100-100-100-P-85-Adobe-
		 FONTSPECIFIC




				   12





X Logical Font Description Conventions			X11, Release 6.4


------------------------------------------------------------------------------
Font		 X FontName
------------------------------------------------------------------------------
Symbol 14 pt	 -Adobe-Symbol-Medium-R-Normal--20-140-100-100-P-107-Adobe-
		 FONTSPECIFIC
Symbol 18 pt	 -Adobe-Symbol-Medium-R-Normal--25-180-100-100-P-142-Adobe-
		 FONTSPECIFIC
Symbol 24 pt	 -Adobe-Symbol-Medium-R-Normal--34-240-100-100-P-191-Adobe-
		 FONTSPECIFIC
Times Bold 10	 -Adobe-Times-Bold-R-Normal--14-100-100-100-P-76-ISO8859-1
pt
Times Bold	 -Adobe-Times-Bold-I-Normal--14-100-100-100-P-77-ISO8859-1
Italic 10 pt
Times Italic	 -Adobe-Times-Medium-I-Normal--14-100-100-100-P-73-ISO8859-1
10 pt
Times Roman 10	 -Adobe-Times-Medium-R-Normal--14-100-100-100-P-74-ISO8859-1
pt
------------------------------------------------------------------------------


3.2.  Font Properties

All font properties are optional but will generally include the font
name fields and, on a font-by-font basis, any other useful font descrip-
tive and use information that may be required to use the font intelli-
gently.  The XLFD specifies an extensive set of standard X font proper-
ties, their interpretation, and fallback rules when the property is not
defined for a given font.  The goal is to provide client applications
with enough font information to be able to make automatic formatting and
display decisions with good typographic results.

Font property names use the ISO 8859-1 encoding.

Additional standard X font property definitions may be defined in the
future and private properties may exist in X fonts at any time.  Private
font properties should be defined to conform to the general mechanism
defined in the X protocol to prevent overlap of name space and ambiguous
property names, that is, private font property names are of the form:
"_" (LOW LINE), followed by the organizational identifier, followed by
"_" (LOW LINE), and terminated with the property name.

The Backus-Naur Form syntax description of X font properties is as fol-
lows:

     Properties ::=   OptFontPropList
OptFontPropList ::=   NULL | OptFontProp OptFontPropList
    OptFontProp ::=   PrivateFontProp | XFontProp
PrivateFontProp ::=   STRING8 | Underscore OrganizationId
		      Underscore STRING8








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X Logical Font Description Conventions			X11, Release 6.4


      XFontProp ::=   FOUNDRY | FAMILY_NAME | WEIGHT_NAME |
		      SLANT | SETWIDTH_NAME |
		      ADD_STYLE_NAME | PIXEL_SIZE |
		      POINT_SIZE | RESOLUTION_X | RESOLU-
		      TION_Y | SPACING | AVERAGE_WIDTH |
		      CHARSET_REGISTRY | CHARSET_ENCODING |
		      QUAD_WIDTH | RESOLUTION | MIN_SPACE |
		      NORM_SPACE | MAX_SPACE | END_SPACE |
		      SUPERSCRIPT_X | SUPERSCRIPT_Y | SUB-
		      SCRIPT_X | SUBSCRIPT_Y | UNDER-
		      LINE_POSITION | UNDERLINE_THICKNESS |
		      STRIKEOUT_ASCENT | STRIKEOUT_DESCENT
		      | ITALIC_ANGLE | X_HEIGHT | WEIGHT |
		      FACE_NAME | FULL_NAME | FONT | COPY-
		      RIGHT | AVG_CAPITAL_WIDTH | AVG_LOW-
		      ERCASE_WIDTH | RELATIVE_SETWIDTH |
		      RELATIVE_WEIGHT | CAP_HEIGHT | SUPER-
		      SCRIPT_ SIZE | FIGURE_WIDTH | SUB-
		      SCRIPT_SIZE | SMALL_CAP_SIZE | NOTICE
		      | DESTINATION | FONT_TYPE | FONT_VER-
		      SION | RASTERIZER_NAME | RASTER-
		      IZER_VERSION | RAW_ASCENT |
		      RAW_DESCENT | RAW_* | AXIS_NAMES |
		      AXIS_LIMITS | AXIS_TYPES
     Underscore ::=   OCTET-"_" (LOW LINE)
 OrganizationId ::=   STRING8-the registered name of the
		      organization


3.2.1.	FOUNDRY

FOUNDRY is as defined in the FontName except that the property type is
ATOM.

FOUNDRY cannot be calculated or defaulted if not supplied as a font
property.

3.2.2.	FAMILY_NAME

FAMILY_NAME is as defined in the FontName except that the property type
is ATOM.

FAMILY_NAME cannot be calculated or defaulted if not supplied as a font
property.

3.2.3.	WEIGHT_NAME

WEIGHT_NAME is as defined in the FontName except that the property type
is ATOM.

WEIGHT_NAME can be defaulted if not supplied as a font property, as fol-
lows:





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X Logical Font Description Conventions			X11, Release 6.4


     if (WEIGHT_NAME undefined) then
	WEIGHT_NAME = ATOM("Medium")


3.2.4.	SLANT

SLANT is as defined in the FontName except that the property type is
ATOM.

SLANT can be defaulted if not supplied as a font property, as follows:


     if (SLANT undefined) then
	SLANT = ATOM("R")


3.2.5.	SETWIDTH_NAME

SETWIDTH_NAME is as defined in the FontName except that the property
type is ATOM.

SETWIDTH_NAME can be defaulted if not supplied as a font property, as
follows:


     if (SETWIDTH_NAME undefined) then
	SETWIDTH_NAME = ATOM("Normal")


3.2.6.	ADD_STYLE_NAME

ADD_STYLE_NAME is as defined in the FontName except that the property
type is ATOM.

ADD_STYLE_NAME can be defaulted if not supplied as a font property, as
follows:


     if (ADD_STYLE_NAME undefined) then
	ADD_STYLE_NAME = ATOM("")


3.2.7.	PIXEL_SIZE

PIXEL_SIZE is as defined in the FontName except that the property type
is INT32.

X clients requiring pixel values for the various typographic fixed spa-
ces (em space, en space, and thin space) can use the following algorithm
for computing these values from other properties specified for a font:







				   15





X Logical Font Description Conventions			X11, Release 6.4


     DeciPointsPerInch = 722.7
     EMspace = ROUND ((RESOLUTION_X * POINT_SIZE) / DeciPointsPerInch)
     ENspace = ROUND (EMspace / 2)
     THINspace = ROUND (EMspace / 3)


where a slash (/) denotes real division, an asterisk (*) denotes real
multiplication, and ROUND denotes a function that rounds its real argu-
ment a up or down to the next integer.	This rounding is done according
to X = FLOOR (a + 0.5), where FLOOR is a function that rounds its real
argument down to the nearest integer.

PIXEL_SIZE can be approximated if not supplied as a font property,
according to the following algorithm:


     DeciPointsPerInch = 722.7
     if (PIXEL_SIZE undefined) then
	PIXEL_SIZE = ROUND ((RESOLUTION_Y * POINT_SIZE) / DeciPointsPerInch)


3.2.8.	POINT_SIZE

POINT_SIZE is as defined in the FontName except that the property type
is INT32.

X clients requiring device-independent values for em space, en space,
and thin space can use the following algorithm:


     EMspace = ROUND (POINT_SIZE / 10)
     ENspace = ROUND (POINT_SIZE / 20)
     THINspace = ROUND (POINT_SIZE / 30)


Design POINT_SIZE cannot be calculated or approximated.

3.2.9.	RESOLUTION_X

RESOLUTION_X is as defined in the FontName except that the property type
is CARD32.

RESOLUTION_X cannot be calculated or approximated.

3.2.10.  RESOLUTION_Y

RESOLUTION_Y is as defined in the FontName except that the property type
is CARD32.

