                                   fonts-conf

Name

fonts.conf -- Font configuration files

Synopsis

   /etc/fonts
/fonts.conf
   /etc/fonts
/fonts.dtd
   /etc/fonts
/conf.d
   $XDG_CONFIG_HOME/fontconfig/conf.d
   $XDG_CONFIG_HOME/fontconfig/fonts.conf
   ~/.fonts.conf.d
   ~/.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 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 amends 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
configuration 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 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 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 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 corresponding to each family
style           String  Font style. Overrides weight and slant
stylelang       String  Languages corresponding to each style
fullname        String  Font full names (often includes style)
fullnamelang    String  Languages corresponding to each fullname
slant           Int     Italic, oblique or roman
weight          Int     Light, medium, demibold, bold or black
width           Int     Condensed, normal or expanded
size            Double  Point size
aspect          Double  Stretches glyphs horizontally before hinting
pixelsize       Double  Pixel size
spacing         Int     Proportional, dual-width, monospace or charcell
foundry         String  Font foundry name
antialias       Bool    Whether glyphs can be antialiased
hintstyle       Int     Automatic hinting style
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 (deprecated)
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 (deprecated)
outline         Bool    Whether the glyphs are outlines
scalable        Bool    Whether the glyphs are outlines or have color
dpi             Double  Target dots per inch
rgba            Int     unknown, rgb, bgr, vrgb, vbgr,
                        none - subpixel geometry
scale           Double  Scale factor for point->pixel conversions
                        (deprecated)
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
fontformat      String  String name of the font format
embolden        Bool    Rasterizer should synthetically embolden the font
embeddedbitmap  Bool    Use the embedded bitmap instead of the outline
decorative      Bool    Whether the style is a decorative variant
lcdfilter       Int     Type of LCD filter
namelang        String  Language name to be used for the default value of
                        familylang, stylelang, and fullnamelang
fontfeatures    String  List of the feature tags in OpenType to be enabled
prgname         String  String  Name of the running program
postscriptname  String  Font family name in PostScript
color           Bool    Whether any glyphs have color
symbol          Bool    Whether font uses MS symbol-font encoding
fontvariations  String  comma-separated string of axes in variable font
variable        Bool    Wheter font is Variable Font
fonthashint     Bool    Whether the font has hinting
order           Int     Order number of the font
desktop         String  Current desktop name
namedinstance   Bool    Whether font is a named instance
fontwrapper     String  The font wrapper format, current values are WOFF, WOFF2,
                        SFNT for any other SFNT font, and CFF for standalone
                        CFF fonts.
genericfamily   Int     Type of Generic Family


  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 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 precedence
than lang elements. This permits the document language to drive font selection
when any document specified 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 rendering instructions or any other data through the matching system.
Finally, the list of editing instructions specific 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 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


The '\', '-', ':' and ',' characters in family names must be preceded by a '\'
character to avoid having them misinterpreted. Similarly, values containing '\',
'=', '_', ':' and ',' must also have them preceded by a '\' character. The '\'
characters are stripped out of the family name and values as the font name is
read.

Debugging Applications

To help diagnose font and applications problems, fontconfig is built with a
large amount of internal debugging left enabled. It is controlled by means of
the FC_DEBUG environment variable. The value of this variable is interpreted as
a number, and each bit within that value controls different debugging messages.

Name         Value    Meaning
---------------------------------------------------------
MATCH            1    Brief information about font matching
MATCHV           2    Extensive font matching information
EDIT             4    Monitor match/test/edit execution
FONTSET          8    Track loading of font information at startup
CACHE           16    Watch cache files being written
CACHEV          32    Extensive cache file writing information
PARSE           64    (no longer in use)
SCAN           128    Watch font files being scanned to build caches
SCANV          256    Verbose font file scanning information
MEMORY         512    Monitor fontconfig memory usage
CONFIG        1024    Monitor which config files are loaded
LANGSET       2048    Dump char sets used to construct lang values
MATCH2        4096    Display font-matching transformation in patterns


Add the value of the desired debug levels together and assign that (in base 10)
to the FC_DEBUG environment variable before running the application. Output from
these statements is sent to stdout.

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 letter code.

For languages used in multiple territories with radically different character
sets, fontconfig includes per-territory orthographies. This includes
Azerbaijani, Kurdish, Pashto, Tigrinya and Chinese.

