GType

typedef gsize                           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))

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))

Get 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))

Checks 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)

Checks 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)

Checks 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))

Checks 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)

Checks if type has a GTypeValueTable.

G_TYPE_IS_CLASSED()

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

Checks 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))

Checks 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))

Checks 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))

Checks 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)

Checks 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).

struct GTypeInterface

struct GTypeInterface {
};

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

struct GTypeInstance

struct GTypeInstance {
};

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

struct GTypeClass

struct GTypeClass {
};

An opaque structure used as the base of all classes.

struct GTypeInfo

struct GTypeInfo {
  /* 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;
};

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().

struct GTypeFundamentalInfo

struct GTypeFundamentalInfo {
  GTypeFundamentalFlags  type_flags;
};

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

struct GInterfaceInfo

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

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

struct GTypeValueTable

struct GTypeValueTable {
  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);
};

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

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

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// 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);

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

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return value->data[0].v_pointer;

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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;

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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");
}

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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);

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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))

Get 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)

Get 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)

Get 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))

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

Note that while calling a GInstanceInitFunc(), the class pointer gets modified, so it might not always return the expected pointer.

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))

Get 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)))

Checks if instance is a valid GTypeInstance structure, otherwise issues 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 issues 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)))

Checks if instance is an instance of the type identified by g_type.

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 issues 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)))

Checks if g_class is a class structure of the type identified by g_type.

This macro should only be used in type implementations.

G_TYPE_CHECK_VALUE()

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

Checks 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)))

Checks 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 {
  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);

Get 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);

Get 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 an instantiatable type; when an object is allocated, the private structures for the type 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.

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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.

struct GTypeQuery

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

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:

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typedef struct {
  GObjectClass parent_class;
  gint         static_integer;
  gchar       *dynamic_string;
} TypeAClass;
static void
type_a_base_class_init (TypeAClass *class)
{
  class->dynamic_string = g_strdup ("some string");
}
static void
type_a_base_class_finalize (TypeAClass *class)
{
  g_free (class->dynamic_string);
}
static void
type_a_class_init (TypeAClass *class)
{
  class->static_integer = 42;
}

typedef struct {
  TypeAClass   parent_class;
  gfloat       static_float;
  GString     *dynamic_gstring;
} TypeBClass;
static void
type_b_base_class_init (TypeBClass *class)
{
  class->dynamic_gstring = g_string_new ("some other string");
}
static void
type_b_base_class_finalize (TypeBClass *class)
{
  g_string_free (class->dynamic_gstring);
}
static void
type_b_class_init (TypeBClass *class)
{
  class->static_float = 3.14159265358979323846;
}

Initialization of TypeBClass will first cause initialization of TypeAClass (derived classes reference their parent classes, see g_type_class_ref() on this). Initialization of TypeAClass roughly involves zero-initializing its fields, then calling its GBaseInitFunc() type_a_base_class_init() to allocate its dynamic members (dynamic_string), and finally calling its GClassInitFunc() type_a_class_init() to initialize its static members (static_integer). The first step in the initialization process of TypeBClass is then a plain memory copy of the contents of TypeAClass into TypeBClass and zero-initialization of the remaining fields in TypeBClass. The dynamic members of TypeAClass within TypeBClass now need reinitialization which is performed by calling type_a_base_class_init() with an argument of TypeBClass. After that, the GBaseInitFunc() of TypeBClass, type_b_base_class_init() is called to allocate the dynamic members of TypeBClass (dynamic_gstring), and finally the GClassInitFunc() of TypeBClass, type_b_class_init(), is called to complete the initialization process with the static members (static_float). Corresponding finalization counter parts to the GBaseInitFunc() functions have to be provided to release allocated resources at class finalization time.

GClassFinalizeFunc ()

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

A callback function used by the type system to finalize a class. This function is rarely needed, as dynamically allocated class resources should be handled by GBaseInitFunc() and GBaseFinalizeFunc(). Also, specification of a GClassFinalizeFunc() in the GTypeInfo structure of a static type is invalid, because classes of static types will never be finalized (they are artificially kept alive when their reference count drops to zero).

