gtype.sgml

This GLib version 2.16.1. GLib is the low-level core library that forms the basis for projects such

implementing a fundamental type. Also language bindings should <emphasis>not</emphasis>
use this function but g_object_new() instead.
</para>

@type: 	  An instantiatable type to create an instance for.
@Returns: An allocated and initialized instance, subject to further
	  treatment by the fundamental type implementation.


<!-- ##### FUNCTION g_type_free_instance ##### -->
<para>
Frees an instance of a type, returning it to the instance pool for the type,
if there is one.
</para>
<para>
Like g_type_create_instance(), this function is reserved for implementors of 
fundamental types.
</para>

@instance: an instance of a type.


<!-- ##### FUNCTION g_type_add_class_cache_func ##### -->
<para>
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.
</para>

@cache_data: data to be passed to @cache_func
@cache_func: a #GTypeClassCacheFunc


<!-- ##### FUNCTION g_type_remove_class_cache_func ##### -->
<para>
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.
</para>

@cache_data: data that was given when adding @cache_func
@cache_func: a #GTypeClassCacheFunc


<!-- ##### FUNCTION g_type_class_unref_uncached ##### -->
<para>
A variant of g_type_class_unref() for use in #GTypeClassCacheFunc
implementations. It unreferences a class without consulting the chain
of #GTypeClassCacheFunc<!-- -->s, avoiding the recursion which would occur
otherwise.
</para>

@g_class: The #GTypeClass structure to unreference.


<!-- ##### FUNCTION g_type_add_interface_check ##### -->
<para>
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).
</para>
<para>
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.    
</para>

@check_data: data to pass to @check_func
@check_func: function to be called after each interface
   is initialized.
@Since: 2.4


<!-- ##### FUNCTION g_type_remove_interface_check ##### -->
<para>
Removes an interface check function added with
g_type_add_interface_check().
</para>

@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


<!-- ##### USER_FUNCTION GTypeInterfaceCheckFunc ##### -->
<para>
A callback called after an interface vtable is initialized.
See g_type_add_interface_check().
</para>

@check_data: data passed to g_type_add_interface_check().
@g_iface: the interface that has been initialized
@Since: 2.4


<!-- ##### FUNCTION g_type_value_table_peek ##### -->
<para>
Returns the location of the #GTypeValueTable associated with @type.
<emphasis>Note that this function should only be used from source code
that implements or has internal knowledge of the implementation of
@type.</emphasis>
</para>

@type:    A #GType value.
@Returns: Location of the #GTypeValueTable associated with @type or
          %NULL if there is no #GTypeValueTable associated with @type.


<!-- ##### MACRO G_DEFINE_TYPE ##### -->
<para>
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.
</para>

@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


<!-- ##### MACRO G_DEFINE_TYPE_WITH_CODE ##### -->
<para>
A convenience macro for type implementations.  
Similar to G_DEFINE_TYPE(), but allows to insert custom code into the 
*_get_type() function, e.g. interface implementations via G_IMPLEMENT_INTERFACE().
See G_DEFINE_TYPE_EXTENDED() for an example.
</para>

@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


<!-- ##### MACRO G_DEFINE_ABSTRACT_TYPE ##### -->
<para>
A convenience macro for type implementations. 
Similar to G_DEFINE_TYPE(), but defines an abstract type. 
See G_DEFINE_TYPE_EXTENDED() for an example.
</para>

@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


<!-- ##### MACRO G_DEFINE_ABSTRACT_TYPE_WITH_CODE ##### -->
<para>
A convenience macro for type implementations.
Similar to G_DEFINE_TYPE_WITH_CODE(), but defines an abstract type and allows to 
insert custom code into the *_get_type() function, e.g. interface implementations 
via G_IMPLEMENT_INTERFACE(). See G_DEFINE_TYPE_EXTENDED() for an example.
</para>

@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


<!-- ##### MACRO G_IMPLEMENT_INTERFACE ##### -->
<para>
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.
</para>
<para>
Note that this macro can only be used together with the G_DEFINE_TYPE_*
macros, since it depends on variable names from those macros.
</para>

@TYPE_IFACE: The #GType of the interface to add
@iface_init: The interface init function
@Since: 2.4


