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</style></head><body><div class="book"><div class="titlepage"><div><div><h1 class="title"><a id="xlfd"></a>X Logical Font Description Conventions</h1></div><div><h2 class="subtitle">X Consortium Standard</h2></div><div><div class="authorgroup"><div class="author"><h3 class="author"><span class="firstname">Jim</span> <span class="surname">Flowers</span></h3><div class="affiliation"><span class="orgname">Digital Equipment Corporation<br /></span></div></div><div class="editor"><h4 class="editedby">Edited by</h4><h3 class="editor"><span class="firstname">Stephen </span> <span class="surname">Gildea</span></h3><div class="affiliation"><span class="orgname">X Consortium<br /></span></div></div></div></div><div><p class="releaseinfo">X Version 11, Release 7.7</p></div><div><p class="releaseinfo">Version 1.5</p></div><div><p class="copyright">Copyright © 1988, 1994 X Consortium</p></div><div><div class="legalnotice"><a id="id2525478"></a><p>
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
</p><p>
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
</p><p>
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, 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.
</p><p>
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.
</p><p>X Window System is a trademark of The Open Group.</p></div></div><div><div class="legalnotice"><a id="id2526154"></a><p class="multiLicensing">
Copyright © 1988, 1989
Digital Equipment Corporation, Maynard MA. All rights reserved.
</p><p>
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.
</p></div></div><div><div class="legalnotice"><a id="id2524904"></a><p>
Helvetica and Times are registered trademarks of Linotype Company.
</p><p>
ITC Avant Garde Gothic is a registered trademark of International
Typeface Corporation.
</p><p>
Times Roman is a registered trademark of Monotype Corporation.
</p><p>
Bitstream Amerigo is a registered trademark of Bitstream Inc.
</p><p>
Stone is a registered trademark of Adobe Systems Inc.
</p></div></div></div><hr /></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="chapter"><a href="#Introduction">1. Introduction</a></span></dt><dt><span class="chapter"><a href="#Requirements_and_Goals">2. Requirements and Goals</a></span></dt><dd><dl><dt><span class="sect1"><a href="#Provide_Unique_and_Descriptive_Font_Names">Provide Unique and Descriptive Font Names</a></span></dt><dt><span class="sect1"><a href="#Support_Multiple_Font_Vendors_and_Character_Sets">Support Multiple Font Vendors and Character Sets</a></span></dt><dt><span class="sect1"><a href="#Support_Scalable_and_Polymorphic_Fonts">Support Scalable and Polymorphic Fonts</a></span></dt><dt><span class="sect1"><a href="#Support_Transformations_and_Subsetting_of_Fonts">Support Transformations and Subsetting of Fonts</a></span></dt><dt><span class="sect1"><a href="#Be_Independent_of_X_Server_and_Operating_or_File_System_Implementations">Be Independent of X Server and Operating or File System Implementations</a></span></dt><dt><span class="sect1"><a href="#Support_Arbitrarily_Complex_Font_Matching_and_Substitution">Support Arbitrarily Complex Font Matching and Substitution</a></span></dt><dt><span class="sect1"><a href="#Be_Extensible">Be Extensible</a></span></dt></dl></dd><dt><span class="chapter"><a href="#X_Logical_Font_Description">3. X Logical Font Description</a></span></dt><dd><dl><dt><span class="sect1"><a href="#FontName">FontName</a></span></dt><dd><dl><dt><span class="sect2"><a href="#FontName_Syntax">FontName Syntax</a></span></dt><dt><span class="sect2"><a href="#FontName_Field_Definitions">FontName Field Definitions</a></span></dt><dt><span class="sect2"><a href="#Examples">Examples</a></span></dt></dl></dd><dt><span class="sect1"><a href="#Font_Properties">Font Properties</a></span></dt><dd><dl><dt><span class="sect2"><a href="#FOUNDRY">FOUNDRY</a></span></dt><dt><span class="sect2"><a href="#FAMILY_NAME">FAMILY_NAME</a></span></dt><dt><span class="sect2"><a href="#WEIGHT_NAME">WEIGHT_NAME</a></span></dt><dt><span class="sect2"><a href="#SLANT">SLANT</a></span></dt><dt><span class="sect2"><a href="#SETWIDTH_NAME">SETWIDTH_NAME</a></span></dt><dt><span class="sect2"><a href="#ADD_STYLE_NAME">ADD_STYLE_NAME</a></span></dt><dt><span class="sect2"><a href="#PIXEL_SIZE">PIXEL_SIZE</a></span></dt><dt><span class="sect2"><a href="#POINT_SIZE">POINT_SIZE</a></span></dt><dt><span class="sect2"><a href="#RESOLUTION_X_x">RESOLUTION_X</a></span></dt><dt><span class="sect2"><a href="#RESOLUTION_Y_y">RESOLUTION_Y</a></span></dt><dt><span class="sect2"><a href="#SPACING">SPACING</a></span></dt><dt><span class="sect2"><a href="#AVERAGE_WIDTH">AVERAGE_WIDTH</a></span></dt><dt><span class="sect2"><a href="#CHARSET_REGISTRY">CHARSET_REGISTRY</a></span></dt><dt><span class="sect2"><a href="#CHARSET_ENCODING">CHARSET_ENCODING</a></span></dt><dt><span class="sect2"><a href="#MIN_SPACE">MIN_SPACE</a></span></dt><dt><span class="sect2"><a href="#NORM_SPACE">NORM_SPACE</a></span></dt><dt><span class="sect2"><a href="#MAX_SPACE">MAX_SPACE</a></span></dt><dt><span class="sect2"><a href="#END_SPACE">END_SPACE</a></span></dt><dt><span class="sect2"><a href="#AVG_CAPITAL_WIDTH">AVG_CAPITAL_WIDTH</a></span></dt><dt><span class="sect2"><a href="#AVG_LOWERCASE_WIDTH">AVG_LOWERCASE_WIDTH</a></span></dt><dt><span class="sect2"><a href="#QUAD_WIDTH">QUAD_WIDTH</a></span></dt><dt><span class="sect2"><a href="#FIGURE_WIDTH">FIGURE_WIDTH</a></span></dt><dt><span class="sect2"><a href="#SUPERSCRIPT_X_x">SUPERSCRIPT_X</a></span></dt><dt><span class="sect2"><a href="#SUPERSCRIPT_Y_y">SUPERSCRIPT_Y</a></span></dt><dt><span class="sect2"><a href="#SUBSCRIPT_X_x">SUBSCRIPT_X</a></span></dt><dt><span class="sect2"><a href="#SUBSCRIPT_Y_y">SUBSCRIPT_Y</a></span></dt><dt><span class="sect2"><a href="#SUPERSCRIPT_SIZE">SUPERSCRIPT_SIZE</a></span></dt><dt><span class="sect2"><a href="#SUBSCRIPT_SIZE">SUBSCRIPT_SIZE</a></span></dt><dt><span class="sect2"><a href="#SMALL_CAP_SIZE">SMALL_CAP_SIZE</a></span></dt><dt><span class="sect2"><a href="#UNDERLINE_POSITION">UNDERLINE_POSITION</a></span></dt><dt><span class="sect2"><a href="#UNDERLINE_THICKNESS">UNDERLINE_THICKNESS</a></span></dt><dt><span class="sect2"><a href="#STRIKEOUT_ASCENT">STRIKEOUT_ASCENT</a></span></dt><dt><span class="sect2"><a href="#STRIKEOUT_DESCENT">STRIKEOUT_DESCENT</a></span></dt><dt><span class="sect2"><a href="#ITALIC_ANGLE">ITALIC_ANGLE</a></span></dt><dt><span class="sect2"><a href="#CAP_HEIGHT">CAP_HEIGHT</a></span></dt><dt><span class="sect2"><a href="#X_HEIGHT">X_HEIGHT</a></span></dt><dt><span class="sect2"><a href="#RELATIVE_SETWIDTH">RELATIVE_SETWIDTH</a></span></dt><dt><span class="sect2"><a href="#RELATIVE_WEIGHT">RELATIVE_WEIGHT</a></span></dt><dt><span class="sect2"><a href="#WEIGHT">WEIGHT</a></span></dt><dt><span class="sect2"><a href="#RESOLUTION">RESOLUTION</a></span></dt><dt><span class="sect2"><a href="#Font_support">FONT</a></span></dt><dt><span class="sect2"><a href="#FACE_NAME">FACE_NAME</a></span></dt><dt><span class="sect2"><a href="#FULL_NAME">FULL_NAME</a></span></dt><dt><span class="sect2"><a href="#COPYRIGHT">COPYRIGHT</a></span></dt><dt><span class="sect2"><a href="#NOTICE">NOTICE</a></span></dt><dt><span class="sect2"><a href="#DESTINATION">DESTINATION</a></span></dt><dt><span class="sect2"><a href="#FONT_TYPE">FONT_TYPE</a></span></dt><dt><span class="sect2"><a href="#FONT_VERSION">FONT_VERSION</a></span></dt><dt><span class="sect2"><a href="#RASTERIZER_NAME">RASTERIZER_NAME</a></span></dt><dt><span class="sect2"><a href="#RASTERIZER_VERSION">RASTERIZER_VERSION</a></span></dt><dt><span class="sect2"><a href="#RAW_ASCENT">RAW_ASCENT</a></span></dt><dt><span class="sect2"><a href="#RAW_DESCENT">RAW_DESCENT</a></span></dt><dt><span class="sect2"><a href="#RAW_">RAW_*</a></span></dt><dt><span class="sect2"><a href="#AXIS_NAMES">AXIS_NAMES</a></span></dt><dt><span class="sect2"><a href="#AXIS_LIMITS">AXIS_LIMITS</a></span></dt><dt><span class="sect2"><a href="#AXIS_TYPES">AXIS_TYPES</a></span></dt></dl></dd><dt><span class="sect1"><a href="#Built_in_Font_Property_Atoms">Built-in Font Property Atoms</a></span></dt></dl></dd><dt><span class="chapter"><a href="#Matrix_Transformations">4. Matrix Transformations</a></span></dt><dd><dl><dt><span class="sect1"><a href="#Metrics_and_Font_Properties">Metrics and Font Properties</a></span></dt></dl></dd><dt><span class="chapter"><a href="#Scalable_Fonts">5. Scalable Fonts</a></span></dt><dt><span class="chapter"><a href="#Polymorphic_Fonts">6. Polymorphic Fonts</a></span></dt><dt><span class="chapter"><a href="#Affected_Elements_of_Xlib_and_the_X_Protocol">7. Affected Elements of Xlib and the X Protocol</a></span></dt><dt><span class="chapter"><a href="#BDF_Conformance">8. BDF Conformance</a></span></dt><dd><dl><dt><span class="sect1"><a href="#XLFD_Conformance_Requirements">XLFD Conformance Requirements</a></span></dt><dt><span class="sect1"><a href="#FONT_ASCENT_FONT_DESCENT_and_DEFAULT_CHAR">FONT_ASCENT, FONT_DESCENT, and DEFAULT_CHAR</a></span></dt><dd><dl><dt><span class="sect2"><a href="#FONT_ASCENT">FONT_ASCENT</a></span></dt><dt><span class="sect2"><a href="#FONT_DESCENT">FONT_DESCENT</a></span></dt><dt><span class="sect2"><a href="#DEFAULT_CHAR">DEFAULT_CHAR</a></span></dt></dl></dd></dl></dd></dl></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="Introduction"></a>Chapter 1. Introduction</h2></div></div></div><p>
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 <span class="emphasis"><em>X Window System Protocol</em></span>,
neither specify server-independent conventions for font names
nor provide adequate font properties for logically describing typographic fonts.
