Macro fui_component 

macro_rules! fui_component {
    ($component:ty => $root:ident) => { ... };
    ($component:ty => $root:ident, owner: $owner:ident) => { ... };
    ($component:ty => $root:ident, owners: [$($owner:ident),+ $(,)?]) => { ... };
    (@impl $component:ty => $root:ident, $owner_spec:tt) => { ... };
    (@owner_attachment $this:ident, $root:ident, [root]) => { ... };
    (@owner_attachment $this:ident, $root:ident, [owner $owner:ident]) => { ... };
    (@owner_attachment $this:ident, $root:ident, [owners $($owner:ident),+]) => { ... };
}

Delegates Node and HasFlexBoxRoot to a retained component’s root.

Use owner: or owners: only when the retained root must keep callback state or RAII guards alive after a temporary component wrapper is dropped. A retained page object may own ordinary fields directly without declaring them here.