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                  Description

Type Information

Type Information — The GLib Runtime type identification and
    management system

Functions

<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>

#define

G_TYPE_FUNDAMENTAL()

#define

G_TYPE_MAKE_FUNDAMENTAL()

#define

G_TYPE_IS_ABSTRACT()

#define

G_TYPE_IS_DERIVED()

#define

G_TYPE_IS_FUNDAMENTAL()

#define

G_TYPE_IS_VALUE_TYPE()

#define

G_TYPE_HAS_VALUE_TABLE()

#define

G_TYPE_IS_CLASSED()

#define

G_TYPE_IS_INSTANTIATABLE()

#define

G_TYPE_IS_DERIVABLE()

#define

G_TYPE_IS_DEEP_DERIVABLE()

#define

G_TYPE_IS_INTERFACE()

#define

G_TYPE_FROM_INSTANCE()

#define

G_TYPE_FROM_CLASS()

#define

G_TYPE_FROM_INTERFACE()

#define

G_TYPE_INSTANCE_GET_CLASS()

#define

G_TYPE_INSTANCE_GET_INTERFACE()

#define

G_TYPE_INSTANCE_GET_PRIVATE()

#define

G_TYPE_CLASS_GET_PRIVATE()

#define

G_TYPE_CHECK_INSTANCE()

#define

G_TYPE_CHECK_INSTANCE_CAST()

#define

G_TYPE_CHECK_INSTANCE_TYPE()

#define

G_TYPE_CHECK_INSTANCE_FUNDAMENTAL_TYPE()

#define

G_TYPE_CHECK_CLASS_CAST()

#define

G_TYPE_CHECK_CLASS_TYPE()

#define

G_TYPE_CHECK_VALUE()

#define

G_TYPE_CHECK_VALUE_TYPE()

void

g_type_init ()

void

g_type_init_with_debug_flags ()

const gchar *

g_type_name ()

GQuark

g_type_qname ()

GType

g_type_from_name ()

GType

g_type_parent ()

guint

g_type_depth ()

GType

g_type_next_base ()

gboolean

g_type_is_a ()

gpointer

g_type_class_ref ()

gpointer

g_type_class_peek ()

gpointer

g_type_class_peek_static ()

void

g_type_class_unref ()

gpointer

g_type_class_peek_parent ()

void

g_type_class_add_private ()

void

g_type_add_class_private ()

gpointer

g_type_interface_peek ()

gpointer

g_type_interface_peek_parent ()

gpointer

g_type_default_interface_ref ()

gpointer

g_type_default_interface_peek ()

void

g_type_default_interface_unref ()

GType *

g_type_children ()

GType *

g_type_interfaces ()

GType *

g_type_interface_prerequisites ()

void

g_type_set_qdata ()

gpointer

g_type_get_qdata ()

void

g_type_query ()

void

(*GBaseInitFunc) ()

void

(*GBaseFinalizeFunc) ()

void

(*GClassInitFunc) ()

void

(*GClassFinalizeFunc) ()

void

(*GInstanceInitFunc) ()

void

(*GInterfaceInitFunc) ()

void

(*GInterfaceFinalizeFunc) ()

gboolean

(*GTypeClassCacheFunc) ()

GType

g_type_register_static ()

GType

g_type_register_static_simple ()

GType

g_type_register_dynamic ()

GType

g_type_register_fundamental ()

void

g_type_add_interface_static ()

void

g_type_add_interface_dynamic ()

void

g_type_interface_add_prerequisite ()

GTypePlugin *

g_type_get_plugin ()

GTypePlugin *

g_type_interface_get_plugin ()

GType

g_type_fundamental_next ()

GType

g_type_fundamental ()

GTypeInstance *

g_type_create_instance ()

void

g_type_free_instance ()

void

g_type_add_class_cache_func ()

void

g_type_remove_class_cache_func ()

void

g_type_class_unref_uncached ()

void

g_type_add_interface_check ()

void

g_type_remove_interface_check ()

void

(*GTypeInterfaceCheckFunc) ()

GTypeValueTable *

g_type_value_table_peek ()

void

g_type_ensure ()

guint

g_type_get_type_registration_serial ()

int

g_type_get_instance_count ()

#define

G_DECLARE_FINAL_TYPE()

#define

G_DECLARE_DERIVABLE_TYPE()

#define

G_DECLARE_INTERFACE()

#define

G_DEFINE_TYPE()

#define

G_DEFINE_TYPE_WITH_PRIVATE()

#define

G_DEFINE_TYPE_WITH_CODE()

#define

G_DEFINE_ABSTRACT_TYPE()

#define

G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE()

#define

G_DEFINE_ABSTRACT_TYPE_WITH_CODE()

#define

G_ADD_PRIVATE()

#define

G_PRIVATE_OFFSET()

#define

G_PRIVATE_FIELD()

#define

G_PRIVATE_FIELD_P()

#define

G_DEFINE_INTERFACE()

#define

G_DEFINE_INTERFACE_WITH_CODE()

#define

G_IMPLEMENT_INTERFACE()

#define

G_DEFINE_TYPE_EXTENDED()

#define

G_DEFINE_BOXED_TYPE()

#define

G_DEFINE_BOXED_TYPE_WITH_CODE()

#define

G_DEFINE_POINTER_TYPE()

#define

G_DEFINE_POINTER_TYPE_WITH_CODE()

#define
G_TYPE_CHECKSUM

Types and Values

<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>

typedef
GType

#define
G_TYPE_FUNDAMENTAL_MAX

struct
GTypeInterface

struct
GTypeInstance

struct
GTypeClass

struct
GTypeInfo

struct
GTypeFundamentalInfo

struct
GInterfaceInfo

struct
GTypeValueTable

#define
G_TYPE_FLAG_RESERVED_ID_BIT

enum
GTypeDebugFlags

struct
GTypeQuery

enum
GTypeFlags

enum
GTypeFundamentalFlags

#define
G_TYPE_INVALID

#define
G_TYPE_NONE

#define
G_TYPE_INTERFACE

#define
G_TYPE_CHAR

#define
G_TYPE_UCHAR

#define
G_TYPE_BOOLEAN

#define
G_TYPE_INT

#define
G_TYPE_UINT

#define
G_TYPE_LONG

#define
G_TYPE_ULONG

#define
G_TYPE_INT64

#define
G_TYPE_UINT64

#define
G_TYPE_ENUM

#define
G_TYPE_FLAGS

#define
G_TYPE_FLOAT

#define
G_TYPE_DOUBLE

#define
G_TYPE_STRING

#define
G_TYPE_POINTER

#define
G_TYPE_BOXED

#define
G_TYPE_PARAM

#define
G_TYPE_OBJECT

#define
G_TYPE_GTYPE

#define
G_TYPE_VARIANT

#define
G_TYPE_RESERVED_GLIB_FIRST

#define
G_TYPE_RESERVED_GLIB_LAST

#define
G_TYPE_RESERVED_BSE_FIRST

#define
G_TYPE_RESERVED_BSE_LAST

#define
G_TYPE_RESERVED_USER_FIRST

Includes

#include <glib-object.h>

Description

The GType API is the foundation of the GObject system.  It provides the
facilities for registering and managing all fundamental data types,
user-defined object and interface types.

