Provided by: fontconfig-config_2.13.1-4.4ubuntu1_all bug


       fonts.conf - Font configuration files




       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.

       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.

       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 (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 glyphs can be scaled
         color           Bool    Whether any glyphs have color
         scale           Double  Scale factor for point->pixel conversions (deprecated)
         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
         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
         fontfeatures    String  List of the feature tags in OpenType to be enabled
         namelang        String  Language name to be used for the default value of
                                 familylang, stylelang, and fullnamelang
         prgname         String  String  Name of the running program
         postscriptname  String  Font family name in PostScript

       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

       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.

       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
         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.


       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">

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

       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 7).

       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.

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

       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.

       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.

       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

       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  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 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 <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.

       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.

       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

       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

       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

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

       This element holds at least one <int> element of an Unicode code point or more.

       This element holds at least one <string> element of a RFC-3066-style languages or more.

       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".

       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
         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
         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.

       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 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.

       Holds a single font family name

       These hold a list of <family> elements to be used by the <alias> element.


       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 -->
            Find fonts in these directories

            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>

            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>

            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.
            <prefer><family>Times New Roman</family></prefer>
            <prefer><family>Courier New</family></prefer>

            Provide required aliases for standard names
            Do these after the users configuration file so that
            any aliases there are used preferentially
            <prefer><family>Times New Roman</family></prefer>
            <prefer><family>Andale Mono</family></prefer>

            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>
            <edit name="family" mode="prepend">
       <match target="pattern">
            <test name="family" compare="eq">
            <edit name="family" mode="prepend">


       This    is    an    example   of   a   per-user   configuration   file   that   lives   in

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

            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>
            use WenQuanYi Zen Hei font when serif is requested for Chinese
                 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">
            <test name="family">
            <edit name="family" mode="prepend">
                 <string>WenQuanYi Zen Hei</string>
            use VL Gothic font when sans-serif is requested for Japanese
            <test name="lang" compare="contains">
            <test name="family">
            <edit name="family" mode="prepend">
                 <string>VL Gothic</string>


       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

       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.


       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  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  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.


       fc-cat(1),   fc-cache(1),   fc-list(1),   fc-match(1),   fc-query(1),    SOURCE_DATE_EPOCH


       Fontconfig version 2.13.1

                                           17 May 2022                              FONTS-CONF(5)