Function unstable_scheduleCallback

packages/scheduler/src/forks/Scheduler.js:327–416

(
  priorityLevel: PriorityLevel,
  callback: Callback,
  options?: {delay: number},
)

}

function unstable_scheduleCallback(
  priorityLevel: PriorityLevel,
  callback: Callback,
  options?: {delay: number},
): Task {
  var currentTime = getCurrentTime();

  var startTime;
  if (typeof options === 'object' && options !== null) {
    var delay = options.delay;
    if (typeof delay === 'number' && delay > 0) {
      startTime = currentTime + delay;
    } else {
      startTime = currentTime;
    }
  } else {
    startTime = currentTime;
  }

  var timeout;
  switch (priorityLevel) {
    case ImmediatePriority:
      // Times out immediately
      timeout = -1;
      break;
    case UserBlockingPriority:
      // Eventually times out
      timeout = userBlockingPriorityTimeout;
      break;
    case IdlePriority:
      // Never times out
      timeout = maxSigned31BitInt;
      break;
    case LowPriority:
      // Eventually times out
      timeout = lowPriorityTimeout;
      break;
    case NormalPriority:
    default:
      // Eventually times out
      timeout = normalPriorityTimeout;
      break;
  }

  var expirationTime = startTime + timeout;

  var newTask: Task = {
    id: taskIdCounter++,
    callback,
    priorityLevel,
    startTime,
    expirationTime,
    sortIndex: -1,
  };
  if (enableProfiling) {
    newTask.isQueued = false;
  }