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18 | <!ENTITY version SYSTEM "version.sgml"> | |
19 | ]> | |
20 | <!-- | |
21 | $Id$ | |
22 | ||
23 | Copyright © 2003 Keith Packard | |
24 | ||
25 | Permission to use, copy, modify, distribute, and sell this software and its | |
26 | documentation for any purpose is hereby granted without fee, provided that | |
27 | the above copyright notice appear in all copies and that both that | |
28 | copyright notice and this permission notice appear in supporting | |
29 | documentation, and that the name of Keith Packard not be used in | |
30 | advertising or publicity pertaining to distribution of the software without | |
31 | specific, written prior permission. Keith Packard makes no | |
32 | representations about the suitability of this software for any purpose. It | |
33 | is provided "as is" without express or implied warranty. | |
34 | ||
35 | KEITH PACKARD DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, | |
36 | INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO | |
37 | EVENT SHALL KEITH PACKARD BE LIABLE FOR ANY SPECIAL, INDIRECT OR | |
38 | CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, | |
39 | DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER | |
40 | TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR | |
41 | PERFORMANCE OF THIS SOFTWARE. | |
42 | --> | |
43 | <article> | |
44 | <title>Fontconfig Developers Reference, Version &version; </title> | |
45 | <artheader> | |
46 | <author> | |
47 | <firstname>Keith</firstname> | |
48 | <surname>Packard</surname> | |
49 | <affiliation><orgname> | |
50 | HP Cambridge Research Lab | |
51 | </orgname></affiliation> | |
52 | </author> | |
53 | <authorinitials>KRP</authorinitials> | |
54 | <productname>Fontconfig</productname> | |
55 | <productnumber>&version;</productnumber> | |
56 | <LegalNotice> | |
57 | <simpara> | |
58 | Copyright © 2002 Keith Packard | |
59 | </simpara><simpara> | |
60 | Permission to use, copy, modify, distribute, and sell this software and its | |
61 | documentation for any purpose is hereby granted without fee, provided that | |
62 | the above copyright notice appear in all copies and that both that | |
63 | copyright notice and this permission notice appear in supporting | |
64 | documentation, and that the name of Keith Packard not be used in | |
65 | advertising or publicity pertaining to distribution of the software without | |
66 | specific, written prior permission. Keith Packard makes no | |
67 | representations about the suitability of this software for any purpose. It | |
68 | is provided "as is" without express or implied warranty. | |
69 | </simpara><simpara> | |
70 | KEITH PACKARD DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, | |
71 | INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO | |
72 | EVENT SHALL KEITH PACKARD BE LIABLE FOR ANY SPECIAL, INDIRECT OR | |
73 | CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, | |
74 | DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER | |
75 | TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR | |
76 | PERFORMANCE OF THIS SOFTWARE. | |
77 | </simpara> | |
78 | </LegalNotice> | |
79 | </artheader> | |
80 | <sect1><title>DESCRIPTION</title> | |
81 | <para> | |
82 | Fontconfig is a library designed to provide system-wide font configuration, | |
83 | customization and application access. | |
84 | </para> | |
85 | </sect1> | |
86 | <sect1><title>FUNCTIONAL OVERVIEW</title> | |
87 | <para> | |
88 | Fontconfig contains two essential modules, the configuration module which | |
89 | builds an internal configuration from XML files and the matching module | |
90 | which accepts font patterns and returns the nearest matching font. | |
91 | </para> | |
92 | <sect2><title>FONT CONFIGURATION</title> | |
93 | <para> | |
94 | The configuration module consists of the FcConfig datatype, libexpat and | |
95 | FcConfigParse which walks over an XML tree and ammends a configuration with | |
96 | data found within. From an external perspective, configuration of the | |
97 | library consists of generating a valid XML tree and feeding that to | |
98 | FcConfigParse. The only other mechanism provided to applications for | |
99 | changing the running configuration is to add fonts and directories to the | |
100 | list of application-provided font files. | |
101 | </para><para> | |