For type creation and registration purposes, all types fall into one of
two categories: static or dynamic.  Static types are never loaded or
unloaded at run-time as dynamic types may be.  Static types are created
with g_type_register_static() that gets type specific information passed
in via a GTypeInfo structure.

Dynamic types are created with g_type_register_dynamic() which takes a
GTypePlugin structure instead. The remaining type information (the
GTypeInfo structure) is retrieved during runtime through GTypePlugin
and the g_type_plugin_*() API.

These registration functions are usually called only once from a
function whose only purpose is to return the type identifier for a
specific class.  Once the type (or class or interface) is registered,
it may be instantiated, inherited, or implemented depending on exactly
what sort of type it is.

There is also a third registration function for registering fundamental
types called g_type_register_fundamental() which requires both a GTypeInfo
structure and a GTypeFundamentalInfo structure but it is seldom used
since most fundamental types are predefined rather than user-defined.

Type instance and class structs are limited to a total of 64 KiB,
including all parent types. Similarly, type instances' private data
(as created by g_type_class_add_private()) are limited to a total of
64 KiB. If a type instance needs a large static buffer, allocate it
separately (typically by using GArray or GPtrArray) and put a pointer
to the buffer in the structure.

As mentioned in the GType conventions, type names must
be at least three characters long. There is no upper length limit. The first
character must be a letter (a–z or A–Z) or an underscore ('_'). Subsequent
characters can be letters, numbers or any of '-_+'.

Functions

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value.

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

x

the fundamental type number.

Returns

 the GType

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 cannot be
instantiated and is normally used as an abstract base class for
derived classes.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value

Returns

 TRUE on success

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).

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value

Returns

 TRUE on success

G_TYPE_IS_FUNDAMENTAL()

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

Checks if type
 is a fundamental type.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value

Returns

 TRUE on success

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().

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value

Returns

 TRUE on success

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value

Returns

 TRUE on success

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value

Returns

 TRUE on success

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value

Returns

 TRUE on success

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value

Returns

 TRUE on success

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value

Returns

 TRUE on success

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).

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

A GType value

Returns

 TRUE on success

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance

Location of a valid GTypeInstance structure

Returns

 the GType

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

Location of a valid GTypeClass structure

Returns

 the GType

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_iface

Location of a valid GTypeInterface structure

Returns

 the GType

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance

Location of the GTypeInstance structure

g_type

The GType of the class to be returned

c_type

The C type of the class structure

Returns

 a pointer to the class structure

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance

Location of the GTypeInstance structure

g_type

The GType of the interface to be returned

c_type

The C type of the interface structure

Returns

 a pointer to the interface structure

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance

the instance of a type deriving from private_type

g_type

the type identifying which private data to retrieve

c_type

The C type for the private structure

Returns

 a pointer to the private data structure

Since: 2.4

G_TYPE_CLASS_GET_PRIVATE()

#define G_TYPE_CLASS_GET_PRIVATE(klass, g_type, c_type)   ((c_type*) g_type_class_get_private ((GTypeClass*) (klass), (g_type)))

Gets the private class structure for a particular type.
The private structure must have been registered in the
get_type() function with g_type_add_class_private().

This macro should only be used in type implementations.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

klass

the class of a type deriving from private_type

g_type

the type identifying which private data to retrieve

c_type

The C type for the private structure

Returns

 a pointer to the private data structure

Since: 2.24

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance

Location of a GTypeInstance structure

Returns

 TRUE on success

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance

Location of a GTypeInstance structure

g_type

The type to be returned

c_type

The corresponding C type of g_type

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance

Location of a GTypeInstance structure.

g_type

The type to be checked

Returns

 TRUE on success

G_TYPE_CHECK_INSTANCE_FUNDAMENTAL_TYPE()

#define G_TYPE_CHECK_INSTANCE_FUNDAMENTAL_TYPE(instance, g_type)            (_G_TYPE_CIFT ((instance), (g_type)))

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

This macro should only be used in type implementations.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance

Location of a GTypeInstance structure.

g_type

The fundamental type to be checked

Returns

 TRUE on success

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

Location of a GTypeClass structure

g_type

The type to be returned

c_type

The corresponding C type of class structure of g_type

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

Location of a GTypeClass structure

g_type

The type to be checked

Returns

 TRUE on success

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

value

a GValue

Returns

 TRUE on success

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

value

a GValue

g_type

The type to be checked

Returns

 TRUE on success

g_type_init ()

void
g_type_init (void);

g_type_init has been deprecated since version 2.36 and should not be used in newly-written code.

the type system is now initialised automatically

This function used to initialise the type system.  Since GLib 2.36,
the type system is initialised automatically and this function does
nothing.

g_type_init_with_debug_flags ()

void
g_type_init_with_debug_flags (GTypeDebugFlags debug_flags);

g_type_init_with_debug_flags has been deprecated since version 2.36 and should not be used in newly-written code.

the type system is now initialised automatically

This function used to initialise the type system with debugging
flags.  Since GLib 2.36, the type system is initialised automatically
and this function does nothing.

If you need to enable debugging features, use the GOBJECT_DEBUG
environment variable.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

debug_flags

bitwise combination of GTypeDebugFlags values for
debugging purposes

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

type to return name for

Returns

 static type name or NULL

g_type_qname ()

GQuark
g_type_qname (GType type);

Get the corresponding quark of the type IDs name.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

type to return quark of type name for

Returns

 the type names quark or 0

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).

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

name

type name to lookup

Returns

 corresponding type ID or 0

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

the derived type

Returns

 the parent type

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

a GType

Returns

 the depth of type

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

leaf_type

descendant of root_type
and the type to be returned

root_type

immediate parent of the returned type

Returns

 immediate child of root_type
and anchestor of leaf_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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

type to check anchestry for

is_a_type

possible anchestor of type
or interface that type
could conform to

Returns

 TRUE if type
is a is_a_type

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

type ID of a classed type

Returns

 the GTypeClass
structure for the given type ID.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeClass][<acronym title="Don't free data after the code is done.">transfer none</acronym>]

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).

