Function record 

pub fn record<R>(
    scene: &mut Scene,
    draw: impl FnOnce(&mut Scene) -> R,
) -> (R, Option<SectionParts>)

Record the parts of a scene drawn on its own (a retained scene a widget re-records only when it changes): the parts draw marks in scene, or None when they are not well nested. Any recording around this one is suspended while draw runs, so draw must paint only into scene.