102 | The intent is to make font configurations relatively static, and shared by | |
103 | as many applications as possible. It is hoped that this will lead to more | |
104 | stable font selection when passing names from one application to another. | |
105 | XML was chosen as a configuration file format because it provides a format | |
106 | which is easy for external agents to edit while retaining the correct | |
107 | structure and syntax. | |
108 | </para><para> | |
109 | Font configuration is separate from font matching; applications needing to | |
110 | do their own matching can access the available fonts from the library and | |
111 | perform private matching. The intent is to permit applications to pick and | |
112 | choose appropriate functionality from the library instead of forcing them to | |
113 | choose between this library and a private configuration mechanism. The hope | |
114 | is that this will ensure that configuration of fonts for all applications | |
115 | can be centralized in one place. Centralizing font configuration will | |
116 | simplify and regularize font installation and customization. | |
117 | </para> | |
118 | </sect2> | |
119 | <sect2> | |
120 | <title>FONT PROPERTIES</title> | |
121 | <para> | |
122 | While font patterns may contain essentially any properties, there are some | |
123 | well known properties with associated types. Fontconfig uses some of these | |
124 | properties for font matching and font completion. Others are provided as a | |
125 | convenience for the applications rendering mechanism. | |
126 | </para> | |
127 | <programlisting> | |
128 | Property Definitions | |
129 | ||
130 | Property CPP Symbol Type Description | |
131 | ---------------------------------------------------- | |
132 | family FC_FAMILY String Font family names | |
133 | familylang FC_FAMILYLANG String Language cooresponding to | |
134 | each family name | |
135 | style FC_STYLE String Font style. Overrides weight | |
136 | and slant | |
137 | stylelang FC_STYLELANG String Language cooresponding to | |
138 | each style name | |
139 | fullname FC_FULLNAME String Font face full name where | |
140 | different from family and | |
141 | family + style | |
142 | fullnamelang FC_FULLNAMELANG String Language cooresponding to | |
143 | each fullname | |
144 | slant FC_SLANT Int Italic, oblique or roman | |
145 | weight FC_WEIGHT Int Light, medium, demibold, | |
146 | bold or black | |
147 | size FC_SIZE Double Point size | |
148 | width FC_WIDTH Int Condensed, normal or expanded | |
149 | aspect FC_ASPECT Double Stretches glyphs horizontally | |
150 | before hinting | |
151 | pixelsize FC_PIXEL_SIZE Double Pixel size | |
152 | spacing FC_SPACING Int Proportional, dual-width, | |
153 | monospace or charcell | |
154 | foundry FC_FOUNDRY String Font foundry name | |
155 | antialias FC_ANTIALIAS Bool Whether glyphs can be | |
156 | antialiased | |
157 | hinting FC_HINTING Bool Whether the rasterizer should | |
158 | use hinting | |
159 | hintstyle FC_HINT_STYLE Int Automatic hinting style | |
160 | verticallayout FC_VERTICAL_LAYOUT Bool Use vertical layout | |
161 | autohint FC_AUTOHINT Bool Use autohinter instead of | |
162 | normal hinter | |
163 | globaladvance FC_GLOBAL_ADVANCE Bool Use font global advance data | |
164 | file FC_FILE String The filename holding the font | |
165 | index FC_INDEX Int The index of the font within | |
166 | the file | |
167 | ftface FC_FT_FACE FT_Face Use the specified FreeType | |
168 | face object | |
169 | rasterizer FC_RASTERIZER String Which rasterizer is in use | |
170 | outline FC_OUTLINE Bool Whether the glyphs are outlines | |
171 | scalable FC_SCALABLE Bool Whether glyphs can be scaled | |
172 | scale FC_SCALE Double Scale factor for point->pixel | |
173 | conversions | |
174 | dpi FC_DPI Double Target dots per inch | |
175 | rgba FC_RGBA Int unknown, rgb, bgr, vrgb, | |
176 | vbgr, none - subpixel geometry | |
177 | minspace FC_MINSPACE Bool Eliminate leading from line | |
178 | spacing | |
179 | charset FC_CHARSET CharSet Unicode chars encoded by | |
180 | the font | |
181 | lang FC_LANG String List of RFC-3066-style | |
182 | languages this font supports | |
183 | fontversion FC_FONTVERSION Int Version number of the font | |
184 | capability FC_CAPABILITY String List of layout capabilities in | |
185 | the font | |
186 | embolden FC_EMBOLDEN Bool Rasterizer should | |