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

type ID of a classed type

Returns

 the GTypeClass
structure for the given type ID or NULL if the class does not
currently exist.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeClass][<acronym title="Don't free data after the code is done.">transfer none</acronym>]

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

type ID of a classed type

Returns

 the GTypeClass
structure for the given type ID or NULL if the class does not
currently exist or is dynamically loaded.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeClass][<acronym title="Don't free data after the code is done.">transfer none</acronym>]

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

 a GTypeClass structure to unref.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeClass]

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)))

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

 the GTypeClass structure to
retrieve the parent class for.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeClass]

Returns

 the parent class
of g_class
.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeClass][<acronym title="Don't free data after the code is done.">transfer none</acronym>]

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, and are zero-filled.

Note that the accumulated size of the private structures of
a type and all its parent types cannot exceed 64 KiB.

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 in the type's class_init() function.

Note the use of a structure member "priv" to avoid the overhead
of repeatedly calling MY_OBJECT_GET_PRIVATE().

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typedef struct _MyObject        MyObject;
typedef struct _MyObjectPrivate MyObjectPrivate;

struct _MyObject {
 GObject parent;

 MyObjectPrivate *priv;
};

struct _MyObjectPrivate {
  int some_field;
};

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

static void
my_object_init (MyObject *my_object)
{
  my_object->priv = G_TYPE_INSTANCE_GET_PRIVATE (my_object,
                                                 MY_TYPE_OBJECT,
                                                 MyObjectPrivate);
  // my_object->priv->some_field will be automatically initialised to 0
}

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

  g_return_val_if_fail (MY_IS_OBJECT (my_object), 0);

  priv = my_object->priv;

  return priv->some_field;
}

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

class structure for an instantiatable type

private_size

size of private structure

Since: 2.4

g_type_add_class_private ()

void
g_type_add_class_private (GType class_type,
                          gsize private_size);

Registers a private class structure for a classed type;
when the class is allocated, the private structures for
the class and all of its parent types are allocated
sequentially in the same memory block as the public
structures, and are zero-filled.

This function should be called in the
type's get_type() function after the type is registered.
The private structure can be retrieved using the
G_TYPE_CLASS_GET_PRIVATE() macro.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

class_type

GType of an classed type

private_size

size of private structure

Since: 2.24

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance_class

 a GTypeClass structure.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeClass]

iface_type

an interface ID which this class conforms to

Returns

 the GTypeInterface
structure of iface_type
if implemented by instance_class
, NULL
otherwise.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeInterface][<acronym title="Don't free data after the code is done.">transfer none</acronym>]

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_iface

 a GTypeInterface structure.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeInterface]

Returns

 the
corresponding GTypeInterface structure of the parent type of the
instance type to which g_iface
belongs, or NULL if the parent
type doesn't conform to the interface.

[<acronym title="Don't free data after the code is done.">transfer none</acronym>][<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeInterface]

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_type

an interface type

Returns

 the default
vtable for the interface; call g_type_default_interface_unref()
when you are done using the interface.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeInterface][<acronym title="Don't free data after the code is done.">transfer none</acronym>]

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_type

an interface type

Returns

 the default
vtable for the interface, or NULL if the type is not currently
in use.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeInterface][<acronym title="Don't free data after the code is done.">transfer none</acronym>]

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_iface

 the default vtable
structure for a interface, as returned by g_type_default_interface_ref().

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeInterface]

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
.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

the parent type

n_children

 location to store the length of
the returned array, or NULL.

[<acronym title="Parameter for returning results. Default is transfer full.">out</acronym>][<acronym title="NULL is OK, both for passing and for returning.">allow-none</acronym>]

Returns

 Newly allocated
and 0-terminated array of child types, free with g_free().

[<acronym title="Parameter points to an array of items.">array</acronym> length=n_children][<acronym title="Free data after the code is done.">transfer full</acronym>]

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

the type to list interface types for

n_interfaces

 location to store the length of
the returned array, or NULL.

[<acronym title="Parameter for returning results. Default is transfer full.">out</acronym>][<acronym title="NULL is OK, both for passing and for returning.">allow-none</acronym>]

Returns

 Newly allocated
and 0-terminated array of interface types, free with g_free().

[<acronym title="Parameter points to an array of items.">array</acronym> length=n_interfaces][<acronym title="Free data after the code is done.">transfer full</acronym>]

g_type_interface_prerequisites ()

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

Returns the prerequisites of an interfaces type.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

interface_type

an interface type

n_prerequisites

 location to return the number
of prerequisites, or NULL.

[<acronym title="Parameter for returning results. Default is transfer full.">out</acronym>][<acronym title="NULL is OK, both for passing and for returning.">allow-none</acronym>]

Returns

 a
newly-allocated zero-terminated array of GType containing
the prerequisites of interface_type
.

[<acronym title="Parameter points to an array of items.">array</acronym> length=n_prerequisites][<acronym title="Free data after the code is done.">transfer full</acronym>]

Since: 2.2

g_type_set_qdata ()

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

Attaches arbitrary data to a type.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

a GType

quark

a GQuark id to identify the data

data

the data

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().

Note that this does not take subtyping into account; data
attached to one type with g_type_set_qdata() cannot
be retrieved from a subtype using g_type_get_qdata().

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

a GType

quark

a GQuark id to identify the data

Returns

 the data, or NULL if no data was found.

[<acronym title="Don't free data after the code is done.">transfer none</acronym>]

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

GType of a static, classed type

query

 a user provided structure that is
filled in with constant values upon success.

[<acronym title="Out parameter, where caller must allocate storage.">out caller-allocates</acronym>]

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

The GTypeClass structure to initialize

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

The GTypeClass structure to finalize

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:

Copying common members from the parent class over to the
derived class structure.

Zero initialization of the remaining members not copied
over from the parent class.

Invocation of the GBaseInitFunc() initializers of all parent
types and the class' type.

Invocation of the class' GClassInitFunc() initializer.

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

The GTypeClass structure to initialize.

class_data

The class_data
member supplied via the GTypeInfo structure.

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).

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

The GTypeClass structure to finalize

class_data

The class_data
member supplied via the GTypeInfo structure

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.

The extended members of instance
 are guaranteed to have been filled with
zeros before this function is called.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance

The instance to initialize

g_class

The class of the type the instance is created 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.

The members of iface_data
 are guaranteed to have been filled with
zeros before this function is called.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_iface

The interface structure to initialize

iface_data

The interface_data
supplied via the GInterfaceInfo structure

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_iface

The interface structure to finalize

iface_data

The interface_data
supplied via the GInterfaceInfo structure

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

cache_data

data that was given to the g_type_add_class_cache_func() call

g_class

The GTypeClass structure which is unreferenced

Returns

 TRUE to stop further GTypeClassCacheFuncs from being
called, FALSE to continue

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

parent_type

type from which this type will be derived

type_name

0-terminated string used as the name of the new type

info

GTypeInfo structure for this type

flags

bitwise combination of GTypeFlags values

Returns

 the new type identifier

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().

