SYNOPSIS
/etc/fonts/fonts.conf
/etc/fonts/fonts.dtd
/etc/fonts/conf.d
~/.fonts.conf
DESCRIPTION
Fontconfig is a library designed to provide system-wide font configura-
tion, customization and application access.
FUNCTIONAL OVERVIEW
Fontconfig contains two essential modules, the configuration module
which builds an internal configuration from XML files and the matching
module which accepts font patterns and returns the nearest matching
font.
FONT CONFIGURATION
The configuration module consists of the FcConfig datatype, libexpat
and FcConfigParse which walks over an XML tree and ammends a configura-
tion with data found within. From an external perspective, configura-
tion of the library consists of generating a valid XML tree and feeding
that to FcConfigParse. The only other mechanism provided to applica-
tions for changing the running configuration is to add fonts and direc-
tories to the list of application-provided font files.
The intent is to make font configurations relatively static, and shared
by as many applications as possible. It is hoped that this will lead
to more stable font selection when passing names from one application
to another. XML was chosen as a configuration file format because it
provides a format which is easy for external agents to edit while
retaining the correct structure and syntax.
Font configuration is separate from font matching; applications needing
to do their own matching can access the available fonts from the
library and perform private matching. The intent is to permit applica-
tions to pick and choose appropriate functionality from the library
instead of forcing them to choose between this library and a private
configuration mechanism. The hope is that this will ensure that con-
figuration of fonts for all applications can be centralized in one
place. Centralizing font configuration will simplify and regularize
font installation and customization.
FONT PROPERTIES
While font patterns may contain essentially any properties, there are
some well known properties with associated types. Fontconfig uses some
of these properties for font matching and font completion. Others are
provided as a convenience for the applications rendering mechanism.
Property Type Description
--------------------------------------------------------------
family String Font family names
familylang String Languages cooresponding to each family
hintstyle Int Automatic hinting style
verticallayout Bool Use vertical layout
autohint Bool Use autohinter instead of normal hinter
globaladvance Bool Use font global advance data
file String The filename holding the font
index Int The index of the font within the file
ftface FT_Face Use the specified FreeType face object
rasterizer String Which rasterizer is in use
outline Bool Whether the glyphs are outlines
scalable Bool Whether glyphs can be scaled
scale Double Scale factor for point->pixel conversions
dpi Double Target dots per inch
rgba Int unknown, rgb, bgr, vrgb, vbgr,
none - subpixel geometry
minspace Bool Eliminate leading from line spacing
charset CharSet Unicode chars encoded by the font
lang String List of RFC-3066-style languages this
font supports
fontversion Int Version number of the font
capability String List of layout capabilities in the font
embolden Bool Rasterizer should synthetically embolden the font
FONT MATCHING
Fontconfig performs matching by measuring the distance from a provided
pattern to all of the available fonts in the system. The closest
matching font is selected. This ensures that a font will always be
returned, but doesn't ensure that it is anything like the requested
pattern.
Font matching starts with an application constructed pattern. The
desired attributes of the resulting font are collected together in a
pattern. Each property of the pattern can contain one or more values;
these are listed in priority order; matches earlier in the list are
considered "closer" than matches later in the list.
The initial pattern is modified by applying the list of editing
instructions specific to patterns found in the configuration; each con-
sists of a match predicate and a set of editing operations. They are
executed in the order they appeared in the configuration. Each match
causes the associated sequence of editing operations to be applied.
After the pattern has been edited, a sequence of default substitutions
are performed to canonicalize the set of available properties; this
avoids the need for the lower layers to constantly provide default val-
ues for various font properties during rendering.
The canonical font pattern is finally matched against all available
fonts. The distance from the pattern to the font is measured for each
of several properties: foundry, charset, family, lang, spacing, pixel-
size, style, slant, weight, antialias, rasterizer and outline. This
list is in priority order -- results of comparing earlier elements of
tern. This modified pattern is returned to the application.
The return value contains sufficient information to locate and raster-
ize the font, including the file name, pixel size and other rendering
data. As none of the information involved pertains to the FreeType
library, applications are free to use any rasterization engine or even
to take the identified font file and access it directly.
The match/edit sequences in the configuration are performed in two
passes because there are essentially two different operations necessary
-- the first is to modify how fonts are selected; aliasing families and
adding suitable defaults. The second is to modify how the selected
fonts are rasterized. Those must apply to the selected font, not the
original pattern as false matches will often occur.
FONT NAMES
Fontconfig provides a textual representation for patterns that the
library can both accept and generate. The representation is in three
parts, first a list of family names, second a list of point sizes and
finally a list of additional properties:
<families>-<point sizes>:<name1>=<values1>:<name2>=<values2>...
Values in a list are separated with commas. The name needn't include
either families or point sizes; they can be elided. In addition, there
are symbolic constants that simultaneously indicate both a name and a
value. Here are some examples:
Name Meaning
----------------------------------------------------------
Times-12 12 point Times Roman
Times-12:bold 12 point Times Bold
Courier:italic Courier Italic in the default size
Monospace:matrix=1 .1 0 1 The users preferred monospace font
with artificial obliquing
LANG TAGS
Each font in the database contains a list of languages it supports.
