<refentry id="GTypeModule"> <refmeta> <refentrytitle>GTypeModule</refentrytitle> <manvolnum>3</manvolnum> <refmiscinfo>GOBJECT Library</refmiscinfo> </refmeta> <refnamediv> <refname>GTypeModule</refname><refpurpose>Type loading modules</refpurpose> </refnamediv> <refsynopsisdiv><title>Synopsis</title> <synopsis> #include <glib-object.h> struct <link linkend="GTypeModule-struct">GTypeModule</link>; struct <link linkend="GTypeModuleClass">GTypeModuleClass</link>; <link linkend="gboolean">gboolean</link> <link linkend="g-type-module-use">g_type_module_use</link> (<link linkend="GTypeModule">GTypeModule</link> *module); <link linkend="void">void</link> <link linkend="g-type-module-unuse">g_type_module_unuse</link> (<link linkend="GTypeModule">GTypeModule</link> *module); <link linkend="void">void</link> <link linkend="g-type-module-set-name">g_type_module_set_name</link> (<link linkend="GTypeModule">GTypeModule</link> *module, const <link linkend="gchar">gchar</link> *name); <link linkend="GType">GType</link> <link linkend="g-type-module-register-type">g_type_module_register_type</link> (<link linkend="GTypeModule">GTypeModule</link> *module, <link linkend="GType">GType</link> parent_type, const <link linkend="gchar">gchar</link> *type_name, const <link linkend="GTypeInfo">GTypeInfo</link> *type_info, <link linkend="GTypeFlags">GTypeFlags</link> flags); <link linkend="void">void</link> <link linkend="g-type-module-add-interface">g_type_module_add_interface</link> (<link linkend="GTypeModule">GTypeModule</link> *module, <link linkend="GType">GType</link> instance_type, <link linkend="GType">GType</link> interface_type, const <link linkend="GInterfaceInfo">GInterfaceInfo</link> *interface_info); </synopsis> </refsynopsisdiv> <refsect1> <title>Object Hierarchy</title> <synopsis> <link linkend="GObject">GObject</link> +----GTypeModule </synopsis> </refsect1> <refsect1> <title>Implemented Interfaces</title> <para> GTypeModule implements <link linkend="GTypePlugin">GTypePlugin</link>.</para> </refsect1> <refsect1> <title>Description</title> <para> <link linkend="GTypeModule"><type>GTypeModule</type></link> provides a simple implementation of the <link linkend="GTypePlugin"><type>GTypePlugin</type></link> interface. The model of <link linkend="GTypeModule"><type>GTypeModule</type></link> 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 <link linkend="g-type-module-register-type"><function>g_type_module_register_type()</function></link> and <link linkend="g-type-module-add-interface"><function>g_type_module_add_interface()</function></link>. 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. </para> <para> 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 <link linkend="g-type-module-use"><function>g_type_module_use()</function></link> and <link linkend="g-type-module-unuse"><function>g_type_module_unuse()</function></link>. Typically, when loading a module for the first type, <link linkend="g-type-module-use"><function>g_type_module_use()</function></link> 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, <link linkend="g-type-module-unuse"><function>g_type_module_unuse()</function></link> is called. </para> <para> <link linkend="GTypeModule"><type>GTypeModule</type></link> does not actually provide any implementation of module loading and unloading. To create a particular module type you must derive from <link linkend="GTypeModule"><type>GTypeModule</type></link> and implement the load and unload functions in <link linkend="GTypeModuleClass"><type>GTypeModuleClass</type></link>. </para> </refsect1> <refsect1> <title>Details</title> <refsect2> <title><anchor id="GTypeModule-struct"/>struct GTypeModule</title> <indexterm><primary>GTypeModule</primary></indexterm><programlisting>struct GTypeModule { gchar *name; }; </programlisting> <para> The members of the <structname>GTypeModule</structname> structure should not be accessed directly, except for the <parameter>name</parameter> field. </para></refsect2> <refsect2> <title><anchor id="GTypeModuleClass"/>struct