aboutsummaryrefslogtreecommitdiff
path: root/fontconfig/doc/fontconfig-user.sgml
blob: 22d2ad355154b3b97c9681268c6ff92907ccefb1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V3.1//EN" [
<!ENTITY version SYSTEM "version.sgml">
<!ENTITY confdir SYSTEM "confdir.sgml">
]>
<!--
    Copyright © 2003 Keith Packard
   
    Permission to use, copy, modify, distribute, and sell this software and its
    documentation for any purpose is hereby granted without fee, provided that
    the above copyright notice appear in all copies and that both that
    copyright notice and this permission notice appear in supporting
    documentation, and that the name of the author(s) not be used in
    advertising or publicity pertaining to distribution of the software without
    specific, written prior permission.  The authors make no
    representations about the suitability of this software for any purpose.  It
    is provided "as is" without express or implied warranty.
   
    THE AUTHOR(S) DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
    INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
    EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY SPECIAL, INDIRECT OR
    CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
    DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
    TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
    PERFORMANCE OF THIS SOFTWARE.
-->
<refentry>
<refmeta>
  <refentrytitle>fonts-conf</refentrytitle>
  <manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
	<refname>fonts.conf</refname>
	<refpurpose>Font configuration files</refpurpose>
</refnamediv>
<refsynopsisdiv>
<synopsis>
   &confdir;/fonts.conf
   &confdir;/fonts.dtd
   &confdir;/conf.d
   ~/.fonts.conf.d
   ~/.fonts.conf
</synopsis>
</refsynopsisdiv>
<refsect1><title>Description</title>
  <para>
Fontconfig is a library designed to provide system-wide font configuration,
customization and application access.
  </para>
</refsect1>
<refsect1><title>Functional Overview</title>
  <para>
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.
  </para>
  <refsect2><title>Font Configuration</title>
    <para>
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.  
    </para><para>
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.
    </para><para>
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.
    </para>
  </refsect2>
  <refsect2>
    <title>Font Properties</title>
    <para>
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.
    </para>
    <programlisting>
  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
    </programlisting>
  </refsect2>
  <refsect2>
  <title>Font Matching</title>
    <para>
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.
    </para><para> 
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.
    </para><para>
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.
    </para><para>
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.
    </para><para>
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.
    </para><para>
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.
    </para><para>
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.
    </para><para>
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.
    </para><para>
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.
    </para>
  </refsect2>
  <refsect2><title>Font Names</title>
    <para>
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:
    </para>
    <programlisting>
	&lt;families&gt;-&lt;point sizes&gt;:&lt;name1&gt;=&lt;values1&gt;:&lt;name2&gt;=&lt;values2&gt;...
    </programlisting>
    <para>
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:
    </para>
    <programlisting>
  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
    </programlisting>
    <para>
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.
    </para>
  </refsect2>
</refsect1>
<refsect1 id="debug"><title>Debugging Applications</title>
  <para>
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.
  </para>
  <programlisting>
  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
  </programlisting>
  <para>
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.
  </para>
</refsect1>
<refsect1><title>Lang Tags</title>
  <para>
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.
  </para><para>
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.
  </para><para>
For languages used in multiple territories with radically different
character sets, fontconfig includes per-territory orthographies.  This
includes Azerbaijani, Kurdish, Pashto, Tigrinya and Chinese.
  </para>
</refsect1>
<refsect1><title>Configuration File Format</title>
  <para>
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.
  </para><para>
The fontconfig document type definition resides in the external entity
"fonts.dtd"; this is normally stored in the default font configuration
directory (&confdir;).  Each configuration file should contain the
following structure:
    <programlisting>
	&lt;?xml version="1.0"?&gt;
	&lt;!DOCTYPE fontconfig SYSTEM "fonts.dtd"&gt;
	&lt;fontconfig&gt;
	...
	&lt;/fontconfig&gt;
    </programlisting>
  </para>
<refsect2><title><literal>&lt;fontconfig&gt;</literal></title><para>
This is the top level element for a font configuration and can contain
<literal>&lt;dir&gt;</literal>, <literal>&lt;cachedir&gt;</literal>, <literal>&lt;include&gt;</literal>, <literal>&lt;match&gt;</literal> and <literal>&lt;alias&gt;</literal> elements in any order.
  </para></refsect2>
  <refsect2><title><literal>&lt;dir&gt;</literal></title><para>
This element contains a directory name which will be scanned for font files
to include in the set of available fonts.
  </para></refsect2>
  <refsect2><title><literal>&lt;cachedir&gt;</literal></title><para>
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.  The default directory is ``~/.fontconfig''
and it contains the cache files named ``<literal>&lt;hash value&gt;</literal>-<literal>&lt;architecture&gt;</literal>.cache-<literal>&lt;version</literal>'',
where <literal>&lt;version&gt;</literal> is the font configureation file
version number (currently 3).
  </para></refsect2>
  <refsect2><title><literal>&lt;include ignore_missing="no"&gt;</literal></title><para>
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.
  </para></refsect2>
  <refsect2><title><literal>&lt;config&gt;</literal></title><para>
This element provides a place to consolidate additional configuration
information.  <literal>&lt;config&gt;</literal> can contain <literal>&lt;blank&gt;</literal> and <literal>&lt;rescan&gt;</literal> elements in any
order.
  </para></refsect2>
  <refsect2><title><literal>&lt;blank&gt;</literal></title><para>
Fonts often include "broken" glyphs which appear in the encoding but are
drawn as blanks on the screen.  Within the <literal>&lt;blank&gt;</literal> element, place each
Unicode characters which is supposed to be blank in an <literal>&lt;int&gt;</literal> element.
