An example menu

There are 8 "menus" visible in the screenshot: one menubar, two submenus and 5 sections:

The example illustrates the conceptual connection between these 8 menus. Each large block in the figure represents a menu and the smaller blocks within the large block represent items in that menu. Some items contain references to other menus.

A menu example

Notice that the separators visible in the example appear nowhere in the menu model. This is because separators are not explicitly represented in the menu model. Instead, a separator is inserted between any two non-empty sections of a menu. Section items can have labels just like any other item. In that case, a display system may show a section header instead of a separator.

The motivation for this abstract model of application controls is that modern user interfaces tend to make these controls available outside the application. Examples include global menus, jumplists, dash boards, etc. To support such uses, it is necessary to 'export' information about actions and their representation in menus, which is exactly what the GActionGroup exporter and the GMenuModel exporter do for GActionGroup and GMenuModel. The client-side counterparts to make use of the exported information are GDBusActionGroup and GDBusMenuModel.

The API of GMenuModel is very generic, with iterators for the attributes and links of an item, see g_menu_model_iterate_item_attributes() and g_menu_model_iterate_item_links(). The 'standard' attributes and link types have predefined names: G_MENU_ATTRIBUTE_LABEL, G_MENU_ATTRIBUTE_ACTION, G_MENU_ATTRIBUTE_TARGET, G_MENU_LINK_SECTION and G_MENU_LINK_SUBMENU.

Items in a GMenuModel represent active controls if they refer to an action that can get activated when the user interacts with the menu item. The reference to the action is encoded by the string id in the G_MENU_ATTRIBUTE_ACTION attribute. An action id uniquely identifies an action in an action group. Which action group(s) provide actions depends on the context in which the menu model is used. E.g. when the model is exported as the application menu of a GtkApplication, actions can be application-wide or window-specific (and thus come from two different action groups). By convention, the application-wide actions have names that start with "app.", while the names of window-specific actions start with "win.".

While a wide variety of stateful actions is possible, the following is the minimum that is expected to be supported by all users of exported menu information:

Stateless

A stateless action typically corresponds to an ordinary menu item.

Selecting such a menu item will activate the action (with no parameter).

Boolean State

An action with a boolean state will most typically be used with a "toggle" or "switch" menu item. The state can be set directly, but activating the action (with no parameter) results in the state being toggled.

Selecting a toggle menu item will activate the action. The menu item should be rendered as "checked" when the state is true.

String Parameter and State

Actions with string parameters and state will most typically be used to represent an enumerated choice over the items available for a group of radio menu items. Activating the action with a string parameter is equivalent to setting that parameter as the state.

Radio menu items, in addition to being associated with the action, will have a target value. Selecting that menu item will result in activation of the action with the target value as the parameter. The menu item should be rendered as "selected" when the state of the action is equal to the target value of the menu item.

g_menu_model_is_mutable ()

gboolean
g_menu_model_is_mutable (GMenuModel *model);

Queries if model is mutable.

An immutable GMenuModel will never emit the “items-changed” signal. Consumers of the model may make optimisations accordingly.

Since 2.32

g_menu_model_get_n_items ()

gint
g_menu_model_get_n_items (GMenuModel *model);

Query the number of items in model .

Since 2.32

g_menu_model_get_item_attribute_value ()

GVariant *
g_menu_model_get_item_attribute_value (GMenuModel *model,
                                       gint item_index,
                                       const gchar *attribute,
                                       const GVariantType *expected_type);

Queries the item at position item_index in model for the attribute specified by attribute .

If expected_type is non-NULL then it specifies the expected type of the attribute. If it is NULL then any type will be accepted.

If the attribute exists and matches expected_type (or if the expected type is unspecified) then the value is returned.

If the attribute does not exist, or does not match the expected type then NULL is returned.

Since 2.32

g_menu_model_get_item_attribute ()

gboolean
g_menu_model_get_item_attribute (GMenuModel *model,
                                 gint item_index,
                                 const gchar *attribute,
                                 const gchar *format_string,
                                 ...);

Queries item at position item_index in model for the attribute specified by attribute .

If the attribute exists and matches the GVariantType corresponding to format_string then format_string is used to deconstruct the value into the positional parameters and TRUE is returned.

