fontconfig-devel.sgml revision 953daeba
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 fcrange SYSTEM "fcrange.sgml"> 20<!ENTITY fcstring SYSTEM "fcstring.sgml"> 21<!ENTITY fcstrset SYSTEM "fcstrset.sgml"> 22<!ENTITY fcvalue SYSTEM "fcvalue.sgml"> 23<!ENTITY fcweight SYSTEM "fcweight.sgml"> 24<!ENTITY version SYSTEM "version.sgml"> 25]> 26<!-- 27 fontconfig/doc/local-fontconfig-devel.sgml 28 29 Copyright © 2003 Keith Packard 30 31 Permission to use, copy, modify, distribute, and sell this software and its 32 documentation for any purpose is hereby granted without fee, provided that 33 the above copyright notice appear in all copies and that both that 34 copyright notice and this permission notice appear in supporting 35 documentation, and that the name of the author(s) not be used in 36 advertising or publicity pertaining to distribution of the software without 37 specific, written prior permission. The authors make no 38 representations about the suitability of this software for any purpose. It 39 is provided "as is" without express or implied warranty. 40 41 THE AUTHOR(S) DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, 42 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO 43 EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY SPECIAL, INDIRECT OR 44 CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, 45 DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER 46 TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 47 PERFORMANCE OF THIS SOFTWARE. 48--> 49<article> 50 <title>Fontconfig Developers Reference, Version &version; </title> 51 <artheader> 52 <author> 53 <firstname>Keith</firstname> 54 <surname>Packard</surname> 55 <affiliation><orgname> 56 HP Cambridge Research Lab 57 </orgname></affiliation> 58 </author> 59 <authorinitials>KRP</authorinitials> 60 <productname>Fontconfig</productname> 61 <productnumber>&version;</productnumber> 62 <LegalNotice> 63 <simpara> 64Copyright © 2002 Keith Packard 65 </simpara><simpara> 66Permission to use, copy, modify, distribute, and sell this software and its 67documentation for any purpose is hereby granted without fee, provided that 68the above copyright notice appear in all copies and that both that 69copyright notice and this permission notice appear in supporting 70documentation, and that the name of the author(s) not be used in 71advertising or publicity pertaining to distribution of the software without 72specific, written prior permission. The authors make no 73representations about the suitability of this software for any purpose. It 74is provided "as is" without express or implied warranty. 75 </simpara><simpara> 76THE AUTHOR(S) DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, 77INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO 78EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY SPECIAL, INDIRECT OR 79CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, 80DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER 81TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 82PERFORMANCE OF THIS SOFTWARE. 83 </simpara> 84 </LegalNotice> 85 </artheader> 86<sect1><title>DESCRIPTION</title> 87 <para> 88Fontconfig is a library designed to provide system-wide font configuration, 89customization and application access. 90 </para> 91</sect1> 92<sect1><title>FUNCTIONAL OVERVIEW</title> 93 <para> 94Fontconfig contains two essential modules, the configuration module which 95builds an internal configuration from XML files and the matching module 96which accepts font patterns and returns the nearest matching font. 97 </para> 98 <sect2><title>FONT CONFIGURATION</title> 99 <para> 100The configuration module consists of the FcConfig datatype, libexpat and 101FcConfigParse which walks over an XML tree and amends a configuration with 102data found within. From an external perspective, configuration of the 103library consists of generating a valid XML tree and feeding that to 104FcConfigParse. The only other mechanism provided to applications for 105changing the running configuration is to add fonts and directories to the 106list of application-provided font files. 107 </para><para> 108The intent is to make font configurations relatively static, and shared by 109as many applications as possible. It is hoped that this will lead to more 110stable font selection when passing names from one application to another. 111XML was chosen as a configuration file format because it provides a format 112which is easy for external agents to edit while retaining the correct 113structure and syntax. 