fontconfig/doc/fontconfig-devel.sgml

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    Copyright <20> 2002 Keith Packard
   
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<article>
	<title>Fontconfig Developers Reference</title>
	<artheader>
		<author>
			<firstname>Keith</firstname>
			<surname>Packard</surname>
			<affiliation><orgname>
				HP Cambridge Research Lab
			</orgname></affiliation>
		</author>
		<authorinitials>KRP</authorinitials>
		<productname>Fontconfig</productname>
		<productnumber>2.1.91</productnumber>
		<LegalNotice>
			<simpara>		
Copyright <20> 2002 Keith Packard
			</simpara><simpara>
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.
			</simpara><simpara>
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.
			</simpara>
		</LegalNotice>
	</artheader>
<!--
<refsynopsisdiv>
  <synopsis>
  #include &lt;fontconfig/fontconfig.h&gt;
  #include &lt;fontconfig/fcfreetype.h&gt;
  </synopsis>
</refsynopsisdiv>
-->
<sect1><title>DESCRIPTION</title>
  <para>
Fontconfig is a library designed to provide system-wide font configuration,
customization and application access.
  </para>
</sect1>
<sect1><title>FUNCTIONAL OVERVIEW</title>
  <para>
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.
  </para>
  <sect2><title>FONT CONFIGURATION</title>
    <para>
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.  
    </para><para>
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.
    </para><para>
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.
    </para>
  </sect2>
  <sect2>
    <title>FONT PROPERTIES</title>
    <para>
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.
    </para>
    <programlisting>
                 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
    </programlisting>
  </sect2>
</sect1>
<sect1><title>DATATYPES</title>
  <para>
Fontconfig uses abstract datatypes to hide internal implementation details
for most data structures.  A few structures are exposed where appropriate.
  </para>
  <variablelist>
  <varlistentry>
    <term>FcChar8<term>
    <term>FcChar16<term>
    <term>FcChar32<term>
    <term>FcBool</term>
    <listitem>
    <para>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcMatrix</term><listitem>
    <para>
An FcMatrix holds an affine transformation, usually used to reshape glyphs.
A small set of matrix operations are provided to manipulate these.
    <programlisting>
        typedef struct _FcMatrix {
                double xx, xy, yx, yy;
        } FcMatrix;
    </programlisting>
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcCharSet</term><listitem>
    <para>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcType</term><listitem>
    <para>
Tags the kind of data stored in an FcValue.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcValue</term><listitem>
    <para>
An FcValue object holds a single value with one of a number of different
types.  The 'type' tag indicates which member is valid.
    <programlisting>
        typedef struct _FcValue {
                FcType type;
                union {
                        const FcChar8 *s;
                        int i;
                        FcBool b;
                        double d;
                        const FcMatrix *m;
                        const FcCharSet *c;
                } u;
        } FcValue;
    </programlisting>
    <programlisting>
                  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 *
    </programlisting>
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcPattern</term><listitem>
    <para>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcFontSet</term><listitem>
    <para>
    <programlisting>
        typedef struct _FcFontSet {
                int nfont;
                int sfont;
                FcPattern **fonts;
        } FcFontSet;
    </programlisting>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcStrSet</term><term>FcStrList</term><listitem>
    <para>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcObjectSet</term><listitem>
    <para>
      <programlisting>
        typedef struct _FcObjectSet {
                int nobject;
                int sobject;
                const char **objects;
        } FcObjectSet;
      </programlisting>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcObjectType</term><listitem>
    <para>
      <programlisting>
        typedef struct _FcObjectType {
                const char *object;
                FcType type;
        } FcObjectType;
      </programlisting>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcConstant</term><listitem>
    <para>
      <programlisting>
        typedef struct _FcConstant {
            const FcChar8 *name;
            const char *object;
            int value;
        } FcConstant;
      </programlisting>
Provides for symbolic constants for new pattern elements.  When 'name' is
seen in a font name, an 'object' element is created with value 'value'.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcBlanks</term><listitem>
    <para>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcFileCache</term><listitem>
    <para>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcConfig</term><listitem>
    <para>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcSetName</term><listitem>
    <para>
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.
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcResult</term><listitem>
    <para>
Used as a return type for functions manipulating FcPattern objects.
    <programlisting>
      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
    </programlisting>
    </para>
  </listitem></varlistentry>
  <varlistentry><term>FcAtomic</term><listitem>
    <para>
Used for locking access to config files.  Provides a safe way to update
configuration files.