187 | synthetically embolden the font | |
188 | </programlisting> | |
189 | </sect2> | |
190 | </sect1> | |
191 | <sect1><title>Datatypes</title> | |
192 | <para> | |
193 | Fontconfig uses abstract datatypes to hide internal implementation details | |
194 | for most data structures. A few structures are exposed where appropriate. | |
195 | </para> | |
196 | <sect2><title>FcChar8, FcChar16, FcChar32, FcBool</title> | |
197 | <para> | |
198 | These are primitive datatypes; the FcChar* types hold precisely the number | |
199 | of bits stated (if supported by the C implementation). FcBool holds | |
200 | one of two CPP symbols: FcFalse or FcTrue. | |
201 | </para> | |
202 | </sect2> | |
203 | <sect2><title>FcMatrix</title> | |
204 | <para> | |
205 | An FcMatrix holds an affine transformation, usually used to reshape glyphs. | |
206 | A small set of matrix operations are provided to manipulate these. | |
207 | <programlisting> | |
208 | typedef struct _FcMatrix { | |
209 | double xx, xy, yx, yy; | |
210 | } FcMatrix; | |
211 | </programlisting> | |
212 | </para> | |
213 | </sect2> | |
214 | <sect2><title>FcCharSet</title> | |
215 | <para> | |
216 | An FcCharSet is an abstract type that holds the set of encoded unicode chars | |
217 | in a font. Operations to build and compare these sets are provided. | |
218 | </para> | |
219 | </sect2> | |
220 | <sect2><title>FcType</title> | |
221 | <para> | |
222 | Tags the kind of data stored in an FcValue. | |
223 | </para> | |
224 | </sect2> | |
225 | <sect2><title>FcValue</title> | |
226 | <para> | |
227 | An FcValue object holds a single value with one of a number of different | |
228 | types. The 'type' tag indicates which member is valid. | |
229 | <programlisting> | |
230 | typedef struct _FcValue { | |
231 | FcType type; | |
232 | union { | |
233 | const FcChar8 *s; | |
234 | int i; | |
235 | FcBool b; | |
236 | double d; | |
237 | const FcMatrix *m; | |
238 | const FcCharSet *c; | |
239 | } u; | |
240 | } FcValue; | |
241 | </programlisting> | |
242 | <programlisting> | |
243 | FcValue Members | |
244 | ||
245 | Type Union member Datatype | |
246 | -------------------------------- | |
247 | FcTypeVoid (none) (none) | |
248 | FcTypeInteger i int | |
249 | FcTypeDouble d double | |
250 | FcTypeString s char * | |
251 | FcTypeBool b b | |
252 | FcTypeMatrix m FcMatrix * | |
253 | FcTypeCharSet c FcCharSet * | |
254 | </programlisting> | |
255 | </para> | |
256 | </sect2> | |
257 | <sect2><title>FcPattern</title> | |
258 | <para> | |
259 | holds a set of names with associated value lists; each name refers to a | |
260 | property of a font. FcPatterns are used as inputs to the matching code as | |
261 | well as holding information about specific fonts. Each property can hold | |
262 | one or more values; conventionally all of the same type, although the | |
263 | interface doesn't demand that. | |
264 | </para> | |
265 | </sect2> | |
266 | <sect2><title>FcFontSet</title> | |
267 | <para> | |
268 | <programlisting> | |
269 | typedef struct _FcFontSet { | |
270 | int nfont; | |
271 | int sfont; | |
272 | FcPattern **fonts; | |
273 | } FcFontSet; | |
274 | </programlisting> | |
275 | An FcFontSet contains a list of FcPatterns. Internally fontconfig uses this | |
276 | data structure to hold sets of fonts. Externally, fontconfig returns the | |
277 | results of listing fonts in this format. 'nfont' holds the number of | |
278 | patterns in the 'fonts' array; 'sfont' is used to indicate the size of that | |
279 | array. | |
280 | </para> | |
281 | </sect2> | |
282 | <sect2><title>FcStrSet, FcStrList</title> | |
283 | <para> | |
284 | FcStrSet holds a list of strings that can be appended to and enumerated. | |
285 | Its unique characteristic is that the enumeration works even while strings | |
286 | are appended during enumeration. FcStrList is used during enumeration to | |
287 | safely and correctly walk the list of strings even while that list is edited | |
288 | in the middle of enumeration. | |
289 | </para> | |
290 | </sect2> | |
291 | <sect2><title>FcObjectSet</title> | |
292 | <para> | |
293 | <programlisting> | |
294 | typedef struct _FcObjectSet { | |
295 | int nobject; | |
296 | int sobject; | |
297 | const char **objects; | |
298 | } FcObjectSet; | |
299 | </programlisting> | |
300 | holds a set of names and is used to specify which fields from fonts are | |