This is computed by comparing the Unicode coverage of the font with the
orthography of each language. Languages are tagged using an RFC-3066
compatible naming and occur in two parts -- the ISO 639 language tag
followed a hyphen and then by the ISO 3166 country code. The hyphen
and country code may be elided.
Fontconfig has orthographies for several languages built into the
library. No provision has been made for adding new ones aside from
rebuilding the library. It currently supports 122 of the 139 languages
named in ISO 639-1, 141 of the languages with two-letter codes from ISO
639-2 and another 30 languages with only three-letter codes. Languages
with both two and three letter codes are provided with only the two
"fonts.dtd"; this is normally stored in the default font configuration
directory (/etc/fonts). Each configuration file should contain the
following structure:
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
...
</fontconfig>
<FONTCONFIG>
This is the top level element for a font configuration and can contain
dir, cache, include, match and alias elements in any order.
DIR
This element contains a directory name which will be scanned for font
files to include in the set of available fonts.
CACHE
This element contains a file name for the per-user cache of font infor-
mation. If it starts with '~', it refers to a file in the users home
directory. This file is used to hold information about fonts that
isn't present in the per-directory cache files. It is automatically
maintained by the fontconfig library. The default for this file is
``~/.fonts.cache-version'', where version is the font configuration
file version number (currently 1).
INCLUDE IGNORE_MISSING= NO""
This element contains the name of an additional configuration file or
directory. If a directory, every file within that directory starting
with a number will be processed in sorted order. When the XML datatype
is traversed by FcConfigParse, the contents of the file(s) will also be
incorporated into the configuration by passing the filename(s) to
FcConfigLoadAndParse. If 'ignore_missing' is set to "yes" instead of
the default "no", a missing file or directory will elicit no warning
message from the library.
CONFIG
This element provides a place to consolodate additional configuration
information. config can contain blank and rescan elements in any
order.
BLANK
Fonts often include "broken" glyphs which appear in the encoding but
are drawn as blanks on the screen. Within the blank element, place
each Unicode characters which is supposed to be blank in an int ele-
ment. Characters outside of this set which are drawn as blank will be
elided from the set of characters supported by the font.
RESCAN
The rescan element holds an int element which indicates the default
glob and pattern elements which are used to match fonts.
REJECTFONT
Fonts matched by an rejectfont element are "blacklisted"; such fonts
are excluded from the set of fonts used to resolve list and match
requests as if they didn't exist in the system. Rejectfont elements
include glob and pattern elements which are used to match fonts.
GLOB
Glob elements hold shell-style filename matching patterns (including ?
and *) which match fonts based on their complete pathnames. This can
be used to exclude a set of directories (/usr/share/fonts/uglyfont*),
or particular font file types (*.pcf.gz), but the latter mechanism
relies rather heavily on filenaming conventions which can't be relied
upon.
PATTERN
Pattern elements perform list-style matching on incoming fonts; that
is, they hold a list of elements and associated values. If all of
those elements have a matching value, then the pattern matches the
font. This can be used to select fonts based on attributes of the font
(scalable, bold, etc), which is a more reliable mechanism than using
file extensions. Pattern elements include patelt elements.
PATELT NAME= PROPERTY""
Patelt elements hold a single pattern element and list of values. They
must have a 'name' attribute which indicates the pattern element name.
Patelt elements include int, double, string, matrix, bool, charset and
const elements.
MATCH TARGET= PATTERN""
This element holds first a (possibly empty) list of test elements and
then a (possibly empty) list of edit elements. Patterns which match
all of the tests are subjected to all the edits. If 'target' is set to
"font" instead of the default "pattern", then this element applies to
the font name resulting from a match rather than a font pattern to be
matched.
TEST QUAL= ANY" NAME="PROPERTY" TARGET="DEFAULT" COMPARE="EQ""
This element contains a single value which is compared with the target
('pattern', 'font' or 'default') property "property" (substitute any of
the property names seen above). 'compare' can be one of "eq", "not_eq",
"less", "less_eq", "more", or "more_eq". 'qual' may either be the
default, "any", in which case the match succeeds if any value associ-
ated with the property matches the test value, or "all", in which case
all of the values associated with the property must match the test
value. When used in a <match target="font"> element, the target=
attribute in the <test> element selects between matching the original
pattern or the font. "default" selects whichever target the outer
<match> element has selected.
EDIT NAME= PROPERTY" MODE="ASSIGN" BINDING="WEAK""
"prepend_first" Insert at head of list Insert at head of list
"append" Append after matching Append at end of list
"append_last" Append at end of list Append at end of list
INT, DOUBLE, STRING, BOOL
These elements hold a single value of the indicated type. bool ele-
ments hold either true or false. An important limitation exists in the
parsing of floating point numbers -- fontconfig requires that the man-
tissa start with a digit, not a decimal point, so insert a leading zero
for purely fractional values (e.g. use 0.5 instead of .5 and -0.5
instead of -.5).
