FocusOrder class abstract

Base class for all sort orders for OrderedTraversalPolicy traversal.

Only orders of the same type are comparable. If a set of widgets in the same FocusTraversalGroup contains orders that are not comparable with each other, it will assert, since the ordering between such keys is undefined. To avoid collisions, use a FocusTraversalGroup to group similarly ordered widgets together.

When overriding, FocusOrder.doCompare must be overridden instead of FocusOrder.compareTo, which calls FocusOrder.doCompare to do the actual comparison.

See also:

• FocusTraversalGroup, a widget that groups together and imposes a traversal policy on the Focus nodes below it in the widget hierarchy.
• FocusTraversalOrder, a widget that assigns an order to a widget subtree for the OrderedTraversalPolicy to use.
• NumericFocusOrder, for a focus order that describes its order with a double.
• LexicalFocusOrder, a focus order that assigns a string-based lexical traversal order to a FocusTraversalOrder widget.