GType

A numerical value which represents the unique identifier of a registered type.

G_TYPE_FUNDAMENTAL()

#define G_TYPE_FUNDAMENTAL(type)	(g_type_fundamental (type))

Returns the fundamental type which is the ancestor of type. Fundamental types are types that serve as ultimate bases for the derived types, thus they are the roots of distinct inheritance hierarchies.

G_TYPE_FUNDAMENTAL_MAX

#define	G_TYPE_FUNDAMENTAL_MAX		(255 << G_TYPE_FUNDAMENTAL_SHIFT)

An integer constant that represents the number of identifiers reserved for types that are assigned at compile-time.

G_TYPE_MAKE_FUNDAMENTAL()

#define	G_TYPE_MAKE_FUNDAMENTAL(x)	((GType) ((x) << G_TYPE_FUNDAMENTAL_SHIFT))

Returns the type ID for the fundamental type number x. Use g_type_fundamental_next() instead of this macro to create new fundamental types.

G_TYPE_IS_ABSTRACT()

#define G_TYPE_IS_ABSTRACT(type)                (g_type_test_flags ((type), G_TYPE_FLAG_ABSTRACT))

Returns TRUE if type is an abstract type. An abstract type can not be instantiated and is normally used as an abstract base class for derived classes.

G_TYPE_IS_DERIVED()

#define G_TYPE_IS_DERIVED(type)                 ((type) > G_TYPE_FUNDAMENTAL_MAX)

Returns TRUE if type is derived (or in object-oriented terminology: inherited) from another type (this holds true for all non-fundamental types).

G_TYPE_IS_FUNDAMENTAL()

#define G_TYPE_IS_FUNDAMENTAL(type)             ((type) <= G_TYPE_FUNDAMENTAL_MAX)

Returns TRUE if type is a fundamental type.

G_TYPE_IS_VALUE_TYPE()

#define G_TYPE_IS_VALUE_TYPE(type)              (g_type_check_is_value_type (type))

Returns TRUE if type is a value type and can be used with g_value_init().

G_TYPE_HAS_VALUE_TABLE()

#define G_TYPE_HAS_VALUE_TABLE(type)            (g_type_value_table_peek (type) != NULL)

Returns TRUE if type has a GTypeValueTable.

G_TYPE_IS_CLASSED()

#define G_TYPE_IS_CLASSED(type)                 (g_type_test_flags ((type), G_TYPE_FLAG_CLASSED))

Returns TRUE if type is a classed type.

G_TYPE_IS_INSTANTIATABLE()

#define G_TYPE_IS_INSTANTIATABLE(type)          (g_type_test_flags ((type), G_TYPE_FLAG_INSTANTIATABLE))

Returns TRUE if type can be instantiated. Instantiation is the process of creating an instance (object) of this type.

G_TYPE_IS_DERIVABLE()

#define G_TYPE_IS_DERIVABLE(type)               (g_type_test_flags ((type), G_TYPE_FLAG_DERIVABLE))

Returns TRUE if type is a derivable type. A derivable type can be used as the base class of a flat (single-level) class hierarchy.

G_TYPE_IS_DEEP_DERIVABLE()

#define G_TYPE_IS_DEEP_DERIVABLE(type)          (g_type_test_flags ((type), G_TYPE_FLAG_DEEP_DERIVABLE))

Returns TRUE if type is a deep derivable type. A deep derivable type can be used as the base class of a deep (multi-level) class hierarchy.

G_TYPE_IS_INTERFACE()

#define G_TYPE_IS_INTERFACE(type)               (G_TYPE_FUNDAMENTAL (type) == G_TYPE_INTERFACE)

Returns TRUE if type is an interface type. An interface type provides a pure API, the implementation of which is provided by another type (which is then said to conform to the interface). GLib interfaces are somewhat analogous to Java interfaces and C++ classes containing only pure virtual functions, with the difference that GType interfaces are not derivable (but see g_type_interface_add_prerequisite() for an alternative).

GTypeInterface

typedef struct {
} GTypeInterface;

An opaque structure used as the base of all interface types.

GTypeInstance

typedef struct {
} GTypeInstance;

An opaque structure used as the base of all type instances.

GTypeClass

typedef struct {
} GTypeClass;

An opaque structure used as the base of all classes.