</p><p>
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
<code class="function">ListFonts</code>
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.
</p><p>
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
<code class="function">FontName</code>,
the XLFD also provides for a standard set of key
<code class="function">FontProperties</code>
that describe the font in more detail.
</p><p>
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.
</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="Requirements_and_Goals"></a>Chapter 2. Requirements and Goals</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="sect1"><a href="#Provide_Unique_and_Descriptive_Font_Names">Provide Unique and Descriptive Font Names</a></span></dt><dt><span class="sect1"><a href="#Support_Multiple_Font_Vendors_and_Character_Sets">Support Multiple Font Vendors and Character Sets</a></span></dt><dt><span class="sect1"><a href="#Support_Scalable_and_Polymorphic_Fonts">Support Scalable and Polymorphic Fonts</a></span></dt><dt><span class="sect1"><a href="#Support_Transformations_and_Subsetting_of_Fonts">Support Transformations and Subsetting of Fonts</a></span></dt><dt><span class="sect1"><a href="#Be_Independent_of_X_Server_and_Operating_or_File_System_Implementations">Be Independent of X Server and Operating or File System Implementations</a></span></dt><dt><span class="sect1"><a href="#Support_Arbitrarily_Complex_Font_Matching_and_Substitution">Support Arbitrarily Complex Font Matching and Substitution</a></span></dt><dt><span class="sect1"><a href="#Be_Extensible">Be Extensible</a></span></dt></dl></div><p>
The XLFD meets the short-term and long-term goals to have a
standard logical font description that:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
Provides unique, descriptive font names that support simple pattern
matching
</p></li><li class="listitem"><p>
Supports multiple font vendors, arbitrary character sets, and encodings
</p></li><li class="listitem"><p>
Supports naming and instancing of scalable and polymorphic fonts
</p></li><li class="listitem"><p>
Supports transformations and subsetting of fonts
</p></li><li class="listitem"><p>
Is independent of X server and operating or file system implementations
</p></li><li class="listitem"><p>
Supports arbitrarily complex font matching or substitution
</p></li><li class="listitem"><p>
Is extensible
</p></li></ul></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Provide_Unique_and_Descriptive_Font_Names"></a>Provide Unique and Descriptive Font Names</h2></div></div></div><p>
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.
</p><p>
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.
</p></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Support_Multiple_Font_Vendors_and_Character_Sets"></a>Support Multiple Font Vendors and Character Sets</h2></div></div></div><p>
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.
</p><p>
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.
</p></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Support_Scalable_and_Polymorphic_Fonts"></a>Support Scalable and Polymorphic Fonts</h2></div></div></div><p>
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.
</p></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Support_Transformations_and_Subsetting_of_Fonts"></a>Support Transformations and Subsetting of Fonts</h2></div></div></div><p>
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.
</p></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Be_Independent_of_X_Server_and_Operating_or_File_System_Implementations"></a>Be Independent of X Server and Operating or File System Implementations</h2></div></div></div><p>
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).
</p></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Support_Arbitrarily_Complex_Font_Matching_and_Substitution"></a>Support Arbitrarily Complex Font Matching and Substitution</h2></div></div></div><p>
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.
</p></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Be_Extensible"></a>Be Extensible</h2></div></div></div><p>
properties can be added to conforming fonts without making existing
X client or server implementations obsolete.
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="X_Logical_Font_Description"></a>Chapter 3. X Logical Font Description</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="sect1"><a href="#FontName">FontName</a></span></dt><dd><dl><dt><span class="sect2"><a href="#FontName_Syntax">FontName Syntax</a></span></dt><dt><span class="sect2"><a href="#FontName_Field_Definitions">FontName Field Definitions</a></span></dt><dt><span class="sect2"><a href="#Examples">Examples</a></span></dt></dl></dd><dt><span class="sect1"><a href="#Font_Properties">Font Properties</a></span></dt><dd><dl><dt><span class="sect2"><a href="#FOUNDRY">FOUNDRY</a></span></dt><dt><span class="sect2"><a href="#FAMILY_NAME">FAMILY_NAME</a></span></dt><dt><span class="sect2"><a href="#WEIGHT_NAME">WEIGHT_NAME</a></span></dt><dt><span class="sect2"><a href="#SLANT">SLANT</a></span></dt><dt><span class="sect2"><a href="#SETWIDTH_NAME">SETWIDTH_NAME</a></span></dt><dt><span class="sect2"><a href="#ADD_STYLE_NAME">ADD_STYLE_NAME</a></span></dt><dt><span class="sect2"><a href="#PIXEL_SIZE">PIXEL_SIZE</a></span></dt><dt><span class="sect2"><a href="#POINT_SIZE">POINT_SIZE</a></span></dt><dt><span class="sect2"><a href="#RESOLUTION_X_x">RESOLUTION_X</a></span></dt><dt><span class="sect2"><a href="#RESOLUTION_Y_y">RESOLUTION_Y</a></span></dt><dt><span class="sect2"><a href="#SPACING">SPACING</a></span></dt><dt><span class="sect2"><a href="#AVERAGE_WIDTH">AVERAGE_WIDTH</a></span></dt><dt><span class="sect2"><a href="#CHARSET_REGISTRY">CHARSET_REGISTRY</a></span></dt><dt><span class="sect2"><a href="#CHARSET_ENCODING">CHARSET_ENCODING</a></span></dt><dt><span class="sect2"><a href="#MIN_SPACE">MIN_SPACE</a></span></dt><dt><span class="sect2"><a href="#NORM_SPACE">NORM_SPACE</a></span></dt><dt><span class="sect2"><a href="#MAX_SPACE">MAX_SPACE</a></span></dt><dt><span class="sect2"><a href="#END_SPACE">END_SPACE</a></span></dt><dt><span class="sect2"><a href="#AVG_CAPITAL_WIDTH">AVG_CAPITAL_WIDTH</a></span></dt><dt><span class="sect2"><a href="#AVG_LOWERCASE_WIDTH">AVG_LOWERCASE_WIDTH</a></span></dt><dt><span class="sect2"><a href="#QUAD_WIDTH">QUAD_WIDTH</a></span></dt><dt><span class="sect2"><a href="#FIGURE_WIDTH">FIGURE_WIDTH</a></span></dt><dt><span class="sect2"><a href="#SUPERSCRIPT_X_x">SUPERSCRIPT_X</a></span></dt><dt><span class="sect2"><a href="#SUPERSCRIPT_Y_y">SUPERSCRIPT_Y</a></span></dt><dt><span class="sect2"><a href="#SUBSCRIPT_X_x">SUBSCRIPT_X</a></span></dt><dt><span class="sect2"><a href="#SUBSCRIPT_Y_y">SUBSCRIPT_Y</a></span></dt><dt><span class="sect2"><a href="#SUPERSCRIPT_SIZE">SUPERSCRIPT_SIZE</a></span></dt><dt><span class="sect2"><a href="#SUBSCRIPT_SIZE">SUBSCRIPT_SIZE</a></span></dt><dt><span class="sect2"><a href="#SMALL_CAP_SIZE">SMALL_CAP_SIZE</a></span></dt><dt><span class="sect2"><a href="#UNDERLINE_POSITION">UNDERLINE_POSITION</a></span></dt><dt><span class="sect2"><a href="#UNDERLINE_THICKNESS">UNDERLINE_THICKNESS</a></span></dt><dt><span class="sect2"><a href="#STRIKEOUT_ASCENT">STRIKEOUT_ASCENT</a></span></dt><dt><span class="sect2"><a href="#STRIKEOUT_DESCENT">STRIKEOUT_DESCENT</a></span></dt><dt><span class="sect2"><a href="#ITALIC_ANGLE">ITALIC_ANGLE</a></span></dt><dt><span class="sect2"><a href="#CAP_HEIGHT">CAP_HEIGHT</a></span></dt><dt><span class="sect2"><a href="#X_HEIGHT">X_HEIGHT</a></span></dt><dt><span class="sect2"><a href="#RELATIVE_SETWIDTH">RELATIVE_SETWIDTH</a></span></dt><dt><span class="sect2"><a href="#RELATIVE_WEIGHT">RELATIVE_WEIGHT</a></span></dt><dt><span class="sect2"><a href="#WEIGHT">WEIGHT</a></span></dt><dt><span class="sect2"><a href="#RESOLUTION">RESOLUTION</a></span></dt><dt><span class="sect2"><a href="#Font_support">FONT</a></span></dt><dt><span class="sect2"><a href="#FACE_NAME">FACE_NAME</a></span></dt><dt><span class="sect2"><a href="#FULL_NAME">FULL_NAME</a></span></dt><dt><span class="sect2"><a href="#COPYRIGHT">COPYRIGHT</a></span></dt><dt><span class="sect2"><a href="#NOTICE">NOTICE</a></span></dt><dt><span class="sect2"><a href="#DESTINATION">DESTINATION</a></span></dt><dt><span class="sect2"><a href="#FONT_TYPE">FONT_TYPE</a></span></dt><dt><span class="sect2"><a href="#FONT_VERSION">FONT_VERSION</a></span></dt><dt><span class="sect2"><a href="#RASTERIZER_NAME">RASTERIZER_NAME</a></span></dt><dt><span class="sect2"><a href="#RASTERIZER_VERSION">RASTERIZER_VERSION</a></span></dt><dt><span class="sect2"><a href="#RAW_ASCENT">RAW_ASCENT</a></span></dt><dt><span class="sect2"><a href="#RAW_DESCENT">RAW_DESCENT</a></span></dt><dt><span class="sect2"><a href="#RAW_">RAW_*</a></span></dt><dt><span class="sect2"><a href="#AXIS_NAMES">AXIS_NAMES</a></span></dt><dt><span class="sect2"><a href="#AXIS_LIMITS">AXIS_LIMITS</a></span></dt><dt><span class="sect2"><a href="#AXIS_TYPES">AXIS_TYPES</a></span></dt></dl></dd><dt><span class="sect1"><a href="#Built_in_Font_Property_Atoms">Built-in Font Property Atoms</a></span></dt></dl></div><p>
XLFD is divided into two basic components:
the
<code class="function">FontName</code>,
which gives all font information needed to uniquely identify a font
in X protocol requests (for example,
<code class="function">OpenFont</code>,
<code class="function">ListFonts</code>,
and so on) and a variable list of optional
<code class="function">FontProperties</code>,
which describe a font in more detail.