RESOLUTION_X cannot be calculated or approximated.







				   16





X Logical Font Description Conventions			X11, Release 6.4


3.2.11.  SPACING

SPACING is as defined in the FontName except that the property type is
ATOM.

SPACING can be calculated if not supplied as a font property, according
to the definitions given above for the FontName.

3.2.12.  AVERAGE_WIDTH

AVERAGE_WIDTH is as defined in the FontName except that the property
type is INT32.

AVERAGE_WIDTH can be calculated if not provided as a font property,
according to the following algorithm:


     if (AVERAGE_WIDTH undefined) then
	AVERAGE_WIDTH = ROUND (MEAN (ABS (width of each glyph in font)) * 10)
	  * (if (dominant writing direction L-to-R) then 1 else -1)


where MEAN is a function that returns the arithmetic mean of its argu-
ments.

X clients that require values for the number of characters per inch
(pitch) of a monospaced font can use the following algorithm using the
AVERAGE_WIDTH and RESOLUTION_X font properties:


     if (SPACING not proportional) then
	CharPitch = (RESOLUTION_X * 10) / AVERAGE_WIDTH


3.2.13.  CHARSET_REGISTRY

CHARSET_REGISTRY is as defined in the FontName except that the property
type is ATOM.

CHARSET_REGISTRY cannot be defaulted if not supplied as a font property.

3.2.14.  CHARSET_ENCODING

CHARSET_ENCODING is as defined in the FontName except that the property
type is ATOM.

CHARSET_ENCODING cannot be defaulted if not supplied as a font property.

3.2.15.  MIN_SPACE

MIN_SPACE is an integer value (of type INT32) that gives the recommended
minimum word-space value to be used with this font.





				   17





X Logical Font Description Conventions			X11, Release 6.4


MIN_SPACE can be approximated if not provided as a font property,
according to the following algorithm:


     if (MIN_SPACE undefined) then
	MIN_SPACE = ROUND(0.75 * NORM_SPACE)


3.2.16.  NORM_SPACE

NORM_SPACE is an integer value (of type INT32) that gives the recom-
mended normal word-space value to be used with this font.

NORM_SPACE can be approximated if not provided as a font property,
according to the following algorithm:


DeciPointsPerInch = 722.7
if (NORM_SPACE undefined) then
   if (SPACE glyph exists) then
      NORM_SPACE = width of SPACE
   else NORM_SPACE = ROUND((0.33 * RESOLUTION_X * POINT_SIZE)/ DeciPointsPerInch)


3.2.17.  MAX_SPACE

MAX_SPACE is an integer value (of type INT32) that gives the recommended
maximum word-space value to be used with this font.

MAX_SPACE can be approximated if not provided as a font property,
according to the following algorithm:


     if (MAX_SPACE undefined) then
	MAX_SPACE = ROUND(1.5 * NORM_SPACE)


3.2.18.  END_SPACE

END_SPACE is an integer value (of type INT32) that gives the recommended
spacing at the end of sentences.

END_SPACE can be approximated if not provided as a font property,
according to the following algorithm:


     if (END_SPACE undefined) then
	END_SPACE = NORM_SPACE


3.2.19.  AVG_CAPITAL_WIDTH

AVG_CAPITAL_WIDTH is an integer value (of type INT32) that gives the
unweighted arithmetic mean of the absolute value of the width of each



				   18





X Logical Font Description Conventions			X11, Release 6.4


capital glyph in the font, in tenths of pixels, multiplied by -1 if the
dominant writing direction for the font is right-to-left.  This property
applies to both Latin and non-Latin fonts.  For Latin fonts, capitals
are the glyphs A through Z.  This property is usually used for font
matching or substitution.

AVG_CAPITAL_WIDTH can be calculated if not provided as a font property,
according to the following algorithm:


     if (AVG_CAPITAL_WIDTH undefined) then
	if (capitals exist) then
	   AVG_CAPITAL_WIDTH = ROUND (MEAN
		    (ABS (width of each capital glyph)) * 10)
	     * (if (dominant writing direction L-to-R) then 1 else -1)
	else AVG_CAPITAL_WIDTH undefined


3.2.20.  AVG_LOWERCASE_WIDTH

AVG_LOWERCASE_WIDTH is an integer value (of type INT32) that gives the
unweighted arithmetic mean width of the absolute value of the width of
each lowercase glyph in the font in tenths of pixels, multiplied by -1
if the dominant writing direction for the font is right-to-left.  For
Latin fonts, lowercase are the glyphs a through z.  This property is
usually used for font matching or substitution.

Where appropriate, AVG_LOWERCASE_WIDTH can be approximated if not pro-
vided as a font property, according to the following algorithm:


     if (AVG_LOWERCASE_WIDTH undefined) then
	if (lowercase exists) then
	   AVG_LOWERCASE_WIDTH = ROUND (MEAN
			    (ABS (width of each lowercase glyph)) * 10)
	  * (if (dominant writing direction L-to-R) then 1 else -1)
	else AVG_LOWERCASE_WIDTH undefined


3.2.21.  QUAD_WIDTH

QUAD_WIDTH is an integer typographic metric (of type INT32) that gives
the width of a quad (em) space.

				  Note

     Because all typographic fixed spaces (em, en, and thin) are
     constant for a given font size (that is, they do not vary
     according to setwidth), the use of this font property has been
     deprecated.  X clients that require typographic fixed space
     values are encouraged to discontinue use of QUAD_WIDTH and
     compute these values from other font properties (for example,
     PIXEL_SIZE).  X clients that require  a font-dependent width
     value should use either the FIGURE_WIDTH or one of the average



				   19





X Logical Font Description Conventions			X11, Release 6.4


     character width font properties (AVERAGE_WIDTH, AVG_CAPI-
     TAL_WIDTH or AVG_LOWERCASE_WIDTH).


3.2.22.  FIGURE_WIDTH

FIGURE_WIDTH is an integer typographic metric (of type INT32) that gives
the width of the tabular figures and the dollar sign, if suitable for
tabular setting (all widths equal).  For Latin fonts, these tabular fig-
ures are the Arabic numerals 0 through 9.

FIGURE_WIDTH can be approximated if not supplied as a font property,
according to the following algorithm:


     if (numerals and DOLLAR sign are defined & widths are equal) then
	FIGURE_WIDTH = width of DOLLAR
     else FIGURE_WIDTH property undefined


3.2.23.  SUPERSCRIPT_X

SUPERSCRIPT_X is an integer value (of type INT32) that gives the recom-
mended horizontal offset in pixels from the position point to the X ori-
gin of synthetic superscript text.  If the current position point is at
[X,Y], then superscripts should begin at [X + SUPERSCRIPT_X, Y - SUPER-
SCRIPT_Y].

SUPERSCRIPT_X can be approximated if not provided as a font property,
according to the following algorithm:


     if (SUPERSCRIPT_X undefined) then
	if (TANGENT(ITALIC_ANGLE) defined) then
	   SUPERSCRIPT_X = ROUND((0.40 * CAP_HEIGHT) / TANGENT(ITALIC_ANGLE))
	else SUPERSCRIPT_X = ROUND(0.40 * CAP_HEIGHT)


where TANGENT is a trigonometric function that returns the tangent of
its argument, which is in 1/64 degrees.

3.2.24.  SUPERSCRIPT_Y

SUPERSCRIPT_Y is an integer value (of type INT32) that gives the recom-
mended vertical offset in pixels from the position point to the Y origin
of synthetic superscript text.	If the current position point is at
[X,Y], then superscripts should begin at [X + SUPERSCRIPT_X, Y - SUPER-
SCRIPT_Y].

