X Logical Font Description Conventions

X Consortium Standard

Jim Flowers

Digital Equipment Corporation

Edited by

Stephen Gildea

X Consortium

X Version 11, Release 7.7

Version 1.5

Copyright © 1988, 1994 X Consortium

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Copyright © 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. Digital 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.

Helvetica and Times are registered trademarks of Linotype Company.

ITC Avant Garde Gothic is a registered trademark of International Typeface

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.

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Table of Contents

1. Introduction

2. Requirements and Goals

Provide Unique and Descriptive Font Names

Support Multiple Font Vendors and Character Sets

Support Scalable and Polymorphic Fonts

Support Transformations and Subsetting of Fonts

Be Independent of X Server and Operating or File System Implementations

Support Arbitrarily Complex Font Matching and Substitution

Be Extensible

3. X Logical Font Description

FontName

FontName Syntax

FontName Field Definitions

Examples

Font Properties

FOUNDRY

FAMILY_NAME

WEIGHT_NAME

SLANT

SETWIDTH_NAME

ADD_STYLE_NAME

PIXEL_SIZE

POINT_SIZE

RESOLUTION_X

RESOLUTION_Y

SPACING

AVERAGE_WIDTH

CHARSET_REGISTRY

CHARSET_ENCODING

MIN_SPACE

NORM_SPACE

MAX_SPACE

END_SPACE

AVG_CAPITAL_WIDTH

AVG_LOWERCASE_WIDTH

QUAD_WIDTH

FIGURE_WIDTH

SUPERSCRIPT_X

SUPERSCRIPT_Y

SUBSCRIPT_X

SUBSCRIPT_Y

SUPERSCRIPT_SIZE

SUBSCRIPT_SIZE

SMALL_CAP_SIZE

UNDERLINE_POSITION

UNDERLINE_THICKNESS

STRIKEOUT_ASCENT

STRIKEOUT_DESCENT

ITALIC_ANGLE

CAP_HEIGHT

X_HEIGHT

RELATIVE_SETWIDTH

RELATIVE_WEIGHT

WEIGHT

RESOLUTION

FONT

FACE_NAME

FULL_NAME

COPYRIGHT

NOTICE

DESTINATION

FONT_TYPE

FONT_VERSION

RASTERIZER_NAME

RASTERIZER_VERSION

RAW_ASCENT

RAW_DESCENT

RAW_*

AXIS_NAMES

AXIS_LIMITS

AXIS_TYPES

Built-in Font Property Atoms

4. Matrix Transformations

Metrics and Font Properties

5. Scalable Fonts

6. Polymorphic Fonts

7. Affected Elements of Xlib and the X Protocol

8. BDF Conformance

XLFD Conformance Requirements

FONT_ASCENT, FONT_DESCENT, and DEFAULT_CHAR

FONT_ASCENT

FONT_DESCENT

DEFAULT_CHAR

Chapter 1. Introduction

It is a requirement that X client applications must be portable across server

implementations, with very different file systems, naming conventions, and font

libraries. However, font access requests, as defined by the X Window System

Protocol, neither specify server-independent conventions 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 Helvetica 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

family.

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 consistent 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 handling

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.

Chapter 2. Requirements and Goals

Table of Contents

Provide Unique and Descriptive Font Names

Support Multiple Font Vendors and Character Sets

Support Scalable and Polymorphic Fonts

Support Transformations and Subsetting of Fonts

Be Independent of X Server and Operating or File System Implementations

Support Arbitrarily Complex Font Matching and Substitution

Be Extensible

The XLFD meets the short-term and long-term goals to have a standard logical

font description that:

● Provides unique, descriptive font names that support simple pattern

matching

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

● Supports naming and instancing of scalable and polymorphic fonts

● Supports transformations and subsetting of fonts

● Is independent of X server and operating or file system implementations

● Supports arbitrarily complex font matching or substitution

● Is extensible

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.

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 standard 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 supported.

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.

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.

Be Independent of X Server and Operating or File System Implementations

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 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).

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.

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.