Configuration File Format

Configuration files for fontconfig are stored in XML format; 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 "urn:fontconfig:fonts.dtd">
<fontconfig>
...
</fontconfig>


  <fontconfig>

This is the top level element for a font configuration and can contain <dir>,
<cachedir>, <include>, <match> and <alias> elements in any order.

  <dir prefix="default" salt="">

This element contains a directory name which will be scanned for font files to
include in the set of available fonts.

If 'prefix' is set to "default" or "cwd", the current working directory will be
added as the path prefix prior to the value. If 'prefix' is set to "xdg", the
value in the XDG_DATA_HOME environment variable will be added as the path
prefix. please see XDG Base Directory Specification for more details. If
'prefix' is set to "relative", the path of current file will be added prior to
the value.

'salt' property affects to determine cache filename. this is useful for example
when having different fonts sets on same path at container and share fonts from
host on different font path.

  <cachedir prefix="default">

This element contains a directory name that is supposed to be stored or read the
cache of font information. If multiple elements are specified in the
configuration file, the directory that can be accessed first in the list will be
used to store the cache files. If it starts with '~', it refers to a directory
in the users home directory. If 'prefix' is set to "xdg", the value in the
XDG_CACHE_HOME environment variable will be added as the path prefix. please see
XDG Base Directory Specification for more details. The default directory is
``$XDG_CACHE_HOME/fontconfig'' and it contains the cache files named ``<hash
value>-<architecture>.cache-<version>'', where <version> is the fontconfig cache
file version number (currently 11 ).

  <include ignore_missing="no" prefix="default">

This element contains the name of an additional configuration file or directory.
If a directory, every file within that directory starting with an ASCII digit
(U+0030 - U+0039) and ending with the string ``.conf'' 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. If 'prefix' is set to "xdg", the value in the XDG_CONFIG_HOME
environment variable will be added as the path prefix. please see XDG Base
Directory Specification for more details.

  <config>

This element provides a place to consolidate additional configuration
information. <config> can contain <blank> and <rescan> elements in any order.

  <description domain="fontconfig-conf">

This element is supposed to hold strings which describe what a config is used
for. This string can be translated through gettext. 'domain' needs to be set the
proper name to apply then. fontconfig will tries to retrieve translations with
'domain' from gettext.

  <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 outside
of this set which are drawn as blank will be elided from the set of characters
supported by the font.

  <remap-dir prefix="default" as-path="" salt="">

This element contains a directory name where will be mapped as the path
'as-path' in cached information. This is useful if the directory name is an
alias (via a bind mount or symlink) to another directory in the system for which
cached font information is likely to exist.

'salt' property affects to determine cache filename as same as <dir> element.

  <reset-dirs />

This element removes all of fonts directories where added by <dir> elements.
This is useful to override fonts directories from system to own fonts
directories only.

  <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.

  <selectfont>

This element is used to deny/allow list fonts from being listed or matched
against. It holds acceptfont and rejectfont elements. This list is applied only
once when caches is loaded. So if you want to filter out by some patterns,
patterns is evaluated with something in cache only. In other words, target
patterns except "scan" won't takes any effects.

  <acceptfont>

Fonts matched by an acceptfont element are "allowlisted"; such fonts are
explicitly included in the set of fonts used to resolve list and match requests;
including them in this list protects them from being "denylisted" by a
rejectfont element. Acceptfont elements include glob and pattern elements which
are used to match fonts.

  <rejectfont>

Fonts matched by an rejectfont element are "denylisted"; 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. If it starts with '~', it
refers to a directory in the users home directory. 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. Note that globs only apply to
directories, not to individual fonts.

  <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. If 'target' is set to "scan",
then this element applies when the font is scanned to build the fontconfig
database.

  <test qual="any" name="property" target="default" compare="eq">

This element contains a single value which is compared with the target
('pattern', 'font', 'scan' or 'default') property "property" (substitute any of
the property names seen above). 'compare' can be one of "eq", "not_eq", "less",
"less_eq", "more", "more_eq", "contains" or "not_contains". '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. 'ignore-blanks'
takes a boolean value. if 'ignore-blanks' is set "true", any blanks in the
string will be ignored on its comparison. this takes effects only when
compare="eq" or compare="not_eq". 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">

This element contains a list of expression elements (any of the value or
operator elements). The expression elements are evaluated at run-time and modify
the property "property". The modification depends on whether "property" 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 ("strong", "weak" or "same") with "same" binding using the
value from the matched pattern element. '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
"delete"                Delete matching value   Delete all values
"delete_all"            Delete all values       Delete all values


  <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). also xsi:nil attribute is supported
to indicate an empty element.

