FONTCONFIG(3)

NAME
fontconfig - Font configuration and customization library

SYNOPSIS
#include <fontconfig/fontconfig.h>
#include <fontconfig/fcfreetype.h>
#include <fontconfig/fcxml.h>

DESCRIPTION
Fontconfig is a library designed to provide system-wide font configuration, customization and application access.

FUNCTIONAL OVERVIEW
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.

  FONT CONFIGURATION
The configuration module consists of the FcConfig datatype, libxml2 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 make simplify and regularize font installation and customization.

  FONT PROPERTIES
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	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
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
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
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	rgb, bgr, vrgb, vbgr - 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 language groups this font is designed for

  FONT MATCHING
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.

Font matching starts with an application constructed pattern. The desired attributes of the resulting font are collected together in an FcPattern object. 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.

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.

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.

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, antialias, family, spacing, pixelsize, style, slant, weight, rasterizer and outline. This list is in priority order -- results of comparing earlier elements of this list weigh more heavily than later elements.

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.

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.

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.

  FONT NAMES
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:
	<families>-<point sizes>:<name1>=<values1>:<name2>=<values2>...
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:

	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

DATATYPES

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;

	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.

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.

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.

    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

FUNCTIONS

  FcMatrix
FcMatrix structures hold an affine transformation in matrix form.

#define FcMatrixInit(m)	((m)->xx = (m)->yy = 1, (m)->xy = (m)->yx = 0)
    Initializes a matrix to the identify transformation.

FcMatrix *FcMatrixCopy (const FcMatrix *mat)
    Allocates a new FcMatrix and copies 'mat' into it.

FcBool FcMatrixEqual (const FcMatrix *mat1, const FcMatrix *mat2)
    Returns FcTrue if 'mat1' and 'mat2' are equal, else FcFalse.

void FcMatrixMultiply (FcMatrix *result, const FcMatrix *a, const FcMatrix *b)
    Multiplies 'a' and 'b' together, placing the result in

void FcMatrixRotate (FcMatrix *m, double c, double s)
    If 'c' is cos(angle) and 's' is sin(angle), FcMatrixRotate rotates the matrix by 'angle'.

void FcMatrixScale (FcMatrix *m, double sx, double sy)
    Scales 'm' by 'sx' in the horizontal dimension and 'sy' in the vertical dimension.

void FcMatrixShear (FcMatrix *m, double sh, double sv)
    Shears 'm' by 'sh' in the horizontal direction and 'sv' in the vertical direction.

  FcCharSet
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 *FcCharSetCreate (void)
    Creates an empty FcCharSet object.

void FcCharSetDestroy (FcCharSet *fcs)
    Frees an FcCharSet object.

FcBool FcCharSetAddChar (FcCharSet *fcs, FcChar32 ucs4)
    Adds a single unicode char to the set, returning FcFalse on failure, either as a result of a constant set or from running out of memory.

FcCharSet *FcCharSetCopy (FcCharSet *src)
    Makes a copy of 'src'; note that this may not actually do anything more than increment the reference count on 'src'.

FcBool FcCharSetEqual (const FcCharSet *a, const FcCharSet *b)
    Returns whether 'a' and 'b' contain the same set of unicode chars.

FcCharSet *FcCharSetIntersect (const FcCharSet *a, const FcCharSet *b)
    Returns a set including only those chars found in both 'a' and 'b'.

FcCharSet *FcCharSetUnion (const FcCharSet *a, const FcCharSet *b);
    Returns a set including only those chars found in either 'a' or 'b'.

FcCharSet *FcCharSetSubtract (const FcCharSet *a, const FcCharSet *b)
    Returns a set including only those chars found in 'a' but not 'b'.

FcBool FcCharSetHasChar (const FcCharSet *fcs, FcChar32 ucs4)
    Returns whether 'fcs' contains the char 'ucs4'.

FcChar32 FcCharSetCount (const FcCharSet *a)
    Returns the total number of unicode chars in 'a'.

FcChar32 FcCharSetIntersectCount (const FcCharSet *a, const FcCharSet *b)
    Returns the number of chars that are in both 'a' and 'b'.

FcChar32 FcCharSetSubtractCount (const FcCharSet *a, const FcCharSet *b)
    Returns the number of chars that are in 'a' but not in 'b'.

  FcValue
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.

void FcValueDestroy (FcValue v)
    Frees any memory referenced by `v'. Values of type FcTypeString, FcTypeMatrix and FcTypeCharSet reference memory, the other types do not.

