Introspection gtk-doc annotations

Table of contents:

Annotation syntax

The basic syntax looks like this:

   1  /**
   2   * lib_symbol_name: (annotation1) (annotation2)
   3   * @param_first: (annotation1) (annotation2) (...): documentation for first 
   4   * @param_second: (annotation1) (annotation2) (...): documentation for second
   5   *
   6   * Description of the symbol.
   7   *
   8   * Returns: (annotation1) (annotation2) (...): Returns stuff which you have to free after use
   9   */

Where lib_symbol_name is the function you want annotate.

first is the name of the first parameter and second is the name of the second parameter.

Return value: is a synonym for Returns:

NOTE: The last colon (:) is necessary in parameter/return value annotations; the annotations will not be included without it.

NOTE: No trailing colon after annotations for symbols names (top line of gtk doc comment). If you include a colon then gtk-doc won't recognize the line.

There are more illustrative examples below.

Possible annotations

Methods and Types

In function/type header:

Parameters

Per parameter:

Parameters and Return values

Per parameter or return value:

Method's Heading

Additional gtk-doc headings:

Transfer Modes

Transfer modes:

• none: the recipient does not own the value

• container: the recipient owns the container, but not the elements. (Only meaningful for container types.)

• full: the recipient owns the entire value. For a refcounted type, this means the recipient owns a ref on the value. For a container type, this means the recipient owns both container and elements.

• floating: alias for none, can be used for floating objects.

container is usually a pointer to a list or hash table, eg GList, GSList, GHashTable etc. elements is what is contained inside the list: integers, strings, GObjects etc.

Callbacks Scope Types

• The scope annotation is only used for parameters which are callbacks, it indicates the duration of the call. It is mainly used by language bindings wanting to know when the resources required to do the call (for instance ffi closures) can be freed. The three different allowed values are:

  • call (default) - Only valid for the duration of the call. Can be called multiple times during the call.

  • async - Only valid for the duration of the first callback invokation. Can only be called once.

  • notified - valid until the GDestroyNotify argument is called. Can be called multiple times before the GDestroyNotify is called.

  Example of a function using the call scope is g_slist_foreach, async: g_file_read_async and notified g_idle_add_full. A few more scope types are possible, but they are not yet added in lack

  of proper use cases. See bug 556489 for some discussion about this.

Default Annotations

To avoid having the developers annotate everything the introspection framework is providing sane default annotation values for a couple of situations:

• inout and out parameters: (transfer full)
• return values (transfer full)
• "gchar*" means (type utf8) (transfer full)
• "const gchar*" means (type utf8) (transfer none)
• "GObject*" defaults to (transfer full)

Default Basic Types

Basic types:

• gpointer: pointer to anything
• gboolean:boolean
• gint[8,16,32,64]: integer
• guint[8,16,32,64]: unsigned integer
• glong: long
• gulong: unsigned long
• GType: a gtype
• gfloat: float
• gdouble: double
• utf8: string encoded in utf8
• filename: filename string
• guint8 array: binary data

Reference to Object Instances

Instances:

• Object: a GObject instance
• Gtk.Button: a Gtk.Button instance

Annotation examples

Transfer

   1 /**
   2  * mylib_get_constant1:
   3  *
   4  * Return value: (transfer full): a constant, free when you used it
   5  */
   6 gchar *
   7 mylib_get_constant1 (void) 
   8 {
   9    return g_strdup("a constant");
  10 }

   1 /**
   2  * mylib_get_constant2:
   3  *
   4  * Return value: (transfer none): another constant
   5  */
   6 const gchar *
   7 mylib_get_string2 (void) 
   8 {
   9    return "another constant";
  10 }

   1 /**
   2  * mylib_get_string_list1:
   3  *
   4  * Return value: (element-type utf8) (transfer full): list of constants,
   5  *               free the list with g_slist_free and the elements with g_free when done.
   6  */
   7 GSList *
   8 mylib_get_string_list1 (void) 
   9 {
  10    GSList *l = NULL;
  11    l = g_slist_append (l, g_strdup ("foo"));
  12    l = g_slist_append (l, g_strdup ("bar"));
  13    return l;
  14 }

   1 /**
   2  * mylib_get_string_list2:
   3  *
   4  * Return value: (element-type utf8) (transfer container): list of constants
   5  *               free the list with g_slist_free when done. 
   6  */
   7 GSList *
   8 mylib_get_string_list2 (void) 
   9 {
  10    GSList *l = NULL;
  11    l = g_slist_append (l, "foo");
  12    l = g_slist_append (l, "bar");
  13    return l;
  14 }

Array length

   1 /**
   2  * gtk_list_store_set_column_types: 
   3  * @store: a #GtkListStore
   4  * @n_columns: Length of @types
   5  * @types: (array length=n_columns): List of types
   6  */
   7 void
   8 gtk_list_store_set_column_types (GtkListStore *list_store,
   9                                  gint          n_columns,
  10                                  GType        *types);

Nullable parameters

   1 /**
   2  * gtk_link_button_new_with_label: 
   3  * @uri: A URI
   4  * @label: (allow-none): A piece of text or NULL
   5  */
   6 GtkWidget *
   7 gtk_link_button_new_with_label (const gchar *uri,
   8                                 const gchar *label);