MATRIX
This element holds the four double elements of an affine transforma-
tion.
NAME
Holds a property name. Evaluates to the first value from the property
of the font, not the pattern.
CONST
Holds the name of a constant; these are always integers and serve as
symbolic names for common font values:
Constant Property Value
-------------------------------------
thin weight 0
extralight weight 40
ultralight weight 40
light weight 50
book weight 75
regular weight 80
normal weight 80
medium weight 100
demibold weight 180
semibold weight 180
bold weight 200
extrabold weight 205
black weight 210
heavy weight 210
roman slant 0
italic slant 100
oblique slant 110
ultracondensed width 50
extracondensed width 63
condensed width 75
semicondensed width 87
normal width 100
semiexpanded width 113
expanded width 125
extraexpanded width 150
hintfull hintstyle 3
OR, AND, PLUS, MINUS, TIMES, DIVIDE
These elements perform the specified operation on a list of expression
elements. or and and are boolean, not bitwise.
EQ, NOT_EQ, LESS, LESS_EQ, MORE, MORE_EQ
These elements compare two values, producing a boolean result.
NOT
Inverts the boolean sense of its one expression element
IF
This element takes three expression elements; if the value of the first
is true, it produces the value of the second, otherwise it produces the
value of the third.
ALIAS
Alias elements provide a shorthand notation for the set of common match
operations needed to substitute one font family for another. They con-
tain a family element followed by optional prefer, accept and default
elements. Fonts matching the family element are edited to prepend the
list of prefered families before the matching family, append the
acceptable familys after the matching family and append the default
families to the end of the family list.
FAMILY
Holds a single font family name
PREFER, ACCEPT, DEFAULT
These hold a list of family elements to be used by the alias element.
/article
EXAMPLE CONFIGURATION FILE
SYSTEM CONFIGURATION FILE
This is an example of a system-wide configuration file
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<!-- /etc/fonts/fonts.conf file to configure system font access -->
<fontconfig>
<!--
Find fonts in these directories
-->
<dir>/usr/share/fonts</dir>
<dir>/usr/X11R6/lib/X11/fonts</dir>
<!--
Accept deprecated 'mono' alias, replacing it with 'monospace'
-->
<match target="pattern">
<!--
Load per-user customization file, but don't complain
if it doesn't exist
-->
<include ignore_missing="yes">~/.fonts.conf</include>
<!--
Load local customization files, but don't complain
if there aren't any
-->
<include ignore_missing="yes">conf.d</include>
<include ignore_missing="yes">local.conf</include>
<!--
Alias well known font names to available TrueType fonts.
These substitute TrueType faces for similar Type1
faces to improve screen appearance.
-->
<alias>
<family>Times</family>
<prefer><family>Times New Roman</family></prefer>
<default><family>serif</family></default>
</alias>
<alias>
<family>Helvetica</family>
<prefer><family>Arial</family></prefer>
<default><family>sans</family></default>
</alias>
<alias>
<family>Courier</family>
<prefer><family>Courier New</family></prefer>
<default><family>monospace</family></default>
</alias>
<!--
Provide required aliases for standard names
Do these after the users configuration file so that
any aliases there are used preferentially
-->
<alias>
<family>serif</family>
<prefer><family>Times New Roman</family></prefer>
</alias>
<alias>
<family>sans</family>
<prefer><family>Arial</family></prefer>
</alias>
<alias>
<family>monospace</family>
<prefer><family>Andale Mono</family></prefer>
</alias>
</fontconfig>
<dir>~/.fonts</dir>
<!--
use rgb sub-pixel ordering to improve glyph appearance on
LCD screens. Changes affecting rendering, but not matching
should always use target="font".
-->
<match target="font">
<edit name="rgba" mode="assign"><const>rgb</const></edit>
</match>
</fontconfig>
FILES
fonts.conf contains configuration information for the fontconfig
library consisting of directories to look at for font information as
well as instructions on editing program specified font patterns before
attempting to match the available fonts. It is in xml format.
conf.d is the conventional name for a directory of additional configu-
ration files managed by external applications or the local administra-
tor. The filenames starting with decimal digits are sorted in lexico-
graphic order and used as additional configuration files. All of these
files are in xml format. The master fonts.conf file references this
directory in an <include> directive.
fonts.dtd is a DTD that describes the format of the configuration
files.
~/.fonts.conf is the conventional location for per-user font configura-
tion, although the actual location is specified in the global
fonts.conf file.
~/.fonts.cache-* is the conventional repository of font information
that isn't found in the per-directory caches. This file is automati-
cally maintained by fontconfig.
SEE ALSO
fc-cache(1), fc-match(1), fc-list(1)
VERSION
Fontconfig version 2.3.2
27 April 2005 FONTS-CONF(5)
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