Function registerDomTrigger

packages/core/src/defer/dom_triggers.ts:123–210

(
  initialLView: LView,
  tNode: TNode,
  triggerIndex: number,
  walkUpTimes: number | undefined | null,
  registerFn: (
    element: Element,
    callback: VoidFunction,
    injector: Injector,
    options?: O,
  ) => VoidFunction,
  callback: VoidFunction,
  type: TriggerType,
  options?: O,
)

 * @param type Trigger type to distinguish between regular and prefetch triggers.
 */
export function registerDomTrigger<O>(
  initialLView: LView,
  tNode: TNode,
  triggerIndex: number,
  walkUpTimes: number | undefined | null,
  registerFn: (
    element: Element,
    callback: VoidFunction,
    injector: Injector,
    options?: O,
  ) => VoidFunction,
  callback: VoidFunction,
  type: TriggerType,
  options?: O,
) {
  if (!shouldTriggerDeferBlock(type, initialLView)) {
    return;
  }

  const injector = initialLView[INJECTOR];
  const zone = injector.get(NgZone);
  let poll: AfterRenderRef;
  function pollDomTrigger() {
    // If the initial view was destroyed, we don't need to do anything.
    if (isDestroyed(initialLView)) {
      poll.destroy();
      return;
    }

    const lDetails = getLDeferBlockDetails(initialLView, tNode);
    const renderedState = lDetails[DEFER_BLOCK_STATE];

    // If the block was loaded before the trigger was resolved, we don't need to do anything.
    if (
      renderedState !== DeferBlockInternalState.Initial &&
      renderedState !== DeferBlockState.Placeholder
    ) {
      poll.destroy();
      return;
    }

    const triggerLView = getTriggerLView(initialLView, tNode, walkUpTimes);

    // Keep polling until we resolve the trigger's LView.
    if (!triggerLView) {
      // Keep polling.
      return;
    }

    poll.destroy();

    // It's possible that the trigger's view was destroyed before we resolved the trigger element.
    if (isDestroyed(triggerLView)) {
      return;
    }

    const element = getTriggerElement(triggerLView, triggerIndex);
    const cleanup = registerFn(