[<acronym title="Exposed in C code, not necessarily available in other languages.">skip</acronym>]

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

parent_type

type from which this type will be derived

type_name

0-terminated string used as the name of the new type

class_size

size of the class structure (see GTypeInfo)

class_init

location of the class initialization function (see GTypeInfo)

instance_size

size of the instance structure (see GTypeInfo)

instance_init

location of the instance initialization function (see GTypeInfo)

flags

bitwise combination of GTypeFlags values

Returns

 the new type identifier

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

parent_type

type from which this type will be derived

type_name

0-terminated string used as the name of the new type

plugin

GTypePlugin structure to retrieve the GTypeInfo from

flags

bitwise combination of GTypeFlags values

Returns

 the new type identifier or G_TYPE_INVALID if registration failed

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. If type_id
 is already registered, or a
type named type_name
 is already registered, the behaviour is undefined.
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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type_id

a predefined type identifier

type_name

0-terminated string used as the name of the new type

info

GTypeInfo structure for this type

finfo

GTypeFundamentalInfo structure for this type

flags

bitwise combination of GTypeFlags values

Returns

 the predefined type identifier

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 GInterfaceInfo structure
pointed to by info
 is used to manage the relationship.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance_type

GType value of an instantiable type

interface_type

GType value of an interface type

info

GInterfaceInfo structure for this
(instance_type
, interface_type
) combination

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance_type

GType value of an instantiable type

interface_type

GType value of an interface type

plugin

GTypePlugin structure to retrieve the GInterfaceInfo from

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

interface_type

GType value of an interface type

prerequisite_type

GType value of an interface or instantiatable type

g_type_get_plugin ()

GTypePlugin *
g_type_get_plugin (GType type);

Returns the GTypePlugin structure for type
.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

GType to retrieve the plugin for

Returns

 the corresponding plugin
if type
is a dynamic type, NULL otherwise.

[<acronym title="Don't free data after the code is done.">transfer none</acronym>]

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().

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance_type

GType of an instantiatable type

interface_type

GType of an interface type

Returns

 the GTypePlugin for the dynamic
interface interface_type
of instance_type
.

[<acronym title="Don't free data after the code is done.">transfer none</acronym>]

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.

Returns

 the next available fundamental type ID to be registered,
or 0 if the type system ran out of fundamental type IDs

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type_id

valid type ID

Returns

 fundamental type ID

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.

The extended members of the returned instance are guaranteed to be filled
with zeros.

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.

[<acronym title="Exposed in C code, not necessarily available in other languages.">skip</acronym>]

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

an instantiatable type to create an instance for

Returns

 an allocated and initialized instance, subject to further
treatment by the fundamental type implementation

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

instance

an instance of a type

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.

[<acronym title="Exposed in C code, not necessarily available in other languages.">skip</acronym>]

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

cache_data

data to be passed to cache_func

cache_func

a GTypeClassCacheFunc

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.

[<acronym title="Exposed in C code, not necessarily available in other languages.">skip</acronym>]

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

cache_data

data that was given when adding cache_func

cache_func

a GTypeClassCacheFunc

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.

[<acronym title="Exposed in C code, not necessarily available in other languages.">skip</acronym>]

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

g_class

 a GTypeClass structure to unref.

[<acronym title="Override the parsed C type with given type.">type</acronym> GObject.TypeClass]

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.

[<acronym title="Exposed in C code, not necessarily available in other languages.">skip</acronym>]

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

check_data

data to pass to check_func

check_func

function to be called after each interface
is initialized

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().

[<acronym title="Exposed in C code, not necessarily available in other languages.">skip</acronym>]

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

check_data

callback data passed to g_type_add_interface_check()

check_func

callback function passed to 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().

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

check_data

data passed to g_type_add_interface_check()

g_iface

the interface that has been initialized

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
.

[<acronym title="Exposed in C code, not necessarily available in other languages.">skip</acronym>]

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

a GType

Returns

 location of the GTypeValueTable associated with type
or
NULL if there is no GTypeValueTable associated with type

g_type_ensure ()

void
g_type_ensure (GType type);

Ensures that the indicated type
 has been registered with the
type system, and its _class_init() method has been run.

In theory, simply calling the type's _get_type() method (or using
the corresponding macro) is supposed take care of this. However,
_get_type() methods are often marked G_GNUC_CONST for performance
reasons, even though this is technically incorrect (since
G_GNUC_CONST requires that the function not have side effects,
which _get_type() methods do on the first call). As a result, if
you write a bare call to a _get_type() macro, it may get optimized
out by the compiler. Using g_type_ensure() guarantees that the
type's _get_type() method is called.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

a GType

Since: 2.34

g_type_get_type_registration_serial ()

guint
g_type_get_type_registration_serial (void);

Returns an opaque serial number that represents the state of the set
of registered types. Any time a type is registered this serial changes,
which means you can cache information based on type lookups (such as
g_type_from_name()) and know if the cache is still valid at a later
time by comparing the current serial with the one at the type lookup.

Returns

 An unsigned int, representing the state of type registrations

Since: 2.36

g_type_get_instance_count ()

int
g_type_get_instance_count (GType type);

Returns the number of instances allocated of the particular type;
this is only available if GLib is built with debugging support and
the instance_count debug flag is set (by setting the GOBJECT_DEBUG
variable to include instance-count).

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

type

a GType

Returns

 the number of instances allocated of the given type;
if instance counts are not available, returns 0.

Since: 2.44

G_DECLARE_FINAL_TYPE()

#define             G_DECLARE_FINAL_TYPE(ModuleObjName, module_obj_name, MODULE, OBJ_NAME, ParentName)

A convenience macro for emitting the usual declarations in the header file for a type which is not (at the
present time) intended to be subclassed.

You might use it in a header as follows:

1
2
3
4
5
6
7
8
9
10
11
12
13

#ifndef _myapp_window_h_
#define _myapp_window_h_

#include <gtk/gtk.h>

#define MY_APP_TYPE_WINDOW my_app_window_get_type ()
G_DECLARE_FINAL_TYPE (MyAppWindow, my_app_window, MY_APP, WINDOW, GtkWindow)

MyAppWindow *    my_app_window_new    (void);

...

#endif

This results in the following things happening:

the usual my_app_window_get_type() function is declared with a return type of GType

the MyAppWindow types is defined as a typedef of struct _MyAppWindow.  The struct itself is not
defined and should be defined from the .c file before G_DEFINE_TYPE() is used.

the MY_APP_WINDOW() cast is emitted as static inline function along with the MY_APP_IS_WINDOW() type
checking function

the MyAppWindowClass type is defined as a struct containing GtkWindowClass.  This is done for the
convenience of the person defining the type and should not be considered to be part of the ABI.  In
particular, without a firm declaration of the instance structure, it is not possible to subclass the type
and therefore the fact that the size of the class structure is exposed is not a concern and it can be
freely changed at any point in the future.

g_autoptr() support being added for your type, based on the type of your parent class

You can only use this function if your parent type also supports g_autoptr().

