fontconfig-devel.sgml revision a6844aab
1<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook V3.1//EN" [ 2<!ENTITY fcatomic SYSTEM "fcatomic.sgml"> 3<!ENTITY fcblanks SYSTEM "fcblanks.sgml"> 4<!ENTITY fccache SYSTEM "fccache.sgml"> 5<!ENTITY fccharset SYSTEM "fccharset.sgml"> 6<!ENTITY fcconfig SYSTEM "fcconfig.sgml"> 7<!ENTITY fcconstant SYSTEM "fcconstant.sgml"> 8<!ENTITY fcdircache SYSTEM "fcdircache.sgml"> 9<!ENTITY fcfile SYSTEM "fcfile.sgml"> 10<!ENTITY fcfontset SYSTEM "fcfontset.sgml"> 11<!ENTITY fcformat SYSTEM "fcformat.sgml"> 12<!ENTITY fcfreetype SYSTEM "fcfreetype.sgml"> 13<!ENTITY fcinit SYSTEM "fcinit.sgml"> 14<!ENTITY fclangset SYSTEM "fclangset.sgml"> 15<!ENTITY fcmatrix SYSTEM "fcmatrix.sgml"> 16<!ENTITY fcobjectset SYSTEM "fcobjectset.sgml"> 17<!ENTITY fcobjecttype SYSTEM "fcobjecttype.sgml"> 18<!ENTITY fcpattern SYSTEM "fcpattern.sgml"> 19<!ENTITY fcstring SYSTEM "fcstring.sgml"> 20<!ENTITY fcstrset SYSTEM "fcstrset.sgml"> 21<!ENTITY fcvalue SYSTEM "fcvalue.sgml"> 22<!ENTITY version SYSTEM "version.sgml"> 23]> 24<!-- 25 fontconfig/doc/local-fontconfig-devel.sgml 26 27 Copyright © 2003 Keith Packard 28 29 Permission to use, copy, modify, distribute, and sell this software and its 30 documentation for any purpose is hereby granted without fee, provided that 31 the above copyright notice appear in all copies and that both that 32 copyright notice and this permission notice appear in supporting 33 documentation, and that the name of Keith Packard not be used in 34 advertising or publicity pertaining to distribution of the software without 35 specific, written prior permission. Keith Packard makes no 36 representations about the suitability of this software for any purpose. It 37 is provided "as is" without express or implied warranty. 38 39 THE AUTHOR(S) DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, 40 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO 41 EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY SPECIAL, INDIRECT OR 42 CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, 43 DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER 44 TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 45 PERFORMANCE OF THIS SOFTWARE. 46--> 47<article> 48 <title>Fontconfig Developers Reference, Version &version; </title> 49 <artheader> 50 <author> 51 <firstname>Keith</firstname> 52 <surname>Packard</surname> 53 <affiliation><orgname> 54 HP Cambridge Research Lab 55 </orgname></affiliation> 56 </author> 57 <authorinitials>KRP</authorinitials> 58 <productname>Fontconfig</productname> 59 <productnumber>&version;</productnumber> 60 <LegalNotice> 61 <simpara> 62Copyright © 2002 Keith Packard 63 </simpara><simpara> 64Permission to use, copy, modify, distribute, and sell this software and its 65documentation for any purpose is hereby granted without fee, provided that 66the above copyright notice appear in all copies and that both that 67copyright notice and this permission notice appear in supporting 68documentation, and that the name of Keith Packard not be used in 69advertising or publicity pertaining to distribution of the software without 70specific, written prior permission. Keith Packard makes no 71representations about the suitability of this software for any purpose. It 72is provided "as is" without express or implied warranty. 73 </simpara><simpara> 74THE AUTHOR(S) DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, 75INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO 76EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY SPECIAL, INDIRECT OR 77CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, 78DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER 79TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 80PERFORMANCE OF THIS SOFTWARE. 81 </simpara> 82 </LegalNotice> 83 </artheader> 84<sect1><title>DESCRIPTION</title> 85 <para> 86Fontconfig is a library designed to provide system-wide font configuration, 87customization and application access. 88 </para> 89</sect1> 90<sect1><title>FUNCTIONAL OVERVIEW</title> 91 <para> 92Fontconfig contains two essential modules, the configuration module which 93builds an internal configuration from XML files and the matching module 94which accepts font patterns and returns the nearest matching font. 95 </para> 96 <sect2><title>FONT CONFIGURATION</title> 97 <para> 98The configuration module consists of the FcConfig datatype, libexpat and 99FcConfigParse which walks over an XML tree and ammends a configuration with 100data found within. From an external perspective, configuration of the 101library consists of generating a valid XML tree and feeding that to 102FcConfigParse. The only other mechanism provided to applications for 103changing the running configuration is to add fonts and directories to the 104list of application-provided font files. 