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3. Datatypes

Fontconfig uses abstract datatypes to hide internal implementation details -for most data structures. A few structures are exposed where appropriate. -

3.1. 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. -

3.2. 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;
-

3.3. 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. -

3.4. FcType

Tags the kind of data stored in an FcValue. -

3.5. 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 *
-

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. -

3.7. 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. -

3.8. FcStrSet, FcStrList

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. -

3.9. 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. -

3.10. 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. -

3.11. 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'. -

3.12. 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. -

3.13. 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. -

3.14. 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. -

3.15. 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. -

3.16. 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
-        FcResultOutOfMemory     Malloc failed
-

3.17. FcAtomic

Used for locking access to config files. Provides a safe way to update -configuration files. -

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