301 | placed in the the list of returned patterns when listing fonts. | |
302 | </para> | |
303 | </sect2> | |
304 | <sect2><title>FcObjectType</title> | |
305 | <para> | |
306 | <programlisting> | |
307 | typedef struct _FcObjectType { | |
308 | const char *object; | |
309 | FcType type; | |
310 | } FcObjectType; | |
311 | </programlisting> | |
312 | marks the type of a pattern element generated when parsing font names. | |
313 | Applications can add new object types so that font names may contain the new | |
314 | elements. | |
315 | </para> | |
316 | </sect2> | |
317 | <sect2><title>FcConstant</title> | |
318 | <para> | |
319 | <programlisting> | |
320 | typedef struct _FcConstant { | |
321 | const FcChar8 *name; | |
322 | const char *object; | |
323 | int value; | |
324 | } FcConstant; | |
325 | </programlisting> | |
326 | Provides for symbolic constants for new pattern elements. When 'name' is | |
327 | seen in a font name, an 'object' element is created with value 'value'. | |
328 | </para> | |
329 | </sect2> | |
330 | <sect2><title>FcBlanks</title> | |
331 | <para> | |
332 | holds a list of Unicode chars which are expected to be blank; unexpectedly | |
333 | blank chars are assumed to be invalid and are elided from the charset | |
334 | associated with the font. | |
335 | </para> | |
336 | </sect2> | |
337 | <sect2><title>FcFileCache</title> | |
338 | <para> | |
339 | holds the per-user cache information for use while loading the font | |
340 | database. This is built automatically for the current configuration when | |
341 | that is loaded. Applications must always pass '0' when one is requested. | |
342 | </para> | |
343 | </sect2> | |
344 | <sect2><title>FcConfig</title> | |
345 | <para> | |
346 | holds a complete configuration of the library; there is one default | |
347 | configuration, other can be constructed from XML data structures. All | |
348 | public entry points that need global data can take an optional FcConfig* | |
349 | argument; passing 0 uses the default configuration. FcConfig objects hold two | |
350 | sets of fonts, the first contains those specified by the configuration, the | |
351 | second set holds those added by the application at run-time. Interfaces | |
352 | that need to reference a particulat set use one of the FcSetName enumerated | |
353 | values. | |
354 | </para> | |
355 | </sect2> | |
356 | <sect2><title>FcSetName</title> | |
357 | <para> | |
358 | Specifies one of the two sets of fonts available in a configuration; | |
359 | FcSetSystem for those fonts specified in the configuration and | |
360 | FcSetApplication which holds fonts provided by the application. | |
361 | </para> | |
362 | </sect2> | |
363 | <sect2><title>FcResult</title> | |
364 | <para> | |
365 | Used as a return type for functions manipulating FcPattern objects. | |
366 | <programlisting> | |
367 | FcResult Values | |
368 | Result Code Meaning | |
369 | ----------------------------------------------------------- | |
370 | FcResultMatch Object exists with the specified ID | |
371 | FcResultNoMatch Object doesn't exist at all | |
372 | FcResultTypeMismatch Object exists, but the type doesn't match | |
373 | FcResultNoId Object exists, but has fewer values | |
374 | than specified | |
375 | FcResultOutOfMemory Malloc failed | |
376 | </programlisting> | |
377 | </para> | |
378 | </sect2> | |
379 | <sect2><title>FcAtomic</title> | |
380 | <para> | |
381 | Used for locking access to config files. Provides a safe way to update | |
382 | configuration files. | |
383 | </para> | |
384 | </sect2> | |
385 | </sect1> | |
386 | <sect1><title>FUNCTIONS</title> | |
387 | <para> | |
388 | These are grouped by functionality, often using the main datatype being | |
389 | manipulated. | |
390 | </para> | |
391 | <sect2><title>Initialization</title> | |
392 | <para> | |
393 | These functions provide some control over how the library is initialized. | |
394 | </para> | |
395 | &fcinit; | |
396 | </sect2> | |
397 | <sect2><title>FcPattern</title> | |
398 | <para> | |
399 | An FcPattern is an opaque type that holds both patterns to match against the | |
400 | available fonts, as well as the information about each font. | |
401 | </para> | |
402 | &fcpattern; | |
403 | </sect2> | |
404 | <sect2><title>FcFontSet</title> | |
405 | <para> | |
406 | An FcFontSet simply holds a list of patterns; these are used to return the | |
407 | results of listing available fonts. | |