</p><p>
The
<code class="function">FontName</code>
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
<code class="function">FONT</code>
item in the X Consortium Character Bitmap Distribution Format Standard
(BDF V2.1).
</p><p>
The
<code class="function">FontProperties</code>
are supplied on a font-by-font basis and are returned
as data in certain X protocol requests as part of the
<code class="function">XFontStruct</code>
data structure.
The names and associated data values for each of the
<code class="function">FontProperties</code>
may also appear as items of the
<code class="function">STARTPROPERTIES</code>...<code class="function">ENDPROPERTIES</code>list
in the BDF V2.1 specification.
</p><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="FontName"></a>FontName</h2></div></div></div><p>
Each
<code class="function">FontName</code>
is logically composed of two strings: a
<code class="function">FontNameRegistry</code>
prefix that is followed by a
<code class="function">FontNameSuffix</code>.
The
<code class="function">FontName</code>
uses the ISO 8859-1 encoding.
The
<code class="function">FontNameRegistry</code>
is an
x-registered-name (a name that has been registered with the X Consortium)
that identifies the registration authority that owns the specified
<code class="function">FontNameSuffix</code>
syntax and semantics.
</p><p>
All font names that conform to this specification are to use a
<code class="function">FontNameRegistry</code>
prefix, which is defined to be the string "-"
(HYPHEN).
All
<code class="function">FontNameRegistry</code>
prefixes of the form: +<span class="emphasis"><em>version</em></span>-,
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
<code class="function">FontNameRegistry</code>
prefixes or fonts that support other registries
is server implementation dependent.
</p><p>
In the X protocol specification,
the
<code class="function">FontName</code>
is required to be a string;
hence, numeric field values are represented in the name as string equivalents.
All
<code class="function">FontNameSuffix</code>
fields are also defined as
<code class="function">FontProperties</code>;
numeric property values are represented as signed or unsigned integers,
as appropriate.
</p><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FontName_Syntax"></a>FontName Syntax</h3></div></div></div><p>
The
<code class="function">FontName</code>
is a structured, parsable string (of type STRING8)
whose Backus-Naur Form syntax description is as follows:
</p><div class="informaltable"><table border="0"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><tbody><tr><td align="left">FontName ::=</td><td align="left">
XFontNameRegistry XFontNameSuffix |
PrivFontNameRegistry PrivFontNameSuffix
</td></tr><tr><td align="left">XFontNameRegistry ::=</td><td align="left">XFNDelim | XFNExtPrefix Version XFNDelim</td></tr><tr><td align="left">XFontNameSuffix ::=</td><td align="left">
FOUNDRY XFNDelim FAMILY_NAME XFNDelim WEIGHT_NAME
XFNDelim SLANT XFNDelim SETWIDTH_NAME XFNDelim ADD_STYLE_NAME
XFNDelim PIXEL_SIZE XFNDelim POINT_SIZE
XFNDelim RESOLUTION_X XFNDelim RESOLUTION_Y XFNDelim
SPACING XFNDelim AVERAGE_WIDTH XFNDelim CHARSET_REGISTRY
XFNDelim CHARSET_ENCODING
</td></tr><tr><td align="left">Version ::=</td><td align="left">
STRING8 - the XLFD version that defines an extension
to the font name syntax (for example, "1.4")
</td></tr><tr><td align="left">XFNExtPrefix ::=</td><td align="left">OCTET - "+" (PLUS)</td></tr><tr><td align="left">XFNDelim ::=</td><td align="left">OCTET - "-" (HYPHEN)</td></tr><tr><td align="left">PrivFontNameRegistry ::=</td><td align="left">STRING8 - other than those strings reserved by XLFD</td></tr><tr><td align="left">PrivFontNameSuffix ::=</td><td align="left">STRING8</td></tr></tbody></table></div><p>
Field values are constructed as strings of ISO 8859-1 graphic characters,
excluding the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
'-' (HYPHEN), the XLFD font name delimiter character
</p></li><li class="listitem"><p>
'?' (QUESTION MARK) and "*" (ASTERISK), the X protocol
font name wildcard characters
</p></li><li class="listitem"><p>
',' (COMMA), used by Xlib to separate XLFD font names in a font set.
</p></li><li class="listitem"><p>
'"' (QUOTATION MARK), used by some commercial products to quote a
font name.
</p></li></ul></div><p>
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
<code class="function">FontName</code>
field; for example, the string "ITC Avant Garde Gothic" might be a
FAMILY_NAME.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FontName_Field_Definitions"></a>FontName Field Definitions</h3></div></div></div><p>
This section discusses the
<code class="function">FontName</code>:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
FOUNDRY field
</p></li><li class="listitem"><p>
FAMILY_NAME field
</p></li><li class="listitem"><p>
WEIGHT_NAME field
</p></li><li class="listitem"><p>
SLANT field
</p></li><li class="listitem"><p>
SETWIDTH_NAME field
</p></li><li class="listitem"><p>
ADD_STYLE_NAME field
</p></li><li class="listitem"><p>
PIXEL_SIZE field
</p></li><li class="listitem"><p>
POINT_SIZE field
</p></li><li class="listitem"><p>
RESOLUTION_X and RESOLUTION_Y fields
</p></li><li class="listitem"><p>
SPACING field
</p></li><li class="listitem"><p>
AVERAGE_WIDTH field
</p></li><li class="listitem"><p>
CHARSET_REGISTRY and CHARSET_ENCODING fields
</p></li></ul></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="FOUNDRY_Field"></a>FOUNDRY Field</h4></div></div></div><p>
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.
</p><p>
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.
</p><p>
It is up to the type supplier to register with the X Consortium a
suitable name for this
<code class="function">FontName</code>
field according to the registration procedures defined by the Consortium.
</p><p>
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.
</p><p>
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="FAMILY_NAME_Field"></a>FAMILY_NAME Field</h4></div></div></div><p>
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.
</p><p>
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.
</p><p>
The following are examples of FAMILY_NAME:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
Helvetica
</p></li><li class="listitem"><p>
ITC Avant Garde Gothic
</p></li><li class="listitem"><p>
Times
</p></li><li class="listitem"><p>
Times Roman
</p></li><li class="listitem"><p>
Bitstream Amerigo
</p></li><li class="listitem"><p>
Stone
</p></li></ul></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="WEIGHT_NAME_Field"></a>WEIGHT_NAME Field</h4></div></div></div><p>
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 <a class="xref" href="#Polymorphic_Fonts" title="Chapter 6. Polymorphic Fonts"><em>Polymorphic Fonts</em></a>).
</p><p>
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.
</p><p>
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.
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="SLANT_Field"></a>SLANT Field</h4></div></div></div><p>
SLANT is a code-string that indicates the overall posture of the
typeface design used in the font.
The encoding is as follows:
</p><div class="informaltable"><table border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /></colgroup><thead><tr><th align="left">Code</th><th align="left">English Translation</th><th align="left">Description</th></tr></thead><tbody><tr><td align="left">"R"</td><td align="left">Roman</td><td align="left">Upright design</td></tr><tr><td align="left">"I"</td><td align="left">Italic</td><td align="left">Italic design, slanted clockwise from the vertical</td></tr><tr><td align="left">"O"</td><td align="left">Oblique</td><td align="left">Obliqued upright design, slanted clockwise from the vertical</td></tr><tr><td align="left">"RI"</td><td align="left">Reverse Italic</td><td align="left">Italic design, slanted counterclockwise from the vertical</td></tr><tr><td align="left">"RO"</td><td align="left">Reverse Oblique</td><td align="left">Obliqued upright design, slanted counterclockwise from the vertical</td></tr><tr><td align="left">"OT"</td><td align="left">Other</td><td align="left">Other</td></tr><tr><td align="left">numeric</td><td align="left">Polymorphic</td><td align="left">See <a class="xref" href="#Polymorphic_Fonts" title="Chapter 6. Polymorphic Fonts"><em>Polymorphic Fonts</em></a>.</td></tr></tbody></table></div><p>
The SLANT codes are for programming convenience only and usually are
converted into their equivalent human-understandable form before being
presented to a user.
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="SETWIDTH_NAME_Field"></a>SETWIDTH_NAME Field</h4></div></div></div><p>
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 <a class="xref" href="#Polymorphic_Fonts" title="Chapter 6. Polymorphic Fonts"><em>Polymorphic Fonts</em></a>).
