Sets or obtains the modal status of window.
true if the window is set to be modal and establishes a grab when shown.
Modal windows prevent interaction with other windows in the same application. To keep modal dialogs on top of main application windows, use Window.TransientFor to make the dialog transient for the parent; most window managers will then disallow lowering the dialog below the parent.
There are two status: modal (true) and non-modal (false).