xref: /xsrc/external/mit/fontconfig/dist/doc/fontconfig-devel/x31.html

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><H1
CLASS="SECT1"
><A
NAME="AEN31"
>3. Datatypes</A
></H1
><P
>Fontconfig uses abstract datatypes to hide internal implementation details
for most data structures.  A few structures are exposed where appropriate.
  </P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN34"
>3.1. FcChar8, FcChar16, FcChar32, FcBool</A
></H2
><P
>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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN37"
>3.2. FcMatrix</A
></H2
><P
>An FcMatrix holds an affine transformation, usually used to reshape glyphs.
A small set of matrix operations are provided to manipulate these.
    <PRE
CLASS="PROGRAMLISTING"
>        typedef struct _FcMatrix {
                double xx, xy, yx, yy;
        } FcMatrix;
    </PRE
>
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN41"
>3.3. FcCharSet</A
></H2
><P
>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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN44"
>3.4. FcLangSet</A
></H2
><P
>An FcLangSet is an abstract type that holds the set of languages supported
by a font.  Operations to build and compare these sets are provided. These
are computed for a font based on orthographic information built into the
fontconfig library. Fontconfig has orthographies for all of the ISO 639-1
languages except for MS, NA, PA, PS, QU, RN, RW, SD, SG, SN, SU and ZA. If
you have orthographic information for any of these languages, please submit
them.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN47"
>3.5. FcLangResult</A
></H2
><P
>An FcLangResult is an enumeration used to return the results of comparing
two language strings or FcLangSet objects. FcLangEqual means the
objects match language and territory. FcLangDifferentTerritory means
the objects match in language but differ in territory.
FcLangDifferentLang means the objects differ in language.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN50"
>3.6. FcType</A
></H2
><P
>Tags the kind of data stored in an FcValue.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN53"
>3.7. FcValue</A
></H2
><P
>An FcValue object holds a single value with one of a number of different
types.  The 'type' tag indicates which member is valid.
    <PRE
CLASS="PROGRAMLISTING"
>        typedef struct _FcValue {
                FcType type;
                union {
                        const FcChar8 *s;
                        int i;
                        FcBool b;
                        double d;
                        const FcMatrix *m;
                        const FcCharSet *c;
			void *f;
			const FcLangSet *l;
                } u;
        } FcValue;
    </PRE
>
    <PRE
CLASS="PROGRAMLISTING"
>                  FcValue Members

        Type            Union member    Datatype
        --------------------------------
        FcTypeVoid      (none)          (none)
        FcTypeInteger   i               int
        FcTypeDouble    d               double
        FcTypeString    s               FcChar8 *
        FcTypeBool      b               b
        FcTypeMatrix    m               FcMatrix *
        FcTypeCharSet   c               FcCharSet *
	FcTypeFTFace	f		void * (FT_Face)
	FcTypeLangSet	l		FcLangSet *
    </PRE
>
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN58"
>3.8. FcPattern</A
></H2
><P
>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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN61"
>3.9. FcFontSet</A
></H2
><P
>    <PRE
CLASS="PROGRAMLISTING"
>        typedef struct _FcFontSet {
                int nfont;
                int sfont;
                FcPattern **fonts;
        } FcFontSet;
    </PRE
>
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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN65"
>3.10. FcStrSet, FcStrList</A
></H2
><P
>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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN68"
>3.11. FcObjectSet</A
></H2
><P
>      <PRE
CLASS="PROGRAMLISTING"
>        typedef struct _FcObjectSet {
                int nobject;
                int sobject;
                const char **objects;
        } FcObjectSet;
      </PRE
>
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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN72"
>3.12. FcObjectType</A
></H2
><P
>      <PRE
CLASS="PROGRAMLISTING"
>        typedef struct _FcObjectType {
                const char *object;
                FcType type;
        } FcObjectType;
      </PRE
>
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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN76"
>3.13. FcConstant</A
></H2
><P
>      <PRE
CLASS="PROGRAMLISTING"
>        typedef struct _FcConstant {
            const FcChar8 *name;
            const char *object;
            int value;
        } FcConstant;
      </PRE
>
Provides for symbolic constants for new pattern elements.  When 'name' is
seen in a font name, an 'object' element is created with value 'value'.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN80"
>3.14. FcBlanks</A
></H2
><P
>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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN83"
>3.15. FcFileCache</A
></H2
><P
>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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN86"
>3.16. FcConfig</A
></H2
><P
>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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN89"
>3.17. FcSetName</A
></H2
><P
>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.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN92"
>3.18. FcResult</A
></H2
><P
>Used as a return type for functions manipulating FcPattern objects.
    <PRE
CLASS="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
        FcResultOutOfMemory     Malloc failed
    </PRE
>
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN96"
>3.19. FcAtomic</A
></H2
><P
>Used for locking access to config files.  Provides a safe way to update
configuration files.
    </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN99"
>3.20. FcCache</A
></H2
><P
>Holds information about the fonts contained in a single directory. Normal
applications need not worry about this as caches for font access are
automatically managed by the library. Applications dealing with cache
management may want to use some of these objects in their work, however the
included 'fc-cache' program generally suffices for all of that.
    </P
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