Chapter 3. X Logical Font Description

Table of Contents

FontName

FontName Syntax

FontName Field Definitions

Examples

Font Properties

FOUNDRY

FAMILY_NAME

WEIGHT_NAME

SLANT

SETWIDTH_NAME

ADD_STYLE_NAME

PIXEL_SIZE

POINT_SIZE

RESOLUTION_X

RESOLUTION_Y

SPACING

AVERAGE_WIDTH

CHARSET_REGISTRY

CHARSET_ENCODING

MIN_SPACE

NORM_SPACE

MAX_SPACE

END_SPACE

AVG_CAPITAL_WIDTH

AVG_LOWERCASE_WIDTH

QUAD_WIDTH

FIGURE_WIDTH

SUPERSCRIPT_X

SUPERSCRIPT_Y

SUBSCRIPT_X

SUBSCRIPT_Y

SUPERSCRIPT_SIZE

SUBSCRIPT_SIZE

SMALL_CAP_SIZE

UNDERLINE_POSITION

UNDERLINE_THICKNESS

STRIKEOUT_ASCENT

STRIKEOUT_DESCENT

ITALIC_ANGLE

CAP_HEIGHT

X_HEIGHT

RELATIVE_SETWIDTH

RELATIVE_WEIGHT

WEIGHT

RESOLUTION

FONT

FACE_NAME

FULL_NAME

COPYRIGHT

NOTICE

DESTINATION

FONT_TYPE

FONT_VERSION

RASTERIZER_NAME

RASTERIZER_VERSION

RAW_ASCENT

RAW_DESCENT

RAW_*

AXIS_NAMES

AXIS_LIMITS

AXIS_TYPES

Built-in Font Property Atoms

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 Standard (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 FontProperties may also

appear as items of the STARTPROPERTIES...ENDPROPERTIESlist in the BDF V2.1

specification.

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 registration authority

that owns the specified FontNameSuffix syntax and semantics.

All font names that conform to this specification are to use a FontNameRegistry

prefix, which is defined to be the string "-" (HYPHEN). All FontNameRegistry

prefixes of the form: +version-, where the specified 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 appending new fields to the current structure,

each delimited by the existing field delimiter. The availability of other

FontNameRegistry prefixes or 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 FontProperties; numeric property

values are represented as signed or unsigned integers, as appropriate.

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

PrivFontNameSuffix

XFontNameRegistry :: XFNDelim | XFNExtPrefix Version XFNDelim

=

FOUNDRY XFNDelim FAMILY_NAME XFNDelim WEIGHT_NAME XFNDelim

SLANT XFNDelim SETWIDTH_NAME XFNDelim ADD_STYLE_NAME

XFontNameSuffix ::= XFNDelim PIXEL_SIZE XFNDelim POINT_SIZE XFNDelim

RESOLUTION_X XFNDelim RESOLUTION_Y XFNDelim SPACING

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 characters,

excluding the following:

● '-' (HYPHEN), the XLFD font name delimiter character

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

characters

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

● '"' (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 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.

FontName Field Definitions

This section discusses the FontName:

● FOUNDRY field

● FAMILY_NAME field

● WEIGHT_NAME field

● SLANT field

● SETWIDTH_NAME field

● ADD_STYLE_NAME field

● PIXEL_SIZE field

● POINT_SIZE field

● RESOLUTION_X and RESOLUTION_Y fields

● SPACING field

● AVERAGE_WIDTH field

● CHARSET_REGISTRY and CHARSET_ENCODING fields

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 tweaking 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 suitable name

for this FontName field according to the registration procedures defined by the

Consortium.

The X Consortium shall define procedures for registering foundry and other

names and shall maintain and publish, as part of its public distribution, a

registry of such registered names for use in XLFD font names and properties.

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 presentation 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. FAMILY_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:

● Helvetica

● ITC Avant Garde Gothic

● Times

● Times Roman

● Bitstream Amerigo

● Stone

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 presentation to a font user.

The value "0" is used to indicate a polymorphic font (see Polymorphic Fonts).

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 typographic feel to a Bold

font from another family.

WEIGHT_NAME is captured as an arbitrary string because it is an important 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 calculated weight, respectively.