If the attribute does not exist, or it does exist but has the wrong type, then the positional parameters are ignored and FALSE is returned.

This function is a mix of g_menu_model_get_item_attribute_value() and g_variant_get(), followed by a g_variant_unref(). As such, format_string must make a complete copy of the data (since the GVariant may go away after the call to g_variant_unref()). In particular, no '&' characters are allowed in format_string .

Since 2.32

g_menu_model_get_item_link ()

GMenuModel *
g_menu_model_get_item_link (GMenuModel *model,
                            gint item_index,
                            const gchar *link);

Queries the item at position item_index in model for the link specified by link .

If the link exists, the linked GMenuModel is returned. If the link does not exist, NULL is returned.

Since 2.32

g_menu_model_iterate_item_attributes ()

GMenuAttributeIter *
g_menu_model_iterate_item_attributes (GMenuModel *model,
                                      gint item_index);

Creates a GMenuAttributeIter to iterate over the attributes of the item at position item_index in model .

You must free the iterator with g_object_unref() when you are done.

Since 2.32

g_menu_model_iterate_item_links ()

GMenuLinkIter *
g_menu_model_iterate_item_links (GMenuModel *model,
                                 gint item_index);

Creates a GMenuLinkIter to iterate over the links of the item at position item_index in model .

You must free the iterator with g_object_unref() when you are done.

Since 2.32

g_menu_model_items_changed ()

void
g_menu_model_items_changed (GMenuModel *model,
                            gint position,
                            gint removed,
                            gint added);

Requests emission of the “items-changed” signal on model .

This function should never be called except by GMenuModel subclasses. Any other calls to this function will very likely lead to a violation of the interface of the model.

The implementation should update its internal representation of the menu before emitting the signal. The implementation should further expect to receive queries about the new state of the menu (and particularly added menu items) while signal handlers are running.

The implementation must dispatch this call directly from a mainloop entry and not in response to calls -- particularly those from the GMenuModel API. Said another way: the menu must not change while user code is running without returning to the mainloop.

Since 2.32

g_menu_attribute_iter_get_next ()

gboolean
g_menu_attribute_iter_get_next (GMenuAttributeIter *iter,
                                const gchar **out_name,
                                GVariant **value);

This function combines g_menu_attribute_iter_next() with g_menu_attribute_iter_get_name() and g_menu_attribute_iter_get_value().

First the iterator is advanced to the next (possibly first) attribute. If that fails, then FALSE is returned and there are no other effects.

If successful, name and value are set to the name and value of the attribute that has just been advanced to. At this point, g_menu_attribute_iter_get_name() and g_menu_attribute_iter_get_value() will return the same values again.

The value returned in name remains valid for as long as the iterator remains at the current position. The value returned in value must be unreffed using g_variant_unref() when it is no longer in use.

Since 2.32

g_menu_attribute_iter_get_name ()

const gchar *
g_menu_attribute_iter_get_name (GMenuAttributeIter *iter);

Gets the name of the attribute at the current iterator position, as a string.

The iterator is not advanced.

Since 2.32

g_menu_attribute_iter_get_value ()

GVariant *
g_menu_attribute_iter_get_value (GMenuAttributeIter *iter);

Gets the value of the attribute at the current iterator position.

The iterator is not advanced.

Since 2.32

g_menu_attribute_iter_next ()

gboolean
g_menu_attribute_iter_next (GMenuAttributeIter *iter);

Attempts to advance the iterator to the next (possibly first) attribute.

TRUE is returned on success, or FALSE if there are no more attributes.

You must call this function when you first acquire the iterator to advance it to the first attribute (and determine if the first attribute exists at all).

Since 2.32

g_menu_link_iter_get_name ()

const gchar *
g_menu_link_iter_get_name (GMenuLinkIter *iter);

Gets the name of the link at the current iterator position.

The iterator is not advanced.

Since 2.32

g_menu_link_iter_get_next ()

gboolean
g_menu_link_iter_get_next (GMenuLinkIter *iter,
                           const gchar **out_link,
                           GMenuModel **value);

This function combines g_menu_link_iter_next() with g_menu_link_iter_get_name() and g_menu_link_iter_get_value().

