Gnome::Gio::ActionGroup

A group of actions

Description

Gnome::Gio::ActionGroup represents a group of actions. Actions can be used to expose functionality in a structured way, either from one part of a program to another, or to the outside world. Action groups are often used together with a GMenuModel that provides additional representation data for displaying the actions to the user, e.g. in a menu.

The main way to interact with the actions in a GActionGroup is to activate them with activate-action(). Activating an action may require a GVariant parameter. The required type of the parameter can be inquired with get-action-parameter-type(). Actions may be disabled, see get-action-enabled(). Activating a disabled action has no effect.

Actions may optionally have a state in the form of a GVariant. The current state of an action can be inquired with get-action-state(). Activating a stateful action may change its state, but it is also possible to set the state by calling change-action-state()`.

As typical example, consider a text editing application which has an option to change the current font to ‘bold’. A good way to represent this would be a stateful action, with a boolean state. Activating the action would toggle the state.

Each action in the group has a unique name (which is a string). All method calls, except list-actions() take the name of an action as an argument.

The Gnome::Gio::ActionGroup API is meant to be the ‘public’ API to the action group. The calls here are exactly the interaction that ‘external forces’ (eg: UI, incoming D-Bus messages, etc.) are supposed to have with actions. ‘Internal’ APIs (ie: ones meant only to be accessed by the action group implementation) are found on subclasses. This is why you will find - for example - get-action-enabled() but not an equivalent set() call.

Signals are emitted on the action group in response to state changes on individual actions.

Synopsis

Declaration

unit class Gnome::Gio::ActionGroup;

Methods

action-added

Emits the action-added signal on action-group. This function should only be called by GActionGroup implementations.

method action-added ( Str $action_name )

Str $action_name; the name of an action in the group

action-enabled-changed

Emits the action-enabled-changed signal on action-group. This function should only be called by GActionGroup implementations.

method action-enabled-changed ( Str $action_name, Int $enabled )

Str $action_name; the name of an action in the group
Int $enabled; whether or not the action is now enabled

action-removed

Emits the action-removed signal on action-group. This function should only be called by GActionGroup implementations.

method action-removed ( Str $action_name )

Str $action_name; the name of an action in the group

action-state-changed

Emits the action-state-changed signal on action-group. This function should only be called by GActionGroup implementations.

method action-state-changed ( Str $action_name, N-GObject $state )

Str $action_name; the name of an action in the group
N-GObject $state; the new state of the named action

activate-action

Activate the named action within action-group. If the action is expecting a parameter, then the correct type of parameter must be given as $parameter. If the action is expecting no parameters then parameter must be undefined. See get-action-parameter-type().

method activate-action ( Str $action_name, N-GObject $parameter )

Str $action_name; the name of the action to activate
N-GObject $parameter; (nullable): parameters to the activation

change-action-state

Request for the state of the named action within action-group to be changed to value. The action must be stateful and value must be of the correct type. See get-action-state-type(). This call merely requests a change. The action may refuse to change its state or may change its state to something other than value. See get-action-state-hint(). If the value GVariant is floating, it is consumed.

method change-action-state ( Str $action_name, N-GObject $value )

Str $action_name; the name of the action to request the change on
N-GObject $value; the new state

get-action-enabled

Checks if the named action within action-group is currently enabled. An action must be enabled in order to be activated or in order to have its state changed from outside callers.

Returns: whether or not the action is currently enabled

method get-action-enabled ( Str $action_name --> Bool )

Str $action_name; the name of the action to query

get-action-parameter-type

Queries the type of the parameter that must be given when activating the named action within action-group. When activating the action using [[activate-action]], the GVariant given to that function must be of the type returned by this function. In the case that this function returns undefined, you must not give any GVariant, but undefined instead. The parameter type of a particular action will never change but it is possible for an action to be removed and for a new action to be added with the same name but a different parameter type.

Returns: (nullable): the parameter type

method get-action-parameter-type (
  Str $action_name --> Gnome::Glib::VariantType
)

Str $action_name; the name of the action to query

get-action-state

Queries the current state of the named action within action-group. If the action is not stateful then undefined will be returned. If the action is stateful then the type of the return value is the type given by [[get-action-state-type]]. The return value (if non-undefined) should be freed with [[g-variant-unref]] when it is no longer required.

Returns: the current state of the action

method get-action-state (
  Str $action_name --> Gnome::Glib::Variant
)

Str $action_name; the name of the action to query

get-action-state-hint

Requests a hint about the valid range of values for the state of the named action within action-group. If undefined is returned it either means that the action is not stateful or that there is no hint about the valid range of values for the state of the action. If a GVariant array is returned then each item in the array is a possible value for the state. If a GVariant pair (ie: two-tuple) is returned then the tuple specifies the inclusive lower and upper bound of valid values for the state. In any case, the information is merely a hint. It may be possible to have a state value outside of the hinted range and setting a value within the range may fail. The return value (if non-undefined) should be freed with [[g-variant-unref]] when it is no longer required.