SUPERSCRIPT_Y can be approximated if not provided as a font property,
according to the following algorithm:






				   20





X Logical Font Description Conventions			X11, Release 6.4


     if (SUPERSCRIPT_Y undefined) then
	SUPERSCRIPT_Y = ROUND(0.40 * CAP_HEIGHT)


3.2.25.  SUBSCRIPT_X

SUBSCRIPT_X is an integer value (of type INT32) that gives the recom-
mended horizontal offset in pixels from the position point to the X ori-
gin of synthetic subscript text.  If the current position point is at
[X,Y], then subscripts should begin at [X + SUBSCRIPT_X, Y + SUB-
SCRIPT_Y].

SUBSCRIPT_X can be approximated if not provided as a font property,
according to the following algorithm:


     if (SUBSCRIPT_X undefined) then
	if (TANGENT(ITALIC_ANGLE) defined) then
	   SUBSCRIPT_X = ROUND((0.40 * CAP_HEIGHT) / TANGENT(ITALIC_ANGLE))
	else SUBSCRIPT_X = ROUND(0.40 * CAP_HEIGHT)


3.2.26.  SUBSCRIPT_Y

SUBSCRIPT_Y is an integer value (of type INT32) that gives the recom-
mended vertical offset in pixels from the position point to the Y origin
of synthetic subscript text.  If the current position point is at [X,Y],
then subscripts should begin at [X + SUBSCRIPT_X, Y + SUBSCRIPT_Y].

SUBSCRIPT_Y can be approximated if not provided as a font property,
according to the following algorithm:


     if (SUBSCRIPT_Y undefined) then
	SUBSCRIPT_Y = ROUND(0.40 * CAP_HEIGHT)


3.2.27.  SUPERSCRIPT_SIZE

SUPERSCRIPT_SIZE is an integer value (of type INT32) that gives the rec-
ommended body size of synthetic superscripts to be used with this font,
in pixels.  This will generally be smaller than the size of the current
font; that is, superscripts are imaged from a smaller font offset
according to SUPERSCRIPT_X and SUPERSCRIPT_Y.

SUPERSCRIPT_SIZE can be approximated if not provided as a font property,
according to the following algorithm:


     if (SUPERSCRIPT_SIZE undefined) then
	SUPERSCRIPT_SIZE = ROUND(0.60 * PIXEL_SIZE)






				   21





X Logical Font Description Conventions			X11, Release 6.4


3.2.28.  SUBSCRIPT_SIZE

SUBSCRIPT_SIZE is an integer value (of type INT32) that gives the recom-
mended body size of synthetic subscripts to be used with this font, in
pixels.  As with SUPERSCRIPT_SIZE, this will generally be smaller than
the size of the current font; that is, subscripts are imaged from a
smaller font offset according to SUBSCRIPT_X and SUBSCRIPT_Y.

SUBSCRIPT_SIZE can be approximated if not provided as a font property,
according to the algorithm:


     if (SUBSCRIPT_SIZE undefined) then
	SUBSCRIPT_SIZE = ROUND(0.60 * PIXEL_SIZE)


3.2.29.  SMALL_CAP_SIZE

SMALL_CAP_SIZE is an integer value (of type INT32) that gives the recom-
mended body size of synthetic small capitals to be used with this font,
in pixels.  Small capitals are generally imaged from a smaller font of
slightly more weight.  No offset [X,Y] is necessary.

SMALL_CAP_SIZE can be approximated if not provided as a font property,
according to the following algorithm:


     if (SMALL_CAP_SIZE undefined) then
	SMALL_CAP_SIZE = ROUND(PIXEL_SIZE * ((X_HEIGHT
				   + ((CAP_HEIGHT - X_HEIGHT) / 3)) / CAP_HEIGHT))


3.2.30.  UNDERLINE_POSITION

UNDERLINE_POSITION is an integer value (of type INT32) that gives the
recommended vertical offset in pixels from the baseline to the top of
the underline.	If the current position point is at [X,Y], the top of
the baseline is given by [X, Y + UNDERLINE_POSITION].

UNDERLINE_POSITION can be approximated if not provided as a font prop-
erty, according to the following algorithm:


     if (UNDERLINE_POSITION undefined) then
	UNDERLINE_POSITION = ROUND((maximum descent) / 2)

where maximum descent is the maximum descent (below the baseline) in
pixels of any glyph in the font.

3.2.31.  UNDERLINE_THICKNESS

UNDERLINE_THICKNESS is an integer value (of type INT32) that gives the
recommended underline thickness, in pixels.




				   22





X Logical Font Description Conventions			X11, Release 6.4


UNDERLINE_THICKNESS can be approximated if not provided as a font prop-
erty, according to the following algorithm:


     CapStemWidth = average width of the stems of capitals
     if (UNDERLINE_THICKNESS undefined) then
	UNDERLINE_THICKNESS = CapStemWidth


3.2.32.  STRIKEOUT_ASCENT

STRIKEOUT_ASCENT is an integer value (of type INT32) that gives the ver-
tical ascent for boxing or voiding glyphs in this font.  If the current
position is at [X,Y] and the string extent is EXTENT, the upper-left
corner of the strikeout box is at [X, Y - STRIKEOUT_ASCENT] and the
lower-right corner of the box is at [X + EXTENT, Y + STRIKEOUT_DESCENT].

STRIKEOUT_ASCENT can be approximated if not provided as a font property,
according to the following algorithm:


     if (STRIKEOUT_ASCENT undefined)
	STRIKEOUT_ASCENT = maximum ascent

where maximum ascent is the maximum ascent (above the baseline) in pix-
els of any glyph in the font.

3.2.33.  STRIKEOUT_DESCENT

STRIKEOUT_DESCENT is an integer value (of type INT32) that gives the
vertical descent for boxing or voiding glyphs in this font.  If the cur-
rent position is at [X,Y] and the string extent is EXTENT, the upper-
left corner of the strikeout box is at [X, Y - STRIKEOUT_ASCENT] and the
lower-right corner of the box is at [X + EXTENT, Y + STRIKEOUT_DESCENT].

STRIKEOUT_DESCENT can be approximated if not provided as a font prop-
erty, according to the following algorithm:


     if (STRIKEOUT_DESCENT undefined)
	STRIKEOUT_DESCENT = maximum descent

where maximum descent is the maximum descent (below the baseline) in
pixels of any glyph in the font.

3.2.34.  ITALIC_ANGLE

ITALIC_ANGLE is an integer value (of type INT32) that gives the nominal
posture angle of the typeface design, in 1/64 degrees, measured from the
glyph origin counterclockwise from the three o'clock position.

ITALIC_ANGLE can be defaulted if not provided as a font property,
according to the following algorithm:




				   23





X Logical Font Description Conventions			X11, Release 6.4


     if (ITALIC_ANGLE undefined) then
	ITALIC_ANGLE = (90 * 64)


3.2.35.  CAP_HEIGHT

CAP_HEIGHT is an integer value (of type INT32) that gives the nominal
height of the capital letters contained in the font, as specified by the
FOUNDRY or typeface designer.

Certain clients require CAP_HEIGHT to compute scale factors and posi-
tioning offsets for synthesized glyphs where this information or
designed glyphs are not explicitly provided by the font (for example,
small capitals, superiors, inferiors, and so on).  CAP_HEIGHT is also a
critical factor in font matching and substitution.

CAP_HEIGHT can be approximated if not provided as a font property,
according to the following algorithm:


     if (CAP_HEIGHT undefined) then
	if (Latin font) then
	   CAP_HEIGHT = XCharStruct.ascent[glyph X]
	else if (capitals exist) then
	    CAP_HEIGHT = XCharStruct.ascent[some unaccented capital glyph]
	else CAP_HEIGHT undefined


3.2.36.  X_HEIGHT

X_HEIGHT is an integer value (of type INT32) that gives the nominal
height above the baseline of the lowercase glyphs contained in the font,
as specified by the FOUNDRY or typeface designer.

As with CAP_HEIGHT, X_HEIGHT is required by certain clients to compute
scale factors for synthesized small capitals where this information is
not explicitly provided by the font resource.  X_HEIGHT is a critical
factor in font matching and substitution.

