/// <summary>
/// Returns an observable firing boolean every time the visibility of a <see cref="FlyoutBase"/> changes.
/// </summary>
/// <param name="flyout"></param>
/// <returns></returns>
public static IObservable <bool> ObserveIsVisible(this FlyoutBase flyout)
{
return(Observable
.Merge(
flyout.ObserveClosed().Select(_ => false),
flyout.ObserveOpened().Select(_ => true)));
}