Because the type macro (MY_APP_TYPE_WINDOW in the above example) is not a callable, you must continue to
manually define this as a macro for yourself.

The declaration of the _get_type() function is the first thing emitted by the macro.  This allows this macro
to be used in the usual way with export control and API versioning macros.

If you want to declare your own class structure, use G_DECLARE_DERIVABLE_TYPE().

If you are writing a library, it is important to note that it is possible to convert a type from using
G_DECLARE_FINAL_TYPE() to G_DECLARE_DERIVABLE_TYPE() without breaking API or ABI.  As a precaution, you
should therefore use G_DECLARE_FINAL_TYPE() until you are sure that it makes sense for your class to be
subclassed.  Once a class structure has been exposed it is not possible to change its size or remove or
reorder items without breaking the API and/or ABI.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

ModuleObjName

The name of the new type, in camel case (like GtkWidget)

module_obj_name

The name of the new type in lowercase, with words
separated by '_' (like 'gtk_widget')

MODULE

The name of the module, in all caps (like 'GTK')

OBJ_NAME

The bare name of the type, in all caps (like 'WIDGET')

ParentName

the name of the parent type, in camel case (like GtkWidget)

Since: 2.44

G_DECLARE_DERIVABLE_TYPE()

#define             G_DECLARE_DERIVABLE_TYPE(ModuleObjName, module_obj_name, MODULE, OBJ_NAME, ParentName)

A convenience macro for emitting the usual declarations in the header file for a type which will is intended
to be subclassed.

You might use it in a header as follows:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

#ifndef _gtk_frobber_h_
#define _gtk_frobber_h_

#define GTK_TYPE_FROBBER gtk_frobber_get_type ()
GDK_AVAILABLE_IN_3_12
G_DECLARE_DERIVABLE_TYPE (GtkFrobber, gtk_frobber, GTK, FROBBER, GtkWidget)

struct _GtkFrobberClass
{
  GtkWidgetClass parent_class;

  void (* handle_frob)  (GtkFrobber *frobber,
                         guint       n_frobs);

  gpointer padding[12];
};

GtkWidget *    gtk_frobber_new   (void);

...

#endif

This results in the following things happening:

the usual gtk_frobber_get_type() function is declared with a return type of GType

the GtkFrobber struct is created with GtkWidget as the first and only item.  You are expected to use
a private structure from your .c file to store your instance variables.

the GtkFrobberClass type is defined as a typedef to struct _GtkFrobberClass, which is left undefined.
You should do this from the header file directly after you use the macro.

the GTK_FROBBER() and GTK_FROBBER_CLASS() casts are emitted as static inline functions along with
the GTK_IS_FROBBER() and GTK_IS_FROBBER_CLASS() type checking functions and GTK_FROBBER_GET_CLASS()
function.

g_autoptr() support being added for your type, based on the type of your parent class

You can only use this function if your parent type also supports g_autoptr().

Because the type macro (GTK_TYPE_FROBBER in the above example) is not a callable, you must continue to
manually define this as a macro for yourself.

The declaration of the _get_type() function is the first thing emitted by the macro.  This allows this macro
to be used in the usual way with export control and API versioning macros.

If you are writing a library, it is important to note that it is possible to convert a type from using
G_DECLARE_FINAL_TYPE() to G_DECLARE_DERIVABLE_TYPE() without breaking API or ABI.  As a precaution, you
should therefore use G_DECLARE_FINAL_TYPE() until you are sure that it makes sense for your class to be
subclassed.  Once a class structure has been exposed it is not possible to change its size or remove or
reorder items without breaking the API and/or ABI.  If you want to declare your own class structure, use
G_DECLARE_DERIVABLE_TYPE().  If you want to declare a class without exposing the class or instance
structures, use G_DECLARE_FINAL_TYPE().

If you must use G_DECLARE_DERIVABLE_TYPE() you should be sure to include some padding at the bottom of your
class structure to leave space for the addition of future virtual functions.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

ModuleObjName

The name of the new type, in camel case (like GtkWidget)

module_obj_name

The name of the new type in lowercase, with words
separated by '_' (like 'gtk_widget')

MODULE

The name of the module, in all caps (like 'GTK')

OBJ_NAME

The bare name of the type, in all caps (like 'WIDGET')

ParentName

the name of the parent type, in camel case (like GtkWidget)

Since: 2.44

G_DECLARE_INTERFACE()

#define             G_DECLARE_INTERFACE(ModuleObjName, module_obj_name, MODULE, OBJ_NAME, PrerequisiteName)

A convenience macro for emitting the usual declarations in the header file for a GInterface type.

You might use it in a header as follows:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

#ifndef _my_model_h_
#define _my_model_h_

#define MY_TYPE_MODEL my_model_get_type ()
GDK_AVAILABLE_IN_3_12
G_DECLARE_INTERFACE (MyModel, my_model, MY, MODEL, GObject)

struct _MyModelInterface
{
  GTypeInterface g_iface;

  gpointer (* get_item)  (MyModel *model);
};

gpointer my_model_get_item (MyModel *model);

...

#endif

This results in the following things happening:

the usual my_model_get_type() function is declared with a return type of GType

the MyModelInterface type is defined as a typedef to struct _MyModelInterface,
which is left undefined. You should do this from the header file directly after
you use the macro.

the MY_MODEL() cast is emitted as static inline functions along with
the MY_IS_MODEL() type checking function and MY_MODEL_GET_IFACE() function.

g_autoptr() support being added for your type, based on your prerequisite type.

You can only use this function if your prerequisite type also supports g_autoptr().

Because the type macro (MY_TYPE_MODEL in the above example) is not a callable, you must continue to
manually define this as a macro for yourself.

The declaration of the _get_type() function is the first thing emitted by the macro.  This allows this macro
to be used in the usual way with export control and API versioning macros.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

ModuleObjName

The name of the new type, in camel case (like GtkWidget)

module_obj_name

The name of the new type in lowercase, with words
separated by '_' (like 'gtk_widget')

MODULE

The name of the module, in all caps (like 'GTK')

OBJ_NAME

The bare name of the type, in all caps (like 'WIDGET')

PrerequisiteName

the name of the prerequisite type, in camel case (like GtkWidget)

Since: 2.44

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TN

The name of the new type, in Camel case.

t_n

The name of the new type, in lowercase, with words
separated by '_'.

T_P

The GType of the parent type.

