4.2  Eventspaces

Procedures
    check-for-break
    current-eventspace
    event-dispatch-handler
    eventspace-handler-thread
    eventspace-shutdown?
    eventspace?
    get-top-level-edit-target-window
    get-top-level-focus-window
    get-top-level-windows
    make-eventspace
    queue-callback
    sleep/yield
    special-control-key
    special-option-key
    yield