SLANT Field

SLANT is a code-string that indicates the overall posture of the typeface

design used in the font. The encoding is as follows:

┌───────┬───────────────┬─────────────────────────────────────────────────────┐

│Code │English │Description │

│ │Translation │ │

├───────┼───────────────┼─────────────────────────────────────────────────────┤

│"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 counterclockwise │

│ │ │from the vertical │

├───────┼───────────────┼─────────────────────────────────────────────────────┤

│"OT" │Other │Other │

├───────┼───────────────┼─────────────────────────────────────────────────────┤

│numeric│Polymorphic │See Polymorphic Fonts. │

└───────┴───────────────┴─────────────────────────────────────────────────────┘

The SLANT codes are for programming convenience only and usually are converted

into their equivalent human-understandable form before being presented to a

user.

SETWIDTH_NAME Field

SETWIDTH_NAME is a string that gives the font's typographic proportionate

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 Polymorphic Fonts).

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 proportionate width.

The following are examples of SETWIDTH_NAME:

● Normal

● Condensed

● Narrow

● Double Wide

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 identify the

particular font. The character "[" anywhere in the field is used to indicate a

polymorphic font (see Polymorphic Fonts).

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:

● Serif

● Sans Serif

● Informal

● Decorated

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 Matrix

Transformations). 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 Scalable Fonts).

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.

SN 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 Matrix Transformations). This field usually

incorporates additional vertical spacing that is considered 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 Scalable Fonts).

POINT_SIZE and RESOLUTION_Y are used by X clients to query fonts according to

device-independent size to maintain constant text size on the display

regardless of the PIXEL_SIZE used for the font.

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

Scalable Fonts). 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.

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 │Description │

│ │Translation │ │

├────┼────────────┼───────────────────────────────────────────────────────────┤

│ │ │A font whose logical character widths vary for each glyph. │

│"P" │Proportional│Note that no other restrictions are placed on the metrics │

│ │ │of a proportional font. │

├────┼────────────┼───────────────────────────────────────────────────────────┤

│ │ │A font whose logical character widths are constant (that │

│"M" │Monospaced │is, every glyph in the font has the same logical width). No│

│ │ │other restrictions are placed on the metrics of a │

│ │ │monospaced font. │

├────┼────────────┼───────────────────────────────────────────────────────────┤

│ │ │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-bottom to form text lines). By definition, all │

│ │ │glyphs have the same logical character width, and no glyphs│

│ │ │have "ink" outside of the character cell. There is no │

│"C" │CharCell │kerning (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 vertical 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. │

└────┴────────────┴───────────────────────────────────────────────────────────┘

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 Scalable Fonts).

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 character set

registry. CHARSET_REGISTRY is an x-registered-name that identifies the

registration authority that owns the specified encoding. CHARSET_ENCODING is a

registered name that identifies the coded character 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 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 dependent.

To prevent collisions when defining character set names, it is recommended that

CHARSET_REGISTRY and CHARSET_ENCODING name pairs be constructed according to

the following conventions:

CharsetRegistry ::= StdCharsetRegistryName | PrivCharsetRegistryName

CharsetEncoding ::= StdCharsetEncodingName | PrivCharsetEncodingName

StdCharsetRegistryName StdOrganizationId StdNumber | StdOrganizationId

::= StdNumber Dot Year

PrivCharsetRegistryName OrganizationId STRING8

::=

StdCharsetEncodingName STRING8-numeric part number of referenced 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

calculated 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

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 ::= "\0" (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 number. 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.

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│-Bitstream-Charter-Medium-R-Normal--12-120-75-75-P-68-ISO8859-1 │

│12 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Charter│ │

│Bold 12│-Bitstream-Charter-Bold-R-Normal--12-120-75-75-P-76-ISO8859-1 │

│pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Charter│ │

│Bold │-Bitstream-Charter-Bold-I-Normal--12-120-75-75-P-75-ISO8859-1 │

│Italic │ │

│12 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Charter│ │

│Italic │-Bitstream-Charter-Medium-I-Normal--12-120-75-75-P-66-ISO8859-1 │

│12 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Courier│-Adobe-Courier-Medium-R-Normal--8-80-75-75-M-50-ISO8859-1 │

│8 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Courier│-Adobe-Courier-Medium-R-Normal--10-100-75-75-M-60-ISO8859-1 │

│10 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Courier│-Adobe-Courier-Medium-R-Normal--12-120-75-75-M-70-ISO8859-1 │

│12 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Courier│-Adobe-Courier-Medium-R-Normal--24-240-75-75-M-150-ISO8859-1 │

