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GTypeModule

GTypeModule — Type loading modules

Types and Values

Object Hierarchy

    GObject
    ╰── GTypeModule

Implemented Interfaces

GTypeModule implements GTypePlugin.

Includes

#include <glib-object.h>

Description

GTypeModule provides a simple implementation of the GTypePlugin interface. The model of GTypeModule is a dynamically loaded module which implements some number of types and interface implementations. When the module is loaded, it registers its types and interfaces using g_type_module_register_type() and g_type_module_add_interface(). As long as any instances of these types and interface implementations are in use, the module is kept loaded. When the types and interfaces are gone, the module may be unloaded. If the types and interfaces become used again, the module will be reloaded. Note that the last unref cannot happen in module code, since that would lead to the caller's code being unloaded before g_object_unref() returns to it.

Keeping track of whether the module should be loaded or not is done by using a use count - it starts at zero, and whenever it is greater than zero, the module is loaded. The use count is maintained internally by the type system, but also can be explicitly controlled by g_type_module_use() and g_type_module_unuse(). Typically, when loading a module for the first type, g_type_module_use() will be used to load it so that it can initialize its types. At some later point, when the module no longer needs to be loaded except for the type implementations it contains, g_type_module_unuse() is called.

GTypeModule does not actually provide any implementation of module loading and unloading. To create a particular module type you must derive from GTypeModule and implement the load and unload functions in GTypeModuleClass.

Functions

g_type_module_use ()

gboolean
g_type_module_use (GTypeModule *module);

Increases the use count of a GTypeModule by one. If the use count was zero before, the plugin will be loaded. If loading the plugin fails, the use count is reset to its prior value.

Parameters

module

a GTypeModule

 

Returns

FALSE if the plugin needed to be loaded and loading the plugin failed.


g_type_module_unuse ()

void
g_type_module_unuse (GTypeModule *module);

Decreases the use count of a GTypeModule by one. If the result is zero, the module will be unloaded. (However, the GTypeModule will not be freed, and types associated with the GTypeModule are not unregistered. Once a GTypeModule is initialized, it must exist forever.)

Parameters

module

a GTypeModule

 

g_type_module_set_name ()

void
g_type_module_set_name (GTypeModule *module,
                        const gchar *name);

Sets the name for a GTypeModule

Parameters

module

a GTypeModule.

 

name

a human-readable name to use in error messages.

 

g_type_module_register_type ()

GType
g_type_module_register_type (GTypeModule *module,
                             GType parent_type,
                             const gchar *type_name,
                             const GTypeInfo *type_info,
                             GTypeFlags flags);

Looks up or registers a type that is implemented with a particular type plugin. If a type with name type_name was previously registered, the GType identifier for the type is returned, otherwise the type is newly registered, and the resulting GType identifier returned.

When reregistering a type (typically because a module is unloaded then reloaded, and reinitialized), module and parent_type must be the same as they were previously.

As long as any instances of the type exist, the type plugin will not be unloaded.

Parameters

module

a GTypeModule

 

parent_type

the type for the parent class

 

type_name

name for the type

 

type_info

type information structure

 

flags

flags field providing details about the type

 

Returns

the new or existing type ID


g_type_module_add_interface ()

void
g_type_module_add_interface (GTypeModule *module,
                             GType instance_type,
                             GType interface_type,
                             const GInterfaceInfo *interface_info);

Registers an additional interface for a type, whose interface lives in the given type plugin. If the interface was already registered for the type in this plugin, nothing will be done.

As long as any instances of the type exist, the type plugin will not be unloaded.

Parameters

module

a GTypeModule

 

instance_type

type to which to add the interface.

 

interface_type

interface type to add

 

interface_info

type information structure

 

g_type_module_register_enum ()

GType
g_type_module_register_enum (GTypeModule *module,
                             const gchar *name,
                             const GEnumValue *const_static_values);

Looks up or registers an enumeration that is implemented with a particular type plugin. If a type with name type_name was previously registered, the GType identifier for the type is returned, otherwise the type is newly registered, and the resulting GType identifier returned.

As long as any instances of the type exist, the type plugin will not be unloaded.

Parameters

module

a GTypeModule

 

name

name for the type

 

const_static_values

an array of GEnumValue structs for the possible enumeration values. The array is terminated by a struct with all members being 0.

 

Returns

the new or existing type ID

Since: 2.6


g_type_module_register_flags ()

GType
g_type_module_register_flags (GTypeModule *module,
                              const gchar *name,
                              const GFlagsValue *const_static_values);

Looks up or registers a flags type that is implemented with a particular type plugin. If a type with name type_name was previously registered, the GType identifier for the type is returned, otherwise the type is newly registered, and the resulting GType identifier returned.

