Activatable widgets can be connected to a #GtkAction and reflects the state of its action. A #GtkActivatable can also provide feedback through its action, as they are responsible for activating their related actions.

Implementing GtkActivatable

When extending a class that is already #GtkActivatable; it is only necessary to implement the #GtkActivatable->sync_action_properties() and #GtkActivatable->update() methods and chain up to the parent implementation, however when introducing a new #GtkActivatable class; the #GtkActivatable:related-action and #GtkActivatable:use-action-appearance properties need to be handled by the implementor. Handling these properties is mostly a matter of installing the action pointer and boolean flag on your instance, and calling [gtk.activatable.Activatable.doSetRelatedAction] and [gtk.activatable.Activatable.syncActionProperties] at the appropriate times.

A class fragment implementing #GtkActivatable

enum {
...

PROP_ACTIVATABLE_RELATED_ACTION,
PROP_ACTIVATABLE_USE_ACTION_APPEARANCE
}

struct _FooBarPrivate
{

 ...

 GtkAction      *action;
 gboolean        use_action_appearance;
};

...

static void foo_bar_activatable_interface_init         (GtkActivatableIface  *iface);
static void foo_bar_activatable_update                 (GtkActivatable       *activatable,
						           GtkAction            *action,
						           const gchar          *property_name);
static void foo_bar_activatable_sync_action_properties (GtkActivatable       *activatable,
						           GtkAction            *action);
...

static void
foo_bar_class_init (FooBarClass *klass)
{

 ...

 g_object_class_override_property (gobject_class, PROP_ACTIVATABLE_RELATED_ACTION, "related-action");
 g_object_class_override_property (gobject_class, PROP_ACTIVATABLE_USE_ACTION_APPEARANCE, "use-action-appearance");

 ...
}

static void
foo_bar_activatable_interface_init (GtkActivatableIface  *iface)
{
 iface->update = foo_bar_activatable_update;
 iface->sync_action_properties = foo_bar_activatable_sync_action_properties;
}

... Break the reference using gtk_activatable_do_set_related_action()...

static void
foo_bar_dispose (GObject *object)
{
 FooBar *bar = FOO_BAR (object);
 FooBarPrivate *priv = FOO_BAR_GET_PRIVATE (bar);

 ...

 if (priv->action)
   {
     gtk_activatable_do_set_related_action (GTK_ACTIVATABLE (bar), NULL);
     priv->action = NULL;
   }
 G_OBJECT_CLASS (foo_bar_parent_class)->dispose (object);
}

... Handle the “related-action” and “use-action-appearance” properties ...

static void
foo_bar_set_property (GObject         *object,
                     guint            prop_id,
                     const GValue    *value,
                     GParamSpec      *pspec)
{
 FooBar *bar = FOO_BAR (object);
 FooBarPrivate *priv = FOO_BAR_GET_PRIVATE (bar);

 switch (prop_id)
   {

     ...

   case PROP_ACTIVATABLE_RELATED_ACTION:
     foo_bar_set_related_action (bar, g_value_get_object (value));
     break;
   case PROP_ACTIVATABLE_USE_ACTION_APPEARANCE:
     foo_bar_set_use_action_appearance (bar, g_value_get_boolean (value));
     break;
   default:
     G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
     break;
   }
}

static void
foo_bar_get_property (GObject         *object,
                        guint            prop_id,
                        GValue          *value,
                        GParamSpec      *pspec)
{
 FooBar *bar = FOO_BAR (object);
 FooBarPrivate *priv = FOO_BAR_GET_PRIVATE (bar);

 switch (prop_id)
   {

     ...

   case PROP_ACTIVATABLE_RELATED_ACTION:
     g_value_set_object (value, priv->action);
     break;
   case PROP_ACTIVATABLE_USE_ACTION_APPEARANCE:
     g_value_set_boolean (value, priv->use_action_appearance);
     break;
   default:
     G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
     break;
   }
}

static void
foo_bar_set_use_action_appearance (FooBar   *bar,
				   gboolean  use_appearance)
{
 FooBarPrivate *priv = FOO_BAR_GET_PRIVATE (bar);

 if (priv->use_action_appearance != use_appearance)
   {
     priv->use_action_appearance = use_appearance;

     gtk_activatable_sync_action_properties (GTK_ACTIVATABLE (bar), priv->action);
   }
}

... call gtk_activatable_do_set_related_action() and then assign the action pointer,
no need to reference the action here since gtk_activatable_do_set_related_action() already
holds a reference here for you...
static void
foo_bar_set_related_action (FooBar    *bar,
			    GtkAction *action)
{
 FooBarPrivate *priv = FOO_BAR_GET_PRIVATE (bar);

 if (priv->action == action)
   return;

 gtk_activatable_do_set_related_action (GTK_ACTIVATABLE (bar), action);

 priv->action = action;
}

... Selectively reset and update activatable depending on the use-action-appearance property ...
static void
gtk_button_activatable_sync_action_properties (GtkActivatable       *activatable,
		                                  GtkAction            *action)
{
 GtkButtonPrivate *priv = GTK_BUTTON_GET_PRIVATE (activatable);

 if (!action)
   return;

 if (gtk_action_is_visible (action))
   gtk_widget_show (GTK_WIDGET (activatable));
 else
   gtk_widget_hide (GTK_WIDGET (activatable));

 gtk_widget_set_sensitive (GTK_WIDGET (activatable), gtk_action_is_sensitive (action));

 ...

 if (priv->use_action_appearance)
   {
     if (gtk_action_get_stock_id (action))
	foo_bar_set_stock (button, gtk_action_get_stock_id (action));
     else if (gtk_action_get_label (action))
	foo_bar_set_label (button, gtk_action_get_label (action));

     ...

   }
}

static void
foo_bar_activatable_update (GtkActivatable       *activatable,
			       GtkAction            *action,
			       const gchar          *property_name)
{
 FooBarPrivate *priv = FOO_BAR_GET_PRIVATE (activatable);

 if (strcmp (property_name, "visible") == 0)
   {
     if (gtk_action_is_visible (action))
	gtk_widget_show (GTK_WIDGET (activatable));
     else
	gtk_widget_hide (GTK_WIDGET (activatable));
   }
 else if (strcmp (property_name, "sensitive") == 0)
   gtk_widget_set_sensitive (GTK_WIDGET (activatable), gtk_action_is_sensitive (action));

 ...

 if (!priv->use_action_appearance)
   return;

 if (strcmp (property_name, "stock-id") == 0)
   foo_bar_set_stock (button, gtk_action_get_stock_id (action));
 else if (strcmp (property_name, "label") == 0)
   foo_bar_set_label (button, gtk_action_get_label (action));

 ...
}