│24 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Courier│ │

│Bold 10│-Adobe-Courier-Bold-R-Normal--10-100-75-75-M-60-ISO8859-1 │

│pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Courier│ │

│Bold │-Adobe-Courier-Bold-O-Normal--10-100-75-75-M-60-ISO8859-1 │

│Oblique│ │

│10 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Courier│ │

│Oblique│-Adobe-Courier-Medium-O-Normal--10-100-75-75-M-60-ISO8859-1 │

│10 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│100-dpi│  │

│Fonts │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Symbol │-Adobe-Symbol-Medium-R-Normal--14-100-100-100-P-85-Adobe-FONTSPECIFIC │

│10 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Symbol │-Adobe-Symbol-Medium-R-Normal--20-140-100-100-P-107-Adobe-FONTSPECIFIC│

│14 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Symbol │-Adobe-Symbol-Medium-R-Normal--25-180-100-100-P-142-Adobe-FONTSPECIFIC│

│18 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│Symbol │-Adobe-Symbol-Medium-R-Normal--34-240-100-100-P-191-Adobe-FONTSPECIFIC│

│24 pt │ │

├───────┼──────────────────────────────────────────────────────────────────────┤

│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 │-Adobe-Times-Medium-R-Normal--14-100-100-100-P-74-ISO8859-1 │

│10 pt │ │

└───────┴──────────────────────────────────────────────────────────────────────┘

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 descriptive and use

information that may be required to use the font intelligently. The XLFD

specifies an extensive set of standard X font properties, 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 follows:

Properties ::= OptFontPropList

OptFontPropList NULL | OptFontProp OptFontPropList

::=

OptFontProp ::= PrivateFontProp | XFontProp

PrivateFontProp STRING8 | Underscore OrganizationId Underscore STRING8

::=

FOUNDRY | FAMILY_NAME | WEIGHT_NAME | SLANT | SETWIDTH_NAME |

ADD_STYLE_NAME | PIXEL_SIZE | POINT_SIZE | RESOLUTION_X |

RESOLUTION_Y | SPACING | AVERAGE_WIDTH | CHARSET_REGISTRY |

CHARSET_ENCODING | QUAD_WIDTH | RESOLUTION | MIN_SPACE |

NORM_SPACE | MAX_SPACE | END_SPACE | SUPERSCRIPT_X |

SUPERSCRIPT_Y | SUBSCRIPT_X | SUBSCRIPT_Y | UNDERLINE_POSITION

XFontProp ::= | UNDERLINE_THICKNESS | STRIKEOUT_ASCENT | STRIKEOUT_DESCENT |

ITALIC_ANGLE | X_HEIGHT | WEIGHT | FACE_NAME | FULL_NAME | FONT

| COPYRIGHT | AVG_CAPITAL_WIDTH | AVG_LOWERCASE_WIDTH |

RELATIVE_SETWIDTH | RELATIVE_WEIGHT | CAP_HEIGHT | SUPERSCRIPT_

SIZE | FIGURE_WIDTH | SUBSCRIPT_SIZE | SMALL_CAP_SIZE | NOTICE

| DESTINATION | FONT_TYPE | FONT_VERSION | RASTERIZER_NAME |

RASTERIZER_VERSION | RAW_ASCENT | RAW_DESCENT | RAW_* |

AXIS_NAMES | AXIS_LIMITS | AXIS_TYPES

Underscore ::= OCTET-"_" (LOW LINE)

OrganizationId STRING8-the registered name of the organization

::=

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.

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.

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 follows:

if (WEIGHT_NAME undefined) then

WEIGHT_NAME = ATOM("Medium")

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")

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")

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("")

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 spaces (em

space, en space, and thin space) can use the following algorithm for computing

these values from other properties specified for a font:

DeciPointsPerInch = 722.7

EMspace = ROUND ((RESOLUTION_X * POINT_SIZE) / DeciPointsPerInch)

ENspace = ROUND (EMspace / 2)

THINspace = ROUND (EMspace / 3)\fP

where a slash (/) denotes real division, an asterisk (*) denotes real

multiplication, and ROUND denotes a function that rounds its real argument 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)

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.

RESOLUTION_X

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

CARD32.

RESOLUTION_X cannot be calculated or approximated.

RESOLUTION_Y

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

CARD32.