GInstanceInitFunc ()

void                (*GInstanceInitFunc)                (GTypeInstance *instance,
                                                         gpointer g_class);

A callback function used by the type system to initialize a new instance of a type. This function initializes all instance members and allocates any resources required by it. Initialization of a derived instance involves calling all its parent types instance initializers, so the class member of the instance is altered during its initialization to always point to the class that belongs to the type the current initializer was introduced for.

GInterfaceInitFunc ()

void                (*GInterfaceInitFunc)               (gpointer g_iface,
                                                         gpointer iface_data);

A callback function used by the type system to initialize a new interface. This function should initialize all internal data and allocate any resources required by the interface.

GInterfaceFinalizeFunc ()

void                (*GInterfaceFinalizeFunc)           (gpointer g_iface,
                                                         gpointer iface_data);

A callback function used by the type system to finalize an interface. This function should destroy any internal data and release any resources allocated by the corresponding GInterfaceInitFunc() function.

GTypeClassCacheFunc ()

gboolean            (*GTypeClassCacheFunc)              (gpointer cache_data,
                                                         GTypeClass *g_class);

A callback function which is called when the reference count of a class drops to zero. It may use g_type_class_ref() to prevent the class from being freed. You should not call g_type_class_unref() from a GTypeClassCacheFunc function to prevent infinite recursion, use g_type_class_unref_uncached() instead.

The functions have to check the class id passed in to figure whether they actually want to cache the class of this type, since all classes are routed through the same GTypeClassCacheFunc chain.

enum GTypeFlags

typedef enum {
  G_TYPE_FLAG_ABSTRACT		= (1 << 4),
  G_TYPE_FLAG_VALUE_ABSTRACT = (1 << 5)
} GTypeFlags;

Bit masks used to check or determine characteristics of a type.

enum GTypeFundamentalFlags

typedef enum {
  G_TYPE_FLAG_CLASSED           = (1 << 0),
  G_TYPE_FLAG_INSTANTIATABLE    = (1 << 1),
  G_TYPE_FLAG_DERIVABLE         = (1 << 2),
  G_TYPE_FLAG_DEEP_DERIVABLE    = (1 << 3)
} GTypeFundamentalFlags;

Bit masks used to check or determine specific characteristics of a fundamental type.

g_type_register_static ()

GType               g_type_register_static              (GType parent_type,
                                                         const gchar *type_name,
                                                         const GTypeInfo *info,
                                                         GTypeFlags flags);

Registers type_name as the name of a new static type derived from parent_type. The type system uses the information contained in the GTypeInfo structure pointed to by info to manage the type and its instances (if not abstract). The value of flags determines the nature (e.g. abstract or not) of the type.

g_type_register_static_simple ()

GType               g_type_register_static_simple       (GType parent_type,
                                                         const gchar *type_name,
                                                         guint class_size,
                                                         GClassInitFunc class_init,
                                                         guint instance_size,
                                                         GInstanceInitFunc instance_init,
                                                         GTypeFlags flags);

Registers type_name as the name of a new static type derived from parent_type. The value of flags determines the nature (e.g. abstract or not) of the type. It works by filling a GTypeInfo struct and calling g_type_register_static().

Since 2.12

g_type_register_dynamic ()

GType               g_type_register_dynamic             (GType parent_type,
                                                         const gchar *type_name,
                                                         GTypePlugin *plugin,
                                                         GTypeFlags flags);

Registers type_name as the name of a new dynamic type derived from parent_type. The type system uses the information contained in the GTypePlugin structure pointed to by plugin to manage the type and its instances (if not abstract). The value of flags determines the nature (e.g. abstract or not) of the type.

g_type_register_fundamental ()