GTypeInfo

typedef struct {
  /* interface types, classed types, instantiated types */
  guint16                class_size;
  
  GBaseInitFunc          base_init;
  GBaseFinalizeFunc      base_finalize;
  
  /* interface types, classed types, instantiated types */
  GClassInitFunc         class_init;
  GClassFinalizeFunc     class_finalize;
  gconstpointer          class_data;
  
  /* instantiated types */
  guint16                instance_size;
  guint16                n_preallocs;
  GInstanceInitFunc      instance_init;
  
  /* value handling */
  const GTypeValueTable	*value_table;
} GTypeInfo;

This structure is used to provide the type system with the information required to initialize and destruct (finalize) a type's class and its instances. The initialized structure is passed to the g_type_register_static() function (or is copied into the provided GTypeInfo structure in the g_type_plugin_complete_type_info()). The type system will perform a deep copy of this structure, so its memory does not need to be persistent across invocation of g_type_register_static().

GTypeFundamentalInfo

typedef struct {
  GTypeFundamentalFlags  type_flags;
} GTypeFundamentalInfo;

A structure that provides information to the type system which is used specifically for managing fundamental types.

GInterfaceInfo

typedef struct {
  GInterfaceInitFunc     interface_init;
  GInterfaceFinalizeFunc interface_finalize;
  gpointer               interface_data;
} GInterfaceInfo;

A structure that provides information to the type system which is used specifically for managing interface types.

GTypeValueTable

typedef struct {
  void     (*value_init)         (GValue       *value);
  void     (*value_free)         (GValue       *value);
  void     (*value_copy)         (const GValue *src_value,
				  GValue       *dest_value);
  /* varargs functionality (optional) */
  gpointer (*value_peek_pointer) (const GValue *value);
  gchar	    *collect_format;
  gchar*   (*collect_value)      (GValue       *value,
				  guint         n_collect_values,
				  GTypeCValue  *collect_values,
				  guint		collect_flags);
  gchar	    *lcopy_format;
  gchar*   (*lcopy_value)        (const GValue *value,
				  guint         n_collect_values,
				  GTypeCValue  *collect_values,
				  guint		collect_flags);
} GTypeValueTable;

The GTypeValueTable provides the functions required by the GValue implementation, to serve as a container for values of a type.

{
  value->data[0].v_pointer = g_strdup ("");
}

{
  /* only free strings without a specific flag for static storage */
  if (!(value->data[1].v_uint & G_VALUE_NOCOPY_CONTENTS))
    g_free (value->data[0].v_pointer);
}

{
  dest_value->data[0].v_pointer = g_strdup (src_value->data[0].v_pointer);
}

{
  return value->data[0].v_pointer;
}

{
  if (!collect_values[0].v_pointer)
    value->data[0].v_pointer = g_strdup ("");
  else if (collect_flags & G_VALUE_NOCOPY_CONTENTS)
    {
      value->data[0].v_pointer = collect_values[0].v_pointer;
      /* keep a flag for the value_free() implementation to not free this string */
      value->data[1].v_uint = G_VALUE_NOCOPY_CONTENTS;
    }
  else
    value->data[0].v_pointer = g_strdup (collect_values[0].v_pointer);

  return NULL;
}

{
  if (collect_values[0].v_pointer)
    {
      GObject *object = G_OBJECT (collect_values[0].v_pointer);

      /* never honour G_VALUE_NOCOPY_CONTENTS for ref-counted types */
      value->data[0].v_pointer = g_object_ref (object);
      return NULL;
    }
  else
    return g_strdup_printf ("Object passed as invalid NULL pointer");
}

{
  gchar **string_p = collect_values[0].v_pointer;

  if (!string_p)
    return g_strdup_printf ("string location passed as NULL");

  if (collect_flags & G_VALUE_NOCOPY_CONTENTS)
    *string_p = value->data[0].v_pointer;
  else
    *string_p = g_strdup (value->data[0].v_pointer);

}

{
  GObject **object_p = collect_values[0].v_pointer;

  if (!object_p)
    return g_strdup_printf ("object location passed as NULL");
  if (!value->data[0].v_pointer)
    *object_p = NULL;
  else if (collect_flags & G_VALUE_NOCOPY_CONTENTS) /* always honour */
    *object_p = value->data[0].v_pointer;
  else
    *object_p = g_object_ref (value->data[0].v_pointer);
  return NULL;
}

G_TYPE_FROM_INSTANCE()

#define G_TYPE_FROM_INSTANCE(instance)                          (G_TYPE_FROM_CLASS (((GTypeInstance*) (instance))->g_class))

Returns the type identifier from a given instance structure.

This macro should only be used in type implementations.

G_TYPE_FROM_CLASS()

#define G_TYPE_FROM_CLASS(g_class)                              (((GTypeClass*) (g_class))->g_type)

Returns the type identifier from a given class structure.