Since: 2.4

G_DEFINE_TYPE_WITH_PRIVATE()

#define G_DEFINE_TYPE_WITH_PRIVATE(TN, t_n, T_P)            G_DEFINE_TYPE_EXTENDED (TN, t_n, T_P, 0, G_ADD_PRIVATE (TN))

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

Note that private structs added with this macros must have a struct
name of the form TN
 Private.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TN

The name of the new type, in Camel case.

t_n

The name of the new type, in lowercase, with words
separated by '_'.

T_P

The GType of the parent type.

Since: 2.38

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 you 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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TN

The name of the new type, in Camel case.

t_n

The name of the new type in lowercase, with words separated by '_'.

T_P

The GType of the parent type.

_C_

Custom code that gets inserted in the *_get_type() function.

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TN

The name of the new type, in Camel case.

t_n

The name of the new type, in lowercase, with words
separated by '_'.

T_P

The GType of the parent type.

Since: 2.4

G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE()

#define G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE(TN, t_n, T_P)   G_DEFINE_TYPE_EXTENDED (TN, t_n, T_P, G_TYPE_FLAG_ABSTRACT, G_ADD_PRIVATE (TN))

Similar to G_DEFINE_TYPE_WITH_PRIVATE(), but defines an abstract type.
See G_DEFINE_TYPE_EXTENDED() for an example.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TN

The name of the new type, in Camel case.

t_n

The name of the new type, in lowercase, with words
separated by '_'.

T_P

The GType of the parent type.

Since: 2.38

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 you 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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TN

The name of the new type, in Camel case.

t_n

The name of the new type, in lowercase, with words
separated by '_'.

T_P

The GType of the parent type.

_C_

Custom code that gets inserted in the type_name_get_type()
function.

Since: 2.4

G_ADD_PRIVATE()

#define             G_ADD_PRIVATE(TypeName)

A convenience macro to ease adding private data to instances of a new type
in the _C_
 section of G_DEFINE_TYPE_WITH_CODE() or
G_DEFINE_ABSTRACT_TYPE_WITH_CODE().

For instance:

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typedef struct _MyObject MyObject;
typedef struct _MyObjectClass MyObjectClass;

typedef struct {
  gint foo;
  gint bar;
} MyObjectPrivate;

G_DEFINE_TYPE_WITH_CODE (MyObject, my_object, G_TYPE_OBJECT,
                         G_ADD_PRIVATE (MyObject))

Will add MyObjectPrivate as the private data to any instance of the MyObject
type.

G_DEFINE_TYPE_* macros will automatically create a private function
based on the arguments to this macro, which can be used to safely
retrieve the private data from an instance of the type; for instance:

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gint
my_object_get_foo (MyObject *obj)
{
  MyObjectPrivate *priv = my_object_get_instance_private (obj);

  g_return_val_if_fail (MY_IS_OBJECT (obj), 0);

  return priv->foo;
}

void
my_object_set_bar (MyObject *obj,
                   gint      bar)
{
  MyObjectPrivate *priv = my_object_get_instance_private (obj);

  g_return_if_fail (MY_IS_OBJECT (obj));

  if (priv->bar != bar)
    priv->bar = bar;
}

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

Also note that private structs added with these macros must have a struct
name of the form TypeNamePrivate.

It is safe to call _get_instance_private on NULL or invalid object since
it's only adding an offset to the instance pointer. In that case the returned
pointer must not be dereferenced.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TypeName

the name of the type in CamelCase

Since: 2.38

G_PRIVATE_OFFSET()

#define             G_PRIVATE_OFFSET(TypeName, field)

Evaluates to the offset of the field
 inside the instance private data
structure for TypeName
.

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

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TypeName

the name of the type in CamelCase

field

the name of the field in the private data structure

Since: 2.38

G_PRIVATE_FIELD()

#define             G_PRIVATE_FIELD(TypeName, inst, field_type, field_name)

Evaluates to the field_name
 inside the inst
 private data
structure for TypeName
.

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

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TypeName

the name of the type in CamelCase

inst

the instance of TypeName
you wish to access

field_type

the type of the field in the private data structure

field_name

the name of the field in the private data structure

Since: 2.38

G_PRIVATE_FIELD_P()

#define             G_PRIVATE_FIELD_P(TypeName, inst, field_name)

Evaluates to a pointer to the field_name
 inside the inst
 private data
structure for TypeName
.

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

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TypeName

the name of the type in CamelCase

inst

the instance of TypeName
you wish to access

field_name

the name of the field in the private data structure

Since: 2.38

G_DEFINE_INTERFACE()

#define G_DEFINE_INTERFACE(TN, t_n, T_P)		    G_DEFINE_INTERFACE_WITH_CODE(TN, t_n, T_P, ;)

A convenience macro for GTypeInterface definitions, which declares
a default vtable initialization function and defines a *_get_type()
function.

The macro expects the interface initialization function to have the
name t_n ## _default_init, and the interface structure to have the
name TN ## Interface.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TN

The name of the new type, in Camel case.

t_n

The name of the new type, in lowercase, with words separated by '_'.

T_P

The GType of the prerequisite type for the interface, or 0
(G_TYPE_INVALID) for no prerequisite type.

Since: 2.24

G_DEFINE_INTERFACE_WITH_CODE()

#define G_DEFINE_INTERFACE_WITH_CODE(TN, t_n, T_P, _C_)     _G_DEFINE_INTERFACE_EXTENDED_BEGIN(TN, t_n, T_P) {_C_;} _G_DEFINE_INTERFACE_EXTENDED_END()

A convenience macro for GTypeInterface definitions. Similar to
G_DEFINE_INTERFACE(), but allows you to insert custom code into the
*_get_type() function, e.g. additional interface implementations
via G_IMPLEMENT_INTERFACE(), or additional prerequisite types. See
G_DEFINE_TYPE_EXTENDED() for a similar example using
G_DEFINE_TYPE_WITH_CODE().

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TN

The name of the new type, in Camel case.

t_n

The name of the new type, in lowercase, with words separated by '_'.

T_P

The GType of the prerequisite type for the interface, or 0
(G_TYPE_INVALID) for no prerequisite type.

_C_

Custom code that gets inserted in the *_get_type() function.

Since: 2.24

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TYPE_IFACE

The GType of the interface to add

iface_init

The interface init function

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 volatile gsize g_define_type_id__volatile = 0;
  if (g_once_init_enter (&g_define_type_id__volatile))
    {
      GType g_define_type_id =
        g_type_register_static_simple (GTK_TYPE_WIDGET,
                                       g_intern_static_string ("GtkGadget"),
                                       sizeof (GtkGadgetClass),
                                       (GClassInitFunc) gtk_gadget_class_intern_init,
                                       sizeof (GtkGadget),
                                       (GInstanceInitFunc) gtk_gadget_init,
                                       0);
      {
        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);
      }
      g_once_init_leave (&g_define_type_id__volatile, g_define_type_id);
    }
  return g_define_type_id__volatile;
}

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.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TN

The name of the new type, in Camel case.

t_n

The name of the new type, in lowercase, with words
separated by '_'.