</p><p>
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.
</p><p>
The following are examples of SETWIDTH_NAME:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
Normal
</p></li><li class="listitem"><p>
Condensed
</p></li><li class="listitem"><p>
Narrow
</p></li><li class="listitem"><p>
Double Wide
</p></li></ul></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="ADD_STYLE_NAME_Field"></a>ADD_STYLE_NAME Field</h4></div></div></div><p>
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 <a class="xref" href="#Polymorphic_Fonts" title="Chapter 6. Polymorphic Fonts"><em>Polymorphic Fonts</em></a>).
</p><p>
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.
</p><p>
The following are examples of ADD_STYLE_NAME:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
Serif
</p></li><li class="listitem"><p>
Sans Serif
</p></li><li class="listitem"><p>
Informal
</p></li><li class="listitem"><p>
Decorated
</p></li></ul></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="PIXEL_SIZE_Field"></a>PIXEL_SIZE Field</h4></div></div></div><p>
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 <a class="xref" href="#Matrix_Transformations" title="Chapter 4. Matrix Transformations"><em>Matrix Transformations</em></a>).
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 <a class="xref" href="#Scalable_Fonts" title="Chapter 5. Scalable Fonts"><em>Scalable Fonts</em></a>).
</p><p>
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.
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="SN_POINT_SIZE_Field"></a>SN POINT_SIZE Field</h4></div></div></div><p>
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 <a class="xref" href="#Matrix_Transformations" title="Chapter 4. Matrix Transformations"><em>Matrix Transformations</em></a>).
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 <a class="xref" href="#Scalable_Fonts" title="Chapter 5. Scalable Fonts"><em>Scalable Fonts</em></a>).
</p><p>
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.
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="RESOLUTION_X_and_RESOLUTION_Y_Fields"></a>RESOLUTION_X and RESOLUTION_Y Fields</h4></div></div></div><p>
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 <a class="xref" href="#Scalable_Fonts" title="Chapter 5. Scalable Fonts"><em>Scalable Fonts</em></a>).
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).
</p><p>
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.
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="SPACING_Field"></a>SPACING Field</h4></div></div></div><p>
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:
</p><div class="informaltable"><table border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /></colgroup><thead><tr><th align="left">Code</th><th align="left">English Translation</th><th align="left">Description</th></tr></thead><tbody><tr><td align="left">"P"</td><td align="left">Proportional</td><td align="left">
A font whose logical character widths vary for each glyph.
Note that no other restrictions are placed on the metrics
of a proportional font.
</td></tr><tr><td align="left">"M"</td><td align="left">Monospaced</td><td align="left">
A font whose logical character widths are constant
(that is, every glyph in the font has the same logical width).
No other restrictions are placed on the metrics of a monospaced font.
</td></tr><tr><td align="left">"C"</td><td align="left">CharCell</td><td align="left">
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 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.
</td></tr></tbody></table></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="AVERAGE_WIDTH_Field"></a>AVERAGE_WIDTH Field</h4></div></div></div><p>
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 <a class="xref" href="#Scalable_Fonts" title="Chapter 5. Scalable Fonts"><em>Scalable Fonts</em></a>).
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="CHARSET_REGISTRY_and_CHARSET_ENCODING_Fields"></a>CHARSET_REGISTRY and CHARSET_ENCODING Fields</h4></div></div></div><p>
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.
</p><p>
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.
</p><p>
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:
</p><div class="informaltable"><table border="0"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><tbody><tr><td align="left">CharsetRegistry ::=</td><td align="left">StdCharsetRegistryName | PrivCharsetRegistryName</td></tr><tr><td align="left">CharsetEncoding ::=</td><td align="left">StdCharsetEncodingName | PrivCharsetEncodingName</td></tr><tr><td align="left">StdCharsetRegistryName ::=</td><td align="left">StdOrganizationId StdNumber | StdOrganizationId StdNumber Dot Year</td></tr><tr><td align="left">PrivCharsetRegistryName ::=</td><td align="left">OrganizationId STRING8</td></tr><tr><td align="left">StdCharsetEncodingName ::=</td><td align="left">STRING8-numeric part number of referenced standard</td></tr><tr><td align="left">PrivCharsetEncodingName ::=</td><td align="left">STRING8</td></tr><tr><td align="left">StdOrganizationId ::=</td><td align="left">STRING8-the registered name or acronym of the referenced standard organization</td></tr><tr><td align="left">StdNumber ::=</td><td align="left">STRING8-referenced standard number</td></tr><tr><td align="left">OrganizationId ::=</td><td align="left">STRING8-the registered name or acronym of the organization</td></tr><tr><td align="left">Dot ::=</td><td align="left">OCTET-"." (FULL STOP)</td></tr><tr><td align="left">Year ::=</td><td align="left">STRING8-numeric year (for example, 1989)</td></tr></tbody></table></div><p>
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.
</p><p>
The ISO Latin-1 character set shall be registered by the X Consortium as the
CHARSET_REGISTRY-CHARSET_ENCODING value pair: "ISO8859-1".
</p><p>
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.
</p><p>
The BNF for the subsetting hint is
</p><div class="informaltable"><table border="0"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><tbody><tr><td align="left">Subset ::=</td><td align="left">LeftBracket RangeList RightBracket</td></tr><tr><td align="left">RangeList ::=</td><td align="left">Range | Range Space RangeList</td></tr><tr><td align="left">Range ::=</td><td align="left">Number | Number Underscore Number</td></tr><tr><td align="left">Number ::=</td><td align="left">"0x" HexNumber | DecNumber</td></tr><tr><td align="left">HexNumber ::=</td><td align="left">HexDigit | HexDigit HexNumber</td></tr><tr><td align="left">DecNumber ::=</td><td align="left">DecDigit | DecDigit DecNumber</td></tr><tr><td align="left">DecDigit ::=</td><td align="left">"0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"</td></tr><tr><td align="left">HexDigit ::=</td><td align="left">DecDigit | "a" | "b" | "c" | "d" | "e" | "f"</td></tr><tr><td align="left">LeftBracket ::=</td><td align="left">"[" (LEFT SQUARE BRACKET)</td></tr><tr><td align="left">RightBracket ::=</td><td align="left">"]" (RIGHT SQUARE BRACKET)</td></tr><tr><td align="left">Space ::=</td><td align="left">"\0" (SPACE)</td></tr><tr><td align="left">Underscore ::=</td><td align="left">"_" (LOW LINE)</td></tr></tbody></table></div><p>
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.
</p><p>
For example,
</p><pre class="literallayout">
-misc-fixed-medium-r-normal--0-0-0-0-c-0-iso8859-1[65 70 80_90]
</pre><p>
tells the font source that the client is interested only in characters
65, 70, and 80-90.
</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="Examples"></a>Examples</h3></div></div></div><p>
The following examples of font names are derived from the screen fonts
shipped with the X Consortium distribution.
</p><div class="informaltable"><table border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><thead><tr><th align="left">Font</th><th align="left">X FontName</th></tr></thead><tbody><tr><td align="left"><code class="function">75-dpi Fonts</code></td><td class="auto-generated"> </td></tr><tr><td align="left">Charter 12 pt</td><td align="left">-Bitstream-Charter-Medium-R-Normal--12-120-75-75-P-68-ISO8859-1</td></tr><tr><td align="left">Charter Bold 12 pt</td><td align="left">-Bitstream-Charter-Bold-R-Normal--12-120-75-75-P-76-ISO8859-1</td></tr><tr><td align="left">Charter Bold Italic 12 pt</td><td align="left">-Bitstream-Charter-Bold-I-Normal--12-120-75-75-P-75-ISO8859-1</td></tr><tr><td align="left">Charter Italic 12 pt</td><td align="left">-Bitstream-Charter-Medium-I-Normal--12-120-75-75-P-66-ISO8859-1</td></tr><tr><td align="left">Courier 8 pt</td><td align="left">-Adobe-Courier-Medium-R-Normal--8-80-75-75-M-50-ISO8859-1</td></tr><tr><td align="left">Courier 10 pt</td><td align="left">-Adobe-Courier-Medium-R-Normal--10-100-75-75-M-60-ISO8859-1</td></tr><tr><td align="left">Courier 12 pt</td><td align="left">-Adobe-Courier-Medium-R-Normal--12-120-75-75-M-70-ISO8859-1</td></tr><tr><td align="left">Courier 24 pt</td><td align="left">-Adobe-Courier-Medium-R-Normal--24-240-75-75-M-150-ISO8859-1</td></tr><tr><td align="left">Courier Bold 10 pt</td><td align="left">-Adobe-Courier-Bold-R-Normal--10-100-75-75-M-60-ISO8859-1</td></tr><tr><td align="left">Courier Bold Oblique 10 pt</td><td align="left">-Adobe-Courier-Bold-O-Normal--10-100-75-75-M-60-ISO8859-1</td></tr><tr><td align="left">Courier Oblique 10 pt</td><td align="left">-Adobe-Courier-Medium-O-Normal--10-100-75-75-M-60-ISO8859-1</td></tr><tr><td align="left"><code class="function">100-dpi Fonts</code></td><td class="auto-generated"> </td></tr><tr><td align="left">Symbol 10 pt</td><td align="left">-Adobe-Symbol-Medium-R-Normal--14-100-100-100-P-85-Adobe-FONTSPECIFIC</td></tr><tr><td align="left">Symbol 14 pt</td><td align="left">-Adobe-Symbol-Medium-R-Normal--20-140-100-100-P-107-Adobe-FONTSPECIFIC</td></tr><tr><td align="left">Symbol 18 pt</td><td align="left">-Adobe-Symbol-Medium-R-Normal--25-180-100-100-P-142-Adobe-FONTSPECIFIC</td></tr><tr><td align="left">Symbol 24 pt</td><td align="left">-Adobe-Symbol-Medium-R-Normal--34-240-100-100-P-191-Adobe-FONTSPECIFIC</td></tr><tr><td align="left">Times Bold 10 pt</td><td align="left">-Adobe-Times-Bold-R-Normal--14-100-100-100-P-76-ISO8859-1</td></tr><tr><td align="left">Times Bold Italic 10 pt</td><td align="left">-Adobe-Times-Bold-I-Normal--14-100-100-100-P-77-ISO8859-1</td></tr><tr><td align="left">Times Italic 10 pt</td><td align="left">-Adobe-Times-Medium-I-Normal--14-100-100-100-P-73-ISO8859-1</td></tr><tr><td align="left">Times Roman 10 pt</td><td align="left">-Adobe-Times-Medium-R-Normal--14-100-100-100-P-74-ISO8859-1</td></tr></tbody></table></div></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Font_Properties"></a>Font Properties</h2></div></div></div><p>
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.
