Function scheduleCallbackWithExpiration

code/composition/public/app.js:13717–13740

(expirationTime)

  var timeHeuristicForUnitOfWork = 1;

  function scheduleCallbackWithExpiration(expirationTime) {
    if (callbackExpirationTime !== NoWork) {
      // A callback is already scheduled. Check its expiration time (timeout).
      if (expirationTime > callbackExpirationTime) {
        // Existing callback has sufficient timeout. Exit.
        return;
      } else {
        // Existing callback has insufficient timeout. Cancel and schedule a
        // new one.
        cancelDeferredCallback(callbackID);
      }
      // The request callback timer is already running. Don't start a new one.
    } else {
      startRequestCallbackTimer();
    }

    // Compute a timeout for the given expiration time.
    var currentMs = now() - originalStartTimeMs;
    var expirationMs = expirationTimeToMs(expirationTime);
    var timeout = expirationMs - currentMs;

    callbackExpirationTime = expirationTime;
    callbackID = scheduleDeferredCallback(performAsyncWork, { timeout: timeout });
  }

  // requestWork is called by the scheduler whenever a root receives an update.
  // It's up to the renderer to call renderRoot at some point in the future.