FcValue FcValueSave (FcValue v)
    Returns a copy of `v' duplicating any object referenced by it so that `v' may be safely destroyed without harming the new value.

  FcPattern
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 *FcPatternCreate (void)
    Creates a pattern with no properties; used to build patterns from scratch.

void FcPatternDestroy (FcPattern *p)
    Destroys a pattern, in the process destroying all related values.

FcBool FcPatternAdd (FcPattern *p, const char *object, FcValue value, FcBool append)
    Adds a single value to the list of values associated with the property named `object'. If `append' is FcTrue, the value is added at the end of any existing list, otherwise it is inserted at the begining. `value' is saved (with FcValueSave) when inserted into the pattern so that the library retains no reference to any application-supplied data structure.

FcBool FcPatternAddInteger (FcPattern *p, const char *object, int i)
FcBool FcPatternAddDouble (FcPattern *p, const char *object, double d)
FcBool FcPatternAddString (FcPattern *p, const char *object, const char *s)
FcBool FcPatternAddMatrix (FcPattern *p, const char *object, const FcMatrix *s)
FcBool FcPatternAddCharSet (FcPattern *p, const char *object, const FcCharSet *c)
FcBool FcPatternAddBool (FcPattern *p, const char *object, FcBool b)
    These are all convenience functions that insert objects of the specified type into the pattern. Use these in preference to FcPatternAdd as they will provide compile-time typechecking. These all append values to any existing list of values.

FcResult FcPatternGet (FcPattern *p, const char *object, int id, FcValue *v)
    Returns in `v' the `id'th value associated with the property `object'. The value returned is not a copy, but rather refers to the data stored within the pattern directly. Applications must not free this value.

FcResult FcPatternGetInteger (FcPattern *p, const char *object, int n, int *i);
FcResult FcPatternGetDouble (FcPattern *p, const char *object, int n, double *d);
FcResult FcPatternGetString (FcPattern *p, const char *object, int n, char **const s);
FcResult FcPatternGetMatrix (FcPattern *p, const char *object, int n, FcMatrix **s);
FcResult FcPatternGetCharSet (FcPattern *p, const char *object, int n, FcCharSet **c);
FcResult FcPatternGetBool (FcPattern *p, const char *object, int n, FcBool *b);
    These are convenience functions that call FcPatternGet and verify that the returned data is of the expected type. They return FcResultTypeMismatch if this is not the case. Note that these (like FcPatternGet) do not make a copy of any data structure referenced by the return value. Use these in preference to FcPatternGet to provide compile-time typechecking.

FcPattern *FcPatternBuild (FcPattern *orig, ...);
FcPattern *FcPatternVaBuild (FcPattern *orig, va_list va)
    Builds a pattern using a list of objects, types and values. Each value to be entered in the pattern is specified with three arguments:

    1. Object name, a string describing the property to be added.

    2. Object type, one of the FcType enumerated values

    3. Value, not an FcValue, but the raw type as passed to any of the FcPatternAdd<type> functions. Must match the type of the second argument.

    The argument list is terminated by a null object name, no object type nor value need be passed for this. The values are added to `pattern', if `pattern' is null, a new pattern is created. In either case, the pattern is returned. Example:

        pattern = FcPatternBuild (0, FC_FAMILY, FtTypeString, "Times", (char *) 0);

    FcPatternVaBuild is used when the arguments are already in the form of a varargs value.

FcBool FcPatternDel (FcPattern *p, const char *object)
    Deletes all values associated with the property `object', returning whether the property existed or not.

void FcPatternPrint (FcPattern *p)
    Prints an easily readable version of the pattern to stdout. There is no provision for reparsing data in this format, it's just for diagnostics and debugging.

void FcDefaultSubstitute (FcPattern *pattern)
    Supplies default values for underspecified font patterns:

    •   Patterns without a specified style or weight are set to Medium

    •   Patterns without a specified style or slant are set to Roman

    •   Patterns without a specified pixel size are given one computed from any specified point size (default 12), dpi (default 75) and scale (default 1).

FcPattern *FcNameParse (const char *name)
    Converts 'name' from the standard text format described above into a pattern.

FcChar8 *FcNameUnparse (FcPattern *pat)
    Converts the given pattern into the standard text format described above. The return value is not static, but instead refers to newly allocated memory which should be freed by the caller.