This macro should only be used in type implementations.

G_TYPE_FROM_INTERFACE()

#define G_TYPE_FROM_INTERFACE(g_iface)                          (((GTypeInterface*) (g_iface))->g_type)

Returns the type identifier from a given interface structure.

This macro should only be used in type implementations.

G_TYPE_INSTANCE_GET_CLASS()

#define G_TYPE_INSTANCE_GET_CLASS(instance, g_type, c_type)     (_G_TYPE_IGC ((instance), (g_type), c_type))

Returns the class structure of a given instance, casted to a specified ancestor type g_type of the instance.

This macro should only be used in type implementations.

G_TYPE_INSTANCE_GET_INTERFACE()

#define G_TYPE_INSTANCE_GET_INTERFACE(instance, g_type, c_type) (_G_TYPE_IGI ((instance), (g_type), c_type))

Returns the interface structure for interface g_type of a given instance.

This macro should only be used in type implementations.

G_TYPE_INSTANCE_GET_PRIVATE()

#define G_TYPE_INSTANCE_GET_PRIVATE(instance, g_type, c_type)   ((c_type*) g_type_instance_get_private ((GTypeInstance*) (instance), (g_type)))

Gets the private structure for a particular type. The private structure must have been registered in the class_init function with g_type_class_add_private().

This macro should only be used in type implementations.

Since 2.4

G_TYPE_CHECK_INSTANCE()

#define G_TYPE_CHECK_INSTANCE(instance)				(_G_TYPE_CHI ((GTypeInstance*) (instance)))

Returns TRUE if instance is a valid GTypeInstance structure, otherwise emits a warning and returns FALSE.

This macro should only be used in type implementations.

G_TYPE_CHECK_INSTANCE_CAST()

#define G_TYPE_CHECK_INSTANCE_CAST(instance, g_type, c_type)    (_G_TYPE_CIC ((instance), (g_type), c_type))

Checks that instance is an instance of the type identified by g_type and emits a warning if this is not the case. Returns instance casted to a pointer to c_type.

This macro should only be used in type implementations.

G_TYPE_CHECK_INSTANCE_TYPE()

#define G_TYPE_CHECK_INSTANCE_TYPE(instance, g_type)            (_G_TYPE_CIT ((instance), (g_type)))

Returns TRUE if instance is an instance of the type identified by g_type. Otherwise emits a warning and returns FALSE.

This macro should only be used in type implementations.

G_TYPE_CHECK_CLASS_CAST()

#define G_TYPE_CHECK_CLASS_CAST(g_class, g_type, c_type)        (_G_TYPE_CCC ((g_class), (g_type), c_type))

Checks that g_class is a class structure of the type identified by g_type and emits a warning if this is not the case. Returns g_class casted to a pointer to c_type.

This macro should only be used in type implementations.

G_TYPE_CHECK_CLASS_TYPE()

#define G_TYPE_CHECK_CLASS_TYPE(g_class, g_type)                (_G_TYPE_CCT ((g_class), (g_type)))

Returns TRUE if g_class is a class structure of the type identified by g_type. Otherwise emits a warning and returns FALSE.

This macro should only be used in type implementations.

G_TYPE_CHECK_VALUE()

#define G_TYPE_CHECK_VALUE(value)				(_G_TYPE_CHV ((value)))

Returns TRUE if value has been initialized to hold values of a value type.

This macro should only be used in type implementations.

G_TYPE_CHECK_VALUE_TYPE()

#define G_TYPE_CHECK_VALUE_TYPE(value, g_type)			(_G_TYPE_CVH ((value), (g_type)))

Returns TRUE if value has been initialized to hold values of type g_type.

This macro should only be used in type implementations.

G_TYPE_FLAG_RESERVED_ID_BIT

#define	G_TYPE_FLAG_RESERVED_ID_BIT	((GType) (1 << 0))

A bit in the type number that's supposed to be left untouched.

g_type_init ()

void                g_type_init                         (void);

Prior to any use of the type system, g_type_init() has to be called to initialize the type system and assorted other code portions (such as the various fundamental type implementations or the signal system).

enum GTypeDebugFlags

typedef enum	/*< skip >*/
{
  G_TYPE_DEBUG_NONE	= 0,
  G_TYPE_DEBUG_OBJECTS	= 1 << 0,
  G_TYPE_DEBUG_SIGNALS	= 1 << 1,
  G_TYPE_DEBUG_MASK	= 0x03
} GTypeDebugFlags;