105 </para><para> 106The intent is to make font configurations relatively static, and shared by 107as many applications as possible. It is hoped that this will lead to more 108stable font selection when passing names from one application to another. 109XML was chosen as a configuration file format because it provides a format 110which is easy for external agents to edit while retaining the correct 111structure and syntax. 112 </para><para> 113Font configuration is separate from font matching; applications needing to 114do their own matching can access the available fonts from the library and 115perform private matching. The intent is to permit applications to pick and 116choose appropriate functionality from the library instead of forcing them to 117choose between this library and a private configuration mechanism. The hope 118is that this will ensure that configuration of fonts for all applications 119can be centralized in one place. Centralizing font configuration will 120simplify and regularize font installation and customization. 121 </para> 122 </sect2> 123 <sect2> 124 <title>FONT PROPERTIES</title> 125 <para> 126While font patterns may contain essentially any properties, there are some 127well known properties with associated types. Fontconfig uses some of these 128properties for font matching and font completion. Others are provided as a 129convenience for the applications rendering mechanism. 130 </para> 131 <programlisting> 132 Property Definitions 133 134 Property CPP Symbol Type Description 135 ---------------------------------------------------- 136 family FC_FAMILY String Font family names 137 familylang FC_FAMILYLANG String Language cooresponding to 138 each family name 139 style FC_STYLE String Font style. Overrides weight 140 and slant 141 stylelang FC_STYLELANG String Language cooresponding to 142 each style name 143 fullname FC_FULLNAME String Font face full name where 144 different from family and 145 family + style 146 fullnamelang FC_FULLNAMELANG String Language cooresponding to 147 each fullname 148 slant FC_SLANT Int Italic, oblique or roman 149 weight FC_WEIGHT Int Light, medium, demibold, 150 bold or black 151 size FC_SIZE Double Point size 152 width FC_WIDTH Int Condensed, normal or expanded 153 aspect FC_ASPECT Double Stretches glyphs horizontally 154 before hinting 155 pixelsize FC_PIXEL_SIZE Double Pixel size 156 spacing FC_SPACING Int Proportional, dual-width, 157 monospace or charcell 158 foundry FC_FOUNDRY String Font foundry name 159 antialias FC_ANTIALIAS Bool Whether glyphs can be 160 antialiased 161 hinting FC_HINTING Bool Whether the rasterizer should 162 use hinting 163 hintstyle FC_HINT_STYLE Int Automatic hinting style 164 verticallayout FC_VERTICAL_LAYOUT Bool Use vertical layout 165 autohint FC_AUTOHINT Bool Use autohinter instead of 166 normal hinter 167 globaladvance FC_GLOBAL_ADVANCE Bool Use font global advance data 168 file FC_FILE String The filename holding the font 169 index FC_INDEX Int The index of the font within 170 the file 171 ftface FC_FT_FACE FT_Face Use the specified FreeType 172 face object 173 rasterizer FC_RASTERIZER String Which rasterizer is in use 174 outline FC_OUTLINE Bool Whether the glyphs are outlines 175 scalable FC_SCALABLE Bool Whether glyphs can be scaled 176 scale FC_SCALE Double Scale factor for point->pixel 177 conversions 178 dpi FC_DPI Double Target dots per inch 179 rgba FC_RGBA Int unknown, rgb, bgr, vrgb, 180 vbgr, none - subpixel geometry 181 lcdfilter FC_LCD_FILTER Int Type of LCD filter 182 minspace FC_MINSPACE Bool Eliminate leading from line 183 spacing 184 charset FC_CHARSET CharSet Unicode chars encoded by 185 the font 186 lang FC_LANG LangSet Set of RFC-3066-style 187 languages this font supports 188 fontversion FC_FONTVERSION Int Version number of the font 189 capability FC_CAPABILITY String List of layout capabilities in 190 the font 191 embolden FC_EMBOLDEN Bool Rasterizer should 192 synthetically embolden the font 193 </programlisting> 194 </sect2> 195</sect1> 196<sect1><title>Datatypes</title> 197 <para> 198Fontconfig uses abstract datatypes to hide internal implementation details 199for most data structures. A few structures are exposed where appropriate. 