T_P

The GType of the parent type.

_f_

GTypeFlags to pass to g_type_register_static()

_C_

Custom code that gets inserted in the *_get_type() function.

Since: 2.4

G_DEFINE_BOXED_TYPE()

#define G_DEFINE_BOXED_TYPE(TypeName, type_name, copy_func, free_func) G_DEFINE_BOXED_TYPE_WITH_CODE (TypeName, type_name, copy_func, free_func, {})

A convenience macro for boxed type implementations, which defines a
type_name_get_type() function registering the boxed type.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TypeName

The name of the new type, in Camel case

type_name

The name of the new type, in lowercase, with words
separated by '_'

copy_func

the GBoxedCopyFunc for the new type

free_func

the GBoxedFreeFunc for the new type

Since: 2.26

G_DEFINE_BOXED_TYPE_WITH_CODE()

#define G_DEFINE_BOXED_TYPE_WITH_CODE(TypeName, type_name, copy_func, free_func, _C_) _G_DEFINE_BOXED_TYPE_BEGIN (TypeName, type_name, copy_func, free_func) {_C_;} _G_DEFINE_TYPE_EXTENDED_END()

A convenience macro for boxed type implementations.
Similar to G_DEFINE_BOXED_TYPE(), but allows to insert custom code into the
type_name_get_type() function, e.g. to register value transformations with
g_value_register_transform_func(), for instance:

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G_DEFINE_BOXED_TYPE_WITH_CODE (GdkRectangle, gdk_rectangle,
                               gdk_rectangle_copy,
                               gdk_rectangle_free,
                               register_rectangle_transform_funcs (g_define_type_id))

Similarly to the G_DEFINE_TYPE family of macros, the GType of the newly
defined boxed type is exposed in the g_define_type_id variable.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TypeName

The name of the new type, in Camel case

type_name

The name of the new type, in lowercase, with words
separated by '_'

copy_func

the GBoxedCopyFunc for the new type

free_func

the GBoxedFreeFunc for the new type

_C_

Custom code that gets inserted in the *_get_type() function

Since: 2.26

G_DEFINE_POINTER_TYPE()

#define G_DEFINE_POINTER_TYPE(TypeName, type_name) G_DEFINE_POINTER_TYPE_WITH_CODE (TypeName, type_name, {})

A convenience macro for pointer type implementations, which defines a
type_name_get_type() function registering the pointer type.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TypeName

The name of the new type, in Camel case

type_name

The name of the new type, in lowercase, with words
separated by '_'

Since: 2.26

G_DEFINE_POINTER_TYPE_WITH_CODE()

#define G_DEFINE_POINTER_TYPE_WITH_CODE(TypeName, type_name, _C_) _G_DEFINE_POINTER_TYPE_BEGIN (TypeName, type_name) {_C_;} _G_DEFINE_TYPE_EXTENDED_END()

A convenience macro for pointer type implementations.
Similar to G_DEFINE_POINTER_TYPE(), but allows to insert
custom code into the type_name_get_type() function.

Parameters

<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>

TypeName

The name of the new type, in Camel case

type_name

The name of the new type, in lowercase, with words
separated by '_'

_C_

Custom code that gets inserted in the *_get_type() function

Since: 2.26

G_TYPE_CHECKSUM

#define G_TYPE_CHECKSUM (g_checksum_get_type ())

The GType for a boxed type holding a GChecksum.

Since: 2.36

Types and Values

GType

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

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.

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().

Members

<colgroup>
<col width="300px" class="struct_members_name">
<col class="struct_members_description">
<col width="200px" class="struct_members_annotations">
</colgroup>

guint16 class_size;

Size of the class structure (required for interface, classed and instantiatable types)

GBaseInitFunc base_init;

Location of the base initialization function (optional)

GBaseFinalizeFunc base_finalize;

Location of the base finalization function (optional)

GClassInitFunc class_init;

Location of the class initialization function for
classed and instantiatable types. Location of the default vtable
inititalization function for interface types. (optional) This function
is used both to fill in virtual functions in the class or default vtable,
and to do type-specific setup such as registering signals and object
properties.

GClassFinalizeFunc class_finalize;

Location of the class finalization function for
classed and instantiatable types. Location of the default vtable
finalization function for interface types. (optional)

gconstpointer class_data;

User-supplied data passed to the class init/finalize functions

guint16 instance_size;

Size of the instance (object) structure (required for instantiatable types only)

guint16 n_preallocs;

Prior to GLib 2.10, it specified the number of pre-allocated (cached) instances to reserve memory for (0 indicates no caching). Since GLib 2.10, it is ignored, since instances are allocated with the slice allocator now.

GInstanceInitFunc instance_init;

Location of the instance initialization function (optional, for instantiatable types only)

const GTypeValueTable *value_table;

A GTypeValueTable function table for generic handling of GValues
of this type (usually only useful for fundamental types)

struct GTypeFundamentalInfo

struct GTypeFundamentalInfo {
  GTypeFundamentalFlags  type_flags;
};

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

Members

<colgroup>
<col width="300px" class="struct_members_name">
<col class="struct_members_description">
<col width="200px" class="struct_members_annotations">
</colgroup>

GTypeFundamentalFlags type_flags;

GTypeFundamentalFlags describing the characteristics of the fundamental type

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.

Members

<colgroup>
<col width="300px" class="struct_members_name">
<col class="struct_members_description">
<col width="200px" class="struct_members_annotations">
</colgroup>

GInterfaceInitFunc interface_init;

location of the interface initialization function

GInterfaceFinalizeFunc interface_finalize;

location of the interface finalization function

gpointer interface_data;

user-supplied data passed to the interface init/finalize functions

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);
  const gchar *collect_format;
  gchar*   (*collect_value)      (GValue       *value,
				  guint         n_collect_values,
				  GTypeCValue  *collect_values,
				  guint		collect_flags);
  const 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.