RESOLUTION_X cannot be calculated or approximated.

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.

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 arguments.

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

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.

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.

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.

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)

NORM_SPACE

NORM_SPACE is an integer value (of type INT32) that gives the recommended

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)

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)

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

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 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

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 provided 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

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 character width font properties (AVERAGE_WIDTH,

AVG_CAPITAL_WIDTH or AVG_LOWERCASE_WIDTH).

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 figures 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

SUPERSCRIPT_X

SUPERSCRIPT_X is an integer value (of type INT32) that gives the recommended

horizontal offset in pixels from the position point to the X origin of

synthetic superscript text. If the current position point is at [X,Y], then

superscripts should begin at [X + SUPERSCRIPT_X, Y - SUPERSCRIPT_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.

SUPERSCRIPT_Y

SUPERSCRIPT_Y is an integer value (of type INT32) that gives the recommended

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 - SUPERSCRIPT_Y].

SUPERSCRIPT_Y can be approximated if not provided as a font property, according

to the following algorithm:

if (SUPERSCRIPT_Y undefined) then

SUPERSCRIPT_Y = ROUND(0.40 * CAP_HEIGHT)

SUBSCRIPT_X

SUBSCRIPT_X is an integer value (of type INT32) that gives the recommended

horizontal offset in pixels from the position point to the X 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_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)

SUBSCRIPT_Y

SUBSCRIPT_Y is an integer value (of type INT32) that gives the recommended

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)

SUPERSCRIPT_SIZE

SUPERSCRIPT_SIZE is an integer value (of type INT32) that gives the recommended

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)

SUBSCRIPT_SIZE

SUBSCRIPT_SIZE is an integer value (of type INT32) that gives the recommended

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)

SMALL_CAP_SIZE

SMALL_CAP_SIZE is an integer value (of type INT32) that gives the recommended

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))

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 property,

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.

UNDERLINE_THICKNESS

UNDERLINE_THICKNESS is an integer value (of type INT32) that gives the

recommended underline thickness, in pixels.

UNDERLINE_THICKNESS can be approximated if not provided as a font property,

according to the following algorithm:

CapStemWidth = average width of the stems of capitals

if (UNDERLINE_THICKNESS undefined) then

UNDERLINE_THICKNESS = CapStemWidth

STRIKEOUT_ASCENT

STRIKEOUT_ASCENT is an integer value (of type INT32) that gives the vertical

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 pixels of

any glyph in the font.

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 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_DESCENT can be approximated if not provided as a font property,

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.

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:

if (ITALIC_ANGLE undefined) then

ITALIC_ANGLE = (90 * 64)

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 positioning

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

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, according 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

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 algorithm:

SETWIDTH = AVG_CAPITAL_WIDTH / (CAP_HEIGHT * 10)

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

setwidth.

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.

RELATIVE_WEIGHT ranges from 10 to 90 or is 0 if undefined or unknown. The

following reference values are defined:

┌────┬────────────────┬───────────────────────────────────────────────────────┐

│Code│English │Description │

│ │Translation │ │

├────┼────────────────┼───────────────────────────────────────────────────────┤

│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 function of

the font's weight axis.

WEIGHT

Calculated WEIGHT is an unsigned integer value (of type CARD32) that gives the

calculated weight of the font, computed as the ratio of capital 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 different

families because both the RELATIVE_WEIGHT and the WEIGHT_NAME are assigned by

the typeface supplier, according to its tradition and practice, and therefore,

are somewhat subjective. Calculated WEIGHT provides a font-independent way of

identifying the weight across all fonts and all font vendors.

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 components are

required to accommodate displays with nonsquare aspect ratios, the use of this

font property has been deprecated, 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.

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.

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.

FULL_NAME

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

some old fonts.

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 captured as a

comment that could later be thrown away for efficiency reasons).

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

property.

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 country, the

USA having no design copyright protection currently while various 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.

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 optimal 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 display

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 │Description │

│ │Translation │ │

├────┼────────────┼───────────────────────────────────────────────────────────┤

│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 legibility and │

│ │ │readability. │

└────┴────────────┴───────────────────────────────────────────────────────────┘

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.