200 </para> 201 <sect2><title>FcChar8, FcChar16, FcChar32, FcBool</title> 202 <para> 203These are primitive datatypes; the FcChar* types hold precisely the number 204of bits stated (if supported by the C implementation). FcBool holds 205one of two CPP symbols: FcFalse or FcTrue. 206 </para> 207 </sect2> 208 <sect2><title>FcMatrix</title> 209 <para> 210An FcMatrix holds an affine transformation, usually used to reshape glyphs. 211A small set of matrix operations are provided to manipulate these. 212 <programlisting> 213 typedef struct _FcMatrix { 214 double xx, xy, yx, yy; 215 } FcMatrix; 216 </programlisting> 217 </para> 218 </sect2> 219 <sect2><title>FcCharSet</title> 220 <para> 221An FcCharSet is an abstract type that holds the set of encoded unicode chars 222in a font. Operations to build and compare these sets are provided. 223 </para> 224 </sect2> 225 <sect2><title>FcLangSet</title> 226 <para> 227An FcLangSet is an abstract type that holds the set of languages supported 228by a font. Operations to build and compare these sets are provided. These 229are computed for a font based on orthographic information built into the 230fontconfig library. Fontconfig has orthographies for all of the ISO 639-1 231languages except for MS, NA, PA, PS, QU, RN, RW, SD, SG, SN, SU and ZA. If 232you have orthographic information for any of these languages, please submit 233them. 234 </para> 235 </sect2> 236 <sect2><title>FcLangResult</title> 237 <para> 238An FcLangResult is an enumeration used to return the results of comparing 239two language strings or FcLangSet objects. FcLangEqual means the 240objects match language and territory. FcLangDifferentTerritory means 241the objects match in language but differ in territory. 242FcLangDifferentLang means the objects differ in language. 243 </para> 244 </sect2> 245 <sect2><title>FcType</title> 246 <para> 247Tags the kind of data stored in an FcValue. 248 </para> 249 </sect2> 250 <sect2><title>FcValue</title> 251 <para> 252An FcValue object holds a single value with one of a number of different 253types. The 'type' tag indicates which member is valid. 254 <programlisting> 255 typedef struct _FcValue { 256 FcType type; 257 union { 258 const FcChar8 *s; 259 int i; 260 FcBool b; 261 double d; 262 const FcMatrix *m; 263 const FcCharSet *c; 264 void *f; 265 const FcLangSet *l; 266 } u; 267 } FcValue; 268 </programlisting> 269 <programlisting> 270 FcValue Members 271 272 Type Union member Datatype 273 -------------------------------- 274 FcTypeVoid (none) (none) 275 FcTypeInteger i int 276 FcTypeDouble d double 277 FcTypeString s FcChar8 * 278 FcTypeBool b b 279 FcTypeMatrix m FcMatrix * 280 FcTypeCharSet c FcCharSet * 281 FcTypeFTFace f void * (FT_Face) 282 FcTypeLangSet l FcLangSet * 283 </programlisting> 284 </para> 285 </sect2> 286 <sect2><title>FcPattern</title> 287 <para> 288holds a set of names with associated value lists; each name refers to a 289property of a font. FcPatterns are used as inputs to the matching code as 290well as holding information about specific fonts. Each property can hold 291one or more values; conventionally all of the same type, although the 292interface doesn't demand that. 293 </para> 294 </sect2> 295 <sect2><title>FcFontSet</title> 296 <para> 297 <programlisting> 298 typedef struct _FcFontSet { 299 int nfont; 300 int sfont; 301 FcPattern **fonts; 302 } FcFontSet; 303 </programlisting> 304An FcFontSet contains a list of FcPatterns. Internally fontconfig uses this 305data structure to hold sets of fonts. Externally, fontconfig returns the 306results of listing fonts in this format. 'nfont' holds the number of 307patterns in the 'fonts' array; 'sfont' is used to indicate the size of that 308array. 309 </para> 310 </sect2> 311 <sect2><title>FcStrSet, FcStrList</title> 312 <para> 313FcStrSet holds a list of strings that can be appended to and enumerated. 314Its unique characteristic is that the enumeration works even while strings 315are appended during enumeration. FcStrList is used during enumeration to 316safely and correctly walk the list of strings even while that list is edited 317in the middle of enumeration. 