Members

<colgroup>
<col width="300px" class="struct_members_name">
<col class="struct_members_description">
<col width="200px" class="struct_members_annotations">
</colgroup>

value_init ()

Default initialize values
contents by poking values
directly into the value->data array. The data array of
the GValue passed into this function was zero-filled
with memset(), so no care has to be taken to free any
old contents. E.g. for the implementation of a string
value that may never be NULL, the implementation might
look like:

1

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

value_free ()

Free any old contents that might be left in the
data array of the passed in value
. No resources may
remain allocated through the GValue contents after
this function returns. E.g. for our above string type:

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2
3

// 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);

value_copy ()

dest_value
is a GValue with zero-filled data section
and src_value
is a properly setup GValue of same or
derived type.
The purpose of this function is to copy the contents of
src_value
into dest_value
in a way, that even after
src_value
has been freed, the contents of dest_value
remain valid. String type example:

1

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

value_peek_pointer ()

If the value contents fit into a pointer, such as objects
or strings, return this pointer, so the caller can peek at
the current contents. To extend on our above string example:

1

return value->data[0].v_pointer;

const gchar *collect_format;

A string format describing how to collect the contents of
this value bit-by-bit. Each character in the format represents
an argument to be collected, and the characters themselves indicate
the type of the argument. Currently supported arguments are:

'i' - Integers. passed as collect_values[].v_int.

'l' - Longs. passed as collect_values[].v_long.

'd' - Doubles. passed as collect_values[].v_double.

'p' - Pointers. passed as collect_values[].v_pointer.
It should be noted that for variable argument list construction,
ANSI C promotes every type smaller than an integer to an int, and
floats to doubles. So for collection of short int or char, 'i'
needs to be used, and for collection of floats 'd'.

collect_value ()

The collect_value() function is responsible for converting the
values collected from a variable argument list into contents
suitable for storage in a GValue. This function should setup
value
similar to value_init(); e.g. for a string value that
does not allow NULL pointers, it needs to either spew an error,
or do an implicit conversion by storing an empty string.
The value
passed in to this function has a zero-filled data
array, so just like for value_init() it is guaranteed to not
contain any old contents that might need freeing.
n_collect_values
is exactly the string length of collect_format
,
and collect_values
is an array of unions GTypeCValue with
length n_collect_values
, containing the collected values
according to collect_format
.
collect_flags
is an argument provided as a hint by the caller.
It may contain the flag G_VALUE_NOCOPY_CONTENTS indicating,
that the collected value contents may be considered "static"
for the duration of the value
lifetime.
Thus an extra copy of the contents stored in collect_values
is
not required for assignment to value
.
For our above string example, we continue with:

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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;

It should be noted, that it is generally a bad idea to follow the
G_VALUE_NOCOPY_CONTENTS hint for reference counted types. Due to
reentrancy requirements and reference count assertions performed
by the signal emission code, reference counts should always be
incremented for reference counted contents stored in the value->data
array.  To deviate from our string example for a moment, and taking
a look at an exemplary implementation for collect_value() of
GObject:

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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");
}

The reference count for valid objects is always incremented,
regardless of collect_flags
. For invalid objects, the example
returns a newly allocated string without altering value
.
Upon success, collect_value() needs to return NULL. If, however,
an error condition occurred, collect_value() may spew an
error by returning a newly allocated non-NULL string, giving
a suitable description of the error condition.
The calling code makes no assumptions about the value
contents being valid upon error returns, value
is simply thrown away without further freeing. As such, it is
a good idea to not allocate GValue contents, prior to returning
an error, however, collect_values() is not obliged to return
a correctly setup value
for error returns, simply because
any non-NULL return is considered a fatal condition so further
program behaviour is undefined.

const gchar *lcopy_format;

Format description of the arguments to collect for lcopy_value
,
analogous to collect_format
. Usually, lcopy_format
string consists
only of 'p's to provide lcopy_value() with pointers to storage locations.

lcopy_value ()

This function is responsible for storing the value
contents into
arguments passed through a variable argument list which got
collected into collect_values
according to lcopy_format
.
n_collect_values
equals the string length of lcopy_format
,
and collect_flags
may contain G_VALUE_NOCOPY_CONTENTS.
In contrast to collect_value(), lcopy_value() is obliged to
always properly support G_VALUE_NOCOPY_CONTENTS.
Similar to collect_value() the function may prematurely abort
by returning a newly allocated string describing an error condition.
To complete the string example:

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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);

And an illustrative version of lcopy_value() for
reference-counted types:

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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_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.

enum GTypeDebugFlags

GTypeDebugFlags has been deprecated since version 2.36 and should not be used in newly-written code.

g_type_init() is now done automatically

These flags used to be passed to g_type_init_with_debug_flags() which
is now deprecated.

If you need to enable debugging features, use the GOBJECT_DEBUG
environment variable.

Members

<colgroup>
<col width="300px" class="enum_members_name">
<col class="enum_members_description">
<col width="200px" class="enum_members_annotations">
</colgroup>

G_TYPE_DEBUG_NONE

Print no messages

G_TYPE_DEBUG_OBJECTS

Print messages about object bookkeeping

G_TYPE_DEBUG_SIGNALS

Print messages about signal emissions

G_TYPE_DEBUG_INSTANCE_COUNT

Keep a count of instances of each type

G_TYPE_DEBUG_MASK

Mask covering all debug flags

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.

Members

<colgroup>
<col width="300px" class="struct_members_name">
<col class="struct_members_description">
<col width="200px" class="struct_members_annotations">
</colgroup>

GType type;

the GType value of the type

const gchar *type_name;

the name of the type

guint class_size;

the size of the class structure

guint instance_size;

the size of the instance structure

enum GTypeFlags

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

Members

<colgroup>
<col width="300px" class="enum_members_name">
<col class="enum_members_description">
<col width="200px" class="enum_members_annotations">
</colgroup>

G_TYPE_FLAG_ABSTRACT

Indicates an abstract type. No instances can be
 created for an abstract type

G_TYPE_FLAG_VALUE_ABSTRACT

Indicates an abstract value type, i.e. a type
 that introduces a value table, but can't be used for
 g_value_init()

enum GTypeFundamentalFlags

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

Members

<colgroup>
<col width="300px" class="enum_members_name">
<col class="enum_members_description">
<col width="200px" class="enum_members_annotations">
</colgroup>

G_TYPE_FLAG_CLASSED

Indicates a classed type

G_TYPE_FLAG_INSTANTIATABLE

Indicates an instantiable type (implies classed)

G_TYPE_FLAG_DERIVABLE

Indicates a flat derivable type

G_TYPE_FLAG_DEEP_DERIVABLE

Indicates a deep derivable type (implies derivable)

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_VARIANT

#define G_TYPE_VARIANT                  G_TYPE_MAKE_FUNDAMENTAL (21)

The fundamental type corresponding to GVariant.

All floating GVariant instances passed through the GType system are
consumed.

Note that callbacks in closures, and signal handlers
for signals of return type G_TYPE_VARIANT, must never return floating
variants.

Note: GLib 2.24 did include a boxed type with this name. It was replaced
with this fundamental type in 2.26.

Since: 2.26

G_TYPE_RESERVED_GLIB_FIRST

#define G_TYPE_RESERVED_GLIB_FIRST (22)

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().

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