/* GObject - GLib Type, Object, Parameter and Signal Library

 * Copyright (C) 2000 Red Hat, Inc.

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General

 * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.

 */

#include "config.h"

#include "gtypeplugin.h"

/**

 * SECTION:gtypeplugin

 * @short_description: An interface for dynamically loadable types

 * @see_also: #GTypeModule and g_type_register_dynamic().

 * @title: GTypePlugin

 *

 * The GObject type system supports dynamic loading of types.

 * The #GTypePlugin interface is used to handle the lifecycle

 * of dynamically loaded types. It goes as follows:

 *

 * 1. The type is initially introduced (usually upon loading the module

 *    the first time, or by your main application that knows what modules

 *    introduces what types), like this:

 *    |[ 

 *    new_type_id = g_type_register_dynamic (parent_type_id,

 *                                           "TypeName",

 *                                           new_type_plugin,

 *                                           type_flags);

 *    ]|

 *    where @new_type_plugin is an implementation of the

 *    #GTypePlugin interface.

 *

 * 2. The type's implementation is referenced, e.g. through

 *    g_type_class_ref() or through g_type_create_instance() (this is

 *    being called by g_object_new()) or through one of the above done on

 *    a type derived from @new_type_id.

 *

 * 3. This causes the type system to load the type's implementation by

 *    calling g_type_plugin_use() and g_type_plugin_complete_type_info()

 *    on @new_type_plugin.

 * 

 * 4. At some point the type's implementation isn't required anymore,

 *    e.g. after g_type_class_unref() or g_type_free_instance() (called

 *    when the reference count of an instance drops to zero).

 *

 * 5. This causes the type system to throw away the information retrieved

 *    from g_type_plugin_complete_type_info() and then it calls

 *    g_type_plugin_unuse() on @new_type_plugin.

 * 

 * 6. Things may repeat from the second step.

 *

 * So basically, you need to implement a #GTypePlugin type that

 * carries a use_count, once use_count goes from zero to one, you need

 * to load the implementation to successfully handle the upcoming

 * g_type_plugin_complete_type_info() call. Later, maybe after

 * succeeding use/unuse calls, once use_count drops to zero, you can

 * unload the implementation again. The type system makes sure to call

 * g_type_plugin_use() and g_type_plugin_complete_type_info() again

 * when the type is needed again.

 *

 * #GTypeModule is an implementation of #GTypePlugin that already

 * implements most of this except for the actual module loading and

 * unloading. It even handles multiple registered types per module.

 */

/* --- functions --- */

GType

g_type_plugin_get_type (void)

{

  static GType type_plugin_type = 0;

  if (!type_plugin_type)

    {

      const GTypeInfo type_plugin_info = {

	sizeof (GTypePluginClass),

	NULL,           /* base_init */

	NULL,           /* base_finalize */

      };

      type_plugin_type = g_type_register_static (G_TYPE_INTERFACE, g_intern_static_string ("GTypePlugin"), &type_plugin_info, 0);

    }

  return type_plugin_type;

}

/**

 * g_type_plugin_use:

 * @plugin: a #GTypePlugin

 *

 * Calls the @use_plugin function from the #GTypePluginClass of

 * @plugin.  There should be no need to use this function outside of

 * the GObject type system itself.

 */

void

g_type_plugin_use (GTypePlugin *plugin)

{

  GTypePluginClass *iface;

  g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));

  iface = G_TYPE_PLUGIN_GET_CLASS (plugin);

  iface->use_plugin (plugin);

}

/**

 * g_type_plugin_unuse:

 * @plugin: a #GTypePlugin

 *

 * Calls the @unuse_plugin function from the #GTypePluginClass of

 * @plugin.  There should be no need to use this function outside of

 * the GObject type system itself.

 */

void

g_type_plugin_unuse (GTypePlugin *plugin)

{

  GTypePluginClass *iface;

  g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));

  iface = G_TYPE_PLUGIN_GET_CLASS (plugin);

  iface->unuse_plugin (plugin);

}

/**

 * g_type_plugin_complete_type_info:

 * @plugin: a #GTypePlugin

 * @g_type: the #GType whose info is completed

 * @info: the #GTypeInfo struct to fill in

 * @value_table: the #GTypeValueTable to fill in

 * 

 * Calls the @complete_type_info function from the #GTypePluginClass of @plugin.

 * There should be no need to use this function outside of the GObject 

 * type system itself.

 */

void

g_type_plugin_complete_type_info (GTypePlugin     *plugin,

				  GType            g_type,

				  GTypeInfo       *info,

				  GTypeValueTable *value_table)

{

  GTypePluginClass *iface;

  g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));

  g_return_if_fail (info != NULL);

  g_return_if_fail (value_table != NULL);

  iface = G_TYPE_PLUGIN_GET_CLASS (plugin);

  iface->complete_type_info (plugin,

			     g_type,

			     info,

			     value_table);

}

/**

 * g_type_plugin_complete_interface_info:

 * @plugin: the #GTypePlugin

 * @instance_type: the #GType of an instantiable type to which the interface

 *  is added

 * @interface_type: the #GType of the interface whose info is completed

 * @info: the #GInterfaceInfo to fill in

 *

 * Calls the @complete_interface_info function from the

 * #GTypePluginClass of @plugin. There should be no need to use this

 * function outside of the GObject type system itself.

 */

void

g_type_plugin_complete_interface_info (GTypePlugin    *plugin,

				       GType           instance_type,

				       GType           interface_type,

				       GInterfaceInfo *info)

{

  GTypePluginClass *iface;

  g_return_if_fail (G_IS_TYPE_PLUGIN (plugin));

  g_return_if_fail (info != NULL);

  iface = G_TYPE_PLUGIN_GET_CLASS (plugin);

  iface->complete_interface_info (plugin,

				  instance_type,

				  interface_type,

				  info);

}