318 </para> 319 </sect2> 320 <sect2><title>FcObjectSet</title> 321 <para> 322 <programlisting> 323 typedef struct _FcObjectSet { 324 int nobject; 325 int sobject; 326 const char **objects; 327 } FcObjectSet; 328 </programlisting> 329holds a set of names and is used to specify which fields from fonts are 330placed in the the list of returned patterns when listing fonts. 331 </para> 332 </sect2> 333 <sect2><title>FcObjectType</title> 334 <para> 335 <programlisting> 336 typedef struct _FcObjectType { 337 const char *object; 338 FcType type; 339 } FcObjectType; 340 </programlisting> 341marks the type of a pattern element generated when parsing font names. 342Applications can add new object types so that font names may contain the new 343elements. 344 </para> 345 </sect2> 346 <sect2><title>FcConstant</title> 347 <para> 348 <programlisting> 349 typedef struct _FcConstant { 350 const FcChar8 *name; 351 const char *object; 352 int value; 353 } FcConstant; 354 </programlisting> 355Provides for symbolic constants for new pattern elements. When 'name' is 356seen in a font name, an 'object' element is created with value 'value'. 357 </para> 358 </sect2> 359 <sect2><title>FcBlanks</title> 360 <para> 361holds a list of Unicode chars which are expected to be blank; unexpectedly 362blank chars are assumed to be invalid and are elided from the charset 363associated with the font. 364 </para> 365 </sect2> 366 <sect2><title>FcFileCache</title> 367 <para> 368holds the per-user cache information for use while loading the font 369database. This is built automatically for the current configuration when 370that is loaded. Applications must always pass '0' when one is requested. 371 </para> 372 </sect2> 373 <sect2><title>FcConfig</title> 374 <para> 375holds a complete configuration of the library; there is one default 376configuration, other can be constructed from XML data structures. All 377public entry points that need global data can take an optional FcConfig* 378argument; passing 0 uses the default configuration. FcConfig objects hold two 379sets of fonts, the first contains those specified by the configuration, the 380second set holds those added by the application at run-time. Interfaces 381that need to reference a particulat set use one of the FcSetName enumerated 382values. 383 </para> 384 </sect2> 385 <sect2><title>FcSetName</title> 386 <para> 387Specifies one of the two sets of fonts available in a configuration; 388FcSetSystem for those fonts specified in the configuration and 389FcSetApplication which holds fonts provided by the application. 390 </para> 391 </sect2> 392 <sect2><title>FcResult</title> 393 <para> 394Used as a return type for functions manipulating FcPattern objects. 395 <programlisting> 396 FcResult Values 397 Result Code Meaning 398 ----------------------------------------------------------- 399 FcResultMatch Object exists with the specified ID 400 FcResultNoMatch Object doesn't exist at all 401 FcResultTypeMismatch Object exists, but the type doesn't match 402 FcResultNoId Object exists, but has fewer values 403 than specified 404 FcResultOutOfMemory Malloc failed 405 </programlisting> 406 </para> 407 </sect2> 408 <sect2><title>FcAtomic</title> 409 <para> 410Used for locking access to config files. Provides a safe way to update 411configuration files. 412 </para> 413 </sect2> 414 <sect2><title>FcCache</title> 415 <para> 416Holds information about the fonts contained in a single directory. Normal 417applications need not worry about this as caches for font access are 418automatically managed by the library. Applications dealing with cache 419management may want to use some of these objects in their work, however the 420included 'fc-cache' program generally suffices for all of that. 421 </para> 422 </sect2> 423</sect1> 424<sect1><title>FUNCTIONS</title> 425 <para> 426These are grouped by functionality, often using the main datatype being 427manipulated. 428 </para> 429 <sect2><title>Initialization</title> 430 <para> 431These functions provide some control over how the library is initialized. 432 </para> 433 &fcinit; 434 </sect2> 435 <sect2><title>FcPattern</title> 436 <para> 437An FcPattern is an opaque type that holds both patterns to match against the 438available fonts, as well as the information about each font. 439 </para> 440 &fcpattern; 441 &fcformat; 442 </sect2> 443 <sect2><title>FcFontSet</title> 444 <para> 445An FcFontSet simply holds a list of patterns; these are used to return the 446results of listing available fonts. 