This class handles the state for one {@link EventHandler event handler} during integration steps.
Each time the integrator proposes a step, the event handler switching function should be checked. This class handles the state of one handler during one integration step, with references to the state at the end of the preceding step. This information is used to decide if the handler should trigger an event or not during the proposed step (and hence the step should be reduced to ensure the event occurs at a bound rather than inside the step).
@version $Revision: 1073158 $ $Date: 2011-02-21 22:46:52 +0100 (lun. 21 févr. 2011) $
@since 1.2