X_HEIGHT can be approximated if not provided as a font property, accord-
ing to the following algorithm:


     if (X_HEIGHT undefined) then
	if (Latin font) then
	   X_HEIGHT = XCharStruct.ascent[glyph x]
	else if (lowercase exists) then
	     X_HEIGHT = XCharStruct.ascent[some unaccented lc glyph without an ascender]
	else X_HEIGHT undefined








				   24





X Logical Font Description Conventions			X11, Release 6.4


3.2.37.  RELATIVE_SETWIDTH

RELATIVE_SETWIDTH is an unsigned integer value (of type CARD32) that
gives the coded proportionate width of the font, relative to all known
fonts of the same typeface family, according to the type designer's or
FOUNDRY's judgment.

RELATIVE_SETWIDTH ranges from 10 to 90 or is 0 if undefined or unknown.
The following reference values are defined:

---------------------------------------------------------------------------
Code	English Translation   Description
---------------------------------------------------------------------------
0	Undefined	      Undefined or unknown
10	UltraCondensed	      The lowest ratio of average width to height
20	ExtraCondensed
30	Condensed	      Condensed, Narrow, Compressed, ...
40	SemiCondensed
50	Medium		      Medium, Normal, Regular, ...
60	SemiExpanded	      SemiExpanded, DemiExpanded, ...
70	Expanded
80	ExtraExpanded	      ExtraExpanded, Wide, ...
90	UltraExpanded	      The highest ratio of average width to height
---------------------------------------------------------------------------


RELATIVE_SETWIDTH can be defaulted if not provided as a font property,
according to the following algorithm:


     if (RELATIVE_SETWIDTH undefined) then
	RELATIVE_SETWIDTH = 50


For polymorphic fonts, RELATIVE_SETWIDTH is not necessarily a linear
function of the font's setwidth axis.

X clients that want to obtain a calculated proportionate width of the
font (that is, a font-independent way of identifying the proportionate
width across all fonts and all font vendors) can use the following algo-
rithm:


     SETWIDTH = AVG_CAPITAL_WIDTH / (CAP_HEIGHT * 10)


where SETWIDTH is a real number with zero being the narrowest calculated
setwidth.

3.2.38.  RELATIVE_WEIGHT

RELATIVE_WEIGHT is an unsigned integer value (of type CARD32) that gives
the coded weight of the font, relative to all known fonts of the same
typeface family, according to the type designer's or FOUNDRY's judgment.



				   25





X Logical Font Description Conventions			X11, Release 6.4


RELATIVE_WEIGHT ranges from 10 to 90 or is 0 if undefined or unknown.
The following reference values are defined:

-----------------------------------------------------------------------
Code	English Translation   Description
-----------------------------------------------------------------------
0	Undefined	      Undefined or unknown
10	UltraLight	      The lowest ratio of stem width to height
20	ExtraLight
30	Light
40	SemiLight	      SemiLight, Book, ...
50	Medium		      Medium, Normal, Regular,...
60	SemiBold	      SemiBold, DemiBold, ...
70	Bold
80	ExtraBold	      ExtraBold, Heavy, ...
90	UltraBold	      UltraBold, Black, ..., the highest ratio
			      of stem width to height
-----------------------------------------------------------------------


RELATIVE_WEIGHT can be defaulted if not provided as a font property,
according to the following algorithm:


     if (RELATIVE_WEIGHT undefined) then
	RELATIVE_WEIGHT = 50


For polymorphic fonts, RELATIVE_WEIGHT is not necessarily a linear func-
tion of the font's weight axis.

3.2.39.  WEIGHT

Calculated WEIGHT is an unsigned integer value (of type CARD32) that
gives the calculated weight of the font, computed as the ratio of capi-
tal stem width to CAP_HEIGHT, in the range 0 to 1000, where 0 is the
lightest weight.

WEIGHT can be calculated if not supplied as a font property, according
to the following algorithm:


     CapStemWidth = average width of the stems of capitals
     if (WEIGHT undefined) then
	WEIGHT = ROUND ((CapStemWidth * 1000) / CAP_HEIGHT)


A calculated value for weight is necessary when matching fonts from dif-
ferent families because both the RELATIVE_WEIGHT and the WEIGHT_NAME are
assigned by the typeface supplier, according to its tradition and prac-
tice, and therefore, are somewhat subjective.  Calculated WEIGHT pro-
vides a font-independent way of identifying the weight across all fonts
and all font vendors.




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X Logical Font Description Conventions			X11, Release 6.4


3.2.40.  RESOLUTION

RESOLUTION is an integer value (of type INT32) that gives the resolution
for which this font was created, measured in 1/100 pixels per point.

				  Note

     As independent horizontal and vertical design resolution com-
     ponents are required to accommodate displays with nonsquare
     aspect ratios, the use of this font property has been depre-
     cated, and independent RESOLUTION_X and RESOLUTION_Y font name
     fields/properties have been defined (see sections 3.1.2.9 and
     3.1.2.10).  X clients are encouraged to discontinue use of the
     RESOLUTION property and are encouraged to use the appropriate
     X,Y resolution properties, as required.


3.2.41.  FONT

FONT is a string (of type ATOM) that gives the full XLFD name of the
font--that is, the value can be used to open another instance of the
same font.

If not provided, the FONT property cannot be calculated.

3.2.42.  FACE_NAME

FACE_NAME is a human-understandable string (of type ATOM) that gives the
full device-independent typeface name, including the owner, weight,
slant, set, and so on but not the resolution, size, and so on.	This
property may be used as feedback during font selection.

FACE_NAME cannot be calculated or approximated if not provided as a font
property.

3.2.43.  FULL_NAME

FULL_NAME is the same as FACE_NAME.  Its use is deprecated, but it is
found on some old fonts.

3.2.44.  COPYRIGHT

COPYRIGHT is a human-understandable string (of type ATOM) that gives the
copyright information of the legal owner of the digital font data.

This information is a required component of a font but is independent of
the particular format used to represent it (that is, it cannot be cap-
tured as a comment that could later be thrown away for efficiency rea-
sons).

COPYRIGHT cannot be calculated or approximated if not provided as a font
property.





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3.2.45.  NOTICE

NOTICE is a human-understandable string (of type ATOM) that gives the
copyright information of the legal owner of the font design or, if not
applicable, the trademark information for the typeface FAMILY_NAME.

Typeface design and trademark protection laws vary from country to coun-
try, the USA having no design copyright protection currently while vari-
ous countries in Europe offer both design and typeface family name
trademark protection.  As with COPYRIGHT, this information is a required
component of a font but is independent of the particular format used to
represent it.

NOTICE cannot be calculated or approximated if not provided as a font
property.

3.2.46.  DESTINATION

DESTINATION is an unsigned integer code (of type CARD32) that gives the
font design destination, that is, whether it was designed as a screen
proofing font to match printer font glyph widths (WYSIWYG), as an opti-
mal video font (possibly with corresponding printer font) for extended
screen viewing (video text), and so on.

The font design considerations are very different, and at current dis-
play resolutions, the readability and legibility of these two kinds of
screen fonts are very different.  DESTINATION allows publishing clients
that use X to model the printed page and video text clients, such as on-
line documentation browsers, to query for X screen fonts that suit their
particular requirements.

The encoding is as follows:

--------------------------------------------------------------------
Code	English Translation   Description
--------------------------------------------------------------------
0	WYSIWYG 	      The font is optimized to match the
			      typographic design and metrics of an
			      equivalent printer font.
1	Video text	      The font is optimized for screen leg-
			      ibility and readability.
--------------------------------------------------------------------



3.2.47.  FONT_TYPE

FONT_TYPE is a human-understandable string (of type ATOM) that describes
the format of the font data as they are read from permanent storage by
the current font source.  It is a static attribute of the source data.
It can be used by clients to select a type of bitmap or outline font
without regard to the rasterizer used to render the font.





