1c4d480185
Previously, ControlList::get<T>() would use default constructed objects to indicate that a ControlList does not have the requested Control. This has several disadvantages: 1) It requires types to be default constructible, 2) it does not differentiate between a default constructed object and an object that happens to have the same state as a default constructed object. std::optional<T> additionally stores the information if the object is valid or not, and therefore is more expressive than a default constructed object. Signed-off-by: Christian Rauch <Rauch.Christian@gmx.de> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>