114 </para><para> 115Font configuration is separate from font matching; applications needing to 116do their own matching can access the available fonts from the library and 117perform private matching. The intent is to permit applications to pick and 118choose appropriate functionality from the library instead of forcing them to 119choose between this library and a private configuration mechanism. The hope 120is that this will ensure that configuration of fonts for all applications 121can be centralized in one place. Centralizing font configuration will 122simplify and regularize font installation and customization. 123 </para> 124 </sect2> 125 <sect2> 126 <title>FONT PROPERTIES</title> 127 <para> 128While font patterns may contain essentially any properties, there are some 129well known properties with associated types. Fontconfig uses some of these 130properties for font matching and font completion. Others are provided as a 131convenience for the application's rendering mechanism. 132 </para> 133 <programlisting> 134 Property Definitions 135 136 Property C Preprocessor Symbol Type Description 137 ---------------------------------------------------- 138 family FC_FAMILY String Font family names 139 familylang FC_FAMILYLANG String Language corresponding to 140 each family name 141 style FC_STYLE String Font style. Overrides weight 142 and slant 143 stylelang FC_STYLELANG String Language corresponding to 144 each style name 145 fullname FC_FULLNAME String Font face full name where 146 different from family and 147 family + style 148 fullnamelang FC_FULLNAMELANG String Language corresponding to 149 each fullname 150 slant FC_SLANT Int Italic, oblique or roman 151 weight FC_WEIGHT Int Light, medium, demibold, 152 bold or black 153 size FC_SIZE Double Point size 154 width FC_WIDTH Int Condensed, normal or expanded 155 aspect FC_ASPECT Double Stretches glyphs horizontally 156 before hinting 157 pixelsize FC_PIXEL_SIZE Double Pixel size 158 spacing FC_SPACING Int Proportional, dual-width, 159 monospace or charcell 160 foundry FC_FOUNDRY String Font foundry name 161 antialias FC_ANTIALIAS Bool Whether glyphs can be 162 antialiased 163 hinting FC_HINTING Bool Whether the rasterizer should 164 use hinting 165 hintstyle FC_HINT_STYLE Int Automatic hinting style 166 verticallayout FC_VERTICAL_LAYOUT Bool Use vertical layout 167 autohint FC_AUTOHINT Bool Use autohinter instead of 168 normal hinter 169 globaladvance FC_GLOBAL_ADVANCE Bool Use font global advance data (deprecated) 170 file FC_FILE String The filename holding the font 171 index FC_INDEX Int The index of the font within 172 the file 173 ftface FC_FT_FACE FT_Face Use the specified FreeType 174 face object 175 rasterizer FC_RASTERIZER String Which rasterizer is in use (deprecated) 176 outline FC_OUTLINE Bool Whether the glyphs are outlines 177 scalable FC_SCALABLE Bool Whether glyphs can be scaled 178 scale FC_SCALE Double Scale factor for point->pixel 179 conversions (deprecated) 180 symbol FC_SYMBOL Bool Whether font uses MS symbol-font encoding 181 color FC_COLOR Bool Whether any glyphs have color 182 dpi FC_DPI Double Target dots per inch 183 rgba FC_RGBA Int unknown, rgb, bgr, vrgb, 184 vbgr, none - subpixel geometry 185 lcdfilter FC_LCD_FILTER Int Type of LCD filter 186 minspace FC_MINSPACE Bool Eliminate leading from line 187 spacing 188 charset FC_CHARSET CharSet Unicode chars encoded by 189 the font 190 lang FC_LANG LangSet Set of RFC-3066-style 191 languages this font supports 192 fontversion FC_FONTVERSION Int Version number of the font 193 capability FC_CAPABILITY String List of layout capabilities in 194 the font 195 fontformat FC_FONTFORMAT String String name of the font format 196 embolden FC_EMBOLDEN Bool Rasterizer should 197 synthetically embolden the font 198 embeddedbitmap FC_EMBEDDED_BITMAP Bool Use the embedded bitmap instead 199 of the outline 200 decorative FC_DECORATIVE Bool Whether the style is a decorative 201 variant 202 fontfeatures FC_FONT_FEATURES String List of extra feature tags in 203 OpenType to be enabled 204 namelang FC_NAMELANG String Language name to be used for the 205 default value of familylang, 206 stylelang and fullnamelang 207 prgname FC_PRGNAME String Name of the running program 208 hash FC_HASH String SHA256 hash value of the font data 209 with "sha256:" prefix (deprecated) 210 postscriptname FC_POSTSCRIPT_NAME String Font name in PostScript 211 </programlisting> 212 </sect2> 213</sect1> 214<sect1><title>Datatypes</title> 215 <para> 216Fontconfig uses abstract data types to hide internal implementation details 217for most data structures. A few structures are exposed where appropriate. 