Demonstrates the use of undo & redo methods while drawing.
⌘-Z to undo while drawing.
⌘-Y to redo what you have
Esc to cancel the current sketch.
control.undo method works on the current
sketch, removing the most recently added point.
control.redo method adds back items that were
removed from an undo. To fully erase a sketch, call the
View the draw-undo-redo.js source to see how this is done.