Characters outside of this set which are drawn as blank will be elided from
the set of characters supported by the font.
  </para></refsect2>
  <refsect2><title><literal>&lt;rescan&gt;</literal></title><para>
The <literal>&lt;rescan&gt;</literal> element holds an <literal>&lt;int&gt;</literal> 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.
  </para></refsect2>
  <refsect2><title><literal>&lt;selectfont&gt;</literal></title><para>
This element is used to black/white list fonts from being listed or matched
against.  It holds acceptfont and rejectfont elements.
  </para></refsect2>
  <refsect2><title><literal>&lt;acceptfont&gt;</literal></title><para>
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.
  </para></refsect2>
  <refsect2><title><literal>&lt;rejectfont&gt;</literal></title><para>
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.
  </para></refsect2>
  <refsect2><title><literal>&lt;glob&gt;</literal></title><para>
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.
  </para></refsect2>
  <refsect2><title><literal>&lt;pattern&gt;</literal></title><para>
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.
  </para></refsect2>
  <refsect2><title><literal>&lt;patelt name="property"&gt;</literal></title><para>
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.
  </para></refsect2>
  <refsect2><title><literal>&lt;match target="pattern"&gt;</literal></title><para>
This element holds first a (possibly empty) list of <literal>&lt;test&gt;</literal> elements and then
a (possibly empty) list of <literal>&lt;edit&gt;</literal> 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.
  </para></refsect2>
  <refsect2><title><literal>&lt;test qual="any" name="property" target="default" compare="eq"&gt;</literal></title><para>
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 &lt;match target="font"&gt; element,
the target= attribute in the &lt;test&gt; element selects between matching
the original pattern or the font.  "default" selects whichever target the
outer &lt;match&gt; element has selected.
  </para></refsect2>
  <refsect2><title><literal>&lt;edit name="property" mode="assign" binding="weak"&gt;</literal></title><para>
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 <literal>&lt;test&gt;</literal> 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:
    <programlisting>
  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
    </programlisting>
  </para></refsect2>
  <refsect2><title><literal>&lt;int&gt;</literal>, <literal>&lt;double&gt;</literal>, <literal>&lt;string&gt;</literal>, <literal>&lt;bool&gt;</literal></title><para>
These elements hold a single value of the indicated type.  <literal>&lt;bool&gt;</literal>
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).
  </para></refsect2>
  <refsect2><title><literal>&lt;matrix&gt;</literal></title><para>
This element holds the four <literal>&lt;double&gt;</literal> elements of an affine
transformation.
  </para></refsect2>
  <refsect2><title><literal>&lt;range&gt;</literal></title><para>
This element holds the two <literal>&lt;int&gt;</literal> elements of a range
representation.
  </para></refsect2>
  <refsect2><title><literal>&lt;charset&gt;</literal></title><para>
This element holds at least one <literal>&lt;int&gt;</literal> element of
an Unicode code point or more.
  </para></refsect2>
  <refsect2><title><literal>&lt;langset&gt;</literal></title><para>
This element holds at least one <literal>&lt;string&gt;</literal> element of
a RFC-3066-style languages or more.
  </para></refsect2>
  <refsect2><title><literal>&lt;name&gt;</literal></title><para>
Holds a property name.  Evaluates to the first value from the property of
the font, not the pattern.
  </para></refsect2>
  <refsect2><title><literal>&lt;const&gt;</literal></title><para>
Holds the name of a constant; these are always integers and serve as
symbolic names for common font values:
    <programlisting>
  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
    </programlisting>
      </para>
    </refsect2>
  <refsect2>
      <title><literal>&lt;or&gt;</literal>, <literal>&lt;and&gt;</literal>, <literal>&lt;plus&gt;</literal>, <literal>&lt;minus&gt;</literal>, <literal>&lt;times&gt;</literal>, <literal>&lt;divide&gt;</literal></title>
      <para>
These elements perform the specified operation on a list of expression
elements.  <literal>&lt;or&gt;</literal> and <literal>&lt;and&gt;</literal> are boolean, not bitwise.
      </para>
    </refsect2>
  <refsect2>
    <title><literal>&lt;eq&gt;</literal>, <literal>&lt;not_eq&gt;</literal>, <literal>&lt;less&gt;</literal>, <literal>&lt;less_eq&gt;</literal>, <literal>&lt;more&gt;</literal>, <literal>&lt;more_eq&gt;</literal>, <literal>&lt;contains&gt;</literal>, <literal>&lt;not_contains</literal></title>
    <para>
These elements compare two values, producing a boolean result.
  </para></refsect2>
  <refsect2><title><literal>&lt;not&gt;</literal></title><para>
Inverts the boolean sense of its one expression element
  </para></refsect2>
  <refsect2><title><literal>&lt;if&gt;</literal></title><para>
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.
  </para></refsect2>
  <refsect2><title><literal>&lt;alias&gt;</literal></title><para>
Alias elements provide a shorthand notation for the set of common match
operations needed to substitute one font family for another.  They contain a
<literal>&lt;family&gt;</literal> element followed by optional <literal>&lt;prefer&gt;</literal>, <literal>&lt;accept&gt;</literal> and <literal>&lt;default&gt;</literal>
elements.  Fonts matching the <literal>&lt;family&gt;</literal> element are edited to prepend the
list of <literal>&lt;prefer&gt;</literal>ed families before the matching <literal>&lt;family&gt;</literal>, append the
<literal>&lt;accept&gt;</literal>able families after the matching <literal>&lt;family&gt;</literal> and append the <literal>&lt;default&gt;</literal>
families to the end of the family list.
  </para></refsect2>
  <refsect2><title><literal>&lt;family&gt;</literal></title><para>
Holds a single font family name
  </para></refsect2>
  <refsect2><title><literal>&lt;prefer&gt;</literal>, <literal>&lt;accept&gt;</literal>, <literal>&lt;default&gt;</literal></title><para>
These hold a list of <literal>&lt;family&gt;</literal> elements to be used by the <literal>&lt;alias&gt;</literal> element.
  </para></refsect2>
</refsect1>
<refsect1><title>EXAMPLE CONFIGURATION FILE</title>
  <refsect2><title>System configuration file</title>
    <para>
This is an example of a system-wide configuration file
    </para>
    <programlisting>
&lt;?xml version="1.0"?&gt;
&lt;!DOCTYPE fontconfig SYSTEM "fonts.dtd"&gt;
&lt;!-- &confdir;/fonts.conf file to configure system font access --&gt;
&lt;fontconfig&gt;
&lt;!-- 
	Find fonts in these directories
--&gt;
&lt;dir&gt;/usr/share/fonts&lt;/dir&gt;
&lt;dir&gt;/usr/X11R6/lib/X11/fonts&lt;/dir&gt;