    </para>
  </listitem></varlistentry>
  </variablelist>
</sect1>
<sect1><title>FUNCTIONS</title>
  <para>
Functions are grouped by the main datatype involved
  </para>
  <sect2><title>FcMatrix</title>
    <para>
FcMatrix structures hold an affine transformation in matrix form.
    </para>
    &fcmatrix;
  </sect2>
  <sect2><title>FcCharSet</title>
    <para>
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.
    </para>
    &fccharset;
  </sect2>
  <sect2><title>FcValue</title>
    <para>
FcValue is a structure containing a type tag and a union of all possible
datatypes.  The tag is an enum of type 
<emphasis>FcType</emphasis>
and is intended to provide a measure of run-time
typechecking, although that depends on careful programming.
    </para>
    &fcvalue;
  </sect2>
  <sect2><title>FcPattern</title>
    <para>
An FcPattern is an opaque type that holds both patterns to match against the
available fonts, as well as the information about each font.
    </para>
    &fcpattern;
  </sect2>
  <sect2><title>FcFontSet</title>
    <para>
An FcFontSet simply holds a list of patterns; these are used to return the
results of listing available fonts.
    </para>
    <variablelist>
    <varlistentry><term>
FcFontSet *FcFontSetCreate (void);
    </term><listitem><para>
Creates an empty font set.
    </para></listitem></varlistentry>
    <varlistentry><term>
void FcFontSetDestroy (FcFontSet *s);
    </term><listitem><para>
Destroys a font set.  Note that this destroys any referenced patterns as
well.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcFontSetAdd (FcFontSet *s, FcPattern *font);
    </term><listitem><para>
Adds a pattern to a font set.  Note that the pattern is not copied before
being inserted into the set.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>FcObjectSet</title>
    <para>
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.
    </para>
    <variablelist>
    <varlistentry><term>
FcObjectSet *FcObjectSetCreate (void);
    </term><listitem><para>
Creates an empty set.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcObjectSetAdd (FcObjectSet *os, const char *object);
    </term><listitem><para>
Adds a proprety name to the set.
    </para></listitem></varlistentry>
    <varlistentry><term>
void FcObjectSetDestroy (FcObjectSet *os);
    </term><listitem><para>
Destroys an object set.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcObjectSet *FcObjectSetBuild (const char *first, ...);
FcObjectSet *FcObjectSetVaBuild (const char *first, va_list va);
    </term><listitem><para>
These build an object set from a null-terminated list of property names.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>FcObjectType</title>
    <para>
Provides for applcation-specified font name object types so that new
pattern elements can be generated from font names.
    </para>
    <variablelist>
    <varlistentry><term>
FcBool FcNameRegisterObjectTypes (const FcObjectType *types, int ntype);
    </term><listitem><para>
Register 'ntype' new object types.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcNameUnregisterObjectTypes (const FcObjectType *types, int ntype);
    </term><listitem><para>
Unregister 'ntype' object types.
    </para></listitem></varlistentry>
    <varlistentry><term>
const FcObjectType *FcNameGetObjectType (const char *object);
    </term><listitem><para>
Return the object type for the pattern element named 'object'.
    </para></listitem></varlistentry>  
  </variablelist></sect2>
  <sect2><title>FcConstant</title>
    <para>
Provides for application-specified symbolic constants for font names.
    </para>
    <variablelist>
    <varlistentry><term>
FcBool FcNameRegisterConstants (const FcConstant *consts, int nconsts);
    </term><listitem><para>
Register 'nconsts' new symbolic constants.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcNameUnregisterConstants (const FcConstant *consts, int nconsts);
    </term><listitem><para>
Unregister 'nconsts' symbolic constants.
    </para></listitem></varlistentry>
    <varlistentry><term>
const FcConstant *FcNameGetConstant (FcChar8 *string);
    </term><listitem><para>
Return the FcConstant structure related to symbolic constant 'string'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcNameConstant (FcChar8 *string, int *result);
    </term><listitem><para>
Returns whether a symbolic constant with name 'string' is registered,
placing the value of the constant in 'result' if present.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>FcBlanks</title>
    <para>
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.
    </para>
    <variablelist>
    <varlistentry><term>
FcBlanks *FcBlanksCreate (void);
    </term><listitem><para>
Creates an empty FcBlanks object.
