use crate::*;

/// Show an item only when a condition is true.
pub struct When<A>(pub bool, pub A);

impl<E: Output, A: Render<E>> Content<E> for When<A> {
    fn layout (&self, to: E::Area) -> E::Area {
        let Self(cond, item) = self;
        let mut area = E::Area::zero();
        if *cond {
            let item_area = item.layout(to);
            area[0] = item_area.x();
            area[1] = item_area.y();
            area[2] = item_area.w();
            area[3] = item_area.h();
        }
        area.into()
    }
    fn render (&self, to: &mut E) {
        let Self(cond, item) = self;
        if *cond { item.render(to) }
    }
}