Method measureMutateElementResources_

src/service/mutator-impl.js:180–240

* Handles element mutation (and measurement) APIs in the Resources system. * * @param {!Element} element * @param {?function()} measurer * @param {function()} mutator * @param {boolean} skipRemeasure * @return {!Promise}

(
    element,
    measurer,
    mutator,
    skipRemeasure = false
  )

   * @return {!Promise}
   */
  measureMutateElementResources_(
    element,
    measurer,
    mutator,
    skipRemeasure = false
  ) {
    const calcRelayoutTop = () => {
      const box = this.viewport_.getLayoutRect(element);
      if (box.width != 0 && box.height != 0) {
        return box.top;
      }
      return -1;
    };
    let relayoutTop = -1;
    // TODO(jridgewell): support state
    return this.vsync_.runPromise({
      measure: () => {
        if (measurer) {
          measurer();
        }

        if (!skipRemeasure) {
          relayoutTop = calcRelayoutTop();
        }
      },
      mutate: () => {
        mutator();

        // `skipRemeasure` is set by callers when we know that `mutator`
        // cannot cause a change in size/position e.g. toggleLoading().
        if (skipRemeasure) {
          return;
        }

        if (element.classList.contains('i-amphtml-element')) {
          const r = Resource.forElement(element);
          r.requestMeasure();
        }
        const ampElements = element.getElementsByClassName('i-amphtml-element');
        for (let i = 0; i < ampElements.length; i++) {
          const r = Resource.forElement(ampElements[i]);
          r.requestMeasure();
        }
        this.resources_.schedulePass(FOUR_FRAME_DELAY_);

        if (relayoutTop != -1) {
          this.resources_.setRelayoutTop(relayoutTop);
        }
        // Need to measure again in case the element has become visible or
        // shifted.
        this.vsync_.measure(() => {
          const updatedRelayoutTop = calcRelayoutTop();
          if (updatedRelayoutTop != -1 && updatedRelayoutTop != relayoutTop) {
            this.resources_.setRelayoutTop(updatedRelayoutTop);
            this.resources_.schedulePass(FOUR_FRAME_DELAY_);
          }
          this.resources_.maybeHeightChanged();
        });