static void 
mafw_my_renderer_get_property(MafwExtension *self,
	 		      const gchar *key,
			      MafwExtensionPropertyCallback callback,
			      gpointer user_data)
{
	MafwMyRenderer *renderer;
	GValue *value = NULL;
	GError *error = NULL;

	g_return_if_fail(MAFW_IS_MY_RENDERER(self));
	g_return_if_fail(callback != NULL);
	g_return_if_fail(key != NULL);

	renderer = MAFW_MY_RENDERER(self);
	if (!strcmp(key, MAFW_PROPERTY_RENDERER_VOLUME)) {
		value = g_new0(GValue, 1);
		g_value_init(value, G_TYPE_UINT);
		g_value_set_uint(value, volume);
	}
	else if (!strcmp(key, MAFW_PROPERTY_RENDERER_MUTE)) {
           ...
	}
	else {
		/* Unsupported property */
		error = g_error_new(MAFW_MY_RENDERER_ERROR,
				    MAFW_EXTENSION_ERROR_GET_PROPERTY,
				    "Unsupported property");
	}

	callback(self, key, value, user_data, error);
}

static gboolean
mafw_my_renderer_set_property(MafwExtension *self,
                              const gchar *key,
                              const GValue *value)
{
	MafwMyRenderer *renderer;

	g_return_if_fail(MAFW_IS_MY_RENDERER(self));
	g_return_if_fail(key != NULL);

	renderer = MAFW_MY_RENDERER(self);

	if (!strcmp(key, MAFW_PROPERTY_RENDERER_VOLUME)) {
		guint volume = g_value_get_uint(value);
		volume = CLAMP(volume, 0, 100);
                _do_set_volume(renderer, volume);
	}
	else if (!strcmp(key, MAFW_PROPERTY_RENDERER_MUTE)) {
         ...
        }
	else {
		/* Unsupported property */
                return FALSE;
	}

	mafw_extension_emit_property_changed(self, key, value);

        return TRUE;
}

static void mafw_my_renderer_class_init(MafwMyRendererClass *klass)
{
        ...
        MAFW_EXTENSION_CLASS(klass)->get_extension_property =
          (gpointer) mafw_my_renderer_get_property;
        MAFW_EXTENSION_CLASS(klass)->set_extension_property =
          (gpointer) mafw_my_renderer_set_property;
        ...
}
        

static void mafw_my_renderer_init(MafwMyRenderer *self)
{
        ...
	mafw_extension_add_property(MAFW_EXTENSION(self), "volume", G_TYPE_UINT);
	mafw_extension_add_property(MAFW_EXTENSION(self), "mute", G_TYPE_BOOLEAN);
        ...
}