218 </para> 219 <sect2><title>FcChar8, FcChar16, FcChar32, FcBool</title> 220 <para> 221These are primitive data types; the FcChar* types hold precisely the number 222of bits stated (if supported by the C implementation). FcBool holds 223one of two C preprocessor symbols: FcFalse or FcTrue. 224 </para> 225 </sect2> 226 <sect2><title>FcMatrix</title> 227 <para> 228An FcMatrix holds an affine transformation, usually used to reshape glyphs. 229A small set of matrix operations are provided to manipulate these. 230 <programlisting> 231 typedef struct _FcMatrix { 232 double xx, xy, yx, yy; 233 } FcMatrix; 234 </programlisting> 235 </para> 236 </sect2> 237 <sect2><title>FcCharSet</title> 238 <para> 239An FcCharSet is an abstract type that holds the set of encoded Unicode chars 240in a font. Operations to build and compare these sets are provided. 241 </para> 242 </sect2> 243 <sect2><title>FcLangSet</title> 244 <para> 245An FcLangSet is an abstract type that holds the set of languages supported 246by a font. Operations to build and compare these sets are provided. These 247are computed for a font based on orthographic information built into the 248fontconfig library. Fontconfig has orthographies for all of the ISO 639-1 249languages except for MS, NA, PA, PS, QU, RN, RW, SD, SG, SN, SU and ZA. If 250you have orthographic information for any of these languages, please submit 251them. 252 </para> 253 </sect2> 254 <sect2><title>FcLangResult</title> 255 <para> 256An FcLangResult is an enumeration used to return the results of comparing 257two language strings or FcLangSet objects. FcLangEqual means the 258objects match language and territory. FcLangDifferentTerritory means 259the objects match in language but differ in territory. 260FcLangDifferentLang means the objects differ in language. 261 </para> 262 </sect2> 263 <sect2><title>FcType</title> 264 <para> 265Tags the kind of data stored in an FcValue. 266 </para> 267 </sect2> 268 <sect2><title>FcValue</title> 269 <para> 270An FcValue object holds a single value with one of a number of different 271types. The 'type' tag indicates which member is valid. 272 <programlisting> 273 typedef struct _FcValue { 274 FcType type; 275 union { 276 const FcChar8 *s; 277 int i; 278 FcBool b; 279 double d; 280 const FcMatrix *m; 281 const FcCharSet *c; 282 void *f; 283 const FcLangSet *l; 284 } u; 285 } FcValue; 286 </programlisting> 287 <programlisting> 288 FcValue Members 289 290 Type Union member Datatype 291 -------------------------------- 292 FcTypeVoid (none) (none) 293 FcTypeInteger i int 294 FcTypeDouble d double 295 FcTypeString s FcChar8 * 296 FcTypeBool b b 297 FcTypeMatrix m FcMatrix * 298 FcTypeCharSet c FcCharSet * 299 FcTypeFTFace f void * (FT_Face) 300 FcTypeLangSet l FcLangSet * 301 </programlisting> 302 </para> 303 </sect2> 304 <sect2><title>FcPattern</title> 305 <para> 306holds a set of names with associated value lists; each name refers to a 307property of a font. FcPatterns are used as inputs to the matching code as 308well as holding information about specific fonts. Each property can hold 309one or more values; conventionally all of the same type, although the 310interface doesn't demand that. 311 </para> 312 </sect2> 313 <sect2><title>FcFontSet</title> 314 <para> 315 <programlisting> 316 typedef struct _FcFontSet { 317 int nfont; 318 int sfont; 319 FcPattern **fonts; 320 } FcFontSet; 321 </programlisting> 322An FcFontSet contains a list of FcPatterns. Internally fontconfig uses this 323data structure to hold sets of fonts. Externally, fontconfig returns the 324results of listing fonts in this format. 'nfont' holds the number of 325patterns in the 'fonts' array; 'sfont' is used to indicate the size of that 326array. 327 </para> 328 </sect2> 329 <sect2><title>FcStrSet, FcStrList</title> 330 <para> 331FcStrSet holds a list of strings that can be appended to and enumerated. 332Its unique characteristic is that the enumeration works even while strings 333are appended during enumeration. FcStrList is used during enumeration to 334safely and correctly walk the list of strings even while that list is edited 335in the middle of enumeration. 336 </para> 337 </sect2> 338 <sect2><title>FcObjectSet</title> 339 <para> 340 <programlisting> 341 typedef struct _FcObjectSet { 342 int nobject; 343 int sobject; 344 const char **objects; 345 } FcObjectSet; 346 </programlisting> 347holds a set of names and is used to specify which fields from fonts are 348placed in the the list of returned patterns when listing fonts. 