FONTS-CONF(5)FONTS-CONF(5)NAME
fonts.conf - Font configuration files
SYNOPSIS
/etc/fonts/fonts.conf
/etc/fonts/fonts.dtd
~/.fonts.conf
DESCRIPTION
Fontconfig is a library designed to provide system-wide
font configuration, customization and application access.
FUNCTIONAL OVERVIEW
Fontconfig contains two essential modules, the configura-
tion module which builds an internal configuration from
XML files and the matching module which accepts font pat-
terns 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 configuration with data found
within. From an external perspective, configuration of
the library consists of generating a valid XML tree and
feeding that to FcConfigParse. The only other mechanism
provided to applications for changing the running configu-
ration is to add fonts and directories 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 selec-
tion 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; appli-
cations needing to do their own matching can access the
available fonts from the library and perform private
matching. The intent is to permit applications 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 configuration of fonts for all applica-
tions can be centralized in one place. Centralizing font
configuration will simplify and regularize font installa-
tion and customization.
FONT PROPERTIES
While font patterns may contain essentially any proper-
ties, 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 name
style String Font style. Overrides weight and slant
slant Int Italic, oblique or roman
weight Int Light, medium, demibold, bold or black
size Double Point size
aspect Double Stretches glyphs horizontally before hinting
pixelsize Double Pixel size
spacing Int Proportional, monospace or charcell
foundry String Font foundry name
antialias Bool Whether glyphs can be antialiased
hinting Bool Whether the rasterizer should use hinting
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
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 pat-
tern. 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 consid-
ered "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 consists 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 values 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, pixelsize, style, slant,
weight, antialias, rasterizer and outline. This list is
in priority order -- results of comparing earlier elements
of this list weigh more heavily than later elements.
There is one special case to this rule; family names are
split into two bindings; strong and weak. Strong family
names are given greater precedence in the match than lang
elements while weak family names are given lower prece-
dence than lang elements. This permits the document
language to drive font selection when any document speci-
fied font is unavailable.
The pattern representing that font is augmented to include
any properties found in the pattern but not found in the
font itself; this permits the application to pass render-
ing instructions or any other data through the matching
system. Finally, the list of editing instructions spe-
cific to fonts found in the configuration are applied to
the pattern. This modified pattern is returned to the
application.
The return value contains sufficient information to locate
and rasterize 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 per-
formed in two passes because there are essentially two
different operations necessary -- the first is to modify
how fonts are selected; aliasing families and adding suit-
able 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 repre-
sentation is in three parts, first a list of family names,
second a list of point sizes and finally a list of addi-
tional 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 cov-
erage of the font with the orthography of each language.
Languages are tagged using an RFC-3066 compatible naming
and occur in two parts -- the ISO639 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.
CONFIGURATION FILE FORMAT
Configuration files for fontconfig are stored in XML for-
mat; this format makes external configuration tools easier
to write and ensures that they will generate syntactically
correct configuration files. As XML files are plain text,
they can also be manipulated by the expert user using a
text editor.
The fontconfig document type definition resides in the
external entity "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 information. 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 con-
figuration file version number (currently 1).
INCLUDE IGNORE_MISSING= NO""
This element contains the name of an additional configura-
tion file. When the XML datatype is traversed by
FcConfigParse, the contents of the file will also be
incorporated into the configuration by passing the file-
name to FcConfigLoadAndParse. If 'ignore_missing' is set
to "yes" instead of the default "no", a missing file 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 element. Characters out-
side 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 interval between automatic checks for font
configuration changes. Fontconfig will validate all of
the configuration files and directories and automatically
rebuild the internal datastructures when this interval
passes.
MATCH TARGET= PATTERN""
This element holds first a (possibly empty) list of test
elements and then a (possibly empty) list of edit ele-
ments. Patterns which match all of the tests are sub-
jected 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" COMPARE="EQ""
This element contains a single value which is compared
with the pattern 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 associated 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.
EDIT NAME= PROPERTY" MODE="ASSIGN" BINDING="WEAK""
This element contains a list of expression elements (any
of the value or operator elements). The expression ele-
ments are evaluated at run-time and modify the property
"property". The modification depends on whether "prop-
erty" was matched by one of the associated test elements,
if so, the modification may affect the first matched
value. Any values inserted into the property are given
the indicated binding. 'mode' is one of:
Mode With Match Without Match
---------------------------------------------------------------------
"assign" Replace matching value Replace all values
"assign_replace" Replace all values Replace all values
"prepend" Insert before matching Insert at head of list
"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 elements hold either true or false. An important
limitation exists in the parsing of floating point numbers
-- fontconfig requires that the mantissa 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
transformation.
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
-------------------------------------
light weight 0
medium weight 100
demibold weight 180
bold weight 200
black weight 210
roman slant 0
italic slant 100
oblique slant 110
proportional spacing 0
mono spacing 100
charcell spacing 110
unknown rgba 0
rgb rgba 1
bgr rgba 2
vrgb rgba 3
vbgr rgba 4
none rgba 5
OR, AND, PLUS, MINUS, TIMES, DIVIDE
These elements perform the specified operation on a list
of expression elements. or and and are boolean, not bit-
wise.
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 fam-
ily for another. They contain 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/X11R6/lib/X11/fonts/truetype</dir>
<dir>/usr/X11R6/lib/X11/fonts/Type1</dir>
<!--
Accept deprecated 'mono' alias, replacing it with 'monospace'
-->
<match target="pattern">
<test qual="any" name="family"><string>mono</string></test>
<edit name="family" mode="assign"><string>monospace</string></edit>
</match>
<!--
Names not including any well known alias are given 'sans'
-->
<match target="pattern">
<test qual="all" name="family" mode="not_eq">sans</test>
<test qual="all" name="family" mode="not_eq">serif</test>
<test qual="all" name="family" mode="not_eq">monospace</test>
<edit name="family" mode="append_last"><string>sans</string></edit>
</match>
<!--
Load per-user customization file, but don't complain
if it doesn't exist
-->
<include ignore_missing="yes">~/.fonts.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>Verdana</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>Verdana</family></prefer>
</alias>
<alias>
<family>monospace</family>
<prefer><family>Andale Mono</family></prefer>
</alias>
</fontconfig>
USER CONFIGURATION FILE
This is an example of a per-user configuration file that
lives in ~/.fonts.conf
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<!-- ~/.fonts.conf for per-user font configuration -->
<fontconfig>
<!--
Private font directory
-->
<dir>~/misc/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.
fonts.dtd is a DTD that describes the format of the con-
figuration files.
~/.fonts.conf is the conventional location for per-user
font configuration, although the actual location is speci-
fied 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 automatically maintained by fontconfig.
VERSION
Fontconfig version 2.2.0
21 April 2003 FONTS-CONF(5)
