Method startLayout

src/service/resource.js:841–905

* Starts the layout of the resource. Returns the promise that will yield * once layout is complete. Only allowed to be called on a upgraded, built * and displayed element. * @return {!Promise}

()

   * @return {!Promise}
   */
  startLayout() {
    if (this.layoutPromise_) {
      return this.layoutPromise_;
    }
    if (this.state_ == ResourceState_Enum.LAYOUT_COMPLETE) {
      return Promise.resolve();
    }
    if (this.state_ == ResourceState_Enum.LAYOUT_FAILED) {
      return Promise.reject(this.lastLayoutError_);
    }

    devAssert(
      this.state_ != ResourceState_Enum.NOT_BUILT,
      'Not ready to start layout: %s (%s)',
      this.debugid,
      this.state_
    );
    devAssert(this.isDisplayed(), 'Not displayed for layout: %s', this.debugid);

    if (this.state_ != ResourceState_Enum.LAYOUT_SCHEDULED) {
      const err = dev().createExpectedError(
        'startLayout called but not LAYOUT_SCHEDULED',
        'currently: ',
        this.state_
      );
      reportError(err, this.element);
      return Promise.reject(err);
    }

    // Unwanted re-layouts are ignored.
    if (this.layoutCount_ > 0 && !this.element.isRelayoutNeeded()) {
      dev().fine(
        TAG,
        "layout canceled since it wasn't requested:",
        this.debugid,
        this.state_
      );
      this.state_ = ResourceState_Enum.LAYOUT_COMPLETE;
      return Promise.resolve();
    }

    dev().fine(TAG, 'start layout:', this.debugid, 'count:', this.layoutCount_);
    this.layoutCount_++;
    this.state_ = ResourceState_Enum.LAYOUT_SCHEDULED;
    this.abortController_ = new AbortController();
    const {signal} = this.abortController_;

    const promise = new Promise((resolve, reject) => {
      Services.vsyncFor(this.hostWin).mutate(() => {
        let callbackResult;
        try {
          callbackResult = this.element.layoutCallback(signal);
        } catch (e) {
          reject(e);
        }
        Promise.resolve(callbackResult).then(resolve, reject);
      });
      signal.onabort = () => reject(cancellation());