PluggableEventLoop

/**
 * Intended to be used internally from scheduler threads.
 * Every iteration thread should poll loop and add tasks to scheduler work queues.
 * And only then proceed to execute next task.
 * Users should be able to register new event loops and control their affinity.
 * */
trait PluggableEventLoop {

  /**
   * Poll events and return tasks to execute.
   * Implementation should poll events from the underlying event loop and
   * return all callbacks which should be executed due to fired events.
   * */
  def poll(): Vector[Runnable]

  /**
   * Shows if the event loop is paused or resumed.
   * Event loop can pause itself on its own due to implementation-specific circumstances
   * (such as pausing of UI event loops due to focus lost).
   * Event loop can resume itself on its own only if it was paused on its own.
   * */
  def isPaused: Boolean

  /**
   * Request the event loop to become paused.
   * Implementation must respect this request.
   * Event loop can pause itself on its own due to implementation-specific circumstances
   * (such as pausing of UI event loops due to focus lost).
   * */
  def pause(): Unit

  /**
   * Request event loop to be resumed.
   * Implementation may ignore this request.
   * Event loop can resume itself on its own only if it was paused on its own.
   * */
  def resume(): Unit

  /**
   * Request to shut down the event loop.
   * Implementation must respect this request.
   * Event loop cannot shut down on its own.
   * */
  def shutdown(): Unit

}