yield

Yields control to event dispatching. See Eventspaces for details.

A handler procedure invoked by the system during a call to yield can itself call yield, creating an additional level of nested (but single-threaded) event handling.

See also sleep/yield .

• (yield) -> void

  Dispatches an unspecified number of events, but only if the current thread is the current eventspace's handler thread (otherwise, there is no effect).

  
  

• (yield wait-symbol) -> void
      wait-symbol : 'wait

  When called in the handler thread of an eventspace, yields (processing events) until

  • no top-level windows in the eventspace are visible;
  • no timers in the eventspace are running; and
  • no callbacks are queued in the eventspace.

  (When called in a non-handler thread, returns immediately.)

  
  

• (yield sema) -> void
      sema : semaphore

  Blocks on sema. If the current thread is the current eventspace's handler thread, events are dispatched until a sema wait succeeds on an event boundary. For other threads, calling yield with a semaphore is equivalent to calling semaphore-wait.

  Always use (yield sema) instead of a busy-wait loop.