Class recogniser is an almost empty super-class. It's main purpose is to serve as a type-check for it's sub-classes.
A recogniser is an object that maps a user event onto an action. The
events origins from the window on which it occurred and is dispatched by
the dispatching behaviour defined by device->event.
A recogniser may be attached to a graphical
object using graphical ->recogniser' or it may be used from a redefined graphical recogniser->event‘method.
Multiple recognisers may be combined to a single entity using class handler_group.
->active: @off.
The method
recogniser->event
fails for inactive recognisers.
->active
to @on.
Creating instances of this class is no common use.