GType               g_type_register_fundamental         (GType type_id,
                                                         const gchar *type_name,
                                                         const GTypeInfo *info,
                                                         const GTypeFundamentalInfo *finfo,
                                                         GTypeFlags flags);

Registers type_id as the predefined identifier and type_name as the name of a fundamental type. The type system uses the information contained in the GTypeInfo structure pointed to by info and the GTypeFundamentalInfo structure pointed to by finfo to manage the type and its instances. The value of flags determines additional characteristics of the fundamental type.

g_type_add_interface_static ()

void                g_type_add_interface_static         (GType instance_type,
                                                         GType interface_type,
                                                         const GInterfaceInfo *info);

Adds the static interface_type to instantiable_type. The information contained in the GTypeInterfaceInfo structure pointed to by info is used to manage the relationship.

g_type_add_interface_dynamic ()

void                g_type_add_interface_dynamic        (GType instance_type,
                                                         GType interface_type,
                                                         GTypePlugin *plugin);

Adds the dynamic interface_type to instantiable_type. The information contained in the GTypePlugin structure pointed to by plugin is used to manage the relationship.

g_type_interface_add_prerequisite ()

void                g_type_interface_add_prerequisite   (GType interface_type,
                                                         GType prerequisite_type);

Adds prerequisite_type to the list of prerequisites of interface_type. This means that any type implementing interface_type must also implement prerequisite_type. Prerequisites can be thought of as an alternative to interface derivation (which GType doesn't support). An interface can have at most one instantiatable prerequisite type.

g_type_get_plugin ()

GTypePlugin *       g_type_get_plugin                   (GType type);

Returns the GTypePlugin structure for type or NULL if type does not have a GTypePlugin structure.

g_type_interface_get_plugin ()

GTypePlugin *       g_type_interface_get_plugin         (GType instance_type,
                                                         GType interface_type);

Returns the GTypePlugin structure for the dynamic interface interface_type which has been added to instance_type, or NULL if interface_type has not been added to instance_type or does not have a GTypePlugin structure. See g_type_add_interface_dynamic().

g_type_fundamental_next ()

GType               g_type_fundamental_next             (void);

Returns the next free fundamental type id which can be used to register a new fundamental type with g_type_register_fundamental(). The returned type ID represents the highest currently registered fundamental type identifier.

g_type_fundamental ()

GType               g_type_fundamental                  (GType type_id);

Internal function, used to extract the fundamental type ID portion. use G_TYPE_FUNDAMENTAL() instead.

g_type_create_instance ()

GTypeInstance *     g_type_create_instance              (GType type);

Creates and initializes an instance of type if type is valid and can be instantiated. The type system only performs basic allocation and structure setups for instances: actual instance creation should happen through functions supplied by the type's fundamental type implementation. So use of g_type_create_instance() is reserved for implementators of fundamental types only. E.g. instances of the GObject hierarchy should be created via g_object_new() and never directly through g_type_create_instance() which doesn't handle things like singleton objects or object construction. Note: Do not use this function, unless you're implementing a fundamental type. Also language bindings should not use this function but g_object_new() instead.

g_type_free_instance ()

void                g_type_free_instance                (GTypeInstance *instance);

Frees an instance of a type, returning it to the instance pool for the type, if there is one.

Like g_type_create_instance(), this function is reserved for implementors of fundamental types.

g_type_add_class_cache_func ()

void                g_type_add_class_cache_func         (gpointer cache_data,
                                                         GTypeClassCacheFunc cache_func);

Adds a GTypeClassCacheFunc to be called before the reference count of a class goes from one to zero. This can be used to prevent premature class destruction. All installed GTypeClassCacheFunc functions will be chained until one of them returns TRUE. The functions have to check the class id passed in to figure whether they actually want to cache the class of this type, since all classes are routed through the same GTypeClassCacheFunc chain.

g_type_remove_class_cache_func ()

void                g_type_remove_class_cache_func      (gpointer cache_data,
                                                         GTypeClassCacheFunc cache_func);