As long as any instances of the type exist, the type plugin will not be unloaded.

Parameters

module

a GTypeModule

 

name

name for the type

 

const_static_values

an array of GFlagsValue structs for the possible flags values. The array is terminated by a struct with all members being 0.

 

Returns

the new or existing type ID

Since: 2.6


G_DEFINE_DYNAMIC_TYPE()

#define G_DEFINE_DYNAMIC_TYPE(TN, t_n, T_P)          G_DEFINE_DYNAMIC_TYPE_EXTENDED (TN, t_n, T_P, 0, {})

A convenience macro for dynamic 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() and a static *_register_type() functions for use in your module_init().

See G_DEFINE_DYNAMIC_TYPE_EXTENDED() for an example.

Parameters

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: 2.14


G_DEFINE_DYNAMIC_TYPE_EXTENDED()

#define             G_DEFINE_DYNAMIC_TYPE_EXTENDED(TypeName, type_name, TYPE_PARENT, flags, CODE)

A more general version of G_DEFINE_DYNAMIC_TYPE() which allows to specify GTypeFlags and custom code.

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G_DEFINE_DYNAMIC_TYPE_EXTENDED (GtkGadget,
                                gtk_gadget,
                                GTK_TYPE_THING,
                                0,
                                G_IMPLEMENT_INTERFACE_DYNAMIC (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 void     gtk_gadget_class_finalize    (GtkGadgetClass *klass);

static gpointer gtk_gadget_parent_class = NULL;
static GType    gtk_gadget_type_id = 0;

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)
{
  return gtk_gadget_type_id;
}

static void
gtk_gadget_register_type (GTypeModule *type_module)
{
  const GTypeInfo g_define_type_info = {
    sizeof (GtkGadgetClass),
    (GBaseInitFunc) NULL,
    (GBaseFinalizeFunc) NULL,
    (GClassInitFunc) gtk_gadget_class_intern_init,
    (GClassFinalizeFunc) gtk_gadget_class_finalize,
    NULL,   // class_data
    sizeof (GtkGadget),
    0,      // n_preallocs
    (GInstanceInitFunc) gtk_gadget_init, 
    NULL    // value_table
  };
  gtk_gadget_type_id = g_type_module_register_type (type_module,
                                                    GTK_TYPE_THING,
                                                    "GtkGadget",
                                                    &g_define_type_info,
                                                    (GTypeFlags) flags);
  {
    const GInterfaceInfo g_implement_interface_info = {
      (GInterfaceInitFunc) gtk_gadget_gizmo_init
    };
    g_type_module_add_interface (type_module, g_define_type_id, TYPE_GIZMO, &g_implement_interface_info);
  }
}

Parameters

TypeName

The name of the new type, in Camel case.

 

type_name

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

 

TYPE_PARENT

The GType of the parent type.

 

flags

GTypeFlags to pass to g_type_module_register_type()

 

CODE

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

 

Since: 2.14


G_IMPLEMENT_INTERFACE_DYNAMIC()

#define             G_IMPLEMENT_INTERFACE_DYNAMIC(TYPE_IFACE, iface_init)

A convenience macro to ease interface addition in the _C_ section of G_DEFINE_DYNAMIC_TYPE_EXTENDED(). See G_DEFINE_DYNAMIC_TYPE_EXTENDED() for an example.

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

Parameters

TYPE_IFACE

The GType of the interface to add

 

iface_init

The interface init function

 

Since: 2.24


G_ADD_PRIVATE_DYNAMIC()

#define             G_ADD_PRIVATE_DYNAMIC(TypeName)

A convenience macro to ease adding private data to instances of a new dynamic type in the _C_ section of G_DEFINE_DYNAMIC_TYPE_EXTENDED(). See G_ADD_PRIVATE() for details, it is similar but for static types.

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

Parameters

TypeName

the name of the type in CamelCase

 

Since: 2.38

Types and Values

struct GTypeModule

struct GTypeModule {
  gchar *name;
};

The members of the GTypeModule structure should not be accessed directly, except for the name field.

Members

gchar *name;

the name of the module

 

struct GTypeModuleClass

struct GTypeModuleClass {
  GObjectClass parent_class;

  gboolean (* load)   (GTypeModule *module);
  void     (* unload) (GTypeModule *module);
};

In order to implement dynamic loading of types based on GTypeModule, the load and unload functions in GTypeModuleClass must be implemented.

Members

load ()

loads the module and registers one or more types using g_type_module_register_type().

 

unload ()

unloads the module

 

See Also

GTypePlugin, GModule

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