
Prev		Next

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. +

Prev	Home	Next
FUNCTIONAL OVERVIEW		FUNCTIONS