First the iterator is advanced to the next (possibly first) link. If that fails, then FALSE is returned and there are no other effects.

If successful, out_link and value are set to the name and GMenuModel of the link that has just been advanced to. At this point, g_menu_link_iter_get_name() and g_menu_link_iter_get_value() will return the same values again.

The value returned in out_link remains valid for as long as the iterator remains at the current position. The value returned in value must be unreffed using g_object_unref() when it is no longer in use.

Since 2.32

g_menu_link_iter_get_value ()

GMenuModel *
g_menu_link_iter_get_value (GMenuLinkIter *iter);

Gets the linked GMenuModel at the current iterator position.

The iterator is not advanced.

Since 2.32

g_menu_link_iter_next ()

gboolean
g_menu_link_iter_next (GMenuLinkIter *iter);

Attempts to advance the iterator to the next (possibly first) link.

TRUE is returned on success, or FALSE if there are no more links.

You must call this function when you first acquire the iterator to advance it to the first link (and determine if the first link exists at all).

Since 2.32

GMenuModel

typedef struct _GMenuModel GMenuModel;

GMenuModel is an opaque structure type. You must access it using the functions below.

Since 2.32

G_MENU_ATTRIBUTE_ACTION

#define G_MENU_ATTRIBUTE_ACTION "action"

The menu item attribute which holds the action name of the item. Action names are namespaced with an identifier for the action group in which the action resides. For example, "win." for window-specific actions and "app." for application-wide actions.

See also g_menu_model_get_item_attribute() and g_menu_item_set_attribute().

Since 2.32

G_MENU_ATTRIBUTE_ACTION_NAMESPACE

#define G_MENU_ATTRIBUTE_ACTION_NAMESPACE "action-namespace"

The menu item attribute that holds the namespace for all action names in menus that are linked from this item.

Since 2.36

G_MENU_ATTRIBUTE_TARGET

#define G_MENU_ATTRIBUTE_TARGET "target"

The menu item attribute which holds the target with which the item's action will be activated.

See also g_menu_item_set_action_and_target()

Since 2.32

G_MENU_ATTRIBUTE_LABEL

#define G_MENU_ATTRIBUTE_LABEL "label"

The menu item attribute which holds the label of the item.

Since 2.32

G_MENU_ATTRIBUTE_ICON

#define G_MENU_ATTRIBUTE_ICON "icon"

The menu item attribute which holds the icon of the item.

The icon is stored in the format returned by g_icon_serialize().

This attribute is intended only to represent 'noun' icons such as favicons for a webpage, or application icons. It should not be used for 'verbs' (ie: stock icons).

Since 2.38

G_MENU_LINK_SECTION

#define G_MENU_LINK_SECTION "section"

The name of the link that associates a menu item with a section. The linked menu will usually be shown in place of the menu item, using the item's label as a header.

See also g_menu_item_set_link().

Since 2.32

G_MENU_LINK_SUBMENU

#define G_MENU_LINK_SUBMENU "submenu"

The name of the link that associates a menu item with a submenu.

See also g_menu_item_set_link().

Since 2.32

struct GMenuAttributeIter

struct GMenuAttributeIter;

GMenuAttributeIter is an opaque structure type. You must access it using the functions below.

Since 2.32

struct GMenuLinkIter

struct GMenuLinkIter;

GMenuLinkIter is an opaque structure type. You must access it using the functions below.

Since 2.32

The “items-changed” signal

void
user_function (GMenuModel *model,
               gint        position,
               gint        removed,
               gint        added,
               gpointer    user_data)

Emitted when a change has occured to the menu.

The only changes that can occur to a menu is that items are removed or added. Items may not change (except by being removed and added back in the same location). This signal is capable of describing both of those changes (at the same time).

The signal means that starting at the index position , removed items were removed and added items were added in their place. If removed is zero then only items were added. If added is zero then only items were removed.

As an example, if the menu contains items a, b, c, d (in that order) and the signal (2, 1, 3) occurs then the new composition of the menu will be a, b, _, _, _, d (with each _ representing some new item).

Signal handlers may query the model (particularly the added items) and expect to see the results of the modification that is being reported. The signal is emitted after the modification.

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