</p><p>
Font property names use the ISO 8859-1 encoding.
</p><p>
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.
</p><p>
The Backus-Naur Form syntax description of X font properties is as follows:
</p><div class="informaltable"><table border="0"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><tbody><tr><td align="left">Properties ::=</td><td align="left">OptFontPropList</td></tr><tr><td align="left">OptFontPropList ::=</td><td align="left">NULL | OptFontProp OptFontPropList</td></tr><tr><td align="left">OptFontProp ::=</td><td align="left">PrivateFontProp | XFontProp</td></tr><tr><td align="left">PrivateFontProp ::=</td><td align="left">STRING8 | Underscore OrganizationId Underscore STRING8</td></tr><tr><td align="left">XFontProp ::=</td><td align="left">
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 |
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</td></tr><tr><td align="left">Underscore ::=</td><td align="left">OCTET-"_" (LOW LINE)</td></tr><tr><td align="left">OrganizationId ::=</td><td align="left">STRING8-the registered name of the organization</td></tr></tbody></table></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FOUNDRY"></a>FOUNDRY</h3></div></div></div><p>
FOUNDRY is as defined in the
<code class="function">FontName</code>
except that the property type is ATOM.
</p><p>
FOUNDRY cannot be calculated or defaulted if not supplied as a font property.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FAMILY_NAME"></a>FAMILY_NAME</h3></div></div></div><p>
FAMILY_NAME is as defined in the
<code class="function">FontName</code>
except that the property type is ATOM.
</p><p>
FAMILY_NAME cannot be calculated or defaulted if not supplied as a font
property.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="WEIGHT_NAME"></a>WEIGHT_NAME</h3></div></div></div><p>
WEIGHT_NAME is as defined in the
<code class="function">FontName</code>
except that the property type is ATOM.
</p><p>
WEIGHT_NAME can be defaulted if not supplied as a font property, as follows:
</p><pre class="literallayout">
if (WEIGHT_NAME undefined) then
WEIGHT_NAME = ATOM("Medium")
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="SLANT"></a>SLANT</h3></div></div></div><p>
SLANT is as defined in the
<code class="function">FontName</code>
except that the property type is ATOM.
</p><p>
SLANT can be defaulted if not supplied as a font property, as follows:
</p><pre class="literallayout">
if (SLANT undefined) then
SLANT = ATOM("R")
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="SETWIDTH_NAME"></a>SETWIDTH_NAME</h3></div></div></div><p>
SETWIDTH_NAME is as defined in the
<code class="function">FontName</code>
except that the property type is ATOM.
</p><p>
SETWIDTH_NAME can be defaulted if not supplied as a font property, as follows:
</p><pre class="literallayout">
if (SETWIDTH_NAME undefined) then
SETWIDTH_NAME = ATOM("Normal")
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="ADD_STYLE_NAME"></a>ADD_STYLE_NAME</h3></div></div></div><p>
ADD_STYLE_NAME is as defined in the
<code class="function">FontName</code>
except that the property type is ATOM.
</p><p>
ADD_STYLE_NAME can be defaulted if not supplied as a font property, as follows:
</p><pre class="literallayout">
if (ADD_STYLE_NAME undefined) then
ADD_STYLE_NAME = ATOM("")
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="PIXEL_SIZE"></a>PIXEL_SIZE</h3></div></div></div><p>
PIXEL_SIZE is as defined in the
<code class="function">FontName</code>
except that the property type is INT32.
</p><p>
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:
</p><pre class="literallayout">
DeciPointsPerInch = 722.7
EMspace = ROUND ((RESOLUTION_X * POINT_SIZE) / DeciPointsPerInch)
ENspace = ROUND (EMspace / 2)
THINspace = ROUND (EMspace / 3)\fP
</pre><p>
where a slash (/) denotes real division,
an asterisk (*) denotes real multiplication,
and ROUND denotes a function that rounds its real argument
<span class="emphasis"><em>a</em></span> up or down
to the next integer.
This rounding is done according to X = FLOOR (
<span class="emphasis"><em>a</em></span> + 0.5),
where FLOOR is a function that rounds its real argument down to the
nearest integer.
</p><p>
PIXEL_SIZE can be approximated if not supplied as a font property,
according to the following algorithm:
</p><pre class="literallayout">
DeciPointsPerInch = 722.7
if (PIXEL_SIZE undefined) then
PIXEL_SIZE = ROUND ((RESOLUTION_Y * POINT_SIZE) / DeciPointsPerInch)
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="POINT_SIZE"></a>POINT_SIZE</h3></div></div></div><p>
POINT_SIZE is as defined in the
<code class="function">FontName</code>
except that the property type is INT32.
</p><p>
X clients requiring device-independent values for em space,
en space, and thin space can use the following algorithm:
</p><pre class="literallayout">
EMspace = ROUND (POINT_SIZE / 10)
ENspace = ROUND (POINT_SIZE / 20)
THINspace = ROUND (POINT_SIZE / 30)
</pre><p>
Design POINT_SIZE cannot be calculated or approximated.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="RESOLUTION_X_x"></a>RESOLUTION_X</h3></div></div></div><p>
RESOLUTION_X is as defined in the
<code class="function">FontName</code>
except that the property type is CARD32.
</p><p>
RESOLUTION_X cannot be calculated or approximated.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="RESOLUTION_Y_y"></a>RESOLUTION_Y</h3></div></div></div><p>
RESOLUTION_Y is as defined in the
<code class="function">FontName</code>
except that the property type is CARD32.
</p><p>
RESOLUTION_X cannot be calculated or approximated.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="SPACING"></a>SPACING</h3></div></div></div><p>
SPACING is as defined in the
<code class="function">FontName</code>
except that the property type is ATOM.
</p><p>
SPACING can be calculated if not supplied as a font property,
according to the definitions given above for the
<code class="function">FontName</code>.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="AVERAGE_WIDTH"></a>AVERAGE_WIDTH</h3></div></div></div><p>
AVERAGE_WIDTH is as defined in the
<code class="function">FontName</code>
except that the property type is INT32.
</p><p>
AVERAGE_WIDTH can be calculated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
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)
</pre><p>
where MEAN is a function that returns the arithmetic mean of its arguments.
</p><p>
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:
</p><pre class="literallayout">
if (SPACING not proportional) then
CharPitch = (RESOLUTION_X * 10) / AVERAGE_WIDTH
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="CHARSET_REGISTRY"></a>CHARSET_REGISTRY</h3></div></div></div><p>
CHARSET_REGISTRY is as defined in the
<code class="function">FontName</code>
except that the property type is ATOM.
</p><p>
CHARSET_REGISTRY cannot be defaulted if not supplied as a font property.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="CHARSET_ENCODING"></a>CHARSET_ENCODING</h3></div></div></div><p>
CHARSET_ENCODING is as defined in the
<code class="function">FontName</code>
except that the property type is ATOM.
</p><p>
CHARSET_ENCODING cannot be defaulted if not supplied as a font property.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="MIN_SPACE"></a>MIN_SPACE</h3></div></div></div><p>
MIN_SPACE is an integer value (of type INT32)
that gives the recommended minimum word-space value to be used with this font.
</p><p>
MIN_SPACE can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (MIN_SPACE undefined) then
MIN_SPACE = ROUND(0.75 * NORM_SPACE)
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="NORM_SPACE"></a>NORM_SPACE</h3></div></div></div><p>
NORM_SPACE is an integer value (of type INT32)
that gives the recommended normal word-space value to be used with this font.
</p><p>
NORM_SPACE can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
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)
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="MAX_SPACE"></a>MAX_SPACE</h3></div></div></div><p>
MAX_SPACE is an integer value (of type INT32)
that gives the recommended maximum word-space value to be used with this font.
</p><p>
MAX_SPACE can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (MAX_SPACE undefined) then
MAX_SPACE = ROUND(1.5 * NORM_SPACE)
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="END_SPACE"></a>END_SPACE</h3></div></div></div><p>
END_SPACE is an integer value (of type INT32)
that gives the recommended spacing at the end of sentences.
</p><p>
END_SPACE can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (END_SPACE undefined) then
END_SPACE = NORM_SPACE
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="AVG_CAPITAL_WIDTH"></a>AVG_CAPITAL_WIDTH</h3></div></div></div><p>
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.
</p><p>
AVG_CAPITAL_WIDTH can be calculated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
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
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="AVG_LOWERCASE_WIDTH"></a>AVG_LOWERCASE_WIDTH</h3></div></div></div><p>
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.
</p><p>
Where appropriate,
AVG_LOWERCASE_WIDTH can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
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
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="QUAD_WIDTH"></a>QUAD_WIDTH</h3></div></div></div><p>
QUAD_WIDTH is an integer typographic metric (of type INT32)
that gives the width of a quad (em) space.
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
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).
</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FIGURE_WIDTH"></a>FIGURE_WIDTH</h3></div></div></div><p>
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.
</p><p>
FIGURE_WIDTH can be approximated if not supplied as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (numerals and DOLLAR sign are defined & widths are equal) then
FIGURE_WIDTH = width of DOLLAR
else FIGURE_WIDTH property undefined
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="SUPERSCRIPT_X_x"></a>SUPERSCRIPT_X</h3></div></div></div><p>
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].
