add widget dynamic helper and Split::up

crates/tek_core/src/engine.rs

@@ -42,6 +42,10 @@ pub trait Output<E: Engine> {
     /// Render widget in area
     fn render_in (&mut self, area: E::Area, widget: &dyn Widget<Engine = E>) -> Usually<()>;
 }
+/// Cast to dynamic pointer
+pub fn widget <E: Engine, T: Widget<Engine = E>> (w: &T) -> &dyn Widget<Engine = E> {
+    w as &dyn Widget<Engine = E>
+}
 /// A renderable component
 pub trait Widget: Send + Sync {
     /// Engine for which this component is implemented