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X Logical Font Description Conventions			X11, Release 6.4


Predefined values are as follows:

----------------------------------------------------------------
Value	     When applicable
----------------------------------------------------------------
"Bitmap"     Hand-tuned bitmap fonts.  Some attempt has been
	     made to optimize the visual appearance of the font
	     for the requested size and resolution.
"Prebuilt"   All bitmap format fonts that cannot be described
	     as "Bitmap", that is, hand-tuned.	For example, a
	     bitmap format font that was generated mechanically
	     using a scalable font rasterizer would be consid-
	     ered "Prebuilt", not "Bitmap".
"Type 1"     Any Type 1 font.
"TrueType"   Any TrueType font.
"Speedo"     Any Speedo font.
"F3"	     Any F3 font.
----------------------------------------------------------------


Other values may be registered with the X Consortium.

3.2.48.  FONT_VERSION

FONT_VERSION is a human-understandable string (of type ATOM) that
describes the formal or informal version of the font.  None is a valid
value.

3.2.49.  RASTERIZER_NAME

RASTERIZER_NAME is a human-understandable string (of type ATOM) that is
the specific name of the rasterizer that has performed some rasteriza-
tion operation (such as scaling from outlines) on this font.

To define a RASTERIZER_NAME, the following format is recommended:

RasterizerName ::=   OrganizationId Space Rasterizer
OrganizationId ::=   STRING8--the X Registry ORGANIZATION
		     name of the rasterizer implementor or
		     maintainer.
    Rasterizer ::=   the case-sensitive, human-understand-
		     able product name of the rasterizer.
		     Words within this name should be sep-
		     arated by a single SPACE.
	 Space ::=   OCTET-" " (SPACE)


Examples:
	  X Consortium Bit Scaler
	  X Consortium Type 1 Rasterizer
	  X Consortium Speedo Rasterizer
	  Adobe Type Manager
	  Sun TypeScaler




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X Logical Font Description Conventions			X11, Release 6.4


If RASTERIZER_NAME is not defined, or is None, no rasterization opera-
tion has been applied to the FONT_TYPE.

3.2.50.  RASTERIZER_VERSION

RASTERIZER_VERSION is a human-understandable string (of type ATOM) that
represents the formal or informal version of a font rasterizer.  The
RASTERIZER_VERSION should match the corresponding product version number
known to users, when applicable.

3.2.51.  RAW_ASCENT

For a font with a transformation matrix, RAW_ASCENT is the font ascent
in 1000 pixel metrics (see section 4.1).

3.2.52.  RAW_DESCENT

For a font with a transformation matrix, RAW_DESCENT is the font descent
in 1000 pixel metrics (see section 4.1).

3.2.53.  RAW_*

For a font with a transformation matrix, all font properties that repre-
sent horizontal or vertical sizes or displacements will be accompanied
by a new property, named as the original except prefixed with "RAW_",
that is computed as described in section 4.1.

3.2.54.  AXIS_NAMES

AXIS_NAMES is a list of all the names of the axes for a polymorphic
font, separated by a null (0) byte.  These names are suitable for pre-
sentation in a user interface (see section 6).

3.2.55.  AXIS_LIMITS

AXIS_LIMITS is a list of integers, two for each axis, giving the minimum
and maximum allowable values for that axis of a polymorphic font (see
section 6).

3.2.56.  AXIS_TYPES

AXIS_TYPES is like AXIS_NAMES, but can be registered as having specific
semantics (see section 6).

3.3.  Built-in Font Property Atoms

The following font property atom definitions were predefined in the ini-
tial version of the core protocol:

----------------------------------------------
Font Property/Atom Name   Property Type
----------------------------------------------
MIN_SPACE		  INT32




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----------------------------------------------
Font Property/Atom Name   Property Type
----------------------------------------------
NORM_SPACE		  INT32
MAX_SPACE		  INT32
END_SPACE		  INT32
SUPERSCRIPT_X		  INT32
SUPERSCRIPT_Y		  INT32
SUBSCRIPT_X		  INT32
SUBSCRIPT_Y		  INT32
UNDERLINE_POSITION	  INT32
UNDERLINE_THICKNESS	  INT32
STRIKEOUT_ASCENT	  INT32
STRIKEOUT_DESCENT	  INT32
FONT_ASCENT		  INT32
FONT_DESCENT		  INT32
ITALIC_ANGLE		  INT32
X_HEIGHT		  INT32
QUAD_WIDTH		  INT32 - deprecated
WEIGHT			  CARD32
POINT_SIZE		  INT32
RESOLUTION		  CARD32 - deprecated
COPYRIGHT		  ATOM
FULL_NAME		  ATOM - deprecated
FAMILY_NAME		  ATOM
DEFAULT_CHAR		  CARD32
----------------------------------------------


4.  Matrix Transformations

An XLFD name presented to the server can have the POINT_SIZE or
PIXEL_SIZE field begin with the character "[".	If the first character
of the field is "[", the character must be followed with ASCII represen-
tations of four floating point numbers and a trailing "]", with white
space separating the numbers and optional white space separating the
numbers from the "[" and "]" characters.  Numbers use standard floating
point syntax but use the character "~" to represent a minus sign in the
mantissa or exponent.

The BNF for a matrix transformation string is as follows:

 MatrixString ::=   LeftBracket OptionalSpace Float Space Float Space Float
		    Space Float OptionalSpace RightBracket
OptionalSpace ::=   "" | Space
	Space ::=   SpaceChar | SpaceChar Space
	Float ::=   Mantissa | Mantissa Exponent
     Mantissa ::=   Sign Number | Number
	 Sign ::=   Plus | Tilde
       Number ::=   Integer | Integer Dot Integer | Dot Integer
      Integer ::=   Digit | Digit Integer
	Digit ::=   "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
     Exponent ::=   "e" SignedInteger | "E" SignedInteger




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X Logical Font Description Conventions			X11, Release 6.4


SignedInteger ::=   Sign Integer | Integer
  LeftBracket ::=   OCTET - "[" (LEFT SQUARE BRACKET)
 RightBracket ::=   OCTET - "]" (RIGHT SQUARE BRACKET)
    SpaceChar ::=   OCTET - " " (SPACE)
	Tilde ::=   OCTET - "~" (TILDE)
	 Plus ::=   OCTET - "+" (PLUS)
	  Dot ::=   OCTET - "." (FULL STOP)


The string "[a b c d]" represents a graphical transformation of the
glyphs in the font by the matrix

[   a	b   0	]
[   c	d   0	]
[   0	0   1	]


All transformations occur around the origin of the glyph.  The relation-
ship between the current scalar values and the matrix transformation
values is that the scalar value "N" in the POINT_SIZE field produces the
same glyphs as the matrix "[N/10 0 0 N/10]" in that field, and the
scalar value "N" in the PIXEL_SIZE field produces the same glyphs as the
matrix "[N*RESOLUTION_X/RESOLUTION_Y 0 0 N]" in that field.

If matrices are specified for both the POINT_SIZE and PIXEL_SIZE, they
must bear the following relationship to each other within an implementa-
tion-specific tolerance:
     PIXEL_SIZE_MATRIX = [Sx 0 0 Sy] * POINT_SIZE_MATRIX
where
     Sx = RESOLUTION_X / 72.27
     Sy = RESOLUTION_Y / 72.27

If either the POINT_SIZE or PIXEL_SIZE field is unspecified (either "0"
or wildcarded), the preceding formulas can be used to compute one from
the other.

4.1.  Metrics and Font Properties

In this section, the phrase "1000 pixel metrics" means the metrics that
would be obtained if the rasterizer took the base untransformed design
used to generate the transformed font and scaled it linearly to a height
of 1000 pixels, with no rotation component.  Note that there may be no
way for the application to actually request this font since the raster-
izer may use different outlines or rasterization techniques at that size
from the ones used to generate the transformed font.

