Method setup

src/service/fixed-layer.js:150–206

* Must be always called after DOMReady. * @return {boolean}

()

   * @return {boolean}
   */
  setup() {
    const viewer = Services.viewerForDoc(this.ampdoc);
    if (!getMode().localDev && !viewer.isEmbedded()) {
      // FixedLayer is not needed for standalone documents.
      return false;
    }

    const root = this.ampdoc.getRootNode();
    const stylesheets = root.styleSheets;
    if (!stylesheets) {
      return true;
    }

    this.fixedSelectors_.length = 0;
    this.stickySelectors_.length = 0;

    for (let i = 0; i < stylesheets.length; i++) {
      const stylesheet = stylesheets[i];
      // Rare but may happen if the document is being concurrently disposed.
      if (!stylesheet) {
        dev().error(TAG, 'Aborting setup due to null stylesheet.');
        return true;
      }
      const {disabled, ownerNode} = stylesheet;
      if (
        disabled ||
        !ownerNode ||
        ownerNode.tagName != 'STYLE' ||
        ownerNode.hasAttribute('amp-boilerplate') ||
        ownerNode.hasAttribute('amp-runtime') ||
        ownerNode.hasAttribute('amp-extension')
      ) {
        continue;
      }
      // Don't dereference cssRules early to avoid "Cannot access rules"
      // DOMException due to reading a CORS stylesheet e.g. font.
      this.discoverSelectors_(stylesheet.cssRules);
    }

    this.scanNode_(root);

    if (this.elements_.length > 0) {
      this.observeHiddenMutations();
    }

    const platform = Services.platformFor(this.ampdoc.win);
    if (this.elements_.length > 0 && !this.transfer_ && platform.isIos()) {
      user().warn(
        TAG,
        'Please test this page inside of an AMP Viewer such' +
          " as Google's because the fixed or sticky positioning might have" +
          ' slightly different layout.'
      );
    }

    return true;
  }