</p><p>
SUPERSCRIPT_X can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
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)
</pre><p>
where TANGENT is a trigonometric function that returns the tangent of
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="SUPERSCRIPT_Y_y"></a>SUPERSCRIPT_Y</h3></div></div></div><p>
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].
</p><p>
SUPERSCRIPT_Y can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (SUPERSCRIPT_Y undefined) then
SUPERSCRIPT_Y = ROUND(0.40 * CAP_HEIGHT)
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="SUBSCRIPT_X_x"></a>SUBSCRIPT_X</h3></div></div></div><p>
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].
</p><p>
SUBSCRIPT_X can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
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)
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="SUBSCRIPT_Y_y"></a>SUBSCRIPT_Y</h3></div></div></div><p>
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].
</p><p>
SUBSCRIPT_Y can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (SUBSCRIPT_Y undefined) then
SUBSCRIPT_Y = ROUND(0.40 * CAP_HEIGHT)
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="SUPERSCRIPT_SIZE"></a>SUPERSCRIPT_SIZE</h3></div></div></div><p>
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.
</p><p>
SUPERSCRIPT_SIZE can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (SUPERSCRIPT_SIZE undefined) then
SUPERSCRIPT_SIZE = ROUND(0.60 * PIXEL_SIZE)
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="SUBSCRIPT_SIZE"></a>SUBSCRIPT_SIZE</h3></div></div></div><p>
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.
</p><p>
SUBSCRIPT_SIZE can be approximated if not provided as a font property,
according to the algorithm:
</p><pre class="literallayout">
if (SUBSCRIPT_SIZE undefined) then
SUBSCRIPT_SIZE = ROUND(0.60 * PIXEL_SIZE)
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="SMALL_CAP_SIZE"></a>SMALL_CAP_SIZE</h3></div></div></div><p>
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.
</p><p>
SMALL_CAP_SIZE can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (SMALL_CAP_SIZE undefined) then
SMALL_CAP_SIZE = ROUND(PIXEL_SIZE * ((X_HEIGHT
+ ((CAP_HEIGHT - X_HEIGHT) / 3)) / CAP_HEIGHT))
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="UNDERLINE_POSITION"></a>UNDERLINE_POSITION</h3></div></div></div><p>
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].
</p><p>
UNDERLINE_POSITION can be approximated if not provided as a font
property, according to the following algorithm:
</p><pre class="literallayout">
if (UNDERLINE_POSITION undefined) then
UNDERLINE_POSITION = ROUND((maximum descent) / 2)
</pre><p>
where <span class="emphasis"><em>maximum descent</em></span>
is the maximum descent (below the baseline)
in pixels of any glyph in the font.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="UNDERLINE_THICKNESS"></a>UNDERLINE_THICKNESS</h3></div></div></div><p>
UNDERLINE_THICKNESS is an integer value (of type INT32)
that gives the recommended underline thickness, in pixels.
</p><p>
UNDERLINE_THICKNESS can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
CapStemWidth = average width of the stems of capitals
if (UNDERLINE_THICKNESS undefined) then
UNDERLINE_THICKNESS = CapStemWidth
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="STRIKEOUT_ASCENT"></a>STRIKEOUT_ASCENT</h3></div></div></div><p>
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].
</p><p>
STRIKEOUT_ASCENT can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (STRIKEOUT_ASCENT undefined)
STRIKEOUT_ASCENT = maximum ascent
</pre><p>
where <span class="emphasis"><em>maximum ascent</em></span>
is the maximum ascent (above the baseline)
in pixels of any glyph in the font.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="STRIKEOUT_DESCENT"></a>STRIKEOUT_DESCENT</h3></div></div></div><p>
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].
</p><p>
STRIKEOUT_DESCENT can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (STRIKEOUT_DESCENT undefined)
STRIKEOUT_DESCENT = maximum descent
</pre><p>
where <span class="emphasis"><em>maximum descent</em></span> is the maximum
descent (below the baseline)
in pixels of any glyph in the font.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="ITALIC_ANGLE"></a>ITALIC_ANGLE</h3></div></div></div><p>
ITALIC_ANGLE is an integer value (of type INT32)
measured from the glyph origin counterclockwise from the three o'clock position.
</p><p>
ITALIC_ANGLE can be defaulted if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (ITALIC_ANGLE undefined) then
ITALIC_ANGLE = (90 * 64)
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="CAP_HEIGHT"></a>CAP_HEIGHT</h3></div></div></div><p>
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.
</p><p>
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.
</p><p>
CAP_HEIGHT can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
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
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="X_HEIGHT"></a>X_HEIGHT</h3></div></div></div><p>
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.
</p><p>
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.
</p><p>
X_HEIGHT can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
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
</pre></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="RELATIVE_SETWIDTH"></a>RELATIVE_SETWIDTH</h3></div></div></div><p>
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.
</p><p>
RELATIVE_SETWIDTH ranges from 10 to 90 or is 0 if undefined or unknown.
The following reference values are defined:
</p><div class="informaltable"><table border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /></colgroup><thead><tr><th align="left">Code</th><th align="left">English Translation</th><th align="left">Description</th></tr></thead><tbody><tr><td align="left">0</td><td align="left">Undefined</td><td align="left">Undefined or unknown</td></tr><tr><td align="left">10</td><td align="left">UltraCondensed</td><td align="left">The lowest ratio of average width to height</td></tr><tr><td align="left">20</td><td align="left">ExtraCondensed</td><td class="auto-generated"> </td></tr><tr><td align="left">30</td><td align="left">Condensed</td><td align="left">Condensed, Narrow, Compressed, ...</td></tr><tr><td align="left">40</td><td align="left">SemiCondensed</td><td class="auto-generated"> </td></tr><tr><td align="left">50</td><td align="left">Medium</td><td align="left">Medium, Normal, Regular, ...</td></tr><tr><td align="left">60</td><td align="left">SemiExpanded</td><td align="left">SemiExpanded, DemiExpanded, ...</td></tr><tr><td align="left">70</td><td align="left">Expanded</td><td class="auto-generated"> </td></tr><tr><td align="left">80</td><td align="left">ExtraExpanded</td><td align="left">ExtraExpanded, Wide, ...</td></tr><tr><td align="left">90</td><td align="left">UltraExpanded</td><td align="left">The highest ratio of average width to height</td></tr></tbody></table></div><p>
RELATIVE_SETWIDTH can be defaulted if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (RELATIVE_SETWIDTH undefined) then
RELATIVE_SETWIDTH = 50
</pre><p>
For polymorphic fonts, RELATIVE_SETWIDTH is not necessarily a
linear function of the font's setwidth axis.
</p><p>
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:
</p><pre class="literallayout">
SETWIDTH = AVG_CAPITAL_WIDTH / (CAP_HEIGHT * 10)
</pre><p>
where SETWIDTH is a real number with zero being the narrowest
calculated setwidth.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="RELATIVE_WEIGHT"></a>RELATIVE_WEIGHT</h3></div></div></div><p>
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.
</p><p>
RELATIVE_WEIGHT ranges from 10 to 90 or is 0 if undefined or unknown.
The following reference values are defined:
</p><div class="informaltable"><table border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /></colgroup><thead><tr><th align="left">Code</th><th align="left">English Translation</th><th align="left">Description</th></tr></thead><tbody><tr><td align="left">0</td><td align="left">Undefined</td><td align="left">Undefined or unknown</td></tr><tr><td align="left">10</td><td align="left">UltraLight</td><td align="left">The lowest ratio of stem width to height</td></tr><tr><td align="left">20</td><td align="left">ExtraLight</td><td class="auto-generated"> </td></tr><tr><td align="left">30</td><td align="left">Light</td><td class="auto-generated"> </td></tr><tr><td align="left">40</td><td align="left">SemiLight</td><td align="left">SemiLight, Book, ...</td></tr><tr><td align="left">50</td><td align="left">Medium</td><td align="left">Medium, Normal, Regular,...</td></tr><tr><td align="left">60</td><td align="left">SemiBold</td><td align="left">SemiBold, DemiBold, ...</td></tr><tr><td align="left">70</td><td align="left">Bold</td><td class="auto-generated"> </td></tr><tr><td align="left">80</td><td align="left">ExtraBold</td><td align="left">ExtraBold, Heavy, ...</td></tr><tr><td align="left">90</td><td align="left">UltraBold</td><td align="left">
UltraBold, Black, ..., the highest ratio of stem width to height
</td></tr></tbody></table></div><p>
RELATIVE_WEIGHT can be defaulted if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (RELATIVE_WEIGHT undefined) then
RELATIVE_WEIGHT = 50
</pre><p>
For polymorphic fonts, RELATIVE_WEIGHT is not necessarily a
linear function of the font's weight axis.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="WEIGHT"></a>WEIGHT</h3></div></div></div><p>
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.
</p><p>
WEIGHT can be calculated if not supplied as a font property,
according to the following algorithm:
</p><pre class="literallayout">
CapStemWidth = average width of the stems of capitals
if (WEIGHT undefined) then
WEIGHT = ROUND ((CapStemWidth * 1000) / CAP_HEIGHT)
</pre><p>
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.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="RESOLUTION"></a>RESOLUTION</h3></div></div></div><p>
RESOLUTION is an integer value (of type INT32)
that gives the resolution for which this font was created,
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
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.
</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="Font_support"></a>FONT</h3></div></div></div><p>
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.
</p><p>
If not provided, the FONT property cannot be calculated.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FACE_NAME"></a>FACE_NAME</h3></div></div></div><p>
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.
</p><p>
FACE_NAME cannot be calculated or approximated if not provided as a font
property.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FULL_NAME"></a>FULL_NAME</h3></div></div></div><p>
FULL_NAME is the same as FACE_NAME.
Its use is deprecated, but it is found on some old fonts.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="COPYRIGHT"></a>COPYRIGHT</h3></div></div></div><p>
COPYRIGHT is a human-understandable string (of type ATOM)
that gives the copyright information of the legal owner
of the digital font data.
</p><p>
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).
</p><p>
COPYRIGHT cannot be calculated or approximated if not provided as a font
property.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="NOTICE"></a>NOTICE</h3></div></div></div><p>
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.
</p><p>
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.