408 | </para> | |
409 | &fcfontset; | |
410 | </sect2> | |
411 | <sect2><title>FcObjectSet</title> | |
412 | <para> | |
413 | An FcObjectSet holds a list of pattern property names; it is used to | |
414 | indiciate which properties are to be returned in the patterns from | |
415 | FcFontList. | |
416 | </para> | |
417 | &fcobjectset; | |
418 | </sect2> | |
419 | <sect2><title>FreeType specific functions</title> | |
420 | <para> | |
421 | While the fontconfig library doesn't insist that FreeType be used as the | |
422 | rasterization mechanism for fonts, it does provide some convenience | |
423 | functions. | |
424 | </para> | |
425 | &fcfreetype; | |
426 | </sect2> | |
427 | <sect2><title>FcValue</title> | |
428 | <para> | |
429 | FcValue is a structure containing a type tag and a union of all possible | |
430 | datatypes. The tag is an enum of type | |
431 | <emphasis>FcType</emphasis> | |
432 | and is intended to provide a measure of run-time | |
433 | typechecking, although that depends on careful programming. | |
434 | </para> | |
435 | &fcvalue; | |
436 | </sect2> | |
437 | <sect2><title>FcCharSet</title> | |
438 | <para> | |
439 | An FcCharSet is a boolean array indicating a set of unicode chars. Those | |
440 | associated with a font are marked constant and cannot be edited. | |
441 | FcCharSets may be reference counted internally to reduce memory consumption; | |
442 | this may be visible to applications as the result of FcCharSetCopy may | |
443 | return it's argument, and that CharSet may remain unmodifiable. | |
444 | </para> | |
445 | &fccharset; | |
446 | </sect2> | |
447 | <sect2><title>FcMatrix</title> | |
448 | <para> | |
449 | FcMatrix structures hold an affine transformation in matrix form. | |
450 | </para> | |
451 | &fcmatrix; | |
452 | </sect2> | |
453 | <sect2><title>FcConfig</title> | |
454 | <para> | |
455 | An FcConfig object holds the internal representation of a configuration. | |
456 | There is a default configuration which applications may use by passing 0 to | |
457 | any function using the data within an FcConfig. | |
458 | </para> | |
459 | &fcconfig; | |
460 | </sect2> | |
461 | <sect2><title>FcObjectType</title> | |
462 | <para> | |
463 | Provides for applcation-specified font name object types so that new | |
464 | pattern elements can be generated from font names. | |
465 | </para> | |
466 | &fcobjecttype; | |
467 | </sect2> | |
468 | <sect2><title>FcConstant</title> | |
469 | <para> | |
470 | Provides for application-specified symbolic constants for font names. | |
471 | </para> | |
472 | &fcconstant; | |
473 | </sect2> | |
474 | <sect2><title>FcBlanks</title> | |
475 | <para> | |
476 | An FcBlanks object holds a list of Unicode chars which are expected to | |
477 | be blank when drawn. When scanning new fonts, any glyphs which are | |
478 | empty and not in this list will be assumed to be broken and not placed in | |
479 | the FcCharSet associated with the font. This provides a significantly more | |
480 | accurate CharSet for applications. | |
481 | </para> | |
482 | &fcblanks; | |
483 | </sect2> | |
484 | <sect2><title>FcAtomic</title> | |
485 | <para> | |
486 | These functions provide a safe way to update config files, allowing ongoing | |
487 | reading of the old config file while locked for writing and ensuring that a | |
488 | consistent and complete version of the config file is always available. | |
489 | </para> | |
490 | &fcatomic; | |
491 | </sect2> | |
492 | <sect2><title>File and Directory routines</title> | |
493 | <para> | |
494 | These routines work with font files and directories, including font | |
495 | directory cache files. | |
496 | </para> | |
497 | &fcfile; | |
498 | </sect2> | |
499 | <sect2><title>FcStrSet and FcStrList</title> | |
500 | <para> | |
501 | A data structure for enumerating strings, used to list directories while | |
502 | scanning the configuration as directories are added while scanning. | |
503 | </para> | |
504 | &fcstrset; | |
505 | </sect2> | |
506 | <sect2><title>String utilities</title> | |
507 | <para> | |
508 | Fontconfig manipulates many UTF-8 strings represented with the FcChar8 type. | |
509 | These functions are exposed to help applications deal with these UTF-8 | |
510 | strings in a locale-insensitive manner. | |
511 | </para> | |
512 | &fcstring; | |
513 | </sect2> | |
514 | </sect1> | |
515 | </article> |