In Morph>>#handleMouseDown:, it sets the wasHandled: flag of the
incoming Event to true.

Isn't it more appropriate for wasHandled: to be set by the code that
actually _handles_ the event?  i.e., in #mouseDown:?

In my overridden mouseDown:, I have several code paths that may or may
not choose to handle the event.  The logical approach seemed to be for
each to simply checked #wasHandled and, if not, decide whether it
wants to handle it and, if so, set wasHandled: true, so none of the
subsequent possibilities will attempt to handle it.