Removes a previously installed GTypeClassCacheFunc. The cache maintained by cache_func has to be empty when calling g_type_remove_class_cache_func() to avoid leaks.

g_type_class_unref_uncached ()

void                g_type_class_unref_uncached         (gpointer g_class);

A variant of g_type_class_unref() for use in GTypeClassCacheFunc implementations. It unreferences a class without consulting the chain of GTypeClassCacheFuncs, avoiding the recursion which would occur otherwise.

g_type_add_interface_check ()

void                g_type_add_interface_check          (gpointer check_data,
                                                         GTypeInterfaceCheckFunc check_func);

Adds a function to be called after an interface vtable is initialized for any class (i.e. after the interface_init member of GInterfaceInfo has been called).

This function is useful when you want to check an invariant that depends on the interfaces of a class. For instance, the implementation of GObject uses this facility to check that an object implements all of the properties that are defined on its interfaces.

Since 2.4

g_type_remove_interface_check ()

void                g_type_remove_interface_check       (gpointer check_data,
                                                         GTypeInterfaceCheckFunc check_func);

Removes an interface check function added with g_type_add_interface_check().

Since 2.4

GTypeInterfaceCheckFunc ()

void                (*GTypeInterfaceCheckFunc)          (gpointer check_data,
                                                         gpointer g_iface);

A callback called after an interface vtable is initialized. See g_type_add_interface_check().

Since 2.4

g_type_value_table_peek ()

GTypeValueTable *   g_type_value_table_peek             (GType type);

Returns the location of the GTypeValueTable associated with type. Note that this function should only be used from source code that implements or has internal knowledge of the implementation of type.

G_DEFINE_TYPE()

#define G_DEFINE_TYPE(TN, t_n, T_P)			    G_DEFINE_TYPE_EXTENDED (TN, t_n, T_P, 0, {})

A convenience macro for type implementations, which declares a class initialization function, an instance initialization function (see GTypeInfo for information about these) and a static variable named t_n_parent_class pointing to the parent class. Furthermore, it defines a *_get_type() function. See G_DEFINE_TYPE_EXTENDED() for an example.

Since 2.4

G_DEFINE_TYPE_WITH_CODE()

#define G_DEFINE_TYPE_WITH_CODE(TN, t_n, T_P, _C_)	    _G_DEFINE_TYPE_EXTENDED_BEGIN (TN, t_n, T_P, 0) {_C_;} _G_DEFINE_TYPE_EXTENDED_END()

A convenience macro for type implementations. Similar to G_DEFINE_TYPE(), but allows to insert custom code into the *_get_type() function, e.g. interface implementations via G_IMPLEMENT_INTERFACE(). See G_DEFINE_TYPE_EXTENDED() for an example.

Since 2.4

G_DEFINE_ABSTRACT_TYPE()

#define G_DEFINE_ABSTRACT_TYPE(TN, t_n, T_P)		    G_DEFINE_TYPE_EXTENDED (TN, t_n, T_P, G_TYPE_FLAG_ABSTRACT, {})

A convenience macro for type implementations. Similar to G_DEFINE_TYPE(), but defines an abstract type. See G_DEFINE_TYPE_EXTENDED() for an example.

Since 2.4

G_DEFINE_ABSTRACT_TYPE_WITH_CODE()

#define G_DEFINE_ABSTRACT_TYPE_WITH_CODE(TN, t_n, T_P, _C_) _G_DEFINE_TYPE_EXTENDED_BEGIN (TN, t_n, T_P, G_TYPE_FLAG_ABSTRACT) {_C_;} _G_DEFINE_TYPE_EXTENDED_END()

A convenience macro for type implementations. Similar to G_DEFINE_TYPE_WITH_CODE(), but defines an abstract type and allows to insert custom code into the *_get_type() function, e.g. interface implementations via G_IMPLEMENT_INTERFACE(). See G_DEFINE_TYPE_EXTENDED() for an example.

