Marks that the given code should only be called
from an SWT thread.
When annotated on a method or constructor, this
indicates that all of its methods should only be
called from the SWT thread.
When annotated on a class, indicates that all
of its methods should only be called from the
SWT thread
When annotated on a parameter or field, it
must be either an Observable,
IObservable, or a
CompletionStage, and
it indicates that the given code should only be
set and listened to from SWT.