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FONTS-CONF(5) FONTS-CONF(5)
NAME
fonts.conf - Font configuration files
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 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 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 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 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
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 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 lan-
guage 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 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:
-:=:=...
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 preceeded by a '\' character to avoid having them mis-
interpreted. Similarly, values containing '\', '=', '_',
':' and ',' must also have them preceeded by a '\' charac-
ter. 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, fontcon-
fig 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 inter-
preted as a number, and each bit within that value con-
trols 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 vari-
able 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 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 ISO 639 language tag fol-
lowed 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. Lan-
guages 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-terri-
tory orthographies. This includes Azerbaijani, Kurdish,
Pashto, Tigrinya and Chinese.
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:
...
This is the top level element for a font configuration and
can contain , , , and
elements in any order.
This element contains a directory name which will be
scanned for font files to include in the set of available
fonts.
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-'', where is the font
configuration file version number (currently 2).
"
This element contains the name of an additional configura-
tion 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 pro-
cessed in sorted order. When the XML datatype is tra-
versed 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.
This element provides a place to consolidate additional
configuration information. can contain
and elements in any order.
Fonts often include "broken" glyphs which appear in the
encoding but are drawn as blanks on the screen. Within
the element, place each Unicode characters which
is supposed to be blank in an element. Characters
outside of this set which are drawn as blank will be
elided from the set of characters supported by the font.
The element holds an element which indi-
cates the default interval between automatic checks for
font configuration changes. Fontconfig will validate all
of the configuration files and directories and automati-
cally rebuild the internal datastructures when this inter-
val passes.
This element is used to black/white list fonts from being
listed or matched against. It holds acceptfont and
rejectfont elements.
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.
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 elements hold shell-style filename matching patterns
(including ? and *) which match fonts based on their com-
plete 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 elements perform list-style matching on incoming
fonts; that is, they hold a list of elements and associ-
ated 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 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.
"
This element holds first a (possibly empty) list of
elements and then a (possibly empty) list of 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. If 'target' is set to
"scan", then this element applies when the font is scanned
to build the fontconfig database.
"
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 suc-
ceeds 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 element, the target=
attribute in the element selects between matching
the original pattern or the font. "default" selects
whichever target the outer element has selected.
"
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 ele-
ments, 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 pat-
tern 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
, , ,
These elements hold a single value of the indicated type.
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).
This element holds the four elements of an affine
transformation.
Holds a property name. Evaluates to the first value from
the property of the font, not the pattern.
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
hintnone hintstyle 0
hintslight hintstyle 1
hintmedium hintstyle 2
hintfull hintstyle 3
, , , , ,
These elements perform the specified operation on a list
of expression elements. and are boolean, not
bitwise.
, , , , ,
These elements compare two values, producing a boolean
result.
Inverts the boolean sense of its one expression element
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 elements provide a shorthand notation for the set of
common match operations needed to substitute one font fam-
ily for another. They contain a element followed
by optional , and elements.
Fonts matching the element are edited to prepend
the list of ed families before the matching , append the able families after the matching
and append the families to the end of
the family list.
Holds a single font family name
, ,
These hold a list of elements to be used by the
element.
EXAMPLE CONFIGURATION FILE
SYSTEM CONFIGURATION FILE
This is an example of a system-wide configuration file
/usr/share/fonts
/usr/X11R6/lib/X11/fonts
mono
monospace
sans
serif
monospace
sans
~/.fonts.conf
conf.d
local.conf
Times
Times New Roman
serif
Helvetica
Arial
sans
Courier
Courier New
monospace
serif
Times New Roman
sans
Arial
monospace
Andale Mono
USER CONFIGURATION FILE
This is an example of a per-user configuration file that
lives in ~/.fonts.conf
~/.fonts
rgb
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 addi-
tional configuration files managed by external applica-
tions 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 ref-
erences this directory in an directive.
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.
SEE ALSO
fc-cache(1), fc-match(1), fc-list(1)
VERSION
Fontconfig version 2.4.2
02 December 2006 FONTS-CONF(5)