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Gio.MenuModel

class — extends GObject.Object

GMenuModel represents the contents of a menu — an ordered list of menu items. The items are associated with actions, which can be activated through them. Items can be grouped in sections, and may have submenus associated with them. Both items and sections usually have some representation data, such as labels or icons. The type of the associated action (ie whether it is stateful, and what kind of state it has) can influence the representation of the item.

The conceptual model of menus in GMenuModel is hierarchical: sections and submenus are again represented by GMenuModels. Menus themselves do not define their own roles. Rather, the role of a particular GMenuModel is defined by the item that references it (or, in the case of the ‘root’ menu, is defined by the context in which it is used).

As an example, consider the visible portions of this menu:

An example menu

While this kind of deeply nested menu is no longer considered good UI practice, it serves as a good example of the concepts in GMenuModel. There are 8 ‘menus’ visible in the screenshot: one menubar, two submenus and 5 sections:

  • the toplevel menubar (containing 4 items)
  • the View submenu (containing 3 sections)
  • the first section of the View submenu (containing 2 items)
  • the second section of the View submenu (containing 1 item)
  • the final section of the View submenu (containing 1 item)
  • the Highlight Mode submenu (containing 2 sections)
  • the Sources section (containing 2 items)
  • the Markup section (containing 2 items)

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

<picture> <source srcset="menu-model-dark.svg" media="(prefers-color-scheme: dark)"> <img src="menu-model-light.svg" alt="menu model"> </picture>

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 action group exporter and the menu model exporter do for ActionGroup and MenuModel. The client-side counterparts to make use of the exported information are DBusActionGroup and DBusMenuModel.

The API of GMenuModel is very generic, with iterators for the attributes and links of an item, see MenuModel.iterate_item_attributes and MenuModel.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: - an action with no parameter type and no state - an action with no parameter type and boolean state - an action with string parameter type and string state

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.

Methods

get_item_attribute_value

def get_item_attribute_value(self, item_index: int, attribute: str, expected_type: GLib.VariantType | None = ...) -> GLib.Variant | None

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

If expected_type is non-None then it specifies the expected type of the attribute. If it is None 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 None is returned.

Parameters:

  • item_index — the index of the item
  • attribute — the attribute to query
  • expected_type — the expected type of the attribute, or None
def get_item_link(self, item_index: int, link: str) -> MenuModel | None

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

If the link exists, the linked MenuModel is returned. If the link does not exist, None is returned.

Parameters:

  • item_index — the index of the item
  • link — the link to query

get_n_items

def get_n_items(self) -> int

Query the number of items in model.

is_mutable

def is_mutable(self) -> bool

Queries if model is mutable.

An immutable MenuModel will never emit the MenuModel::items-changed signal. Consumers of the model may make optimisations accordingly.

items_changed

def items_changed(self, position: int, removed: int, added: int) -> None

Requests emission of the MenuModel::items-changed signal on model.

This function should never be called except by MenuModel 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 MenuModel API. Said another way: the menu must not change while user code is running without returning to the mainloop.

Parameters:

  • position — the position of the change
  • removed — the number of items removed
  • added — the number of items added

iterate_item_attributes

def iterate_item_attributes(self, item_index: int) -> MenuAttributeIter

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

You must free the iterator with GObject.Object.unref when you are done.

Parameters:

  • item_index — the index of the item
def iterate_item_links(self, item_index: int) -> MenuLinkIter

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

You must free the iterator with GObject.Object.unref when you are done.

Parameters:

  • item_index — the index of the item

Virtual methods

do_get_item_attribute_value

def do_get_item_attribute_value(self, item_index: int, attribute: str, expected_type: GLib.VariantType | None = ...) -> GLib.Variant | None

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

If expected_type is non-None then it specifies the expected type of the attribute. If it is None 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 None is returned.

Parameters:

  • item_index — the index of the item
  • attribute — the attribute to query
  • expected_type — the expected type of the attribute, or None

do_get_item_attributes

def do_get_item_attributes(self, item_index: int) -> dict[str, GLib.Variant]

Gets all the attributes associated with the item in the menu model.

Parameters:

def do_get_item_link(self, item_index: int, link: str) -> MenuModel | None

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

If the link exists, the linked MenuModel is returned. If the link does not exist, None is returned.

Parameters:

  • item_index — the index of the item
  • link — the link to query
def do_get_item_links(self, item_index: int) -> dict[str, MenuModel]

Gets all the links associated with the item in the menu model.

Parameters:

do_get_n_items

def do_get_n_items(self) -> int

Query the number of items in model.

do_is_mutable

def do_is_mutable(self) -> bool

Queries if model is mutable.

An immutable MenuModel will never emit the MenuModel::items-changed signal. Consumers of the model may make optimisations accordingly.

do_iterate_item_attributes

def do_iterate_item_attributes(self, item_index: int) -> MenuAttributeIter

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

You must free the iterator with GObject.Object.unref when you are done.

Parameters:

  • item_index — the index of the item
def do_iterate_item_links(self, item_index: int) -> MenuLinkIter

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

You must free the iterator with GObject.Object.unref when you are done.

Parameters:

  • item_index — the index of the item

Signals

items-changed

def on_items_changed(self, position: int, removed: int, added: int) -> None: ...

Emitted when a change has occurred 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.