</p><p>
NOTICE cannot be calculated or approximated if not provided as
a font property.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="DESTINATION"></a>DESTINATION</h3></div></div></div><p>
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.
</p><p>
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.
</p><p>
The encoding is as follows:
</p><div class="informaltable"><table border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /></colgroup><thead><tr><th align="left">Code</th><th align="left">English Translation</th><th align="left">Description</th></tr></thead><tbody><tr><td align="left">0</td><td align="left">WYSIWYG</td><td align="left">
The font is optimized to match the typographic design and metrics of an
equivalent printer font.
</td></tr><tr><td align="left">1</td><td align="left">Video text</td><td align="left">
The font is optimized for screen legibility and readability.
</td></tr></tbody></table></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FONT_TYPE"></a>FONT_TYPE</h3></div></div></div><p>
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.
</p><p>
Predefined values are as follows:
</p><div class="informaltable"><table border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><thead><tr><th align="left">Value</th><th align="left">When applicable</th></tr></thead><tbody><tr><td align="left">"Bitmap"</td><td align="left">
Hand-tuned bitmap fonts. Some attempt has been made to optimize the visual
appearance of the font for the requested size and resolution.
</td></tr><tr><td align="left">"Prebuilt"</td><td align="left">
All bitmap format fonts that cannot be described as "Bitmap", that is,
handtuned.
For example, a bitmap format font that was generated mechanically using
a scalable font rasterizer would be considered "Prebuilt", not "Bitmap".
</td></tr><tr><td align="left">"Type 1"</td><td align="left">Any Type 1 font.</td></tr><tr><td align="left">"TrueType"</td><td align="left">Any TrueType font.</td></tr><tr><td align="left">"Speedo"</td><td align="left">Any Speedo font.</td></tr><tr><td align="left">"F3"</td><td align="left">Any F3 font.</td></tr></tbody></table></div><p>
Other values may be registered with the X Consortium.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FONT_VERSION"></a>FONT_VERSION</h3></div></div></div><p>
FONT_VERSION is a human-understandable string (of type ATOM)
that describes the formal or informal version of the font.
<code class="function">None</code> is a valid value.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="RASTERIZER_NAME"></a>RASTERIZER_NAME</h3></div></div></div><p>
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.
</p><p>
To define a RASTERIZER_NAME, the following format is
recommended:
</p><div class="informaltable"><table border="0"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><tbody><tr><td align="left">RasterizerName ::=</td><td align="left">OrganizationId Space Rasterizer</td></tr><tr><td align="left">OrganizationId ::=</td><td align="left">
STRING8—the X Registry ORGANIZATION name of the rasterizer
implementor or maintainer.
</td></tr><tr><td align="left">Rasterizer ::=</td><td align="left">
the case-sensitive, human-understandable product name of the rasterizer.
Words within this name should be separated by a single SPACE.
</td></tr><tr><td align="left">Space ::=</td><td align="left">OCTET−" " (SPACE)</td></tr></tbody></table></div><p>
Examples:
</p><pre class="literallayout">
X Consortium Bit Scaler
X Consortium Type 1 Rasterizer
X Consortium Speedo Rasterizer
Adobe Type Manager
Sun TypeScaler
</pre><p>
If RASTERIZER_NAME is not defined, or is <code class="function">None</code>, no
rasterization operation has been applied to the FONT_TYPE.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="RASTERIZER_VERSION"></a>RASTERIZER_VERSION</h3></div></div></div><p>
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.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="RAW_ASCENT"></a>RAW_ASCENT</h3></div></div></div><p>
For a font with a transformation matrix, RAW_ASCENT is the font ascent
in 1000 pixel metrics
(see <a class="xref" href="#Metrics_and_Font_Properties" title="Metrics and Font Properties">Metrics and Font Properties</a>).
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="RAW_DESCENT"></a>RAW_DESCENT</h3></div></div></div><p>
For a font with a transformation matrix, RAW_DESCENT is the font
descent in 1000 pixel metrics
(see <a class="xref" href="#Metrics_and_Font_Properties" title="Metrics and Font Properties">Metrics and Font Properties</a>).
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="RAW_"></a>RAW_*</h3></div></div></div><p>
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 <a class="xref" href="#Metrics_and_Font_Properties" title="Metrics and Font Properties">Metrics and Font Properties</a>.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="AXIS_NAMES"></a>AXIS_NAMES</h3></div></div></div><p>
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).
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="AXIS_LIMITS"></a>AXIS_LIMITS</h3></div></div></div><p>
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 <a class="xref" href="#Polymorphic_Fonts" title="Chapter 6. Polymorphic Fonts"><em>Polymorphic Fonts</em></a>).
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="AXIS_TYPES"></a>AXIS_TYPES</h3></div></div></div><p>
AXIS_TYPES is like AXIS_NAMES,
but can be registered as having specific semantics
(see section 6).
</p></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Built_in_Font_Property_Atoms"></a>Built-in Font Property Atoms</h2></div></div></div><p>
The following font property atom definitions were predefined in the initial
version of the core protocol:
</p><div class="informaltable"><table border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><thead><tr><th align="left">Font Property/Atom Name</th><th align="left">Property Type</th></tr></thead><tbody><tr><td align="left">MIN_SPACE</td><td align="left">INT32</td></tr><tr><td align="left">NORM_SPACE</td><td align="left">INT32</td></tr><tr><td align="left">MAX_SPACE</td><td align="left">INT32</td></tr><tr><td align="left">END_SPACE</td><td align="left">INT32</td></tr><tr><td align="left">SUPERSCRIPT_X</td><td align="left">INT32</td></tr><tr><td align="left">SUPERSCRIPT_Y</td><td align="left">INT32</td></tr><tr><td align="left">SUBSCRIPT_X</td><td align="left">INT32</td></tr><tr><td align="left">SUBSCRIPT_Y</td><td align="left">INT32</td></tr><tr><td align="left">UNDERLINE_POSITION</td><td align="left">INT32</td></tr><tr><td align="left">UNDERLINE_THICKNESS</td><td align="left">INT32</td></tr><tr><td align="left">STRIKEOUT_ASCENT</td><td align="left">INT32</td></tr><tr><td align="left">STRIKEOUT_DESCENT</td><td align="left">INT32</td></tr><tr><td align="left">FONT_ASCENT</td><td align="left">INT32</td></tr><tr><td align="left">FONT_DESCENT</td><td align="left">INT32</td></tr><tr><td align="left">ITALIC_ANGLE</td><td align="left">INT32</td></tr><tr><td align="left">X_HEIGHT</td><td align="left">INT32</td></tr><tr><td align="left">QUAD_WIDTH</td><td align="left">INT32 −<sup>deprecated</sup></td></tr><tr><td align="left">WEIGHT</td><td align="left">CARD32</td></tr><tr><td align="left">POINT_SIZE</td><td align="left">INT32</td></tr><tr><td align="left">RESOLUTION</td><td align="left">CARD32 −<sup>deprecated</sup></td></tr><tr><td align="left">COPYRIGHT</td><td align="left">ATOM</td></tr><tr><td align="left">FULL_NAME</td><td align="left">ATOM −<sup>deprecated</sup></td></tr><tr><td align="left">FAMILY_NAME</td><td align="left">ATOM</td></tr><tr><td align="left">DEFAULT_CHAR</td><td align="left">CARD32</td></tr></tbody></table></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="Matrix_Transformations"></a>Chapter 4. Matrix Transformations</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="sect1"><a href="#Metrics_and_Font_Properties">Metrics and Font Properties</a></span></dt></dl></div><p>
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.
</p><p>
The BNF for a matrix transformation string is as follows:
</p><div class="informaltable"><table border="0"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><tbody><tr><td align="left">MatrixString ::=</td><td align="left">
LeftBracket OptionalSpace Float Space Float Space
Float Space Float OptionalSpace RightBracket
</td></tr><tr><td align="left">OptionalSpace ::=</td><td align="left">"" | Space</td></tr><tr><td align="left">Space ::=</td><td align="left">SpaceChar | SpaceChar Space</td></tr><tr><td align="left">Float ::=</td><td align="left">Mantissa | Mantissa Exponent</td></tr><tr><td align="left">Mantissa ::=</td><td align="left">Sign Number | Number</td></tr><tr><td align="left">Sign ::=</td><td align="left">Plus | Tilde</td></tr><tr><td align="left">Number ::=</td><td align="left">Integer | Integer Dot Integer | Dot Integer</td></tr><tr><td align="left">Integer ::=</td><td align="left">Digit | Digit Integer</td></tr><tr><td align="left">Digit ::=</td><td align="left">
"0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
</td></tr><tr><td align="left">Exponent ::=</td><td align="left">"e" SignedInteger | "E" SignedInteger</td></tr><tr><td align="left">SignedInteger ::=</td><td align="left">Sign Integer | Integer</td></tr><tr><td align="left">LeftBracket ::=</td><td align="left">OCTET − "[" (LEFT SQUARE BRACKET)</td></tr><tr><td align="left">RightBracket ::=</td><td align="left">OCTET − "]" (RIGHT SQUARE BRACKET)</td></tr><tr><td align="left">SpaceChar ::=</td><td align="left">OCTET − " " (SPACE)</td></tr><tr><td align="left">Tilde ::=</td><td align="left">OCTET − "˜" (TILDE)</td></tr><tr><td align="left">Plus ::=</td><td align="left">OCTET − "+" (PLUS)</td></tr><tr><td align="left">Dot ::=</td><td align="left">OCTET − "." (FULL STOP)</td></tr></tbody></table></div><p>
The string "[a b c d]" represents a graphical transformation of the glyphs
in the font by the matrix
</p><div class="informaltable"><table border="0"><colgroup><col align="left" class="c1" /></colgroup><tbody><tr><td align="left">[ a b 0 ]</td></tr><tr><td align="left">[ c d 0 ]</td></tr><tr><td align="left">[ 0 0 1 ]</td></tr></tbody></table></div><p>
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
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.