  FcFontSet
An FcFontSet simply holds a list of patterns; these are used to return the results of listing available fonts.

FcFontSet *FcFontSetCreate (void)
    Creates an empty font set.

void FcFontSetDestroy (FcFontSet *s);
    Destroys a font set. Note that this destroys any referenced patterns as well.

FcBool FcFontSetAdd (FcFontSet *s, FcPattern *font)
    Adds a pattern to a font set. Note that the pattern is not copied before being inserted into the set.

  FcObjectSet
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 *FcObjectSetCreate (void)
    Creates an empty set.

FcBool FcObjectSetAdd (FcObjectSet *os, const char *object)
    Adds a proprety name to the set.

void FcObjectSetDestroy (FcObjectSet *os)
    Destroys an object set.

FcObjectSet *FcObjectSetBuild (const char *first, ...)
FcObjectSet *FcObjectSetVaBuild (const char *first, va_list va)
    These build an object set from a null-terminated list of property names.

  FcBlanks
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 *FcBlanksCreate (void)
    Creates an empty FcBlanks object.

void FcBlanksDestroy (FcBlanks *b)
    Destroys an FcBlanks object, freeing any associated memory.

FcBool FcBlanksAdd (FcBlanks *b, FcChar32 ucs4)
    Adds a single character to an FcBlanks object, returning FcFalse if this process ran out of memory.

FcBool FcBlanksIsMember (FcBlanks *b, FcChar32 ucs4)
    Returns whether the specified FcBlanks object contains the indicated Unicode value.

  FcConfig
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 *FcConfigCreate (void)
    Creates an empty configuration.

void FcConfigDestroy (FcConfig *config)
    Destroys a configuration and any data associated with it. Note that calling this function with the return from FcConfigGetCurrent will place the library in an indeterminate state.

FcBool FcConfigSetCurrent (FcConfig *config)
    Sets the current default configuration to 'config'. Implicitly calls FcConfigBuildFonts if necessary, returning FcFalse if that call fails.

FcConfig *FcConfigGetCurrent (void)
    Returns the current default configuration.

FcBool FcConfigBuildFonts (FcConfig *config)
    Builds the set of available fonts for the given configuration. Note that any changes to the configuration after this call have indeterminate effects. Returns FcFalse if this operation runs out of memory.

char **FcConfigGetDirs (FcConfig *config)
    Returns the list of font directories specified in 'config'.

char **FcConfigGetConfigFiles (FcConfig *config)
    Returns the list of known configuration files used to generate 'config'. Note that this will not include any configuration done with FcConfigParse.

char *FcConfigGetCache (FcConfig *config)
    Returns the name of the file used to store per-user font information.

FcFontSet *FcConfigGetFonts (FcConfig *config, FcSetName set)
    Returns one of the two sets of fonts from the configuration as specified by 'set'.

FcBlanks *FcConfigGetBlanks (FcConfig *config)
    Returns the FcBlanks object associated with the given configuration, if no blanks were present in the configuration, this function will return 0.

FcBool FcConfigAppFontAddFile (FcConfig *config, const char *file)
    Adds an application-specific font to the configuration.

FcBool FcConfigAppFontAddDir (FcConfig *config, const char *dir)
    Scans the specified directory for fonts, adding each one found to the application-specific set of fonts.

void FcConfigAppFontClear (FcConfig *config)
    Clears the set of application-specific fonts.

FcBool FcConfigSubstitute (FcConfig *config, FcPattern *p, FcMatchKind kind)
    Performs the sequence of pattern modification operations, if 'kind' is FcMatchPattern, then those tagged as pattern operations are applied, else if 'kind' is FcMatchFont, those tagged as font operations are applied.

FcPattern *FcFontMatch (FcConfig *config, FcPattern *p, FcResult *result)
    Returns the font in 'config' most close matching 'p'. This function should be called only after FcConfigSubstitute and FcDefaultSubstitute have been called; otherwise the results will be less useful.

FcFontSet *FcFontList (FcConfig *config, FcPattern *p, FcObjectSet *os)
    Selects fonts matching 'p', creates patterns from those fonts containing only the objects in 'os' and returns the set of unique such patterns.

char *FcConfigFilename (const char *name)
    Given the specified external entity name, return the associated filename. This provides applications a way to convert various configuration file references into filename form.

