Method attach

src/cdk/overlay/overlay-ref.ts:131–211

* Attaches content, given via a Portal, to the overlay. * If the overlay is configured to have a backdrop, it will be created. * * @param portal Portal instance to which to attach the overlay. * @returns The portal attachment result.

(portal: Portal<any>)

   * @returns The portal attachment result.
   */
  attach(portal: Portal<any>): any {
    if (this._disposed) {
      return null;
    }

    // Insert the host into the DOM before attaching the portal, otherwise
    // the animations module will skip animations on repeat attachments.
    this._attachHost();

    const attachResult = this._portalOutlet.attach(portal);
    this._positionStrategy?.attach(this);
    this._updateStackingOrder();
    this._updateElementSize();
    this._updateElementDirection();

    if (this._scrollStrategy) {
      this._scrollStrategy.enable();
    }

    // We need to clean this up ourselves, because we're passing in an
    // `EnvironmentInjector` below which won't ever be destroyed.
    // Otherwise it causes some callbacks to be retained (see #29696).
    this._afterNextRenderRef?.destroy();

    // Update the position once the overlay is fully rendered before attempting to position it,
    // as the position may depend on the size of the rendered content.
    this._afterNextRenderRef = afterNextRender(
      () => {
        // The overlay could've been detached before the callback executed.
        if (this.hasAttached()) {
          this.updatePosition();
        }
      },
      {injector: this._injector},
    );

    // Enable pointer events for the overlay pane element.
    this._togglePointerEvents(true);

    if (this._config.hasBackdrop) {
      this._attachBackdrop();
    }

    if (this._config.panelClass) {
      this._toggleClasses(this._pane, this._config.panelClass, true);
    }

    // Only emit the `attachments` event once all other setup is done.
    this._attachments.next();
    this._completeDetachContent();

    // Track this overlay by the keyboard dispatcher
    this._keyboardDispatcher.add(this);

    if (this._config.disposeOnNavigation) {
      this._locationChanges = this._location.subscribe(() => this.dispose());
    }