    </para></listitem></varlistentry>
    <varlistentry><term>
void FcBlanksDestroy (FcBlanks *b);
    </term><listitem><para>
Destroys an FcBlanks object, freeing any associated memory.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcBlanksAdd (FcBlanks *b, FcChar32 ucs4);
    </term><listitem><para>
Adds a single character to an FcBlanks object, returning FcFalse
if this process ran out of memory.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcBlanksIsMember (FcBlanks *b, FcChar32 ucs4);
    </term><listitem><para>
Returns whether the specified FcBlanks object contains the indicated Unicode
value.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>FcConfig</title>
    <para>
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.
    </para>
    <variablelist>
    <varlistentry><term>
FcConfig *FcConfigCreate (void);
    </term><listitem><para>
Creates an empty configuration.
    </para></listitem></varlistentry>
    <varlistentry><term>
void FcConfigDestroy (FcConfig *config);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcConfigSetCurrent (FcConfig *config);
    </term><listitem><para>
Sets the current default configuration to 'config'.  Implicitly calls
FcConfigBuildFonts if necessary, returning FcFalse if that call fails.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcConfig *FcConfigGetCurrent (void);
    </term><listitem><para>
Returns the current default configuration.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcConfigUptoDate (FcConfig *config);
    </term><listitem><para>
Checks all of the files related to 'config' and returns whether the
in-memory version is in sync with the disk version.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcConfigBuildFonts (FcConfig *config);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcStrList *FcConfigGetConfigDirs (FcConfig *config);
    </term><listitem><para>
Returns the list of font directories specified in the configuration files
for 'config'.  Does not include any subdirectories.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcStrList *FcConfigGetFontDirs (FcConfig *config);
    </term><listitem><para>
Returns the list of font directories in 'config'. This includes the
configured font directories along with any directories below those in the
filesystem.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcStrList *FcConfigGetConfigFiles (FcConfig *config);
    </term><listitem><para>
Returns the list of known configuration files used to generate 'config'.
Note that this will not include any configuration done with FcConfigParse.
    </para></listitem></varlistentry>
    <varlistentry><term>
char *FcConfigGetCache (FcConfig *config);
    </term><listitem><para>
Returns the name of the file used to store per-user font information.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcFontSet *FcConfigGetFonts (FcConfig *config, FcSetName set);
    </term><listitem><para>
Returns one of the two sets of fonts from the configuration as specified 
by 'set'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBlanks *FcConfigGetBlanks (FcConfig *config);
    </term><listitem><para>
Returns the FcBlanks object associated with the given configuration, if no
blanks were present in the configuration, this function will return 0.
    </para></listitem></varlistentry>
    <varlistentry><term>
int FcConfigGetRescanInverval (FcConfig *config);
    </term><listitem><para>
Returns the interval between automatic checks of the configuration (in
seconds) specified in 'config'.  The configuration is checked during
a call to FcFontList when this interval has passed since the last check.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcConfigSetRescanInverval (FcConfig *config, int rescanInterval);
    </term><listitem><para>
Sets the rescan interval; returns FcFalse if an error occurred.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcConfigAppFontAddFile (FcConfig *config, const char *file);
    </term><listitem><para>
Adds an application-specific font to the configuration.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcConfigAppFontAddDir (FcConfig *config, const char *dir);
    </term><listitem><para>
Scans the specified directory for fonts, adding each one found to the
application-specific set of fonts.
    </para></listitem></varlistentry>
    <varlistentry><term>
void FcConfigAppFontClear (FcConfig *config);
    </term><listitem><para>
Clears the set of application-specific fonts.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcConfigSubstituteWithPat (FcConfig *config, FcPattern *p, FcPattern *p_pat FcMatchKind kind);
    </term><listitem><para>
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 and
p_pat is used for &lt;test&gt; elements with target=pattern.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcConfigSubstitute (FcConfig *config, FcPattern *p, FcMatchKind kind);
    </term><listitem><para>
Calls FcConfigSubstituteWithPat setting p_pat to NULL.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcPattern *FcFontMatch (FcConfig *config, FcPattern *p, FcResult *result);
    </term><listitem><para>
Returns the font in 'config' most close matching 'p'.  This function
should be called only after FcConfigSubstitute and FcDefaultSubstitute have
been called for 'p'; otherwise the results will not be correct.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcFontSet *FcFontSort (FcConfig *config, FcPattern *p, FcBool trim, FcCharSet **csp, FcResult *result);
    </term><listitem><para>
Returns the list of fonts sorted by closeness to 'p'.  If 'trim' is FcTrue,
elements in the list which don't include Unicode coverage not provided by
earlier elements in the list are elided.  The union of Unicode coverage of
all of the fonts is returned in 'csp', if 'csp' is not NULL.  This function
should be called only after FcConfigSubstitute and FcDefaultSubstitute have
been called for 'p'; otherwise the results will not be correct.