  <matrix>

This element holds four numerical expressions of an affine transformation. At
their simplest these will be four <double> elements but they can also be more
involved expressions.

  <range>

This element holds the two <int> elements of a range representation.

  <charset>

This element holds at least one <int> element of an Unicode code point or more.
also xsi:nil attribute is supported to indicate an empty element.

  <langset>

This element holds at least one <string> element of a RFC-3066-style languages
or more. also xsi:nil attribute is supported to indicate an empty element.

  <name>

Holds a property name. Evaluates to the first value from the property of the
pattern. If the 'target' attribute is not present, it will default to 'default',
in which case the property is returned from the font pattern during a
target="font" match, and to the pattern during a target="pattern" match. The
attribute can also take the values 'font' or 'pattern' to explicitly choose
which pattern to use. It is an error to use a target of 'font' in a match that
has target="pattern".

  <const>

Holds the name of a constant. also xsi:nil attribute is supported to indicate an
empty element; 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
demilight       weight          55
semilight       weight          55
book            weight          75
regular         weight          80
normal          weight          80
medium          weight          100
demibold        weight          180
semibold        weight          180
bold            weight          200
extrabold       weight          205
ultrabold       weight          205
black           weight          210
heavy           weight          210
extrablack      weight          215
ultrablack      weight          215
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
ultraexpanded   width           200
proportional    spacing         0
dual            spacing         90
mono            spacing         100
charcell        spacing         110
unknown         rgba            0
rgb             rgba            1
bgr             rgba            2
vrgb            rgba            3
vbgr            rgba            4
none            rgba            5
lcdnone         lcdfilter       0
lcddefault      lcdfilter       1
lcdlight        lcdfilter       2
lcdlegacy       lcdfilter       3
hintnone        hintstyle       0
hintslight      hintstyle       1
hintmedium      hintstyle       2
hintfull        hintstyle       3
serif           genericfamily   1
sans-serif      genericfamily   2
monospace       genericfamily   3
cursive         genericfamily   4
fantasy         genericfamily   5
system-ui       genericfamily   6
ui-serif        genericfamily   7
ui-sans-serif   genericfamily   8
ui-monospace    genericfamily   9
ui-rounded      genericfamily   10
emoji           genericfamily   11
math            genericfamily   12
fangsong        genericfamily   13


  <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>, <contains>,
  <not_contains

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 contain a
<family> element followed by optional <prefer>, <accept> and <default> elements.
Fonts matching the <family> element are edited to prepend the list of <prefer>ed
families before the matching <family>, append the <accept>able families 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.

EXAMPLE CONFIGURATION FILE

  System configuration file

This is an example of a system-wide configuration file

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "urn:fontconfig: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">
    <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-serif'
  -->
  <match target="pattern">
    <test qual="all" name="family" compare="not_eq">
      <string>sans-serif</string>
    </test>
    <test qual="all" name="family" compare="not_eq">
      <string>serif</string>
    </test>
    <test qual="all" name="family" compare="not_eq">
      <string>monospace</string>
    </test>
    <edit name="family" mode="append_last">
      <string>sans-serif</string>
    </edit>
  </match>

  <!--
    Load per-user customization file, but don't complain
    if it doesn't exist
  -->
  <include ignore_missing="yes" prefix="xdg">
    fontconfig/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-serif</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-serif</family>
    <prefer>
      <family>Arial</family>
    </prefer>
  </alias>
  <alias>
    <family>monospace</family>
    <prefer>
      <family>Andale Mono</family>
    </prefer>
  </alias>

  <--
    The example of the requirements of OR operator;
    If the 'family' contains 'Courier New' OR 'Courier'
    add 'monospace' as the alternative
  -->
  <match target="pattern">
    <test name="family" compare="eq">
      <string>Courier New</string>
    </test>
    <edit name="family" mode="prepend">
      <string>monospace</string>
    </edit>
  </match>
  <match target="pattern">
    <test name="family" compare="eq">
      <string>Courier</string>
    </test>
    <edit name="family" mode="prepend">
      <string>monospace</string>
    </edit>
  </match>

