The interface implemented by a dialog window. Like with swing's
JDialog or JInternalFrame, you don't actually
add components to the dialog itself, but rather to it's content pane,
which is returned by
Dialog.getContentPane .
author: Rob Clark version: 0.2
Add a runnable that will be invoked when this dialog is closed. This
gives the user of the dialog a way to perform cleanup when the dialog
is closed.
Parameters: r - the runnable