Since 2.4

G_IMPLEMENT_INTERFACE()

#define             G_IMPLEMENT_INTERFACE(TYPE_IFACE, iface_init)

A convenience macro to ease interface addition in the _C_ section of G_DEFINE_TYPE_WITH_CODE() or G_DEFINE_ABSTRACT_TYPE_WITH_CODE(). See G_DEFINE_TYPE_EXTENDED() for an example.

Note that this macro can only be used together with the G_DEFINE_TYPE_* macros, since it depends on variable names from those macros.

Since 2.4

G_DEFINE_TYPE_EXTENDED()

#define G_DEFINE_TYPE_EXTENDED(TN, t_n, T_P, _f_, _C_)	    _G_DEFINE_TYPE_EXTENDED_BEGIN (TN, t_n, T_P, _f_) {_C_;} _G_DEFINE_TYPE_EXTENDED_END()

The most general convenience macro for type implementations, on which G_DEFINE_TYPE(), etc are based.

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G_DEFINE_TYPE_EXTENDED (GtkGadget, 
                        gtk_gadget, 
                        GTK_TYPE_WIDGET,
                        0, 
                        G_IMPLEMENT_INTERFACE (TYPE_GIZMO, 
                                               gtk_gadget_gizmo_init));

expands to

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static void     gtk_gadget_init       (GtkGadget      *self);
static void     gtk_gadget_class_init (GtkGadgetClass *klass);
static gpointer gtk_gadget_parent_class = NULL;
static void     gtk_gadget_class_intern_init (gpointer klass)
{
  gtk_gadget_parent_class = g_type_class_peek_parent (klass);
  gtk_gadget_class_init ((GtkGadgetClass*) klass);
}

GType
gtk_gadget_get_type (void)
{
  static GType g_define_type_id = 0; 
  if (G_UNLIKELY (g_define_type_id == 0)) 
    { 
      static const GTypeInfo g_define_type_info = { 
        sizeof (GtkGadgetClass), 
        (GBaseInitFunc) NULL, 
        (GBaseFinalizeFunc) NULL, 
        (GClassInitFunc) gtk_gadget_class_intern_init, 
        (GClassFinalizeFunc) NULL, 
        NULL,   // class_data 
        sizeof (GtkGadget), 
        0,      // n_preallocs 
        (GInstanceInitFunc) gtk_gadget_init, 
      }; 
      g_define_type_id = g_type_register_static (GTK_TYPE_WIDGET, "GtkGadget", &g_define_type_info, 0); 
      {
        static const GInterfaceInfo g_implement_interface_info = {
          (GInterfaceInitFunc) gtk_gadget_gizmo_init
        };
        g_type_add_interface_static (g_define_type_id, TYPE_GIZMO, &g_implement_interface_info);
      } 
    } 
  return g_define_type_id; 
}

The only pieces which have to be manually provided are the definitions of the instance and class structure and the definitions of the instance and class init functions.

Since 2.4

G_TYPE_INVALID

#define G_TYPE_INVALID			G_TYPE_MAKE_FUNDAMENTAL (0)

An invalid GType used as error return value in some functions which return a GType.

G_TYPE_NONE

#define G_TYPE_NONE			G_TYPE_MAKE_FUNDAMENTAL (1)

A fundamental type which is used as a replacement for the C void return type.

G_TYPE_INTERFACE

#define G_TYPE_INTERFACE		G_TYPE_MAKE_FUNDAMENTAL (2)

The fundamental type from which all interfaces are derived.

G_TYPE_CHAR

#define G_TYPE_CHAR			G_TYPE_MAKE_FUNDAMENTAL (3)

The fundamental type corresponding to gchar. The type designated by G_TYPE_CHAR is unconditionally an 8-bit signed integer. This may or may not be the same type a the C type "gchar".

G_TYPE_UCHAR

#define G_TYPE_UCHAR			G_TYPE_MAKE_FUNDAMENTAL (4)

The fundamental type corresponding to guchar.

