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fonts-conf(5) |
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fonts.conf − Font configuration files
/etc/fonts/fonts.conf
/etc/fonts/fonts.dtd
/etc/fonts/conf.d
~/.fonts.conf.d
~/.fonts.conf
Fontconfig is a library designed to provide system-wide font configuration, customization and application access.
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
size Double Point size
width Int Condensed, normal or expanded
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
hinting Bool Whether the rasterizer should use hinting
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
lcdfilter Int Type of LCD filter
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 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.
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
OBJTYPES 4096 Display message when value typechecks fail
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.
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 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 "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 configuration file version
number (currently 2).
<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 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.
<CONFIG>
This element provides a place to consolidate 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 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 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 black/white list fonts from being
listed or matched against. It holds acceptfont and
rejectfont elements.
<ACCEPTFONT>
Fonts matched by an acceptfont element are
"whitelisted"; 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
"blacklisted" 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
"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. 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", 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. 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
<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.
<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.
<LANGSET>
This element holds at least one <string> element of a
RFC-3066-style languages or more.
<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
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
<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 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.
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">
|
<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>
<!--
|
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>
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>~/.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>
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.
~/.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.
~/.fonts.conf is the conventional location for per-user font configuration, 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 automatically maintained by fontconfig.
fc-cat(1), fc-cache(1), fc-list(1), fc-match(1), fc-query(1)
Fontconfig version 2.9.0
|
fonts-conf(5) | |