Function on_focus 

pub fn on_focus(
    child: impl IntoUiNode,
    handler: Box<dyn FnMut(&FocusChangedArgs) -> HandlerResult + Send>,
) -> UiNode

P Widget got direct keyboard focus.

Preview

You can preview this event using on_pre_focus. Otherwise the handler is only called after the widget content has a chance to stop propagation.

Async

You can use async event handlers with this property.