This controller provides basic controls over the Tooltip widget.
It is just a shell class that is given functionality by the
StatefulWidget. This idea was copied from a FocusNode whose attach
method is called to give the focusNode the context and state of its parent.
A Tooltip widget that delegates to creation and use of the tooltip and
skrim to the outer AlignedTooltipArea. This class is useless if not
nested within a AlignedTooltipArea.
A widget to display a tooltip over target widget. The tooltip can be
displayed on any axis of the widget and fallback to the opposite axis if
the tooltip does cannot fit its content. The tooltip can will be dismissed
by waiting a specified time or again tapping on the target widger or
anywhere on the screen.
This is almost a one to one mapping to Tooltip's _TooltipState except
for the fact it is setup to handle two Tooltip cases. Abstract methods are
replaced with implementations that are specific to the tooltip type.
