Function view 

pub fn view<F: FnOnce(&mut Cx<'_, '_>)>(f: F) -> impl View

Wrap a closure as a View, fixing the closure’s argument type.

rsx! always emits ::egui_reactor::view(|cx| { .. }): passing a bare closure where impl View is expected leaves cx un-inferred, because the FnOnce bound is higher-ranked over the Cx lifetimes. Users writing the escape hatch by hand want this function for the same reason.