Keith Packard HP Cambridge Research Lab KRP Fontconfig 2.1.91 Copyright © 2002 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 Keith Packard not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. Keith Packard makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty. KEITH PACKARD DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL KEITH PACKARD 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. Fontconfig is a library designed to provide system-wide font configuration, customization and application access. Fontconfig contains two essential modules, the configuration module which builds an internal configuration from XML files and the matching module which accepts font patterns and returns the nearest matching font. The configuration module consists of the FcConfig datatype, libexpat and FcConfigParse which walks over an XML tree and ammends a configuration with data found within. From an external perspective, configuration of the library consists of generating a valid XML tree and feeding that to FcConfigParse. The only other mechanism provided to applications for changing the running configuration is to add fonts and directories to the list of application-provided font files. The intent is to make font configurations relatively static, and shared by as many applications as possible. It is hoped that this will lead to more stable font selection when passing names from one application to another. XML was chosen as a configuration file format because it provides a format which is easy for external agents to edit while retaining the correct structure and syntax. Font configuration is separate from font matching; applications needing to do their own matching can access the available fonts from the library and perform private matching. The intent is to permit applications to pick and choose appropriate functionality from the library instead of forcing them to choose between this library and a private configuration mechanism. The hope is that this will ensure that configuration of fonts for all applications can be centralized in one place. Centralizing font configuration will simplify and regularize font installation and customization. While font patterns may contain essentially any properties, there are some well known properties with associated types. Fontconfig uses some of these properties for font matching and font completion. Others are provided as a convenience for the applications rendering mechanism. Property Definitions Property CPP Symbol Type Description ---------------------------------------------------- family FC_FAMILY String Font family name style FC_STYLE String Font style. Overrides weight and slant slant FC_SLANT Int Italic, oblique or roman weight FC_WEIGHT Int Light, medium, demibold, bold or black size FC_SIZE Double Point size aspect FC_ASPECT Double Stretches glyphs horizontally before hinting pixelsize FC_PIXEL_SIZE Double Pixel size spacing FC_SPACING Int Proportional, monospace or charcell foundry FC_FOUNDRY String Font foundry name antialias FC_ANTIALIAS Bool Whether glyphs can be antialiased hinting FC_HINTING Bool Whether the rasterizer should use hinting verticallayout FC_VERTICAL_LAYOUT Bool Use vertical layout autohint FC_AUTOHINT Bool Use autohinter instead of normal hinter globaladvance FC_GLOBAL_ADVANCE Bool Use font global advance data file FC_FILE String The filename holding the font index FC_INDEX Int The index of the font within the file ftface FC_FT_FACE FT_Face Use the specified FreeType face object rasterizer FC_RASTERIZER String Which rasterizer is in use outline FC_OUTLINE Bool Whether the glyphs are outlines scalable FC_SCALABLE Bool Whether glyphs can be scaled scale FC_SCALE Double Scale factor for point->pixel conversions dpi FC_DPI Double Target dots per inch rgba FC_RGBA Int unknown, rgb, bgr, vrgb, vbgr, none - subpixel geometry minspace FC_MINSPACE Bool Eliminate leading from line spacing charset FC_CHARSET CharSet Unicode chars encoded by the font lang FC_LANG String List of RFC-3066-style languages this font supports Fontconfig uses abstract datatypes to hide internal implementation details for most data structures. A few structures are exposed where appropriate. FcChar8 FcChar16 FcChar32 FcBool These are primitive datatypes; the FcChar* types hold precisely the number of bits stated (if supported by the C implementation). FcBool holds one of two CPP symbols: FcFalse or FcTrue. FcMatrix An FcMatrix holds an affine transformation, usually used to reshape glyphs. A small set of matrix operations are provided to manipulate these. typedef struct _FcMatrix { double xx, xy, yx, yy; } FcMatrix; FcCharSet An FcCharSet is an abstract type that holds the set of encoded