Module: Gio::ActionGroup

Defined in:
(unknown)

Overview

GActionGroup 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 [methodGio.ActionGroup.activate_action]. Activating an
action may require a GVariant parameter. The required type of the
parameter can be inquired with [methodGio.ActionGroup.get_action_parameter_type].
Actions may be disabled, see [methodGio.ActionGroup.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 [methodGio.ActionGroup.get_action_state].
Activating a stateful action may change its state, but it is also possible to
set the state by calling [methodGio.ActionGroup.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 [methodGio.ActionGroup.list_actions] take the name of
an action as an argument.

The GActionGroup 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 - [methodGio.ActionGroup.get_action_enabled]
but not an equivalent set() call.

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

Implementations of GActionGroup should provide implementations for
the virtual functions [methodGio.ActionGroup.list_actions] and
[methodGio.ActionGroup.query_action]. The other virtual functions should
not be implemented - their "wrappers" are actually implemented with
calls to [methodGio.ActionGroup.query_action].

Instance Method Summary collapse

Instance Method Details

#action_added(action_name) ⇒ nil

Emits the GAction::Group::action-added signal on action_group.

This function should only be called by GAction::Group implementations.

Parameters:

  • action_name (String) —

    the name of an action in the group

Returns:

  • (nil)

#action_enabled_changed(action_name, enabled) ⇒ nil

Emits the GAction::Group::action-enabled-changed signal on action_group.

This function should only be called by GAction::Group implementations.

Parameters:

  • action_name (String) —

    the name of an action in the group

  • enabled (Boolean) —

    whether or not the action is now enabled

Returns:

  • (nil)

#action_removed(action_name) ⇒ nil

Emits the GAction::Group::action-removed signal on action_group.

This function should only be called by GAction::Group implementations.

Parameters:

  • action_name (String) —

    the name of an action in the group

Returns:

  • (nil)

#action_state_changed(action_name, state) ⇒ nil

Emits the GAction::Group::action-state-changed signal on action_group.

This function should only be called by GAction::Group implementations.

Parameters:

  • action_name (String) —

    the name of an action in the group

  • state (GLib::Variant) —

    the new state of the named action

Returns:

  • (nil)

#activate_action(action_name, parameter) ⇒ nil

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 nil. See
g_action_group_get_action_parameter_type().

If the GAction::Group implementation supports asynchronous remote
activation over D-Bus, this call may return before the relevant
D-Bus traffic has been sent, or any replies have been received. In
order to block on such asynchronous activation calls,
g_dbus_connection_flush() should be called prior to the code, which
depends on the result of the action activation. Without flushing
the D-Bus connection, there is no guarantee that the action would
have been activated.

The following code which runs in a remote app instance, shows an
example of a "quit" action being activated on the primary app
instance over D-Bus. Here g_dbus_connection_flush() is called
before exit(). Without g_dbus_connection_flush(), the "quit" action
may fail to be activated on the primary instance.

// call "quit" action on primary instance
g_action_group_activate_action (G_ACTION_GROUP (app), "quit", NULL);

// make sure the action is activated now
g_dbus_connection_flush (...);

g_debug ("application has been terminated. exiting.");

exit (0);

Parameters:

  • action_name (String) —

    the name of the action to activate

  • parameter (GLib::Variant) —

    parameters to the activation

Returns:

  • (nil)

#change_action_state(action_name, value) ⇒ nil

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 g_action_group_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 g_action_group_get_action_state_hint().

If the value GVariant is floating, it is consumed.

Parameters:

  • action_name (String) —

    the name of the action to request the change on

  • value (GLib::Variant) —

    the new state

Returns:

  • (nil)

#get_action_enabled(action_name) ⇒ Boolean

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.

Parameters:

  • action_name (String) —

    the name of the action to query

Returns:

  • (Boolean) —

    whether or not the action is currently enabled

#get_action_parameter_type(action_name) ⇒ GLib::VariantType

Queries the type of the parameter that must be given when activating
the named action within action_group.

When activating the action using g_action_group_activate_action(),
the #GVariant given to that function must be of the type returned
by this function.

In the case that this function returns nil, you must not give any
#GVariant, but nil 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.

Parameters:

  • action_name (String) —

    the name of the action to query

Returns:

  • (GLib::VariantType) —

    the parameter type

#get_action_state(action_name) ⇒ GLib::Variant

Queries the current state of the named action within action_group.

If the action is not stateful then nil will be returned. If the
action is stateful then the type of the return value is the type
given by g_action_group_get_action_state_type().

The return value (if non-nil) should be freed with
g_variant_unref() when it is no longer required.

Parameters:

  • action_name (String) —

    the name of the action to query

Returns:

  • (GLib::Variant) —

    the current state of the action

#get_action_state_hint(action_name) ⇒ GLib::Variant

Requests a hint about the valid range of values for the state of the
named action within action_group.

If nil 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-nil) should be freed with
g_variant_unref() when it is no longer required.

Parameters:

  • action_name (String) —

    the name of the action to query

Returns:

  • (GLib::Variant) —

    the state range hint

#get_action_state_type(action_name) ⇒ GLib::VariantType

Queries the type of the state of the named action within
action_group.

If the action is stateful then this function returns the
GVariant::Type of the state. All calls to
g_action_group_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 nil.
In that case, g_action_group_get_action_state() will return nil
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.

Parameters:

  • action_name (String) —

    the name of the action to query

Returns:

  • (GLib::VariantType) —

    the state type, if the action is stateful

#has_action(action_name) ⇒ Boolean

Checks if the named action exists within action_group.

Parameters:

  • action_name (String) —

    the name of the action to check for

Returns:

  • (Boolean) —

    whether the named action exists

#list_actions ⇒ Array<String>

Lists the actions contained within action_group.

The caller is responsible for freeing the list with g_strfreev() when
it is no longer required.
actions in the group

Returns:

  • (Array<String>) —

    an array of the names of the

#query_action(action_name, enabled, parameter_type, state_type, state_hint, state) ⇒ Boolean

Queries all aspects of the named action within an action_group.

This function acquires the information available from
g_action_group_has_action(), g_action_group_get_action_enabled(),
g_action_group_get_action_parameter_type(),
g_action_group_get_action_state_type(),
g_action_group_get_action_state_hint() and
g_action_group_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
GAction::Group can now be done by only overriding this one virtual
function.

The interface provides a default implementation of this function that
calls the individual functions, as required, to fetch the
information. The interface also provides default implementations of
those functions that call this function. All implementations,
therefore, must override either this function or all of the others.

If the action exists, true is returned and any of the requested
fields (as indicated by having a non-nil reference passed in) are
filled. If the action doesn't exist, false is returned and the
fields may or may not have been modified.

Parameters:

  • action_name (String) —

    the name of an action in the group

  • enabled (Boolean) —

    if the action is presently enabled

  • parameter_type (GLib::VariantType) —

    the parameter type, or nil if none needed

  • state_type (GLib::VariantType) —

    the state type, or nil if stateless

  • state_hint (GLib::Variant) —

    the state hint, or nil if none

  • state (GLib::Variant) —

    the current state, or nil if stateless

Returns:

  • (Boolean) —

    true if the action exists, else false