Predefined values are as follows:

┌──────────┬──────────────────────────────────────────────────────────────────┐

│Value │When applicable │

├──────────┼──────────────────────────────────────────────────────────────────┤

│ │Hand-tuned bitmap fonts. Some attempt has been made to optimize │

│"Bitmap" │the visual appearance of the font for the requested size and │

│ │resolution. │

├──────────┼──────────────────────────────────────────────────────────────────┤

│ │All bitmap format fonts that cannot be described as "Bitmap", that│

│"Prebuilt"│is, handtuned. For example, a bitmap format font that was │

│ │generated mechanically using a scalable font rasterizer would be │

│ │considered "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.

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.

RASTERIZER_NAME

RASTERIZER_NAME is a human-understandable string (of type ATOM) that is the

specific name of the rasterizer that has performed some rasterization 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.

the case-sensitive, human-understandable product name of the

Rasterizer ::= rasterizer. Words within this name should be separated 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

If RASTERIZER_NAME is not defined, or is None, no rasterization operation has

been applied to the FONT_TYPE.

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.

RAW_ASCENT

For a font with a transformation matrix, RAW_ASCENT is the font ascent in 1000

pixel metrics (see Metrics and Font Properties).

RAW_DESCENT

For a font with a transformation matrix, RAW_DESCENT is the font descent in

1000 pixel metrics (see Metrics and Font Properties).

RAW_*

For a font with a transformation matrix, all font properties that represent

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 Metrics and Font Properties.

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 presentation in a

user interface (see section 6).

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 Polymorphic

Fonts).

AXIS_TYPES

AXIS_TYPES is like AXIS_NAMES, but can be registered as having specific

semantics (see section 6).

Built-in Font Property Atoms

The following font property atom definitions were predefined in the initial

version of the core protocol:

┌───────────────────────┬───────────────────┐

│Font Property/Atom Name│Property Type │

├───────────────────────┼───────────────────┤

│MIN_SPACE │INT32 │

├───────────────────────┼───────────────────┤

│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 │

└───────────────────────┴───────────────────┘

Chapter 4. Matrix Transformations

Table of Contents

Metrics and Font Properties

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 representations 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

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 relationship

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 implementation-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.

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 rasterizer 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) represent

the ink extent of the transformed glyph around its origin.

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

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 displacement. All font

properties that represent vertical heights or displacements have as their value

the y component of the transformed height or displacement. Each such property

will be accompanied by a new property, named as the original except prefixed

with "RAW_", that gives the value of the width, height, or displacement in 1000

pixel metrics.

Chapter 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

● 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.

● 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 anamorphic scaling.

● Global list

The list of names that would be returned by an X server for a ListFonts

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 nonscalable 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 compatibility, they

should be reasonable nonzero values, for example, a resolution 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 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 permitted, but not

required, to use a more sophisticated matching algorithm.

Chapter 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\00]". The polymorphic values may coexist

with other data in the field. It is recommended 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.

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 values.

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

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 unresolved, 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.

Chapter 7. Affected Elements of Xlib and the X Protocol

The following X protocol requests must support the XLFD conventions:

● OpenFont - for the name argument

● ListFonts - for the pattern argument

● ListFontsWithInfo - for the pattern argument

In addition, the following Xlib functions must support the XLFD conventions:

● XLoadFont - for the name argument

● XListFontsWithInfo - for the pattern argument

● XLoadQueryFont - for the name argument

● XListFonts - for the pattern argument

Chapter 8. BDF Conformance

Table of Contents

XLFD Conformance Requirements

FONT_ASCENT, FONT_DESCENT, and DEFAULT_CHAR

FONT_ASCENT

FONT_DESCENT

DEFAULT_CHAR

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 semantics of the font properties that

might be provided in a BDF font. This section identifies the requirements for

BDF fonts that conform to XLFD.

XLFD Conformance Requirements

A BDF font conforms to the XLFD specification if and only if the following

conditions are satisfied:

● The value for the BDF item FONT conforms to the syntax and semantic

definition of a XLFD FontName string.

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

● All XLFD FontName fields are defined.

● 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 follows the definition of

a private property.

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.

FONT_ASCENT

FONT_ASCENT is an integer value (of type INT32) that gives the recommended

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].

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 pixels of

any glyph in the font.

FONT_DESCENT

FONT_DESCENT is an integer value (of type INT32) that gives the recommended

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.

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.