349 </para> 350 </sect2> 351 <sect2><title>FcObjectType</title> 352 <para> 353 <programlisting> 354 typedef struct _FcObjectType { 355 const char *object; 356 FcType type; 357 } FcObjectType; 358 </programlisting> 359marks the type of a pattern element generated when parsing font names. 360Applications can add new object types so that font names may contain the new 361elements. 362 </para> 363 </sect2> 364 <sect2><title>FcConstant</title> 365 <para> 366 <programlisting> 367 typedef struct _FcConstant { 368 const FcChar8 *name; 369 const char *object; 370 int value; 371 } FcConstant; 372 </programlisting> 373Provides for symbolic constants for new pattern elements. When 'name' is 374seen in a font name, an 'object' element is created with value 'value'. 375 </para> 376 </sect2> 377 <sect2><title>FcBlanks</title> 378 <para> 379holds a list of Unicode chars which are expected to be blank; unexpectedly 380blank chars are assumed to be invalid and are elided from the charset 381associated with the font. 382 </para> 383 </sect2> 384 <sect2><title>FcFileCache</title> 385 <para> 386holds the per-user cache information for use while loading the font 387database. This is built automatically for the current configuration when 388that is loaded. Applications must always pass '0' when one is requested. 389 </para> 390 </sect2> 391 <sect2><title>FcConfig</title> 392 <para> 393holds a complete configuration of the library; there is one default 394configuration, other can be constructed from XML data structures. All 395public entry points that need global data can take an optional FcConfig* 396argument; passing 0 uses the default configuration. FcConfig objects hold two 397sets of fonts, the first contains those specified by the configuration, the 398second set holds those added by the application at run-time. Interfaces 399that need to reference a particular set use one of the FcSetName enumerated 400values. 401 </para> 402 </sect2> 403 <sect2><title>FcSetName</title> 404 <para> 405Specifies one of the two sets of fonts available in a configuration; 406FcSetSystem for those fonts specified in the configuration and 407FcSetApplication which holds fonts provided by the application. 408 </para> 409 </sect2> 410 <sect2><title>FcResult</title> 411 <para> 412Used as a return type for functions manipulating FcPattern objects. 413 <programlisting> 414 FcResult Values 415 Result Code Meaning 416 ----------------------------------------------------------- 417 FcResultMatch Object exists with the specified ID 418 FcResultNoMatch Object doesn't exist at all 419 FcResultTypeMismatch Object exists, but the type doesn't match 420 FcResultNoId Object exists, but has fewer values 421 than specified 422 FcResultOutOfMemory malloc failed 423 </programlisting> 424 </para> 425 </sect2> 426 <sect2><title>FcAtomic</title> 427 <para> 428Used for locking access to configuration files. Provides a safe way to update 429configuration files. 430 </para> 431 </sect2> 432 <sect2><title>FcCache</title> 433 <para> 434Holds information about the fonts contained in a single directory. Normal 435applications need not worry about this as caches for font access are 436automatically managed by the library. Applications dealing with cache 437management may want to use some of these objects in their work, however the 438included 'fc-cache' program generally suffices for all of that. 439 </para> 440 </sect2> 441</sect1> 442<sect1><title>FUNCTIONS</title> 443 <para> 444These are grouped by functionality, often using the main data type being 445manipulated. 446 </para> 447 <sect2><title>Initialization</title> 448 <para> 449These functions provide some control over how the library is initialized. 450 </para> 451 &fcinit; 452 </sect2> 453 <sect2><title>FcPattern</title> 454 <para> 455An FcPattern is an opaque type that holds both patterns to match against the 456available fonts, as well as the information about each font. 457 </para> 458 &fcpattern; 459 &fcformat; 460 </sect2> 461 <sect2><title>FcFontSet</title> 462 <para> 463An FcFontSet simply holds a list of patterns; these are used to return the 464results of listing available fonts. 465 </para> 466 &fcfontset; 467 </sect2> 468 <sect2><title>FcObjectSet</title> 469 <para> 470An FcObjectSet holds a list of pattern property names; it is used to 471indicate which properties are to be returned in the patterns from 472FcFontList. 