G_TYPE_BOOLEAN

#define G_TYPE_BOOLEAN			G_TYPE_MAKE_FUNDAMENTAL (5)

The fundamental type corresponding to gboolean.

G_TYPE_INT

#define G_TYPE_INT			G_TYPE_MAKE_FUNDAMENTAL (6)

The fundamental type corresponding to gint.

G_TYPE_UINT

#define G_TYPE_UINT			G_TYPE_MAKE_FUNDAMENTAL (7)

The fundamental type corresponding to guint.

G_TYPE_LONG

#define G_TYPE_LONG			G_TYPE_MAKE_FUNDAMENTAL (8)

The fundamental type corresponding to glong.

G_TYPE_ULONG

#define G_TYPE_ULONG			G_TYPE_MAKE_FUNDAMENTAL (9)

The fundamental type corresponding to gulong.

G_TYPE_INT64

#define G_TYPE_INT64			G_TYPE_MAKE_FUNDAMENTAL (10)

The fundamental type corresponding to gint64.

G_TYPE_UINT64

#define G_TYPE_UINT64			G_TYPE_MAKE_FUNDAMENTAL (11)

The fundamental type corresponding to guint64.

G_TYPE_ENUM

#define G_TYPE_ENUM			G_TYPE_MAKE_FUNDAMENTAL (12)

The fundamental type from which all enumeration types are derived.

G_TYPE_FLAGS

#define G_TYPE_FLAGS			G_TYPE_MAKE_FUNDAMENTAL (13)

The fundamental type from which all flags types are derived.

G_TYPE_FLOAT

#define G_TYPE_FLOAT			G_TYPE_MAKE_FUNDAMENTAL (14)

The fundamental type corresponding to gfloat.

G_TYPE_DOUBLE

#define G_TYPE_DOUBLE			G_TYPE_MAKE_FUNDAMENTAL (15)

The fundamental type corresponding to gdouble.

G_TYPE_STRING

#define G_TYPE_STRING			G_TYPE_MAKE_FUNDAMENTAL (16)

The fundamental type corresponding to nul-terminated C strings.

G_TYPE_POINTER

#define G_TYPE_POINTER			G_TYPE_MAKE_FUNDAMENTAL (17)

The fundamental type corresponding to gpointer.

G_TYPE_BOXED

#define G_TYPE_BOXED			G_TYPE_MAKE_FUNDAMENTAL (18)

The fundamental type from which all boxed types are derived.

G_TYPE_PARAM

#define G_TYPE_PARAM			G_TYPE_MAKE_FUNDAMENTAL (19)

The fundamental type from which all GParamSpec types are derived.

G_TYPE_OBJECT

#define G_TYPE_OBJECT			G_TYPE_MAKE_FUNDAMENTAL (20)

The fundamental type for GObject.

G_TYPE_GTYPE

#define G_TYPE_GTYPE			 (g_gtype_get_type())

The type for GType.

G_TYPE_RESERVED_GLIB_FIRST

#define G_TYPE_RESERVED_GLIB_FIRST (21)

First fundamental type number to create a new fundamental type id with G_TYPE_MAKE_FUNDAMENTAL() reserved for GLib.

G_TYPE_RESERVED_GLIB_LAST

#define G_TYPE_RESERVED_GLIB_LAST (31)

Last fundamental type number reserved for GLib.

G_TYPE_RESERVED_BSE_FIRST

#define G_TYPE_RESERVED_BSE_FIRST (32)

First fundamental type number to create a new fundamental type id with G_TYPE_MAKE_FUNDAMENTAL() reserved for BSE.

G_TYPE_RESERVED_BSE_LAST

#define G_TYPE_RESERVED_BSE_LAST (48)

Last fundamental type number reserved for BSE.

G_TYPE_RESERVED_USER_FIRST

#define G_TYPE_RESERVED_USER_FIRST (49)

First available fundamental type number to create new fundamental type id with G_TYPE_MAKE_FUNDAMENTAL().