Method withElementContainer

src/cdk/drag-drop/drop-list-ref.ts:411–447

* Configures the drop list so that a different element is used as the container for the * dragged items. This is useful for the cases when one might not have control over the * full DOM that sets up the dragging. * Note that the alternate container needs to be a descendant of the drop list.

(container: HTMLElement)

   * @param container New element container to be assigned.
   */
  withElementContainer(container: HTMLElement): this {
    if (container === this._container) {
      return this;
    }

    const element = coerceElement(this.element);

    if (
      (typeof ngDevMode === 'undefined' || ngDevMode) &&
      container !== element &&
      !element.contains(container)
    ) {
      throw new Error(
        'Invalid DOM structure for drop list. Alternate container element must be a descendant of the drop list.',
      );
    }

    const oldContainerIndex = this._scrollableElements.indexOf(this._container);
    const newContainerIndex = this._scrollableElements.indexOf(container);

    if (oldContainerIndex > -1) {
      this._scrollableElements.splice(oldContainerIndex, 1);
    }

    if (newContainerIndex > -1) {
      this._scrollableElements.splice(newContainerIndex, 1);
    }

    if (this._sortStrategy) {
      this._sortStrategy.withElementContainer(container);
    }

    this._cachedShadowRoot = null;
    this._scrollableElements.unshift(container);
    this._container = container;
    return this;
  }

  /** Gets the scrollable parents that are registered with this drop container. */
  getScrollableParents(): readonly HTMLElement[] {