447 </para> 448 &fcfontset; 449 </sect2> 450 <sect2><title>FcObjectSet</title> 451 <para> 452An FcObjectSet holds a list of pattern property names; it is used to 453indiciate which properties are to be returned in the patterns from 454FcFontList. 455 </para> 456 &fcobjectset; 457 </sect2> 458 <sect2><title>FreeType specific functions</title> 459 <para> 460While the fontconfig library doesn't insist that FreeType be used as the 461rasterization mechanism for fonts, it does provide some convenience 462functions. 463 </para> 464 &fcfreetype; 465 </sect2> 466 <sect2><title>FcValue</title> 467 <para> 468FcValue is a structure containing a type tag and a union of all possible 469datatypes. The tag is an enum of type 470<emphasis>FcType</emphasis> 471and is intended to provide a measure of run-time 472typechecking, although that depends on careful programming. 473 </para> 474 &fcvalue; 475 </sect2> 476 <sect2><title>FcCharSet</title> 477 <para> 478An FcCharSet is a boolean array indicating a set of unicode chars. Those 479associated with a font are marked constant and cannot be edited. 480FcCharSets may be reference counted internally to reduce memory consumption; 481this may be visible to applications as the result of FcCharSetCopy may 482return it's argument, and that CharSet may remain unmodifiable. 483 </para> 484 &fccharset; 485 </sect2> 486 <sect2><title>FcLangSet</title> 487 <para> 488An FcLangSet is a set of language names (each of which include language and 489an optional territory). They are used when selecting fonts to indicate which 490languages the fonts need to support. Each font is marked, using language 491orthography information built into fontconfig, with the set of supported 492languages. 493 </para> 494 &fclangset; 495 </sect2> 496 <sect2><title>FcMatrix</title> 497 <para> 498FcMatrix structures hold an affine transformation in matrix form. 499 </para> 500 &fcmatrix; 501 </sect2> 502 <sect2><title>FcConfig</title> 503 <para> 504An FcConfig object holds the internal representation of a configuration. 505There is a default configuration which applications may use by passing 0 to 506any function using the data within an FcConfig. 507 </para> 508 &fcconfig; 509 </sect2> 510 <sect2><title>FcObjectType</title> 511 <para> 512Provides for applcation-specified font name object types so that new 513pattern elements can be generated from font names. 514 </para> 515 &fcobjecttype; 516 </sect2> 517 <sect2><title>FcConstant</title> 518 <para> 519Provides for application-specified symbolic constants for font names. 520 </para> 521 &fcconstant; 522 </sect2> 523 <sect2><title>FcBlanks</title> 524 <para> 525An FcBlanks object holds a list of Unicode chars which are expected to 526be blank when drawn. When scanning new fonts, any glyphs which are 527empty and not in this list will be assumed to be broken and not placed in 528the FcCharSet associated with the font. This provides a significantly more 529accurate CharSet for applications. 530 </para> 531 &fcblanks; 532 </sect2> 533 <sect2><title>FcAtomic</title> 534 <para> 535These functions provide a safe way to update config files, allowing ongoing 536reading of the old config file while locked for writing and ensuring that a 537consistent and complete version of the config file is always available. 538 </para> 539 &fcatomic; 540 </sect2> 541 <sect2><title>File and Directory routines</title> 542 <para> 543These routines work with font files and directories, including font 544directory cache files. 545 </para> 546 &fcfile; 547 &fcdircache; 548 </sect2> 549 <sect2><title>FcCache routines</title> 550 <para> 551These routines work with font directory caches, accessing their contents in 552limited ways. It is not expected that normal applications will need to use 553these functions. 554 </para> 555 &fccache; 556 </sect2> 557 <sect2><title>FcStrSet and FcStrList</title> 558 <para> 559A data structure for enumerating strings, used to list directories while 560scanning the configuration as directories are added while scanning. 561 </para> 562 &fcstrset; 563 </sect2> 564 <sect2><title>String utilities</title> 565 <para> 566Fontconfig manipulates many UTF-8 strings represented with the FcChar8 type. 567These functions are exposed to help applications deal with these UTF-8 568strings in a locale-insensitive manner. 569 </para> 570 &fcstring; 571 </sect2> 572</sect1> 573</article> 574