set_property ("X-extent", Grob::stencil_width_proc);
if (get_property_data ("Y-extent") == SCM_EOL)
set_property ("Y-extent",
set_property ("X-extent", Grob::stencil_width_proc);
if (get_property_data ("Y-extent") == SCM_EOL)
set_property ("Y-extent",