'out' parameters

   1 /**
   2  * g_file_get_contents:
   3  * @filename: name of a file to read contents from, in the GLib file name encoding
   4  * contents: (out): location to store an allocated string, use g_free() to free the returned string
   5  * length: (out) (allow-none): location to store length in bytes of the contents, or NULL
   6  * error: return location for a GError, or NULL
   7  *
   8  * [...]
   9  *
  10  * Returns: TRUE on success, FALSE if an error occurred
  11  */
  12 gboolean g_file_get_contents (const gchar *filename,
  13                               gchar **contents,
  14                               gsize *length,
  15                               GError **error);
  16 
  17 /* this is valid because length has allow-none */
  18 g_file_get_contents ("/etc/motd", &motd, NULL, &error); // VALID
  19 /* but this is not valid, according to those annotations */
  20 g_file_get_contents ("/etc/motd", NULL, NULL, &error); // NOT VALID
  21 

G(S)List contained types

   1 /**
   2  * gtk_container_get_children: 
   3  * @container: A #GtkContainer
   4  *
   5  * Return value: (element-type Gtk.Widget) (transfer container): List of #GtkWidget
   6  */
   7 GList*
   8 gtk_container_get_children (GtkContainer *container);

Direction

   1 /**
   2  * gtk_widget_get_size_request: 
   3  * @width: (out): Int to store width in
   4  * @height: (out): Int to store height in
   5  */

Out parameters

This is a callee-allocates example; the (out) annotation automatically infers this from the fact that there's a double indirection on a structure parameter.

   1 typedef struct _FooSubObj FooSubObj
   2 
   3 /**
   4  * foo_obj_get_sub_obj:
   5  * @obj: A #FooObj
   6  * @subobj: (out): A #FooSubObj
   7  *
   8  * Get a sub object.
   9  */
  10 void
  11 foo_obj_get_sub_obj (FooObj     *obj,
  12                      FooSubObj **subobj)
  13 {
  14   *subobj = foo_sub_object_new ();
  15 }

This is a caller-allocates example; the (out) annotation automatically infers this from the fact that there's only a single indirection on a structure parameter.

   1 typedef struct _FooIter FooIter;
   2 
   3 /**
   4  * foo_obj_get_iter:
   5  * @obj: A #FooObj
   6  * @iter: (out): An iterator, will be initialized
   7  *
   8  * Get an iterator.
   9  */
  10 void
  11 foo_obj_get_iter (FooObj *obj,
  12                   FooIter *iter)
  13 {
  14   iter->state = 0;
  15 }

Rename to

Rename to is an advisory annotation. It's not required to fulfill the advisory when generating or making a language binding. The way it is currently implemented, if you rename a function to a name already in use, it will remove the other binding. This is useful to eliminate unwanted/deprecated functions from the binding.

Another (currently unimplemented) use for the rename annotation would be overloading; for example, overloading of constructors or, like in this example, overloading a method to be both an asynchronous and a synchronous one (depending on the amount and what kind of parameters).

   1 /**
   2  * my_type_perform_async:
   3  * @self: The this ptr
   4  * @data: data
   5  * @callback: callback when async operation finished
   6  * @user_data: user_data for @callback
   7  *
   8  * Asynchronously perform
   9  *
  10  * Rename to: my_type_perform
  11  **/
  12 void
  13 my_type_perform_async (MyType *self, gpointer data,
  14                        GFunc callback,
  15                        gpointer user_data);
  16 
  17 /**
  18  * my_type_perform:
  19  * @self: The this ptr
  20  * @data: data
  21  *
  22  * Perform
  23  **/
  24 void
  25 my_type_perform (MyType *self, gpointer data);

In a language supporting method overloading, because we advised to rename to perform, and because we have another perform already, this could be bound like this:

   1 class MyType {
   2   public void perform (Pointer data) { }
   3   public void perform (Pointer data, GFunc callback, Pointer user_data) { }
   4 }

However, currently the generated gir/typelib will only contain information about my_type_perform_async, which will shadow (ie, remove) the binding of my_type_perform.

Attributes

Attributes are arbitrary key/value pairs that can be attached to almost any item including classes, methods, signals, properties, parameters and return values. These attributes appear in both the .gir and the .typelib files. Attributes can serve as a mechanism for software higher in the toolchain. Attributes are name-spaced using dot as a separator. At least one dot must appear in the key name.

   1 /**
   2  * my_frobnicator_poke_path:
   3  * @frobnicator: A #MyFrobnicator
   4  * @object_path: (gdbus.signature o): An object path.
   5  *
   6  * Manipulate an object path.
   7  *
   8  * Returns: (gdbus.signature o): A new object path. Free with g_free().
   9  *
  10  * Attributes: (gdbus.method PokePath)
  11  */
  12 gchar *
  13 my_frobnicator_poke_path (MyFrobnicator *frobnicator,
  14                           const gchar   *object_path)

Constants

   1 /**
   2  * MY_CONSTANT:
   3  * A constant.
   4  *
   5  * Value: 100
   6  */
   7 #define MY_CONSTANT 10 * 10
   8 

gtk-doc support

If gtk-doc doesn't seem to understand your introspection annotations, you may need to do two things:

1. make sure you are running gtk-doc >= v1.12 (also try latest version from git)

2. add '<xi:include href="xml/annotation-glossary.xml"><xi:fallback /></xi:include>' to your master gtk-doc document; e.g. see the end of tester-docs.xml