The GTypeDebugFlags enumeration values can be passed to g_type_init_with_debug_flags() to trigger debugging messages during runtime. Note that the messages can also be triggered by setting the GOBJECT_DEBUG environment variable to a ':'-separated list of "objects" and "signals".

g_type_init_with_debug_flags ()

void                g_type_init_with_debug_flags        (GTypeDebugFlags debug_flags);

Similar to g_type_init(), but additionally sets debug flags.

g_type_name ()

const gchar*        g_type_name                         (GType type);

Returns the unique name that is assigned to a type ID. Note that this function (like all other GType API) cannot cope with invalid type IDs. G_TYPE_INVALID may be passed to this function, as may be any other validly registered type ID, but randomized type IDs should not be passed in and will most likely lead to a crash.

g_type_qname ()

GQuark              g_type_qname                        (GType type);

Return the corresponding quark of the type IDs name.

g_type_from_name ()

GType               g_type_from_name                    (const gchar *name);

Lookup the type ID from a given type name, returning 0 if no type has been registered under this name (this is the preferred method to find out by name whether a specific type has been registered yet).

g_type_parent ()

GType               g_type_parent                       (GType type);

Return the direct parent type of the passed in type. If the passed in type has no parent, i.e. is a fundamental type, 0 is returned.

g_type_depth ()

guint               g_type_depth                        (GType type);

Returns the length of the ancestry of the passed in type. This includes the type itself, so that e.g. a fundamental type has depth 1.

g_type_next_base ()

GType               g_type_next_base                    (GType leaf_type,
                                                         GType root_type);

Given a leaf_type and a root_type which is contained in its anchestry, return the type that root_type is the immediate parent of. In other words, this function determines the type that is derived directly from root_type which is also a base class of leaf_type. Given a root type and a leaf type, this function can be used to determine the types and order in which the leaf type is descended from the root type.

g_type_is_a ()

gboolean            g_type_is_a                         (GType type,
                                                         GType is_a_type);

If is_a_type is a derivable type, check whether type is a descendant of is_a_type. If is_a_type is an interface, check whether type conforms to it.

g_type_class_ref ()

gpointer            g_type_class_ref                    (GType type);

Increments the reference count of the class structure belonging to type. This function will demand-create the class if it doesn't exist already.

g_type_class_peek ()

gpointer            g_type_class_peek                   (GType type);

This function is essentially the same as g_type_class_ref(), except that the classes reference count isn't incremented. As a consequence, this function may return NULL if the class of the type passed in does not currently exist (hasn't been referenced before).

g_type_class_peek_static ()

gpointer            g_type_class_peek_static            (GType type);

A more efficient version of g_type_class_peek() which works only for static types.

Since 2.4

g_type_class_unref ()

void                g_type_class_unref                  (gpointer g_class);

Decrements the reference count of the class structure being passed in. Once the last reference count of a class has been released, classes may be finalized by the type system, so further dereferencing of a class pointer after g_type_class_unref() are invalid.

g_type_class_peek_parent ()

gpointer            g_type_class_peek_parent            (gpointer g_class);

This is a convenience function often needed in class initializers. It returns the class structure of the immediate parent type of the class passed in. Since derived classes hold a reference count on their parent classes as long as they are instantiated, the returned class will always exist. This function is essentially equivalent to:

g_type_class_peek (g_type_parent (G_TYPE_FROM_CLASS (g_class)));

g_type_class_add_private ()

void                g_type_class_add_private            (gpointer g_class,
                                                         gsize private_size);

Registers a private structure for a instantiatable type; when an object is allocated, the private structures for the type and and all of its parent types are allocated sequentially in the same memory block as the public structures. This function should be called in the type's class_init() function. The private structure can be retrieved using the G_TYPE_INSTANCE_GET_PRIVATE() macro. The following example shows attaching a private structure MyObjectPrivate to an object MyObject defined in the standard GObject fashion.

typedef struct _MyObjectPrivate MyObjectPrivate;

struct _MyObjectPrivate {
  int some_field;
};

#define MY_OBJECT_GET_PRIVATE(o)  \
   (G_TYPE_INSTANCE_GET_PRIVATE ((o), MY_TYPE_OBJECT, MyObjectPrivate))

static void
my_object_class_init (MyObjectClass *klass)
{
  g_type_class_add_private (klass, sizeof (MyObjectPrivate));
}

static int
my_object_get_some_field (MyObject *my_object)
{
  MyObjectPrivate *priv = MY_OBJECT_GET_PRIVATE (my_object);

  return priv->some_field;
}

Since 2.4

g_type_interface_peek ()

gpointer            g_type_interface_peek               (gpointer instance_class,
                                                         GType iface_type);

Returns the GTypeInterface structure of an interface to which the passed in class conforms.

g_type_interface_peek_parent ()

gpointer            g_type_interface_peek_parent        (gpointer g_iface);

Returns the corresponding GTypeInterface structure of the parent type of the instance type to which g_iface belongs. This is useful when deriving the implementation of an interface from the parent type and then possibly overriding some methods.

g_type_default_interface_ref ()

gpointer            g_type_default_interface_ref        (GType g_type);

Increments the reference count for the interface type g_type, and returns the default interface vtable for the type.