Returns: the state range hint

method get-action-state-hint ( Str $action_name --> Gnome::Glib::Variant )

Str $action_name; the name of the action to query

get-action-state-type

Queries the type of the state of the named action within action-group. If the action is stateful then this function returns the GVariantType of the state. All calls to change-action-state() must give a GVariant of this type and g-action-group-get-action-state() will return a GVariant of the same type. If the action is not stateful then this function will return undefined. In that case, [[g-action-group-get-action-state]] will return undefined and you must not call [[g-action-group-change-action-state]]. The state type of a particular action will never change but it is possible for an action to be removed and for a new action to be added with the same name but a different state type.

Returns: (nullable): the state type, if the action is stateful

method get-action-state-type ( Str $action_name --> Gnome::Glib::VariantType )

Str $action_name; the name of the action to query

has-action

Checks if the named action exists within action-group.

Returns: whether the named action exists

method has-action ( Str $action_name --> Bool )

Str $action_name; the name of the action to check for

list-actions

Lists the actions contained within action-group.

Returns: an array of the names of the actions in the group

method list-actions ( --> Array  )

query-action

Queries all aspects of the named action within an action-group. This function acquires the information available from has-action(), get-action-enabled(), get-action-parameter-type(), get-action-state-type(), get-action-state-hint() and get-action-state() with a single function call.

This provides two main benefits. The first is the improvement in efficiency that comes with not having to perform repeated lookups of the action in order to discover different things about it. The second is that implementing GActionGroup can now be done by only overriding this one virtual function.

Returns: A List if the action exists, else an empty List

method query-action ( Str $action_name --> List )

Str $action_name; the name of an action in the group

The returned list holds;

Bool $enabled; if the action is presently enabled
Gnome::Glib::VariantType $parameter_type; the parameter type, or undefined if none needed
Gnome::Glib::VariantType $state_type; the state type, or undefined if stateless
Gnome::Glib::Variant $state_hint; the state hint, or undefined if none
Gnome::Glib::Variant $state; the current state, or undefined if stateless

Signals

There are two ways to connect to a signal. The first option you have is to use register-signal() from Gnome::GObject::Object. The second option is to use connect-object() directly from Gnome::GObject::Signal.

First method

The positional arguments of the signal handler are all obligatory as well as their types. The named attributes :$widget and user data are optional.

# handler method
method mouse-event ( GdkEvent $event, :$widget ) { ... }

# connect a signal on window object
my Gnome::Gtk3::Window $w .= new( ... );
$w.register-signal( self, 'mouse-event', 'button-press-event');

Second method

my Gnome::Gtk3::Window $w .= new( ... );
my Callable $handler = sub (
  N-GObject $native, GdkEvent $event, OpaquePointer $data
) {
  ...
}

$w.connect-object( 'button-press-event', $handler);

Also here, the types of positional arguments in the signal handler are important. This is because both methods register-signal() and connect-object() are using the signatures of the handler routines to setup the native call interface.

Supported signals

action-added

Signals that a new action was just added to the group. This signal is emitted after the action has been added and is now visible.

method handler (
  Str $action_name,
  Int :$_handle_id,
  Gnome::GObject::Object :_widget($action_group),
  *%user-options
);

$action_group; the GActionGroup that changed
$action_name; the name of the action in action-group

action-enabled-changed

Signals that the enabled status of the named action has changed.

method handler (
  Str $action_name,
  Int $enabled,
  Int :$_handle_id,
  Gnome::GObject::Object :_widget($action_group),
  *%user-options
);

$action_group; the GActionGroup that changed
$action_name; the name of the action in action-group
$enabled; whether the action is enabled or not

action-removed

Signals that an action is just about to be removed from the group. This signal is emitted before the action is removed, so the action is still visible and can be queried from the signal handler.

method handler (
  Str $action_name,
  Int :$_handle_id,
  Gnome::GObject::Object :_widget($action_group),
  *%user-options
);

$action_group; the GActionGroup that changed
$action_name; the name of the action in action-group

action-state-changed

Signals that the state of the named action has changed.

method handler (
  Str $action_name,
  Unknown type G_TYPE_VARIANT $value,
  Int :$_handle_id,
  Gnome::GObject::Object :_widget($action_group),
  *%user-options
);

$action_group; the GActionGroup that changed
$action_name; the name of the action in action-group
$value; the new value of the state

Gnome::Gio::ActionGroup

Description

See Also

Synopsis

Declaration

Methods

action-added

action-enabled-changed

action-removed

action-state-changed

activate-action

change-action-state

get-action-enabled

get-action-parameter-type

get-action-state

get-action-state-hint

get-action-state-type

has-action

list-actions

query-action

Signals

First method

Second method

Supported signals

action-added

action-enabled-changed

action-removed

action-state-changed