<!-- ##### MACRO G_DEFINE_TYPE_EXTENDED ##### -->
<para>
The most general convenience macro for type implementations, on which 
G_DEFINE_TYPE(), etc are based. 
</para>
<informalexample><programlisting>
G_DEFINE_TYPE_EXTENDED (GtkGadget, 
                        gtk_gadget, 
                        GTK_TYPE_WIDGET,
                        0, 
                        G_IMPLEMENT_INTERFACE (TYPE_GIZMO, 
                                               gtk_gadget_gizmo_init));
</programlisting>
expands to
<programlisting>
static void     gtk_gadget_init       (GtkGadget      *self);
static void     gtk_gadget_class_init (GtkGadgetClass *klass);
static gpointer gtk_gadget_parent_class = NULL;
static void     gtk_gadget_class_intern_init (gpointer klass)
{
  gtk_gadget_parent_class = g_type_class_peek_parent (klass);
  gtk_gadget_class_init ((GtkGadgetClass*) klass);
}
<!-- -->
GType
gtk_gadget_get_type (void)
{
  static GType g_define_type_id = 0; 
  if (G_UNLIKELY (g_define_type_id == 0)) 
    { 
      static const GTypeInfo g_define_type_info = { 
        sizeof (GtkGadgetClass), 
        (GBaseInitFunc) NULL, 
        (GBaseFinalizeFunc) NULL, 
        (GClassInitFunc) gtk_gadget_class_intern_init, 
        (GClassFinalizeFunc) NULL, 
        NULL,   /* class_data */ 
        sizeof (GtkGadget), 
        0,      /* n_preallocs */ 
        (GInstanceInitFunc) gtk_gadget_init, 
      }; 
      g_define_type_id = g_type_register_static (GTK_TYPE_WIDGET, "GtkGadget", &amp;g_define_type_info, 0); 
      {
        static const GInterfaceInfo g_implement_interface_info = {
          (GInterfaceInitFunc) gtk_gadget_gizmo_init
        };
        g_type_add_interface_static (g_define_type_id, TYPE_GIZMO, &amp;g_implement_interface_info);
      } 
    } 
  return g_define_type_id; 
}
</programlisting>
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.
</informalexample>

@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


<!-- ##### MACRO G_TYPE_INVALID ##### -->
<para>
An invalid #GType used as error return value in some functions which return
a #GType. 
</para>



<!-- ##### MACRO G_TYPE_NONE ##### -->
<para>
A fundamental type which is used as a replacement for the C
<literal>void</literal> return type.
</para>



<!-- ##### MACRO G_TYPE_INTERFACE ##### -->
<para>
The fundamental type from which all interfaces are derived.
</para>



<!-- ##### MACRO G_TYPE_CHAR ##### -->
  <para>
    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".
  </para>



<!-- ##### MACRO G_TYPE_UCHAR ##### -->
<para>
The fundamental type corresponding to #guchar.
</para>



<!-- ##### MACRO G_TYPE_BOOLEAN ##### -->
<para>
The fundamental type corresponding to #gboolean.
</para>



<!-- ##### MACRO G_TYPE_INT ##### -->
<para>
The fundamental type corresponding to #gint.
</para>



<!-- ##### MACRO G_TYPE_UINT ##### -->
<para>
The fundamental type corresponding to #guint.
</para>



<!-- ##### MACRO G_TYPE_LONG ##### -->
<para>
The fundamental type corresponding to #glong.
</para>



<!-- ##### MACRO G_TYPE_ULONG ##### -->
<para>
The fundamental type corresponding to #gulong.
</para>



<!-- ##### MACRO G_TYPE_INT64 ##### -->
<para>
The fundamental type corresponding to #gint64.
</para>



<!-- ##### MACRO G_TYPE_UINT64 ##### -->
<para>
The fundamental type corresponding to #guint64.
</para>



<!-- ##### MACRO G_TYPE_ENUM ##### -->
<para>
The fundamental type from which all enumeration types are derived.
</para>



<!-- ##### MACRO G_TYPE_FLAGS ##### -->
<para>
The fundamental type from which all flags types are derived.
</para>



<!-- ##### MACRO G_TYPE_FLOAT ##### -->
<para>
The fundamental type corresponding to #gfloat.
</para>



<!-- ##### MACRO G_TYPE_DOUBLE ##### -->
<para>
The fundamental type corresponding to #gdouble.
</para>



<!-- ##### MACRO G_TYPE_STRING ##### -->
<para>
The fundamental type corresponding to nul-terminated C strings.
</para>



<!-- ##### MACRO G_TYPE_POINTER ##### -->
<para>
The fundamental type corresponding to #gpointer.
</para>



<!-- ##### MACRO G_TYPE_BOXED ##### -->
<para>
The fundamental type from which all boxed types are derived.
</para>



<!-- ##### MACRO G_TYPE_PARAM ##### -->
<para>
The fundamental type from which all #GParamSpec types are derived.
</para>



<!-- ##### MACRO G_TYPE_OBJECT ##### -->
<para>
The fundamental type for #GObject.
</para>



<!-- ##### MACRO G_TYPE_GTYPE ##### -->
<para>
The type for #GType.
</para>



<!-- ##### MACRO G_TYPE_RESERVED_GLIB_FIRST ##### -->
<para>
First fundamental type number to create a new fundamental type id with
G_TYPE_MAKE_FUNDAMENTAL() reserved for GLib.
</para>



<!-- ##### MACRO G_TYPE_RESERVED_GLIB_LAST ##### -->
<para>
Last fundamental type number reserved for GLib.
</para>



<!-- ##### MACRO G_TYPE_RESERVED_BSE_FIRST ##### -->
<para>
First fundamental type number to create a new fundamental type id with
G_TYPE_MAKE_FUNDAMENTAL() reserved for BSE.
</para>



<!-- ##### MACRO G_TYPE_RESERVED_BSE_LAST ##### -->
<para>
Last fundamental type number reserved for BSE.
</para>



<!-- ##### MACRO G_TYPE_RESERVED_USER_FIRST ##### -->
<para>
First available fundamental type number to create new fundamental 
type id with G_TYPE_MAKE_FUNDAMENTAL().
</para>

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