Method attachShadowDocAsStream

src/multidoc-manager.js:261–308

* Implementation for `attachShadowDocAsStream` function. Attaches the shadow * doc and configures ampdoc for it. * @param {!Element} hostElement * @param {string} url * @param {!{[key: string]: string}=} opt_initParams * @return {!Object}

(hostElement, url, opt_initParams)

   * @return {!Object}
   */
  attachShadowDocAsStream(hostElement, url, opt_initParams) {
    user().assertString(url);
    dev().fine(TAG, 'Attach shadow doc as stream');
    return this.attachShadowDoc_(
      hostElement,
      url,
      opt_initParams,
      (amp, shadowRoot, ampdoc) => {
        // Start streaming.
        let renderStarted = false;
        const writer = createShadowDomWriter(this.win);
        amp['writer'] = writer;
        writer.onBody((doc) => {
          // Install extensions.
          this.mergeShadowHead_(ampdoc, shadowRoot, doc);

          // Append shallow body.
          const body = importShadowBody(
            shadowRoot,
            dev().assertElement(doc.body),
            /* deep */ false
          );
          body.classList.add('amp-shadow');
          ampdoc.setBody(body);
          return body;
        });
        writer.onBodyChunk(() => {
          // TODO(dvoytenko): find a better and more stable way to make
          // content visible. E.g. integrate with dynamic classes. In shadow
          // case specifically, we have to wait for stubbing to complete,
          // which may take awhile due to node importing.
          if (!renderStarted) {
            renderStarted = true;
            setTimeout(() => {
              ampdoc.signals().signal(CommonSignals_Enum.RENDER_START);
              setStyle(hostElement, 'visibility', 'visible');
            }, 50);
          }
        });
        return new Promise((resolve) => {
          writer.onEnd(() => {
            resolve();
            amp.writer = null;
          });
        });
      }
    );
  }

  /**
   * Processes the contents of the shadow document's head.