If the type is not currently in use, then the default vtable for the type will be created and initalized by calling the base interface init and default vtable init functions for the type (the @base_init and class_init members of GTypeInfo). Calling g_type_default_interface_ref() is useful when you want to make sure that signals and properties for an interface have been installed.

Since 2.4

g_type_default_interface_peek ()

gpointer            g_type_default_interface_peek       (GType g_type);

If the interface type g_type is currently in use, returns its default interface vtable.

Since 2.4

g_type_default_interface_unref ()

void                g_type_default_interface_unref      (gpointer g_iface);

Decrements the reference count for the type corresponding to the interface default vtable g_iface. If the type is dynamic, then when no one is using the interface and all references have been released, the finalize function for the interface's default vtable (the class_finalize member of GTypeInfo) will be called.

Since 2.4

g_type_children ()

GType*              g_type_children                     (GType type,
                                                         guint *n_children);

Return a newly allocated and 0-terminated array of type IDs, listing the child types of type. The return value has to be g_free()ed after use.

g_type_interfaces ()

GType*              g_type_interfaces                   (GType type,
                                                         guint *n_interfaces);

Return a newly allocated and 0-terminated array of type IDs, listing the interface types that type conforms to. The return value has to be g_free()ed after use.

g_type_interface_prerequisites ()

GType*              g_type_interface_prerequisites      (GType interface_type,
                                                         guint *n_prerequisites);

Returns the prerequisites of an interfaces type.

Since 2.2

g_type_set_qdata ()

void                g_type_set_qdata                    (GType type,
                                                         GQuark quark,
                                                         gpointer data);

Attaches arbitrary data to a type.

g_type_get_qdata ()

gpointer            g_type_get_qdata                    (GType type,
                                                         GQuark quark);

Obtains data which has previously been attached to type with g_type_set_qdata().

g_type_query ()

void                g_type_query                        (GType type,
                                                         GTypeQuery *query);

Queries the type system for information about a specific type. This function will fill in a user-provided structure to hold type-specific information. If an invalid GType is passed in, the type member of the GTypeQuery is 0. All members filled into the GTypeQuery structure should be considered constant and have to be left untouched.

GTypeQuery

typedef struct {
  GType		type;
  const gchar  *type_name;
  guint		class_size;
  guint		instance_size;
} GTypeQuery;

A structure holding information for a specific type. It is filled in by the g_type_query() function.

GBaseInitFunc ()

void                (*GBaseInitFunc)                    (gpointer g_class);

A callback function used by the type system to do base initialization of the class structures of derived types. It is called as part of the initialization process of all derived classes and should reallocate or reset all dynamic class members copied over from the parent class. For example, class members (such as strings) that are not sufficiently handled by a plain memory copy of the parent class into the derived class have to be altered. See GClassInitFunc() for a discussion of the class intialization process.

GBaseFinalizeFunc ()

void                (*GBaseFinalizeFunc)                (gpointer g_class);

A callback function used by the type system to finalize those portions of a derived types class structure that were setup from the corresponding GBaseInitFunc() function. Class finalization basically works the inverse way in which class intialization is performed. See GClassInitFunc() for a discussion of the class intialization process.

GClassInitFunc ()

void                (*GClassInitFunc)                   (gpointer g_class,
                                                         gpointer class_data);

A callback function used by the type system to initialize the class of a specific type. This function should initialize all static class members. The initialization process of a class involves:

Since derived classes are partially initialized through a memory copy of the parent class, the general rule is that GBaseInitFunc() and GBaseFinalizeFunc() should take care of necessary reinitialization and release of those class members that were introduced by the type that specified these GBaseInitFunc()/GBaseFinalizeFunc(). GClassInitFunc() should only care about initializing static class members, while dynamic class members (such as allocated strings or reference counted resources) are better handled by a GBaseInitFunc() for this type, so proper initialization of the dynamic class members is performed for class initialization of derived types as well. An example may help to correspond the intend of the different class initializers:

typedef struct {
  GObjectClass parent_class