    </para><para>
The returned FcFontSet references FcPattern structures which may be shared
by the return value from multiple FcFontSort calls, applications must not
modify these patterns.  Instead, they should be passed, along with 'p' to
FcFontRenderPrepare which combines them into a complete pattern.
    </para><para>
The FcFontSet returned by FcFontSort is destroyed by caling FcFontSetDestroy.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcPattern *FcFontRenderPrepare (FcConfig *config, FcPattern *pat, FcPattern *font);
    </term><listitem><para>
Creates a new pattern consisting of elements of 'font' not appearing
in 'pat', elements of 'pat' not appearing in 'font' and the best matching
value from 'pat' for elements appearing in both.  The result is passed to
FcConfigSubstitute with 'kind' FcMatchFont and then returned.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcFontSet *FcFontList (FcConfig *config, FcPattern *p, FcObjectSet *os);
    </term><listitem><para>
Selects fonts matching 'p', creates patterns from those fonts containing
only the objects in 'os' and returns the set of unique such patterns.
    </para></listitem></varlistentry>
    <varlistentry><term>
char *FcConfigFilename (const char *name);
    </term><listitem><para>
Given the specified external entity name, return the associated filename.
This provides applications a way to convert various configuration file
references into filename form. 
    </para><para>
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.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>Initialization</title>
    <para>
These functions provide some control over how the library is initialized.
    </para>
    <variablelist>
    <varlistentry><term>
FcConfig *FcInitLoadConfig (void);
    </term><listitem><para>
Loads the default configuration file and returns the resulting configuration.
Does not load any font information.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcConfig *FcInitLoadConfigAndFonts (void);
    </term><listitem><para>
Loads the default configuration file and builds information about the
available fonts.  Returns the resulting configuration.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcInit (void);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
int FcGetVersion (void);
    </term><listitem><para>
Returns the version number of the library.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcInitReinitialize (void);
    </term><listitem><para>
Forces the default configuration file to be reloaded and resets the default
configuration.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcInitBringUptoDate (void);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>FcAtomic</title>
    <para>
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.
    </para>
    <variablelist>
    <varlistentry><term>
FcAtomic * FcAtomicCreate (const FcChar8   *file);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcAtomicLock (FcAtomic *atomic);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcChar8 *FcAtomicNewFile (FcAtomic *atomic);
    </term><listitem><para>
Returns the filename for writing a new version of the file referenced
by 'atomic'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcChar8 *FcAtomicOrigFile (FcAtomic *atomic);
    </term><listitem><para>
Returns the file refernced by 'atomic'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcAtomicReplaceOrig (FcAtomic *atomic);
    </term><listitem><para>
Replaces the original file referenced by 'atomic' with the new file.
    </para></listitem></varlistentry>
    <varlistentry><term>
void FcAtomicDeleteNew (FcAtomic *atomic);
    </term><listitem><para>
Deletes the new file.
    </para></listitem></varlistentry>
    <varlistentry><term>
void FcAtomicUnlock (FcAtomic *atomic);
    </term><listitem><para>
Unlocks the file.
    </para></listitem></varlistentry>
    <varlistentry><term>
void FcAtomicDestroy (FcAtomic *atomic);
    </term><listitem><para>
Destroys 'atomic'.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>FreeType specific functions</title>
    <para>
      <programlisting>
#include &lt;fontconfig/fcfreetype.h&gt;
      </programlisting>
While the fontconfig library doesn't insist that FreeType be used as the
rasterization mechanism for fonts, it does provide some convenience
functions.