</p><p>
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:
</p><div class="blockquote"><blockquote class="blockquote"><p>
PIXEL_SIZE_MATRIX = [Sx 0 0 Sy] * POINT_SIZE_MATRIX
</p></blockquote></div><p>
where
</p><div class="blockquote"><blockquote class="blockquote"><p>
Sx = RESOLUTION_X / 72.27
</p><p>
Sy = RESOLUTION_Y / 72.27
</p></blockquote></div><p>
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.
</p><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Metrics_and_Font_Properties"></a>Metrics and Font Properties</h2></div></div></div><p>
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.
</p><p>
Notes on properties and metrics:
</p><p>
The per-char ink metrics (lbearing, rbearing, ascent, and descent)
represent the ink extent of the transformed glyph around its origin.
</p><p>
The per-char width is the x component of the transformed character width.
</p><p>
The font ascent and descent are the y component of the transformed font
ascent or descent.
</p><p>
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
</p><pre class="literallayout">
-misc-fixed-medium-r-normal--0-[2e1 0 0.0 +10.0]-72-72-c-0-iso8859-1
</pre><p>
the resulting FONT property might be
</p><pre class="literallayout">
-misc-fixed-medium-r-normal--[19.9 0 0 10]-[20 0 0 10]-72-72-c-0-iso8859-1
</pre><p>
The FONT property will always include matrices in both the PIXEL_SIZE
and the POINT_SIZE fields.
</p><p>
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.
</p><p>
There will always be 2 new font properties defined, RAW_ASCENT and
RAW_DESCENT, that hold the ascent and descent in 1000 pixel metrics.
</p><p>
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.
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="Scalable_Fonts"></a>Chapter 5. Scalable Fonts</h2></div></div></div><p>
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).
</p><p>
The following definitions are useful for discussing scalable fonts:
</p><p>
<code class="function">Well-formed XLFD pattern</code>
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
<span class="bold"><strong>Well-formed XLFD pattern</strong></span>
</p><p>
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.
</p></li></ul></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
<code class="function">Scalable font name</code>
</p><p>
A well-formed XLFD pattern containing no wildcards and containing the
digit "0" in the PIXEL_SIZE, POINT_SIZE, and AVERAGE_WIDTH fields.
</p></li></ul></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
<code class="function">Scalable fields</code>
</p><p>
The XLFD fields PIXEL_SIZE, POINT_SIZE, RESOLUTION_X,
RESOLUTION_Y, and AVERAGE_WIDTH.
</p></li></ul></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
<code class="function">Derived instance</code>
</p><p>
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.
</p></li></ul></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
<code class="function">Global list</code>
</p><p>
The list of names that would be returned by an X server for a
<code class="function">ListFonts</code>
protocol request on the pattern "*" if there were no protocol
restrictions on the total number of names returned.
</p></li></ul></div><p>
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.
</p><p>
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.
</p><p>
The X protocol request
<code class="function">OpenFont</code>
on a scalable font name returns a font corresponding to an
implementation-dependent derived instance of that font name.
</p><p>
The X protocol request
<code class="function">ListFonts</code>
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.
<code class="function">ListFonts</code>
returns the resulting list.
</p><p>
For example, given the global list:
</p><pre class="literallayout">
-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
</pre><p>
a <code class="function">ListFonts</code> request with the pattern:
</p><pre class="literallayout">
-*-Times-*-R-Normal--*-120-100-100-P-*-ISO8859-1
</pre><p>
would return:
</p><pre class="literallayout">
-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
</pre><p>
<code class="function">ListFonts</code>
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.
</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="Polymorphic_Fonts"></a>Chapter 6. Polymorphic Fonts</h2></div></div></div><p>
Fonts that can be varied in ways other than size or resolution are called
<span class="emphasis"><em>polymorphic fonts.</em></span> 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.
</p><p>
To support polymorphic fonts, special values indicating variability are
defined for the following XLFD fields:
</p><div class="blockquote"><blockquote class="blockquote"><p>
WEIGHT_NAME
</p><p>
SLANT
</p><p>
SETWIDTH_NAME
</p><p>
ADD_STYLE_NAME
</p></blockquote></div><p>
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.
</p><p>
The font-matching algorithms for a font with polymorphic fields are
identical to the matching algorithms for a font with scalable fields.
</p><p>
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.
</p><p>
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.
</p><p>
Examples:
</p><p>
The Adobe Myriad MM font program has width and weight axes. Weight can
vary from 215 to 830, and width from 300 to 700.
</p><pre class="literallayout">
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
</pre><p>
The Adobe Minion MM Italic font program has width, weight, and optical
size axes.
</p><pre class="literallayout">
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
</pre><p>
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.
</p><pre class="literallayout">
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
</pre><p>
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.
</p><pre class="literallayout">
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
</pre><p>
If an axis allows negative values, a client requests a negative value by
using "~" (TILDE) as a minus sign.
</p><p>
Axis types can be registered with the X Consortium, along with their
semantics.
</p><p>
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
<span class="emphasis"><em>normal</em></span> or
<span class="emphasis"><em>medium</em></span> 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.
</p><p>
The result of specifying an out-of-range value for a polymorphic field is
undefined. The font source may treat this as a
<code class="function">BadName</code> error, treat the
value as if it were the closest legal value, or extrapolate to try to
accommodate the value.
</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="Affected_Elements_of_Xlib_and_the_X_Protocol"></a>Chapter 7. Affected Elements of Xlib and the X Protocol</h2></div></div></div><p>
The following X protocol requests must support the XLFD conventions:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
<code class="function">OpenFont</code>
- for the name argument
</p></li><li class="listitem"><p>
<code class="function">ListFonts</code>
- for the pattern argument
</p></li><li class="listitem"><p>
<code class="function">ListFontsWithInfo</code>
- for the pattern argument
</p></li></ul></div><p>
In addition,
the following Xlib functions must support the XLFD conventions:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
<a href="/libX11/libX11/libX11.html#XLoadFont" class="olink"><code class="function">XLoadFont</code></a>
- for the name argument
</p></li><li class="listitem"><p>
<a href="/libX11/libX11/libX11.html#XListFontsWithInfo" class="olink"><code class="function">XListFontsWithInfo</code></a>
- for the pattern argument
</p></li><li class="listitem"><p>
<a href="/libX11/libX11/libX11.html#XLoadQueryFont" class="olink"><code class="function">XLoadQueryFont</code></a>
- for the name argument
</p></li><li class="listitem"><p>
<a href="/libX11/libX11/libX11.html#XListFonts" class="olink"><code class="function">XListFonts</code></a>
- for the pattern argument
</p></li></ul></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="BDF_Conformance"></a>Chapter 8. BDF Conformance</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="sect1"><a href="#XLFD_Conformance_Requirements">XLFD Conformance Requirements</a></span></dt><dt><span class="sect1"><a href="#FONT_ASCENT_FONT_DESCENT_and_DEFAULT_CHAR">FONT_ASCENT, FONT_DESCENT, and DEFAULT_CHAR</a></span></dt><dd><dl><dt><span class="sect2"><a href="#FONT_ASCENT">FONT_ASCENT</a></span></dt><dt><span class="sect2"><a href="#FONT_DESCENT">FONT_DESCENT</a></span></dt><dt><span class="sect2"><a href="#DEFAULT_CHAR">DEFAULT_CHAR</a></span></dt></dl></dd></dl></div><p>
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.
</p><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="XLFD_Conformance_Requirements"></a>XLFD Conformance Requirements</h2></div></div></div><p>
A BDF font conforms to the XLFD specification if and only if the
following conditions are satisfied:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
The value for the BDF item <code class="function">FONT</code> conforms to the syntax
and semantic definition of a XLFD
<code class="function">FontName</code>
string.
</p></li><li class="listitem"><p>
The
<code class="function">FontName</code>
begins with the X
<code class="function">FontNameRegistry</code>
prefix: "-".
</p></li><li class="listitem"><p>
All XLFD
<code class="function">FontName</code>
fields are defined.
</p></li><li class="listitem"><p>
Any FontProperties provided conform in name and semantics to the XLFD
<code class="function">FontProperty</code>
definitions.
</p></li></ul></div><p>
A simple method of testing for conformance would entail verifying that the
<code class="function">FontNameRegistry</code>
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.
</p></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="FONT_ASCENT_FONT_DESCENT_and_DEFAULT_CHAR"></a>FONT_ASCENT, FONT_DESCENT, and DEFAULT_CHAR</h2></div></div></div><p>
FONT_ASCENT, FONT_DESCENT, and DEFAULT_CHAR are provided in the BDF
specification as properties that are moved to the
<code class="function">XFontStruct</code>
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.
</p><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FONT_ASCENT"></a>FONT_ASCENT</h3></div></div></div><p>
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 <span class="emphasis"><em>n</em></span> is at [X,Y],
then the origin of the next line <span class="emphasis"><em>m = n + 1</em></span>
(allowing for a possible font change) is
[X, Y + FONT_DESCENTn + FONT_ASCENTm].
</p><p>
FONT_ASCENT can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (FONT_ASCENT undefined) then
FONT_ASCENT = maximum ascent
</pre><p>
where maximum ascent is the maximum ascent (above the baseline)
in pixels of any glyph in the font.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="FONT_DESCENT"></a>FONT_DESCENT</h3></div></div></div><p>
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
<span class="emphasis"><em>n</em></span> is at [X,Y],
then the origin of the next line <span class="emphasis"><em>m = n+1</em></span>
(allowing for a possible font change) is
[X, Y + FONT_DESCENTn + FONT_ASCENTm].
</p><p>
The logical extent of the font is inclusive between the Y-coordinate values:
Y - FONT_ASCENT and Y + FONT_DESCENT + 1.
</p><p>
FONT_DESCENT can be approximated if not provided as a font property,
according to the following algorithm:
</p><pre class="literallayout">
if (FONT_DESCENT undefined) then
FONT_DESCENT = maximum descent
</pre><p>
where maximum descent is the maximum descent (below the baseline)
in pixels of any glyph in the font.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="DEFAULT_CHAR"></a>DEFAULT_CHAR</h3></div></div></div><p>
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.
</p><p>
DEFAULT_CHAR cannot be approximated if not provided as a font property.
</p></div></div></div></div></body></html>