&lt;!--
	Accept deprecated 'mono' alias, replacing it with 'monospace'
--&gt;
&lt;match target="pattern"&gt;
	&lt;test qual="any" name="family"&gt;&lt;string&gt;mono&lt;/string&gt;&lt;/test&gt;
	&lt;edit name="family" mode="assign"&gt;&lt;string&gt;monospace&lt;/string&gt;&lt;/edit&gt;
&lt;/match&gt;

&lt;!--
	Names not including any well known alias are given 'sans'
--&gt;
&lt;match target="pattern"&gt;
	&lt;test qual="all" name="family" mode="not_eq"&gt;sans&lt;/test&gt;
	&lt;test qual="all" name="family" mode="not_eq"&gt;serif&lt;/test&gt;
	&lt;test qual="all" name="family" mode="not_eq"&gt;monospace&lt;/test&gt;
	&lt;edit name="family" mode="append_last"&gt;&lt;string&gt;sans&lt;/string&gt;&lt;/edit&gt;
&lt;/match&gt;

&lt;!--
	Load per-user customization file, but don't complain
	if it doesn't exist
--&gt;
&lt;include ignore_missing="yes"&gt;~/.fonts.conf&lt;/include&gt;

&lt;!--
	Load local customization files, but don't complain
	if there aren't any
--&gt;
&lt;include ignore_missing="yes"&gt;conf.d&lt;/include&gt;
&lt;include ignore_missing="yes"&gt;local.conf&lt;/include&gt;