GTypeModuleClass</title> <indexterm><primary>GTypeModuleClass</primary></indexterm><programlisting>struct GTypeModuleClass { GObjectClass parent_class; gboolean (* load) (GTypeModule *module); void (* unload) (GTypeModule *module); }; </programlisting> <para> In order to implement dynamic loading of types based on <link linkend="GTypeModule"><type>GTypeModule</type></link>, the <parameter>load</parameter> and <parameter>unload</parameter> functions in <link linkend="GTypeModuleClass"><type>GTypeModuleClass</type></link> must be implemented. </para><variablelist role="struct"> <varlistentry> <term><link linkend="GObjectClass">GObjectClass</link> <structfield>parent_class</structfield></term> <listitem><simpara> </simpara></listitem> </varlistentry> <varlistentry> <term><link linkend="gboolean">gboolean</link> (*<structfield>load</structfield>) (GTypeModule *module)</term> <listitem><simpara>loads the module and registers one or more types using <link linkend="g-type-module-register-type"><function>g_type_module_register_type()</function></link>. </simpara></listitem> </varlistentry> <varlistentry> <term><link linkend="void">void</link> (*<structfield>unload</structfield>) (GTypeModule *module)</term> <listitem><simpara>unloads the module </simpara></listitem> </varlistentry> </variablelist></refsect2> <refsect2> <title><anchor id="g-type-module-use"/>g_type_module_use ()</title> <indexterm><primary>g_type_module_use</primary></indexterm><programlisting><link linkend="gboolean">gboolean</link> g_type_module_use (<link linkend="GTypeModule">GTypeModule</link> *module);</programlisting> <para> Increases the use count of a <link linkend="GTypeModule"><type>GTypeModule</type></link> by one. If the use count was zero before, the plugin will be loaded. </para><variablelist role="params"> <varlistentry><term><parameter>module</parameter> :</term> <listitem><simpara>a <link linkend="GTypeModule"><type>GTypeModule</type></link> </simpara></listitem></varlistentry> <varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara><literal>FALSE</literal> if the plugin needed to be loaded and loading the plugin failed. </simpara></listitem></varlistentry> </variablelist></refsect2> <refsect2> <title><anchor id="g-type-module-unuse"/>g_type_module_unuse ()</title> <indexterm><primary>g_type_module_unuse</primary></indexterm><programlisting><link linkend="void">void</link> g_type_module_unuse (<link linkend="GTypeModule">GTypeModule</link> *module);</programlisting> <para> Decreases the use count of a <link linkend="GTypeModule"><type>GTypeModule</type></link> by one. If the result is zero, the module will be unloaded. (However, the <link linkend="GTypeModule"><type>GTypeModule</type></link> will not be freed, and types associated with the <link linkend="GTypeModule"><type>GTypeModule</type></link> are not unregistered. Once a <link linkend="GTypeModule"><type>GTypeModule</type></link> is initialized, it must exist forever.) </para><variablelist role="params"> <varlistentry><term><parameter>module</parameter> :</term> <listitem><simpara>a <link linkend="GTypeModule"><type>GTypeModule</type></link> </simpara></listitem></varlistentry> </variablelist></refsect2> <refsect2> <title><anchor id="g-type-module-set-name"/>g_type_module_set_name ()</title> <indexterm><primary>g_type_module_set_name</primary></indexterm><programlisting><link linkend="void">void</link> g_type_module_set_name (<link linkend="GTypeModule">GTypeModule</link> *module, const <link linkend="gchar">gchar</link> *name);</programlisting> <para> Sets the name for a <link linkend="GTypeModule"><type>GTypeModule</type></link> </para><variablelist role="params"> <varlistentry><term><parameter>module</parameter> :</term> <listitem><simpara>a <link linkend="GTypeModule"><type>GTypeModule</type></link>. </simpara></listitem></varlistentry> <varlistentry><term><parameter>name</parameter> :</term> <listitem><simpara>a human-readable name to use in error messages. </simpara></listitem></varlistentry> </variablelist></refsect2> <refsect2> <title><anchor