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Gnome::Gio::MenuModel
Description
Gnome::Gio::MenuModel 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 Gnome::Gio::MenuModel is hierarchical: sections and submenus are again represented by Gnome::Gio::MenuModels. Menus themselves do not define their own roles. Rather, the role of a particular Gnome::Gio::MenuModel 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
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](#a-menu-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](#an-example-menu) appear nowhere in the [menu model](#a-menu-example). 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 Gnome::Gio::MenuModel and Gnome::Gio::MenuModel. The client-side counterparts to make use of the exported information are Gnome::Gio::MenuModel and Gnome::Gio::MenuModel.
The API of Gnome::Gio::MenuModel is very generic, with iterators for the attributes and links of an item, see .iterate-item-attributes() and .iterate-item-links(). The ‘standard’ attributes and link types have predefined names: Gnome::Gio::T-menumodel, Gnome::Gio::T-menumodel, Gnome::Gio::T-menumodel, Gnome::Gio::T-menumodel and Gnome::Gio::T-menumodel.
Items in a Gnome::Gio::MenuModel 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 Gnome::Gio::T-menumodel 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](https://docs.gtk.org/gtk4/class.Application.html), 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.
Uml Diagram
Class initialization
new
:native-object
Create an object using a native object from an object of the same type found elsewhere. See also Gnome::N::TopLevelSupportClass.
multi method new ( N-Object() :$native-object! )
Methods
get-item-attribute This function is not yet available
Queries item at position $item-index in $model for the attribute specified by $attribute.
If the attribute exists and matches the Gnome::Glib::N-VariantType 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 .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 Gnome::Glib::N-Variant may go away after the call to g_variant_unref()). In particular, no '&' characters are allowed in $format-string.
method get-item-attribute ( Int() $item-index, Str $attribute, Str $format-string, … --> Bool )
$item-index; the index of the item.
$attribute; the attribute to query.
$format-string; a Gnome::Glib::N-Variant format string.
…; …. Note that each argument must be specified as a type followed by its value!
Return value; True if the named attribute was found with the expected type.
get-item-attribute-value
Queries the item at position $item-index in $model for the attribute specified by $attribute.
If $expected-type is non-undefined then it specifies the expected type of the attribute. If it is undefined 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 undefined is returned.
method get-item-attribute-value ( Int() $item-index, Str $attribute, N-Object $expected-type --> N-Object )
$item-index; the index of the item.
$attribute; the attribute to query.
$expected-type; the expected type of the attribute, or undefined
Return value; the value of the attribute.
get-item-link
Queries the item at position $item-index in $model for the link specified by $link.
If the link exists, the linked Gnome::Gio::MenuModel is returned. If the link does not exist, undefined is returned.
method get-item-link ( Int() $item-index, Str $link --> N-Object )
$item-index; the index of the item.
$link; the link to query.
Return value; the linked Gnome::Gio::MenuModel, or undefined.
get-n-items
Query the number of items in $model.
method get-n-items (--> Int )
Return value; the number of items.
is-mutable
Queries if $model is mutable.
An immutable Gnome::Gio::MenuModel will never emit the items-changed signal. Consumers of the model may make optimisations accordingly.
method is-mutable (--> Bool )
Return value; True if the model is mutable (ie: "items-changed" may be emitted)..
items-changed
Requests emission of the items-changed signal on $model.
This function should never be called except by Gnome::Gio::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 Gnome::Gio::MenuModel API. Said another way: the menu must not change while user code is running without returning to the mainloop.
method items-changed ( Int() $position, Int() $removed, Int() $added )
$position; the position of the change.
$removed; the number of items removed.
$added; the number of items added.
iterate-item-attributes
Creates a Gnome::Gio::MenuAttributeIter 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.
method iterate-item-attributes ( Int() $item-index --> N-Object )
$item-index; the index of the item.
Return value; a new Gnome::Gio::MenuAttributeIter.
iterate-item-links
Creates a Gnome::Gio::MenuLinkIter 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.
method iterate-item-links ( Int() $item-index --> N-Object )
$item-index; the index of the item.
Return value; a new Gnome::Gio::MenuLinkIter.
Signals
items-changed
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.
method handler ( gint $position, gint $removed, gint $added, Int :$_handle_id, N-GObject :$_native-object, Gnome::Gio::MenuModel :$_widget, *C<user>-options )
$position; the position of the change.
$removed; the number of items removed.
$added; the number of items added.
$_handle_id; The registered event handler id.
$_native-object; The native object provided by the Raku object which registered this event. This a native Gnome::Gio::MenuModel object.
$_widget; The object which registered the signal. User code may have left the object going out of scope.
user-options; A list of named arguments provided at the.register-signal()method from Gnome::GObject::Object.