//! part of [`Env`]
use super::*;
/// Type compound
pub trait Backend<E>: Sized + 'static where E: Env<Backend=Self> {
type Renderer: Render<E>;
type Event: Event<E>;
///TODO move tree'd back to Event
type EventFilter: Filter<E>;
type Style: Style<E>;
type Size: Gonstraints;
}