A null or empty 'name' indicates that the default configuration file should be used; which file this references can be overridden with the FC_CONFIG_FILE environment variable. Next, if the name starts with '~', it refers to a file in the current users home directory. Otherwise if the name doesn't start with '/', it refers to a file in the default configuration directory; the built-in default directory can be overridden with the FC_CONFIG_DIR environment variable.

  Initialization
These functions provide some control over how the library is initialized.

FcBool FcInitConfig (void)
    Initializes the default configuration using the default configuration file

FcBool FcInitFonts (void)
    Initializes the set of fonts available in the default configuration

FcBool FcInit (void)
    Calls FcInitConfig and FcInitFonts to completely initialize the default configuration.

  FreeType specific functions
#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 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'.

  XML specific functions
#include <fontconfig/fcxml.h>
These functions expose the libxml2 datatypes used for font configuration.

xmlDocPtr FcConfigLoad (const char *file)
    Loads a configuration file mapping 'file' into a filename with FcConfigFilename. This doesn't load a complete configuration as any include files referenced from 'file' will not be loaded.

FcBool FcConfigParse (FcConfig *config, xmlDocPtr doc)
    Walks the given configuration and constructs the internal representation in with FcConfigLoad and also parsed.

  File and Directory routines

FcBool FcFileScan (FcFontSet *set, 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'.

FcBool FcDirScan (FcFontSet *set, 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'.

FcBool FcDirSave (FcFontSet *set, const char *dir)
    Creates the per-directory cache file for 'dir' and populates it with the fonts in 'set'.

  String utilities

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.

FcBool FcUtf8Len (FcChar8 *string, int len, int *nchar, int *wchar)
    Counts the number of Unicode chars in 'len' bytes of 'string'. 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 UTF8 string.

char *FcStrCopy (const char *s)
    Allocates memory, copies 's' and returns the resulting buffer. Yes, this is

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.

CONFIGURATION FILE FORMAT
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.

The fontconfig document type definition resides in the external entity "fonts.dtd"; this is normally stored in the default font configuration directory (/etc/fonts). Each configuration file should contain the following structure:

	<?xml version="1.0"?>
	<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
	<fontconfig>
	...
	</fontconfig>

  <fontconfig>
This is the top level element for a font configuration and can contain <dir>, <cache>, <include>, <match> and <alias> elements in any order.

  <dir>
This element contains a directory name which will be scanned for font files to include in the set of available fonts.

  <cache>
This element contains a file name for the per-user cache of font information. If it starts with '~', it refers to a file in the users home directory. This file is used to hold information about fonts that isn't present in the per-directory cache files. It is automatically maintained by the fontconfig library. The default for this file is ``~/.fonts.cache''.

  <include ignore_missing="no">
This element contains the name of an additional configuration file. When the XML datatype is traversed by FcConfigParse, the contents of the file will also be incorporated into the configuration by passing the filename to FcConfigLoadAndParse. If 'ignore_missing' is set to "yes" instead of the default "no", a missing file will elicit no warning message from the library.

  <match target="pattern">
This element holds first a (possibly empty) list of tests and then a (possibly empty) list of edits. 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.

  <test qual="any" name="property" compare="eq">
This element contains a single value which is compared with the pattern property "property" (substitute any of the property names seen above). "more_eq". '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.

  <edit name="property" mode="assign">
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 <test> elements, if so, the modification may affect the first matched value. 'mode' is one of:
    Mode	Operation with match	Operation without match
    "assign"	Replace matching value	Replace all values
    "assign_replace"	Replace all values	Replace all values
    "prepend"	Insert before matching value	Insert at head of list
    "prepend_first"	Insert at head of list	Insert at head of list
    "append"	Append after matching value	Append at end of list
    "append_last"	Append at end of list	Append at end of list

  <int>

  <double>

  <string>

  <bool>
These elements hold a single value of the indicated type. <bool> elements hold either true or false.

  <matrix>
This element holds the four <double> elements of an affine transformation.

  <name>
Holds a property name. Evaluates to the first value from the property of the font, not the pattern.