473 </para> 474 &fcobjectset; 475 </sect2> 476 <sect2><title>FreeType specific functions</title> 477 <para> 478While the fontconfig library doesn't insist that FreeType be used as the 479rasterization mechanism for fonts, it does provide some convenience 480functions. 481 </para> 482 &fcfreetype; 483 </sect2> 484 <sect2><title>FcValue</title> 485 <para> 486FcValue is a structure containing a type tag and a union of all possible 487datatypes. The tag is an enum of type 488<emphasis>FcType</emphasis> 489and is intended to provide a measure of run-time 490typechecking, although that depends on careful programming. 491 </para> 492 &fcvalue; 493 </sect2> 494 <sect2><title>FcCharSet</title> 495 <para> 496An FcCharSet is a boolean array indicating a set of Unicode chars. Those 497associated with a font are marked constant and cannot be edited. 498FcCharSets may be reference counted internally to reduce memory consumption; 499this may be visible to applications as the result of FcCharSetCopy may 500return it's argument, and that CharSet may remain unmodifiable. 501 </para> 502 &fccharset; 503 </sect2> 504 <sect2><title>FcLangSet</title> 505 <para> 506An FcLangSet is a set of language names (each of which include language and 507an optional territory). They are used when selecting fonts to indicate which 508languages the fonts need to support. Each font is marked, using language 509orthography information built into fontconfig, with the set of supported 510languages. 511 </para> 512 &fclangset; 513 </sect2> 514 <sect2><title>FcMatrix</title> 515 <para> 516FcMatrix structures hold an affine transformation in matrix form. 517 </para> 518 &fcmatrix; 519 </sect2> 520 <sect2><title>FcRange</title> 521 <para> 522An FcRange holds two variables to indicate a range in between. 523 </para> 524 &fcrange; 525 </sect2> 526 <sect2><title>FcConfig</title> 527 <para> 528An FcConfig object holds the internal representation of a configuration. 529There is a default configuration which applications may use by passing 0 to 530any function using the data within an FcConfig. 531 </para> 532 &fcconfig; 533 </sect2> 534 <sect2><title>FcObjectType</title> 535 <para> 536Provides for application-specified font name object types so that new 537pattern elements can be generated from font names. 538 </para> 539 &fcobjecttype; 540 </sect2> 541 <sect2><title>FcConstant</title> 542 <para> 543Provides for application-specified symbolic constants for font names. 544 </para> 545 &fcconstant; 546 </sect2> 547 <sect2><title>FcWeight</title> 548 <para> 549Maps weights to and from OpenType weights. 550 </para> 551 &fcweight; 552 </sect2> 553 <sect2><title>FcBlanks</title> 554 <para> 555An FcBlanks object holds a list of Unicode chars which are expected to 556be blank when drawn. When scanning new fonts, any glyphs which are 557empty and not in this list will be assumed to be broken and not placed in 558the FcCharSet associated with the font. This provides a significantly more 559accurate CharSet for applications. 560 </para> 561 &fcblanks; 562 </sect2> 563 <sect2><title>FcAtomic</title> 564 <para> 565These functions provide a safe way to update configuration files, allowing ongoing 566reading of the old configuration file while locked for writing and ensuring that a 567consistent and complete version of the configuration file is always available. 568 </para> 569 &fcatomic; 570 </sect2> 571 <sect2><title>File and Directory routines</title> 572 <para> 573These routines work with font files and directories, including font 574directory cache files. 575 </para> 576 &fcfile; 577 &fcdircache; 578 </sect2> 579 <sect2><title>FcCache routines</title> 580 <para> 581These routines work with font directory caches, accessing their contents in 582limited ways. It is not expected that normal applications will need to use 583these functions. 584 </para> 585 &fccache; 586 </sect2> 587 <sect2><title>FcStrSet and FcStrList</title> 588 <para> 589A data structure for enumerating strings, used to list directories while 590scanning the configuration as directories are added while scanning. 591 </para> 592 &fcstrset; 593 </sect2> 594 <sect2><title>String utilities</title> 595 <para> 596Fontconfig manipulates many UTF-8 strings represented with the FcChar8 type. 597These functions are exposed to help applications deal with these UTF-8 598strings in a locale-insensitive manner. 599 </para> 600 &fcstring; 601 </sect2> 602</sect1> 603</article> 604