unicode chars in a font. Operations to build and compare these sets are provided. FcType Tags the kind of data stored in an FcValue. FcValue An FcValue object holds a single value with one of a number of different types. The 'type' tag indicates which member is valid. typedef struct _FcValue { FcType type; union { const FcChar8 *s; int i; FcBool b; double d; const FcMatrix *m; const FcCharSet *c; } u; } FcValue; FcValue Members Type Union member Datatype -------------------------------- FcTypeVoid (none) (none) FcTypeInteger i int FcTypeDouble d double FcTypeString s char * FcTypeBool b b FcTypeMatrix m FcMatrix * FcTypeCharSet c FcCharSet * FcPattern holds a set of names with associated value lists; each name refers to a property of a font. FcPatterns are used as inputs to the matching code as well as holding information about specific fonts. Each property can hold one or more values; conventionally all of the same type, although the interface doesn't demand that. FcFontSet typedef struct _FcFontSet { int nfont; int sfont; FcPattern **fonts; } FcFontSet; An FcFontSet contains a list of FcPatterns. Internally fontconfig uses this data structure to hold sets of fonts. Externally, fontconfig returns the results of listing fonts in this format. 'nfont' holds the number of patterns in the 'fonts' array; 'sfont' is used to indicate the size of that array. FcStrSetFcStrList FcStrSet holds a list of strings that can be appended to and enumerated. Its unique characteristic is that the enumeration works even while strings are appended during enumeration. FcStrList is used during enumeration to safely and correctly walk the list of strings even while that list is edited in the middle of enumeration. FcObjectSet typedef struct _FcObjectSet { int nobject; int sobject; const char **objects; } FcObjectSet; holds a set of names and is used to specify which fields from fonts are placed in the the list of returned patterns when listing fonts. FcObjectType typedef struct _FcObjectType { const char *object; FcType type; } FcObjectType; marks the type of a pattern element generated when parsing font names. Applications can add new object types so that font names may contain the new elements. FcConstant typedef struct _FcConstant { const FcChar8 *name; const char *object; int value; } FcConstant; Provides for symbolic constants for new pattern elements. When 'name' is seen in a font name, an 'object' element is created with value 'value'. FcBlanks holds a list of Unicode chars which are expected to be blank; unexpectedly blank chars are assumed to be invalid and are elided from the charset associated with the font. FcFileCache holds the per-user cache information for use while loading the font database. This is built automatically for the current configuration when that is loaded. Applications must always pass '0' when one is requested. FcConfig holds a complete configuration of the library; there is one default configuration, other can be constructed from XML data structures. All public entry points that need global data can take an optional FcConfig* argument; passing 0 uses the default configuration. FcConfig objects hold two sets of fonts, the first contains those specified by the configuration, the second set holds those added by the application at run-time. Interfaces that need to reference a particulat set use one of the FcSetName enumerated values. FcSetName Specifies one of the two sets of fonts available in a configuration; FcSetSystem for those fonts specified in the configuration and FcSetApplication which holds fonts provided by the application. FcResult Used as a return type for functions manipulating FcPattern objects. FcResult Values Result Code Meaning ----------------------------------------------------------- FcResultMatch Object exists with the specified ID FcResultNoMatch Object doesn't exist at all FcResultTypeMismatch Object exists, but the type doesn't match FcResultNoId Object exists, but has fewer values than specified FcAtomic Used for locking access to config files. Provides a safe way to update configuration files. Functions are grouped by the main datatype involved FcMatrix structures hold an affine transformation in matrix form. &fcmatrix; An FcCharSet is a boolean array indicating a set of unicode chars. Those associated with a font are marked constant and cannot be edited. FcCharSets may be reference counted internally to reduce memory consumption; this may be visible to applications as the result of FcCharSetCopy may return it's argument, and that CharSet may remain unmodifiable. &fccharset; FcValue is a structure containing a type tag and a union of all possible datatypes. The tag is an enum of type FcType and is