Notes on properties and metrics:

The per-char ink metrics (lbearing, rbearing, ascent, and descent) rep-
resent the ink extent of the transformed glyph around its origin.

The per-char width is the x component of the transformed character
width.




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The font ascent and descent are the y component of the transformed font
ascent or descent.

The FONT property returns a name reflecting the matrix being used--that
is, the name returned can be used to open another instance of the same
font.  The returned name is not necessarily an exact copy of the
requested name.  If, for example, the user requests
   -misc-fixed-medium-r-normal--0-[2e1 0 0.0 +10.0]-72-72-c-0-iso8859-1
the resulting FONT property might be
   -misc-fixed-medium-r-normal--[19.9 0 0 10]-[20 0 0
10]-72-72-c-0-iso8859-1
The FONT property will always include matrices in both the PIXEL_SIZE
and the POINT_SIZE fields.

To allow accurate client positioning of transformed characters, the
attributes field of the XCharInfo contains the width of the character in
1000 pixel metrics.  This attributes field should be interpreted as a
signed integer.

There will always be 2 new font properties defined, RAW_ASCENT and
RAW_DESCENT, that hold the ascent and descent in 1000 pixel metrics.

All font properties that represent horizontal widths or displacements
have as their value the x component of the transformed width or dis-
placement.  All font properties that represent vertical heights or dis-
placements have as their value the y component of the transformed height
or displacement.  Each such property will be accompanied by a new prop-
erty, named as the original except prefixed with "RAW_", that gives the
value of the width, height, or displacement in 1000 pixel metrics.

5.  Scalable Fonts

The XLFD is designed to support scalable fonts.  A scalable font is a
font source from which instances of arbitrary size can be derived.  A
scalable font source might be one or more outlines together with zero or
more hand-tuned bitmap fonts at specific sizes and resolutions, or it
might be a programmatic description together with zero or more bitmap
fonts, or some other format (perhaps even just a single bitmap font).

The following definitions are useful for discussing scalable fonts:

Well-formed XLFD pattern

     A pattern string containing 14 hyphens, one of which is the first
     character of the pattern.	Wildcard characters are permitted in the
     fields of a well-formed XLFD pattern.

Scalable font name

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





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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 font name with
     values to yield a font name that could actually be produced from
     the font source.  A scaling engine is permitted, but not required,
     to interpret the scalable fields in font names to support anamor-
     phic scaling.

Global list

     The list of names that would be returned by an X server for a List-
     Fonts protocol request on the pattern "*" if there were no protocol
     restrictions on the total number of names returned.


The global list consists of font names derived from font sources.  If a
single font source can support multiple character sets (specified in the
CHARSET_REGISTRY and CHARSET_ENCODING fields), each such character set
should be used to form a separate font name in the list.  For a nonscal-
able font source, the simple font name for each character set is
included in the global list.  For a scalable font source, a scalable
font name for each character set is included in the list.  In addition
to the scalable font name, specific derived instance names may also be
included in the list.  The relative order of derived instances with
respect to the scalable font name is not constrained.  Finally, font
name aliases may also be included in the list.	The relative order of
aliases with respect to the real font name is not constrained.

The values of the RESOLUTION_X and RESOLUTION_Y fields of a scalable
font name are implementation dependent, but to maximize backward compat-
ibility, they should be reasonable nonzero values, for example, a reso-
lution close to that provided by the screen (in a single-screen server).
Because some existing applications rely on seeing a collection of point
and pixel sizes, server vendors are strongly encouraged in the near term
to provide a mechanism for including, for each scalable font name, a set
of specific derived instance names.  For font sources that contain a
collection of hand-tuned bitmap fonts, including names of these
instances in the global list is recommended and sufficient.

The X protocol request OpenFont on a scalable font name returns a font
corresponding to an implementation-dependent derived instance of that
font name.

The X protocol request ListFonts on a well-formed XLFD pattern returns
the following.	Starting 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
font name in the list.	For each resulting font name, if the remaining
scalable fields cannot be replaced with values to produce a derived



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instance, remove the font name from the list.  Now take the modified
list, and perform a simple pattern match against the pattern argument.
ListFonts returns the resulting list.

For example, given the global list:

     -Linotype-Times-Bold-I-Normal--0-0-100-100-P-0-ISO8859-1
     -Linotype-Times-Bold-R-Normal--0-0-100-100-P-0-ISO8859-1
     -Linotype-Times-Medium-I-Normal--0-0-100-100-P-0-ISO8859-1
     -Linotype-Times-Medium-R-Normal--0-0-100-100-P-0-ISO8859-1


a ListFonts request with the pattern:


     -*-Times-*-R-Normal--*-120-100-100-P-*-ISO8859-1


would return:

     -Linotype-Times-Bold-R-Normal--0-120-100-100-P-0-ISO8859-1
     -Linotype-Times-Medium-R-Normal--0-120-100-100-P-0-ISO8859-1


ListFonts on a pattern containing wildcards that is not a well-formed
XLFD pattern is only required to return the list obtained by performing
a simple pattern match against the global list.  X servers are permit-
ted, but not required, to use a more sophisticated matching algorithm.

6.  Polymorphic Fonts

Fonts that can be varied in ways other than size or resolution are
called polymorphic fonts.  Multiple Master Type 1 font programs are one
type of a polymorphic font.  Current examples of axes along which the
fonts can be varied are width, weight, and optical size; others might
include formality or x-height.

To support polymorphic fonts, special values indicating variability are
defined for the following XLFD fields:
     WEIGHT_NAME
     SLANT
     SETWIDTH_NAME
     ADD_STYLE_NAME

The string "0" is the special polymorphic value.  In the WEIGHT_NAME,
SLANT, or SETWIDTH_NAME field, "0" must be the entire field.  There may
be multiple polymorphic values in the ADD_STYLE_NAME field.  They are
surrounded by "[" and "]" and separated by a Space, as "[0 0]".  The
polymorphic values may coexist with other data in the field.  It is rec-
ommended that the polymorphic values be at the end of the ADD_STYLE_NAME
field.

The font-matching algorithms for a font with polymorphic fields are
identical to the matching algorithms for a font with scalable fields.



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There are three new font properties to describe the axes of variation,
AXIS_NAMES, AXIS_LIMITS, and AXIS_TYPES.  AXIS_NAMES is a list of all
the names of the axes for the font, separated by a null (0) byte.  These
names are suitable for presentation in a user interface.  AXIS_LIMITS is
a list of integers, two for each axis, giving the minimum and maximum
allowable values for that axis.  AXIS_TYPES is like AXIS_NAMES, but can
be registered as having specific semantics.

The axes are listed in the properties in the same order as they appear
in the font name.  They are matched with font name fields by looking for
the special polymorphic values in the font name.

Examples:

The Adobe Myriad MM font program has width and weight axes.  Weight can
vary from 215 to 830, and width from 300 to 700.

     Name:
	  -Adobe-Myriad MM-0-R-0--0-0-0-0-P-0-ISO8859-1
     AXIS_NAMES:
	  Weight, Width
     AXIS_LIMITS:
	  215, 830, 300, 700
     AXIS_TYPES:
	  Adobe-Weight, Adobe-Width
     Sample derived instance:
	  -Adobe-Myriad MM-412-R-575--*-120-100-100-P-*-ISO8859-1


The Adobe Minion MM Italic font program has width, weight, and optical
size axes.

     Name:
	  -Adobe-Minion MM-0-I-0-[0]-0-0-0-0-P-0-ISO8859-1
     AXIS_NAMES:
	  Weight, Width, Optical size
     AXIS_LIMITS:
	  345, 620, 450, 600, 6, 72
     AXIS_TYPES:
	  Adobe-Weight, Adobe-Width, Adobe-OpticalSize
     Sample derived instance:
	  -Adobe-Minion MM-550-I-480-[18]-*-180-100-100-P-*-ISO8859-1


The Adobe Minion MM Swash Italic font program has the same axes and val-
ues.  This shows how "[0]" in the ADD_STYLE_NAME field can coexist with
other words.