    </para>
    <variablelist>
    <varlistentry><term>
FT_UInt FcFreeTypeCharIndex (FT_Face face, FcChar32 ucs4);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcCharSet *FcFreeTypeCharSet (FT_Face face, FcBlanks *blanks) Scans a
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcPattern *FcFreeTypeQuery (const char *file, int id, FcBlanks *blanks, int *count);
    </term><listitem><para>
Constructs a pattern representing the 'id'th font in 'file'.  The number
of fonts in 'file' is returned in 'count'.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>XML specific functions</title>
    <variablelist>
    <varlistentry><term>
FcBool FcConfigParseAndLoad (FcConfig *config, const FcChar8 *file, FcBool complain);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>File and Directory routines</title>
    <variablelist>
    <varlistentry><term>
FcBool FcFileScan (FcFontSet *set, FcStrSet *dirs, FcFileCache *cache, FcBlanks *blanks, const char *file, FcBool force);
    </term><listitem><para>
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'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcDirScan (FcFontSet *set, FcStrSet *dirs, FcFileCache *cache, FcBlanks *blanks, const char *dir, FcBool force);
    </term><listitem><para>
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'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcDirSave (FcFontSet *set, FcStrSet *dirs, const char *dir);
    </term><listitem><para>
Creates the per-directory cache file for 'dir' and populates it with the
fonts in 'set' and subdirectories in 'dirs'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcDirCacheValid (const FcChar8 *cache_file);
    </term><listitem><para>
Returns FcTrue if 'cache_file' is no older than the directory containing it,
else FcFalse.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>FcStrSet and FcStrList</title>
    <para>
A data structure for enumerating strings, used to list directories while
scanning the configuration as directories are added while scanning.
    </para>
    <variablelist>
    <varlistentry><term>
FcStrSet *FcStrSetCreate (void);
    </term><listitem><para>
Create an empty set.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcStrSetMember (FcStrSet *set, const FcChar8 *s);
    </term><listitem><para>
Returns whether 's' is a member of 'set'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcStrSetAdd (FcStrSet *set, const FcChar8 *s);
    </term><listitem><para>
Adds a copy of 's' to 'set'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcStrSetAddFilename (FcStrSet *set, const FcChar8 *s);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcStrSetDel (FcStrSet *set, const FcChar8 *s);
    </term><listitem><para>
Removes 's' from 'set', returning FcTrue if 's' was a member else FcFalse.
    </para></listitem></varlistentry>
    <varlistentry><term>
void FcStrSetDestroy (FcStrSet *set);
    </term><listitem><para>
Destroys 'set'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcStrList *FcStrListCreate (FcStrSet *set);
    </term><listitem><para>
Creates an enumerator to list the strings in 'set'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcChar8 *FcStrListNext (FcStrList *list);
    </term><listitem><para>
Returns the next string in 'set'.
    </para></listitem></varlistentry>
    <varlistentry><term>
void FcStrListDone (FcStrList *list);
    </term><listitem><para>
Destroys the enumerator 'list'.
    </para></listitem></varlistentry>
  </variablelist></sect2>
  <sect2><title>String utilities</title>
    <variablelist>
    <varlistentry><term>
int FcUtf8ToUcs4 (FcChar8 *src, FcChar32 *dst, int len);
    </term><listitem>
    <para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
int FcUcs4ToUtf8 (FcChar32 src, FcChar8 dst[FC_UTF8_MAX_LEN]);
    </term><listitem><para>
Converts the Unicode char from 'src' into 'dst' and returns the
number of bytes needed to encode the char.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcUtf8Len (FcChar8 *src, int len, int *nchar, int *wchar);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
int FcUtf16ToUcs4 (FcChar8 *src, FcEndian endian, FcChar32 *dst, int len);
    </term><listitem><para>
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'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcBool FcUtf16Len (FcChar8 *src, FcEndian endian, int len, int *nchar, int *wchar);
    </term><listitem><para>
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.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcChar8 *FcStrCopy (const FcChar8 *s);
    </term><listitem><para>
Allocates memory, copies 's' and returns the resulting buffer.  Yes, this
is 'strdup', but that function isn't available on every platform.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcChar8 *FcStrCopyFilename (const FcChar8 *s);
    </term><listitem><para>
Just like FcStrCopy except that it converts any leading '~' characters 
in 's' to the value of the HOME environment variable.
    </para></listitem></varlistentry>
    <varlistentry><term>
int FcStrCmpIgnoreCase (const char *s1, const char *s2);
    </term><listitem><para>
Returns the usual &lt;0, 0, &gt;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.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcChar8 *FcStrDirname (const FcChar8 *file);
    </term><listitem><para>
Returns the directory containing 'file'.
    </para></listitem></varlistentry>
    <varlistentry><term>
FcChar8 *FcStrBasename (const FcChar8 *file);
    </term><listitem><para>
Returns the filename of 'file' stripped of any leading directory names.
    </para></listitem></varlistentry>
  </variablelist></sect2>
</sect1>
</article>