  <const>
Holds the name of a constant; these are always integers and serve as symbolic names for common font values:

    Constant	Property	CPP symbol
    light	weight	FC_WEIGHT_LIGHT
    medium	weight	FC_WEIGHT_MEDIUM
    demibold	weight	FC_WEIGHT_DEMIBOLD
    bold	weight	FC_WEIGHT_BOLD
    black	weight	FC_WEIGHT_BLACK
    roman	slant	FC_SLANT_ROMAN
    italic	slant	FC_SLANT_ITALIC
    oblique	slant	FC_SLANT_OBLIQUE
    proportional	spacing	FC_PROPORTIONAL
    mono	spacing	FC_MONO
    charcell	spacing	FC_CHARCELL
    rgb	rgba	FC_RGBA_RGB
    bgr	rgba	FC_RGBA_BGR
    vrgb	rgba	FC_RGBA_VRGB
    vbgr	rgba	FC_RGBA_VBGR

  <or>

  <and>

  <plus>

  <minus>

  <times>

  <divide>
These elements perform the specified operation on a list of expression elements. <or> and <and> are boolean, not bitwise.

  <eq>

  <not_eq>

  <less>

  <less_eq>

  <more>

  <more_eq>
These elements compare two values, producing a boolean result.

  <not>
Inverts the boolean sense of its one expression element

  <if>
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.

  <alias>
Alias elements provide a shorthand notation for the set of common match operations needed to substitute one font family for another. They contain a <family> element followed by optional <prefer>, <accept> and <default> elements. Fonts matching the <family> element are edited to prepend the list of <prefer>ed families before the matching <family>, append the <accept>able familys after the matching <family> and append the <default> families to the end of the family list.

  <family>
Holds a single font family name

  <prefer>

  <accept>

  <default>
These hold a list of <family> elements to be used by the <alias> element.

EXAMPLE CONFIGURATION FILE

  System configuration file
This is an example of a system-wide configuration file

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<!-- /etc/fonts/fonts.conf file to configure system font access -->
<fontconfig>
<!--
	Find fonts in these directories
-->
<dir>/usr/X11R6/lib/X11/fonts/truetype</dir>
<dir>/usr/X11R6/lib/X11/fonts/Type1</dir>
<!--
	Accept deprecated 'mono' alias, replacing it with 'monospace'
-->
<match target="pattern">
	<test qual="any" name="family"><string>mono</string></test>
	<edit name="family" mode="assign"><string>monospace</string></edit>
</match>
<!--
	Names not including any well known alias are given 'sans'
-->
<match target="pattern">
	<test qual="all" name="family" mode="not_eq">sans</test>
	<test qual="all" name="family" mode="not_eq">serif</test>
	<test qual="all" name="family" mode="not_eq">monospace</test>
	<edit name="family" mode="append_last"><string>sans</string></edit>
</match>
<!--
	Load per-user customization file, but don't complain
	if it doesn't exist
-->
<include ignore_missing="yes">~/.fonts.conf</include>
<!--
	Alias well known font names to available TrueType fonts.
	These substitute TrueType faces for similar Type1
	faces to improve screen appearance.
-->
<alias>
	<family>Times</family>
	<prefer><family>Times New Roman</family></prefer>
	<default><family>serif</family></default>
</alias>
<alias>
	<family>Helvetica</family>
	<prefer><family>Verdana</family></prefer>
	<default><family>sans</family></default>
</alias>
<alias>
	<family>Courier</family>
	<prefer><family>Courier New</family></prefer>
	<default><family>monospace</family></default>
</alias>
<!--
	Provide required aliases for standard names
	Do these after the users configuration file so that
	any aliases there are used preferentially
-->
<alias>
	<family>serif</family>
	<prefer><family>Times New Roman</family></prefer>
</alias>
<alias>
	<family>sans</family>
	<prefer><family>Verdana</family></prefer>
</alias>
<alias>
	<family>monospace</family>
	<prefer><family>Andale Mono</family></prefer>
</alias>
</fontconfig>

  User configuration file
This is an example of a per-user configuration file that lives in ~/.fonts.conf

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<!-- ~/.fonts.conf for per-user font configuration -->
<fontconfig>
<!--
	Private font directory
-->
<dir>~/misc/fonts</dir>
<!--
	use rgb sub-pixel ordering to improve glyph appearance on
	LCD screens.  Changes affecting rendering, but not matching
	should always use target="font".
-->
<match target="font">
	<edit name="rgba" mode="assign"><const>rgb</const></edit>
</match>
</fontconfig>

FILES
fonts.conf 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. fonts.dtd is a DTD that describes the format of the configuration files. ~/.fonts.conf is the conventional location for per-user font configuration, although the actual location is specified in the global fonts.conf file. ~/.fonts.cache is the conventional repository of font information that isn't found in the per-directory caches. This file is automatically maintained by fontconfig.

AUTHOR
Keith Packard, member of the XFree86 Project, Inc.