     Name:
	  -Adobe-Minion MM-0-I-0-Swash[0]-0-0-0-0-P-0-ISO8859-1
     AXIS_NAMES:
	  Weight, Width, Optical size
     AXIS_LIMITS:
	  345, 620, 450, 600, 6, 72



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     AXIS_TYPES:
	  Adobe-Weight, Adobe-Width, Adobe-OpticalSize
     Sample derived instance:
	  -Adobe-Minion MM-550-I-480-Swash[18]-*-180-100-100-P-*-ISO8859-1


The XYZ Abc font, a hypothetical font, has optical size and x-height
axes.  This shows how there can be more than one polymorphic value in
the ADD_STYLE_NAME field.

     Name:
	  -XYZ-Abc-Medium-R-Normal-[0 0]-0-0-0-0-P-0-ISO8859-1
     AXIS_NAMES:
	  Optical size, X-height
     AXIS_LIMITS:
	  6, 72, 400, 600
     AXIS_TYPES:
	  XYZ-OpticalSize, XYZ-Xheight
     Sample derived instance:
	  -XYZ-Abc-Medium-R-Normal-[14 510]-*-140-100-100-P-*-ISO8859-1


If an axis allows negative values, a client requests a negative value by
using "~" (TILDE) as a minus sign.

Axis types can be registered with the X Consortium, along with their
semantics.

If a font name that contains the polymorphic value or a wildcard in a
polymorphic field is presented to a font source, the font source is free
to substitute any value that is convenient.  However, font sources
should try to use a value that would be considered normal or medium for
the particular font.  For example, if an optical size variable is unre-
solved, the font source should provide a value appropriate to the size
of the font.

The result of specifying an out-of-range value for a polymorphic field
is undefined.  The font source may treat this as a BadName error, treat
the value as if it were the closest legal value, or extrapolate to try
to accommodate the value.

7.  Affected Elements of Xlib and the X Protocol

The following X protocol requests must support the XLFD conventions:

o    OpenFont - for the name argument

o    ListFonts - for the pattern argument

o    ListFontsWithInfo - for the pattern argument

In addition, the following Xlib functions must support the XLFD conven-
tions:




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o    XLoadFont - for the name argument

o    XListFontsWithInfo - for the pattern argument

o    XLoadQueryFont - for the name argument

o    XListFonts - for the pattern argument

8.  BDF Conformance

The bitmap font distribution and interchange format adopted by the X
Consortium (BDF V2.1) provides a general mechanism for identifying the
font name of an X font and a variable list of font properties, but it
does not mandate the syntax or semantics of the font name or the seman-
tics of the font properties that might be provided in a BDF font.  This
section identifies the requirements for BDF fonts that conform to XLFD.

8.1.  XLFD Conformance Requirements

A BDF font conforms to the XLFD specification if and only if the follow-
ing conditions are satisfied:

o    The value for the BDF item FONT conforms to the syntax and semantic
     definition of a XLFD FontName string.

o    The FontName begins with the X FontNameRegistry prefix: "-".

o    All XLFD FontName fields are defined.

o    Any FontProperties provided conform in name and semantics to the
     XLFD FontProperty definitions.

A simple method of testing for conformance would entail verifying that
the FontNameRegistry prefix is the string "-", that the number of field
delimiters in the string and coded field values are valid, and that each
font property name either matches a standard XLFD property name or fol-
lows the definition of a private property.

8.2.  FONT_ASCENT, FONT_DESCENT, and DEFAULT_CHAR

FONT_ASCENT, FONT_DESCENT, and DEFAULT_CHAR are provided in the BDF
specification as properties that are moved to the XFontStruct by the BDF
font compiler in generating the X server-specific binary font encoding.
If present, these properties shall comply with the following semantic
definitions.

8.2.1.	FONT_ASCENT

FONT_ASCENT is an integer value (of type INT32) that gives the recom-
mended typographic ascent above the baseline for determining interline
spacing.  Specific glyphs of the font may extend beyond this.  If the
current position point for line n is at [X,Y], then the origin of the
next line m = n + 1 (allowing for a possible font change) is [X, Y +
FONT_DESCENTn + FONT_ASCENTm].



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FONT_ASCENT can be approximated if not provided as a font property,
according to the following algorithm:


     if (FONT_ASCENT undefined) then
	FONT_ASCENT = maximum ascent

where maximum ascent is the maximum ascent (above the baseline) in pix-
els of any glyph in the font.

8.2.2.	FONT_DESCENT

FONT_DESCENT is an integer value (of type INT32) that gives the recom-
mended typographic descent below the baseline for determining interline
spacing.  Specific glyphs of the font may extend beyond this.  If the
current position point for line n is at [X,Y], then the origin of the
next line m = n+1 (allowing for a possible font change) is [X, Y +
FONT_DESCENTn + FONT_ASCENTm].

The logical extent of the font is inclusive between the Y-coordinate
values: Y - FONT_ASCENT and Y + FONT_DESCENT + 1.

FONT_DESCENT can be approximated if not provided as a font property,
according to the following algorithm:


     if (FONT_DESCENT undefined) then
	FONT_DESCENT = maximum descent

where maximum descent is the maximum descent (below the baseline) in
pixels of any glyph in the font.

8.2.3.	DEFAULT_CHAR

The DEFAULT_CHAR is an unsigned integer value (of type CARD32) that
specifies the index of the default character to be used by the X server
when an attempt is made to display an undefined or nonexistent character
in the font.  (For a font using a 2-byte matrix format, the index bytes
are encoded in the integer as byte1 * 65536 + byte2.)  If the
DEFAULT_CHAR itself specifies an undefined or nonexistent character in
the font, then no display is performed.

DEFAULT_CHAR cannot be approximated if not provided as a font property.














