<!-- ##### SECTION Title ##### --> GTypePlugin <!-- ##### SECTION Short_Description ##### --> An interface for dynamically loadable types <!-- ##### SECTION Long_Description ##### --> <para> 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: </para> <para> <orderedlist> <listitem><para> 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: <literal>new_type_id = g_type_register_dynamic (parent_type_id, "TypeName", new_type_plugin, type_flags); </literal> where <literal>new_type_plugin</literal> is an implementation of the #GTypePlugin interface. </para></listitem> <listitem><para> 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 <literal>new_type_id</literal>. </para></listitem> <listitem><para> 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 <literal>new_type_plugin</literal>. </para></listitem> <listitem><para> 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). </para></listitem> <listitem><para> 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 <literal>new_type_plugin</literal>. </para></listitem> <listitem><para> Things may repeat from the second step. </para></listitem> </orderedlist> </para> <para> 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. </para> <para> #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. </para> <!-- ##### SECTION See_Also ##### --> <para> #GTypeModule and g_type_register_dynamic(). </para> <!-- ##### STRUCT GTypePlugin ##### --> <para> The <structname>GTypePlugin</structname> typedef is used as a placeholder for objects that implement the <structname>GTypePlugin</structname> interface. </para> <!-- ##### STRUCT GTypePluginClass ##### --> <para> The #GTypePlugin interface is used by the type system in order to handle the lifecycle of dynamically loaded types. </para> @use_plugin: Increases the use count of the plugin. @unuse_plugin: Decreases the use count of the plugin. @complete_type_info: Fills in the #GTypeInfo and #GTypeValueTable structs for the type. The structs are initialized with <literal>memset(s, 0, sizeof (s))</literal> before calling this function. @complete_interface_info: Fills in missing parts of the #GInterfaceInfo for the interface. The structs is initialized with <literal>memset(s, 0, sizeof (s))</literal> before calling this function. <!-- ##### USER_FUNCTION GTypePluginUse ##### --> <para> The type of the @use_plugin function of #GTypePluginClass, which gets called to increase the use count of @plugin. </para> @plugin: the #GTypePlugin whose use count should be increased <!-- ##### USER_FUNCTION GTypePluginUnuse ##### --> <para> The type of the @unuse_plugin function of #GTypePluginClass. </para> @plugin: the #GTypePlugin whose use count should be decreased <!-- ##### USER_FUNCTION GTypePluginCompleteTypeInfo ##### --> <para> The type of the @complete_type_info function of #GTypePluginClass. </para> @plugin: the #GTypePlugin @g_type: the #GType whose info is completed @info: the #GTypeInfo struct to fill in @value_table: the #GTypeValueTable to fill in <!-- ##### USER_FUNCTION GTypePluginCompleteInterfaceInfo ##### --> <para> The type of the @complete_interface_info function of #GTypePluginClass. </para> @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 <!-- ##### FUNCTION g_type_plugin_use ##### --> <para> 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. </para> @plugin: a #GTypePlugin <!-- ##### FUNCTION g_type_plugin_unuse ##### --> <para> 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. </para> @plugin: a #GTypePlugin <!-- ##### FUNCTION g_type_plugin_complete_type_info ##### --> <para> 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. </para> @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 <!-- ##### FUNCTION g_type_plugin_complete_interface_info ##### --> <para> 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. </para> @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