</fontconfig>


  User configuration file

This is an example of a per-user configuration file that lives in
$XDG_CONFIG_HOME/fontconfig/fonts.conf

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "urn:fontconfig:fonts.dtd">
<!--
  $XDG_CONFIG_HOME/fontconfig/fonts.conf for per-user font configuration
-->
<fontconfig>

  <!--
    Private font directory
  -->
  <dir prefix="xdg">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>
  <!--
    use WenQuanYi Zen Hei font when serif is requested for Chinese
  -->
  <match>
    <!--
      If you don't want to use WenQuanYi Zen Hei font for zh-tw etc,
      you can use zh-cn instead of zh.
      Please note, even if you set zh-cn, it still matches zh.
      if you don't like it, you can use compare="eq"
      instead of compare="contains".
    -->
    <test name="lang" compare="contains">
      <string>zh</string>
    </test>
    <test name="family">
      <string>serif</string>
    </test>
    <edit name="family" mode="prepend">
      <string>WenQuanYi Zen Hei</string>
    </edit>
  </match>
  <!--
    use VL Gothic font when sans-serif is requested for Japanese
  -->
  <match>
    <test name="lang" compare="contains">
      <string>ja</string>
    </test>
    <test name="family">
      <string>sans-serif</string>
    </test>
    <edit name="family" mode="prepend">
      <string>VL Gothic</string>
    </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 configuration
files managed by external applications or the local administrator. The filenames
starting with decimal digits are sorted in lexicographic 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.

$XDG_CONFIG_HOME/fontconfig/conf.d and ~/.fonts.conf.d is the conventional name
for a per-user directory of (typically auto-generated) configuration files,
although the actual location is specified in the global fonts.conf file. please
note that ~/.fonts.conf.d is deprecated now. it will not be read by default in
the future version.

$XDG_CONFIG_HOME/fontconfig/fonts.conf and ~/.fonts.conf is the conventional
location for per-user font configuration, although the actual location is
specified in the global fonts.conf file. please note that ~/.fonts.conf is
deprecated now. it will not be read by default in the future version.

$XDG_CACHE_HOME/fontconfig/*.cache-* and ~/.fontconfig/*.cache-* is the
conventional repository of font information that isn't found in the
per-directory caches. This file is automatically maintained by fontconfig.
please note that ~/.fontconfig/*.cache-* is deprecated now. it will not be read
by default in the future version.

Environment variables

FONTCONFIG_FILE is used to override the default configuration file.

FONTCONFIG_PATH is used to override the default configuration directory.

FONTCONFIG_SYSROOT is used to set a default sysroot directory.

FC_DEBUG is used to output the detailed debugging messages. see [1]Debugging
Applications section for more details.

FC_DBG_MATCH_FILTER is used to filter out the patterns. this takes a
comma-separated list of object names and effects only when FC_DEBUG has MATCH2.
see [2]Debugging Applications section for more details.

FC_LANG is used to specify the default language as the weak binding in the
query. if this isn't set, the default language will be determined from current
locale.

FONTCONFIG_USE_MMAP is used to control the use of mmap(2) for the cache files if
available. this take a boolean value. fontconfig will checks if the cache files
are stored on the filesystem that is safe to use mmap(2). explicitly setting
this environment variable will causes skipping this check and enforce to use or
not use mmap(2) anyway.

SOURCE_DATE_EPOCH is used to ensure fc-cache(1) generates files in a
deterministic manner in order to support reproducible builds. When set to a
numeric representation of UNIX timestamp, fontconfig will prefer this value over
using the modification timestamps of the input files in order to identify which
cache files require regeneration. If SOURCE_DATE_EPOCH is not set (or is newer
than the mtime of the directory), the existing behaviour is unchanged.

See Also

fc-cat(1), fc-cache(1), fc-list(1), fc-match(1), fc-query(1),
[3]SOURCE_DATE_EPOCH.

Version

Fontconfig version 2.18.0

References

   Visible links
   1. file:///tmp/html-2sx4Ix#DEBUG
   2. file:///tmp/html-2sx4Ix#DEBUG
   3. https://reproducible-builds.org/specs/source-date-epoch/
