libweston-desktop implements this private struct. Signed-off-by: Quentin Glidic <sardemff7+git@sardemff7.net> Reviewed-by: Jonas Ådahl <jadahl@gmail.com> Acked-by: Giulio Camuffo <giulio.camuffo@kdab.com> Differential Revision: https://phabricator.freedesktop.org/D1208