重点-updateContainer开始渲染-18

function updateContainer(element, container, parentComponent, callback) {
  console.log('更新流程-->updateContainer本体')
  {
    onScheduleRoot(container, element);
  }

  var current$1 = container.current;
  var eventTime = requestEventTime();
  var lane = requestUpdateLane(current$1);

  {
    markRenderScheduled(lane);
  }

  var context = getContextForSubtree(parentComponent);

  if (container.context === null) {
    container.context = context;
  } else {
    container.pendingContext = context;
  }

  {
    if (isRendering && current !== null && !didWarnAboutNestedUpdates) {
      didWarnAboutNestedUpdates = true;

      error('Render methods should be a pure function of props and state; ' + 'triggering nested component updates from render is not allowed. ' + 'If necessary, trigger nested updates in componentDidUpdate.\n\n' + 'Check the render method of %s.', getComponentNameFromFiber(current) || 'Unknown');
    }
  }

  var update = createUpdate(eventTime, lane); // Caution: React DevTools currently depends on this property
  // being called "element".

  update.payload = {
    element: element
  };
  callback = callback === undefined ? null : callback;

  if (callback !== null) {
    {
      if (typeof callback !== 'function') {
        error('render(...): Expected the last optional `callback` argument to be a ' + 'function. Instead received: %s.', callback);
      }
    }

    update.callback = callback;
  }

  console.log('更新流程-->updateContainer本体,调用enqueueUpdate和scheduleUpdateOnFiber')
  enqueueUpdate(current$1, update);
  var root = scheduleUpdateOnFiber(current$1, lane, eventTime);

  if (root !== null) {
    entangleTransitions(root, current$1, lane);
  }

  return lane;
}