To use Command objects to create an Undo operation.

Modify your application menu to include an Edit menu. In the edit menu create an Undo and a Redo menu item. These should also be mapped to control-z and control-y respectively. This should undo and/or redo any changes that have happened. The granularity of the undo/redo operations is between mouseDown() and mouseUp() or on a single key() event. It should be more than every mouseMove().

This should work for all of your various widgets that you have built so far. If you have done everything correctly, only the model objects need to be tracked for undo/redo because all of the drawing objects are either static or are connected to model objects.

__ 2) Button objects correctly undo and redo.
__ 2) ScrollV and ScrollH correctly undo and redo.
__ 2) TextBox editing correctly does undo/redo.
__ 2) Path changes should correctly undo/redo.