intended to provide a measure of run-time typechecking, although that depends on careful programming. &fcvalue; An FcPattern is an opaque type that holds both patterns to match against the available fonts, as well as the information about each font. &fcpattern; An FcFontSet simply holds a list of patterns; these are used to return the results of listing available fonts. &fcfontset; An FcObjectSet holds a list of pattern property names; it is used to indiciate which properties are to be returned in the patterns from FcFontList. &fcobjectset; Provides for applcation-specified font name object types so that new pattern elements can be generated from font names. &fcobjecttype; Provides for application-specified symbolic constants for font names. &fcconstant; An FcBlanks object holds a list of Unicode chars which are expected to be blank when drawn. When scanning new fonts, any glyphs which are empty and not in this list will be assumed to be broken and not placed in the FcCharSet associated with the font. This provides a significantly more accurate CharSet for applications. &fcblanks; An FcConfig object holds the internal representation of a configuration. There is a default configuration which applications may use by passing 0 to any function using the data within an FcConfig. &fcconfig; These functions provide some control over how the library is initialized. FcConfig *FcInitLoadConfig (void); Loads the default configuration file and returns the resulting configuration. Does not load any font information. FcConfig *FcInitLoadConfigAndFonts (void); Loads the default configuration file and builds information about the available fonts. Returns the resulting configuration. FcBool FcInit (void); Loads the default configuration file and the fonts referenced therein and sets the default configuration to that result. Returns whether this process succeeded or not. If the default configuration has already been loaded, this routine does nothing and returns FcTrue. int FcGetVersion (void); Returns the version number of the library. FcBool FcInitReinitialize (void); Forces the default configuration file to be reloaded and resets the default configuration. FcBool FcInitBringUptoDate (void); Checks the rescan interval in the default configuration, checking the configuration if the interval has passed and reloading the configuration if when any changes are detected. These functions provide a safe way to update config files, allowing ongoing reading of the old config file while locked for writing and ensuring that a consistent and complete version of the config file is always available. FcAtomic * FcAtomicCreate (const FcChar8 *file); Creates a data structure containing data needed to control access to 'file'. Writing is done to a separate file. Once that file is complete, the original configuration file is atomically replaced so that reading process always see a consistent and complete file without the need to lock for reading. FcBool FcAtomicLock (FcAtomic *atomic); Attempts to lock the file referenced by 'atomic'. Returns FcFalse if the file is locked by another process, else returns FcTrue and leaves the file locked. FcChar8 *FcAtomicNewFile (FcAtomic *atomic); Returns the filename for writing a new version of the file referenced by 'atomic'. FcChar8 *FcAtomicOrigFile (FcAtomic *atomic); Returns the file refernced by 'atomic'. FcBool FcAtomicReplaceOrig (FcAtomic *atomic); Replaces the original file referenced by 'atomic' with the new file. void FcAtomicDeleteNew (FcAtomic *atomic); Deletes the new file. void FcAtomicUnlock (FcAtomic *atomic); Unlocks the file. void FcAtomicDestroy (FcAtomic *atomic); Destroys 'atomic'. #include <fontconfig/fcfreetype.h> While the fontconfig library doesn't insist that FreeType be used as the rasterization mechanism for fonts, it does provide some convenience functions. FT_UInt FcFreeTypeCharIndex (FT_Face face, FcChar32 ucs4); Maps a Unicode char to a glyph index. This function uses information from several possible underlying encoding tables to work around broken fonts. As a result, this function isn't designed to be used in performance sensitive areas; results from this function are intended to be cached by higher level functions. FcCharSet *FcFreeTypeCharSet (FT_Face face, FcBlanks *blanks) Scans a FreeType face and returns the set of encoded Unicode chars. This scans several encoding tables to build as complete a list as possible. If 'blanks' is not 0, the glyphs in the font are examined and any blank glyphs not in 'blanks' are not placed in the returned FcCharSet. FcPattern *FcFreeTypeQuery (const char *file, int id, FcBlanks *blanks, int *count); Constructs a pattern representing the 'id'th font in 'file'. The