id="g-type-module-register-type"/>g_type_module_register_type ()</title> <indexterm><primary>g_type_module_register_type</primary></indexterm><programlisting><link linkend="GType">GType</link> g_type_module_register_type (<link linkend="GTypeModule">GTypeModule</link> *module, <link linkend="GType">GType</link> parent_type, const <link linkend="gchar">gchar</link> *type_name, const <link linkend="GTypeInfo">GTypeInfo</link> *type_info, <link linkend="GTypeFlags">GTypeFlags</link> flags);</programlisting> <para> Looks up or registers a type that is implemented with a particular type plugin. If a type with name <parameter>type_name</parameter> was previously registered, the <link linkend="GType"><type>GType</type></link> identifier for the type is returned, otherwise the type is newly registered, and the resulting <link linkend="GType"><type>GType</type></link> identifier returned. </para> <para> When reregistering a type (typically because a module is unloaded then reloaded, and reinitialized), <parameter>module</parameter> and <parameter>parent_type</parameter> must be the same as they were previously. </para> <para> As long as any instances of the type exist, the type plugin will not be unloaded. </para><variablelist role="params"> <varlistentry><term><parameter>module</parameter> :</term> <listitem><simpara> a <link linkend="GTypeModule"><type>GTypeModule</type></link> </simpara></listitem></varlistentry> <varlistentry><term><parameter>parent_type</parameter> :</term> <listitem><simpara> the type for the parent class </simpara></listitem></varlistentry> <varlistentry><term><parameter>type_name</parameter> :</term> <listitem><simpara> name for the type </simpara></listitem></varlistentry> <varlistentry><term><parameter>type_info</parameter> :</term> <listitem><simpara> type information structure </simpara></listitem></varlistentry> <varlistentry><term><parameter>flags</parameter> :</term> <listitem><simpara> flags field providing details about the type </simpara></listitem></varlistentry> <varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara>the new or existing type ID </simpara></listitem></varlistentry> </variablelist></refsect2> <refsect2> <title><anchor id="g-type-module-add-interface"/>g_type_module_add_interface ()</title> <indexterm><primary>g_type_module_add_interface</primary></indexterm><programlisting><link linkend="void">void</link> g_type_module_add_interface (<link linkend="GTypeModule">GTypeModule</link> *module, <link linkend="GType">GType</link> instance_type, <link linkend="GType">GType</link> interface_type, const <link linkend="GInterfaceInfo">GInterfaceInfo</link> *interface_info);</programlisting> <para> 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. </para> <para> As long as any instances of the type exist, the type plugin will not be unloaded. </para><variablelist role="params"> <varlistentry><term><parameter>module</parameter> :</term> <listitem><simpara>a <link linkend="GTypeModule"><type>GTypeModule</type></link> </simpara></listitem></varlistentry> <varlistentry><term><parameter>instance_type</parameter> :</term> <listitem><simpara>type to which to add the interface. </simpara></listitem></varlistentry> <varlistentry><term><parameter>interface_type</parameter> :</term> <listitem><simpara>interface type to add </simpara></listitem></varlistentry> <varlistentry><term><parameter>interface_info</parameter> :</term> <listitem><simpara>type information structure </simpara></listitem></varlistentry> </variablelist></refsect2> </refsect1> <refsect1> <title>See Also</title> <para> <variablelist> <varlistentry> <term><link linkend="GTypePlugin"><type>GTypePlugin</type></link></term> <listitem><para>The abstract type loader interface.</para></listitem> </varlistentry> <varlistentry> <term><link linkend="GModule"><type>GModule</type></link></term> <listitem><para>Portable mechanism for dynamically loaded modules.</para></listitem> </varlistentry> </variablelist> </para> </refsect1> </refentry>