&lt;!--
	Alias well known font names to available TrueType fonts.
	These substitute TrueType faces for similar Type1
	faces to improve screen appearance.
--&gt;
&lt;alias&gt;
	&lt;family&gt;Times&lt;/family&gt;
	&lt;prefer&gt;&lt;family&gt;Times New Roman&lt;/family&gt;&lt;/prefer&gt;
	&lt;default&gt;&lt;family&gt;serif&lt;/family&gt;&lt;/default&gt;
&lt;/alias&gt;
&lt;alias&gt;
	&lt;family&gt;Helvetica&lt;/family&gt;
	&lt;prefer&gt;&lt;family&gt;Arial&lt;/family&gt;&lt;/prefer&gt;
	&lt;default&gt;&lt;family&gt;sans&lt;/family&gt;&lt;/default&gt;
&lt;/alias&gt;
&lt;alias&gt;
	&lt;family&gt;Courier&lt;/family&gt;
	&lt;prefer&gt;&lt;family&gt;Courier New&lt;/family&gt;&lt;/prefer&gt;
	&lt;default&gt;&lt;family&gt;monospace&lt;/family&gt;&lt;/default&gt;
&lt;/alias&gt;

&lt;!--
	Provide required aliases for standard names
	Do these after the users configuration file so that
	any aliases there are used preferentially
--&gt;
&lt;alias&gt;
	&lt;family&gt;serif&lt;/family&gt;
	&lt;prefer&gt;&lt;family&gt;Times New Roman&lt;/family&gt;&lt;/prefer&gt;
&lt;/alias&gt;
&lt;alias&gt;
	&lt;family&gt;sans&lt;/family&gt;
	&lt;prefer&gt;&lt;family&gt;Arial&lt;/family&gt;&lt;/prefer&gt;
&lt;/alias&gt;
&lt;alias&gt;
	&lt;family&gt;monospace&lt;/family&gt;
	&lt;prefer&gt;&lt;family&gt;Andale Mono&lt;/family&gt;&lt;/prefer&gt;
&lt;/alias&gt;
&lt;/fontconfig&gt;
    </programlisting>
  </refsect2>
  <refsect2><title>User configuration file</title>
    <para>
This is an example of a per-user configuration file that lives in
~/.fonts.conf
    </para>
    <programlisting>
&lt;?xml version="1.0"?&gt;
&lt;!DOCTYPE fontconfig SYSTEM "fonts.dtd"&gt;
&lt;!-- ~/.fonts.conf for per-user font configuration --&gt;
&lt;fontconfig&gt;

&lt;!--
	Private font directory
--&gt;
&lt;dir&gt;~/.fonts&lt;/dir&gt;

&lt;!--
	use rgb sub-pixel ordering to improve glyph appearance on
	LCD screens.  Changes affecting rendering, but not matching
	should always use target="font".
--&gt;
&lt;match target="font"&gt;
	&lt;edit name="rgba" mode="assign"&gt;&lt;const&gt;rgb&lt;/const&gt;&lt;/edit&gt;
&lt;/match&gt;
&lt;/fontconfig&gt;
    </programlisting>
  </refsect2>
</refsect1>
<refsect1><title>Files</title>
  <para>
<emphasis>fonts.conf</emphasis>
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.
  </para>
  <para>
<emphasis>conf.d</emphasis>
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 
&lt;include&gt; directive.
  </para>
  <para>
<emphasis>fonts.dtd</emphasis>
is a DTD that describes the format of the configuration files.
  </para>
  <para>
<emphasis>~/.fonts.conf.d</emphasis>
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.
  </para>
  <para>
<emphasis>~/.fonts.conf</emphasis>
is the conventional location for per-user font configuration, although the
actual location is specified in the global fonts.conf file.
  </para>
  <para>
<emphasis> ~/.fontconfig/*.cache-*</emphasis>
is the conventional repository of font information that isn't found in the
per-directory caches.  This file is automatically maintained by fontconfig.
  </para>
</refsect1>
<refsect1><title>Environment variables</title>
  <para>
<emphasis>FONTCONFIG_FILE</emphasis>
is used to override the default configuration file.
  </para>
  <para>
<emphasis>FONTCONFIG_PATH</emphasis>
is used to override the default configuration directory.
  </para>
  <para>
<emphasis>FC_DEBUG</emphasis>
is used to output the detailed debugging messages. see <link linkend="debug">Debugging Applications</link> section for more details.
  </para>
  <para>
<emphasis>FONTCONFIG_USE_MMAP</emphasis>
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.
  </para>
</refsect1>
<refsect1><title>See Also</title>
  <para>
fc-cat(1), fc-cache(1), fc-list(1), fc-match(1), fc-query(1)
  </para>
</refsect1>
<refsect1><title>Version</title>
	    <para>
Fontconfig version &version;
	    </para>
</refsect1>
</refentry>