number of fonts in 'file' is returned in 'count'. FcBool FcConfigParseAndLoad (FcConfig *config, const FcChar8 *file, FcBool complain); Walks the configuration in 'file' and constructs the internal representation in 'config'. Any include files referenced from within 'file' will be loaded with FcConfigLoad and also parsed. If 'complain' is FcFalse, no warning will be displayed if 'file' does not exist. FcBool FcFileScan (FcFontSet *set, FcStrSet *dirs, FcFileCache *cache, FcBlanks *blanks, const char *file, FcBool force); Scans a single file and adds all fonts found to 'set'. If 'force' is FcTrue, then the file is scanned even if associated information is found in 'cache'. If 'file' is a directory, it is added to 'dirs'. FcBool FcDirScan (FcFontSet *set, FcStrSet *dirs, FcFileCache *cache, FcBlanks *blanks, const char *dir, FcBool force); Scans an entire directory and adds all fonts found to 'set'. If 'force' is FcTrue, then the directory and all files within it are scanned even if information is present in the per-directory cache file or 'cache'. Any subdirectories found are added to 'dirs'. FcBool FcDirSave (FcFontSet *set, FcStrSet *dirs, const char *dir); Creates the per-directory cache file for 'dir' and populates it with the fonts in 'set' and subdirectories in 'dirs'. FcBool FcDirCacheValid (const FcChar8 *cache_file); Returns FcTrue if 'cache_file' is no older than the directory containing it, else FcFalse. A data structure for enumerating strings, used to list directories while scanning the configuration as directories are added while scanning. FcStrSet *FcStrSetCreate (void); Create an empty set. FcBool FcStrSetMember (FcStrSet *set, const FcChar8 *s); Returns whether 's' is a member of 'set'. FcBool FcStrSetAdd (FcStrSet *set, const FcChar8 *s); Adds a copy of 's' to 'set'. FcBool FcStrSetAddFilename (FcStrSet *set, const FcChar8 *s); Adds a copy 's' to 'set', The copy is created with FcStrCopyFilename so that leading '~' values are replaced with the value of the HOME environment variable. FcBool FcStrSetDel (FcStrSet *set, const FcChar8 *s); Removes 's' from 'set', returning FcTrue if 's' was a member else FcFalse. void FcStrSetDestroy (FcStrSet *set); Destroys 'set'. FcStrList *FcStrListCreate (FcStrSet *set); Creates an enumerator to list the strings in 'set'. FcChar8 *FcStrListNext (FcStrList *list); Returns the next string in 'set'. void FcStrListDone (FcStrList *list); Destroys the enumerator 'list'. int FcUtf8ToUcs4 (FcChar8 *src, FcChar32 *dst, int len); Converts the next Unicode char from 'src' into 'dst' and returns the number of bytes containing the char. 'src' nust be at least 'len' bytes long. int FcUcs4ToUtf8 (FcChar32 src, FcChar8 dst[FC_UTF8_MAX_LEN]); Converts the Unicode char from 'src' into 'dst' and returns the number of bytes needed to encode the char. FcBool FcUtf8Len (FcChar8 *src, int len, int *nchar, int *wchar); Counts the number of Unicode chars in 'len' bytes of 'src'. Places that count in 'nchar'. 'wchar' contains 1, 2 or 4 depending on the number of bytes needed to hold the largest unicode char counted. The return value indicates whether 'src' is a well-formed UTF8 string. int FcUtf16ToUcs4 (FcChar8 *src, FcEndian endian, FcChar32 *dst, int len); Converts the next Unicode char from 'src' into 'dst' and returns the number of bytes containing the char. 'src' must be at least 'len' bytes long. Bytes of 'src' are combined into 16-bit units according to 'endian'. FcBool FcUtf16Len (FcChar8 *src, FcEndian endian, int len, int *nchar, int *wchar); Counts the number of Unicode chars in 'len' bytes of 'src'. Bytes of 'src' are combined into 16-bit units according to 'endian'. Places that count in 'nchar'. 'wchar' contains 1, 2 or 4 depending on the number of bytes needed to hold the largest unicode char counted. The return value indicates whether 'string' is a well-formed UTF16 string. FcChar8 *FcStrCopy (const FcChar8 *s); Allocates memory, copies 's' and returns the resulting buffer. Yes, this is 'strdup', but that function isn't available on every platform. FcChar8 *FcStrCopyFilename (const FcChar8 *s); Just like FcStrCopy except that it converts any leading '~' characters in 's' to the value of the HOME environment variable. int FcStrCmpIgnoreCase (const char *s1, const char *s2); Returns the usual <0, 0, >0 result of comparing 's1' and 's2'. This test is case-insensitive in the ASCII range and will operate properly with UTF8 encoded strings, although it does not check for well formed strings. FcChar8 *FcStrDirname (const FcChar8 *file); Returns the directory containing 'file'. FcChar8 *FcStrBasename (const FcChar8 *file); Returns the filename of 'file' stripped of any leading directory names.