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				   40









			   Table of Contents


1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . .   1
2. Requirements and Goals  . . . . . . . . . . . . . . . . . . . . .   1
2.1. Provide Unique and Descriptive Font Names . . . . . . . . . . .   2
2.2. Support Multiple Font Vendors and Character Sets  . . . . . . .   2
2.3. Support Scalable and Polymorphic Fonts  . . . . . . . . . . . .   2
2.4. Support Transformations and Subsetting of Fonts . . . . . . . .   2
2.5. Be Independent of X Server and Operating or File System
Implementations  . . . . . . . . . . . . . . . . . . . . . . . . . .   2
2.6. Support Arbitrarily Complex Font Matching and Substitution
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
2.7. Be Extensible . . . . . . . . . . . . . . . . . . . . . . . . .   3
3. X Logical Font Description  . . . . . . . . . . . . . . . . . . .   3
3.1. FontName  . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
3.1.1. FontName Syntax . . . . . . . . . . . . . . . . . . . . . . .   4
3.1.2. FontName Field Definitions  . . . . . . . . . . . . . . . . .   5
3.1.2.1. FOUNDRY Field . . . . . . . . . . . . . . . . . . . . . . .   5
3.1.2.2. FAMILY_NAME Field . . . . . . . . . . . . . . . . . . . . .   6
3.1.2.3. WEIGHT_NAME Field . . . . . . . . . . . . . . . . . . . . .   6
3.1.2.4. SLANT Field . . . . . . . . . . . . . . . . . . . . . . . .   7
3.1.2.5. SETWIDTH_NAME Field . . . . . . . . . . . . . . . . . . . .   7
3.1.2.6. ADD_STYLE_NAME Field  . . . . . . . . . . . . . . . . . . .   8
3.1.2.7. PIXEL_SIZE Field  . . . . . . . . . . . . . . . . . . . . .   8
3.1.2.8. POINT_SIZE Field  . . . . . . . . . . . . . . . . . . . . .   8
3.1.2.9. RESOLUTION_X and RESOLUTION_Y Fields  . . . . . . . . . . .   9
3.1.2.10. SPACING Field  . . . . . . . . . . . . . . . . . . . . . .   9
3.1.2.11. AVERAGE_WIDTH Field  . . . . . . . . . . . . . . . . . . .  10
3.1.2.12. CHARSET_REGISTRY and CHARSET_ENCODING Fields . . . . . . .  10
3.1.3. Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  12
3.2. Font Properties . . . . . . . . . . . . . . . . . . . . . . . .  13
3.2.1. FOUNDRY . . . . . . . . . . . . . . . . . . . . . . . . . . .  14
3.2.2. FAMILY_NAME . . . . . . . . . . . . . . . . . . . . . . . . .  14
3.2.3. WEIGHT_NAME . . . . . . . . . . . . . . . . . . . . . . . . .  14
3.2.4. SLANT . . . . . . . . . . . . . . . . . . . . . . . . . . . .  15
3.2.5. SETWIDTH_NAME . . . . . . . . . . . . . . . . . . . . . . . .  15
3.2.6. ADD_STYLE_NAME  . . . . . . . . . . . . . . . . . . . . . . .  15
3.2.7. PIXEL_SIZE  . . . . . . . . . . . . . . . . . . . . . . . . .  15
3.2.8. POINT_SIZE  . . . . . . . . . . . . . . . . . . . . . . . . .  16
3.2.9. RESOLUTION_X  . . . . . . . . . . . . . . . . . . . . . . . .  16
3.2.10. RESOLUTION_Y . . . . . . . . . . . . . . . . . . . . . . . .  16
3.2.11. SPACING  . . . . . . . . . . . . . . . . . . . . . . . . . .  17
3.2.12. AVERAGE_WIDTH  . . . . . . . . . . . . . . . . . . . . . . .  17
3.2.13. CHARSET_REGISTRY . . . . . . . . . . . . . . . . . . . . . .  17
3.2.14. CHARSET_ENCODING . . . . . . . . . . . . . . . . . . . . . .  17
3.2.15. MIN_SPACE  . . . . . . . . . . . . . . . . . . . . . . . . .  17
3.2.16. NORM_SPACE . . . . . . . . . . . . . . . . . . . . . . . . .  18
3.2.17. MAX_SPACE  . . . . . . . . . . . . . . . . . . . . . . . . .  18
3.2.18. END_SPACE  . . . . . . . . . . . . . . . . . . . . . . . . .  18
3.2.19. AVG_CAPITAL_WIDTH  . . . . . . . . . . . . . . . . . . . . .  18
3.2.20. AVG_LOWERCASE_WIDTH  . . . . . . . . . . . . . . . . . . . .  19
3.2.21. QUAD_WIDTH . . . . . . . . . . . . . . . . . . . . . . . . .  19



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X Logical Font Description Conventions			X11, Release 6.4


3.2.22. FIGURE_WIDTH . . . . . . . . . . . . . . . . . . . . . . . .  20
3.2.23. SUPERSCRIPT_X  . . . . . . . . . . . . . . . . . . . . . . .  20
3.2.24. SUPERSCRIPT_Y  . . . . . . . . . . . . . . . . . . . . . . .  20
3.2.25. SUBSCRIPT_X  . . . . . . . . . . . . . . . . . . . . . . . .  21
3.2.26. SUBSCRIPT_Y  . . . . . . . . . . . . . . . . . . . . . . . .  21
3.2.27. SUPERSCRIPT_SIZE . . . . . . . . . . . . . . . . . . . . . .  21
3.2.28. SUBSCRIPT_SIZE . . . . . . . . . . . . . . . . . . . . . . .  22
3.2.29. SMALL_CAP_SIZE . . . . . . . . . . . . . . . . . . . . . . .  22
3.2.30. UNDERLINE_POSITION . . . . . . . . . . . . . . . . . . . . .  22
3.2.31. UNDERLINE_THICKNESS  . . . . . . . . . . . . . . . . . . . .  22
3.2.32. STRIKEOUT_ASCENT . . . . . . . . . . . . . . . . . . . . . .  23
3.2.33. STRIKEOUT_DESCENT  . . . . . . . . . . . . . . . . . . . . .  23
3.2.34. ITALIC_ANGLE . . . . . . . . . . . . . . . . . . . . . . . .  23
3.2.35. CAP_HEIGHT . . . . . . . . . . . . . . . . . . . . . . . . .  24
3.2.36. X_HEIGHT . . . . . . . . . . . . . . . . . . . . . . . . . .  24
3.2.37. RELATIVE_SETWIDTH  . . . . . . . . . . . . . . . . . . . . .  25
3.2.38. RELATIVE_WEIGHT  . . . . . . . . . . . . . . . . . . . . . .  25
3.2.39. WEIGHT . . . . . . . . . . . . . . . . . . . . . . . . . . .  26
3.2.40. RESOLUTION . . . . . . . . . . . . . . . . . . . . . . . . .  27
3.2.41. FONT . . . . . . . . . . . . . . . . . . . . . . . . . . . .  27
3.2.42. FACE_NAME  . . . . . . . . . . . . . . . . . . . . . . . . .  27
3.2.43. FULL_NAME  . . . . . . . . . . . . . . . . . . . . . . . . .  27
3.2.44. COPYRIGHT  . . . . . . . . . . . . . . . . . . . . . . . . .  27
3.2.45. NOTICE . . . . . . . . . . . . . . . . . . . . . . . . . . .  28
3.2.46. DESTINATION  . . . . . . . . . . . . . . . . . . . . . . . .  28
3.2.47. FONT_TYPE  . . . . . . . . . . . . . . . . . . . . . . . . .  28
3.2.48. FONT_VERSION . . . . . . . . . . . . . . . . . . . . . . . .  29
3.2.49. RASTERIZER_NAME  . . . . . . . . . . . . . . . . . . . . . .  29
3.2.50. RASTERIZER_VERSION . . . . . . . . . . . . . . . . . . . . .  30
3.2.51. RAW_ASCENT . . . . . . . . . . . . . . . . . . . . . . . . .  30
3.2.52. RAW_DESCENT  . . . . . . . . . . . . . . . . . . . . . . . .  30
3.2.53. RAW_*  . . . . . . . . . . . . . . . . . . . . . . . . . . .  30
3.2.54. AXIS_NAMES . . . . . . . . . . . . . . . . . . . . . . . . .  30
3.2.55. AXIS_LIMITS  . . . . . . . . . . . . . . . . . . . . . . . .  30
3.2.56. AXIS_TYPES . . . . . . . . . . . . . . . . . . . . . . . . .  30
3.3. Built-in Font Property Atoms  . . . . . . . . . . . . . . . . .  30
4. Matrix Transformations  . . . . . . . . . . . . . . . . . . . . .  31
4.1. Metrics and Font Properties . . . . . . . . . . . . . . . . . .  32
5. Scalable Fonts  . . . . . . . . . . . . . . . . . . . . . . . . .  33
6. Polymorphic Fonts . . . . . . . . . . . . . . . . . . . . . . . .  35
7. Affected Elements of Xlib and the X Protocol  . . . . . . . . . .  37
8. BDF Conformance . . . . . . . . . . . . . . . . . . . . . . . . .  38
8.1. XLFD Conformance Requirements . . . . . . . . . . . . . . . . .  38
8.2. FONT_ASCENT, FONT_DESCENT, and DEFAULT_CHAR . . . . . . . . . .  38
8.2.1. FONT_ASCENT . . . . . . . . . . . . . . . . . . . . . . . . .  38
8.2.2. FONT_DESCENT  . . . . . . . . . . . . . . . . . . . . . . . .  39
8.2.3. DEFAULT_CHAR  . . . . . . . . . . . . . . . . . . . . . . . .  39










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