By default, Tooltips will present after their associated widget presents
(if the mouse cursor is hovering over that widget, and the tooltip
should appear). But the tooltip is not guaranteed to draw "on top" of
neighboring doodads, unless you choose your Edge carefully depending on
the order you're drawing your widgets.
To solve this, Tooltips can be supervised to DrawOnTop() when they're
activated. To opt in, you simply call the Tooltip.Supervise() function
with your supervisor.
