Class DragRef

src/cdk/drag-drop/drag-ref.ts:162–1663

 * Reference to a draggable item. Used to manipulate or dispose of the item.
 */
export class DragRef<T = any> {
  private _rootElementCleanups: (() => void)[] | undefined;
  private _cleanupShadowRootSelectStart: (() => void) | undefined;

  /** Element displayed next to the user's pointer while the element is dragged. */
  private _preview: PreviewRef | null = null;

  /** Container into which to insert the preview. */
  private _previewContainer: PreviewContainer | undefined;

  /** Reference to the view of the placeholder element. */
  private _placeholderRef: EmbeddedViewRef<any> | null = null;

  /** Element that is rendered instead of the draggable item while it is being sorted. */
  private _placeholder!: HTMLElement;

  /** Coordinates within the element at which the user picked up the element. */
  private _pickupPositionInElement!: Point;

  /** Coordinates on the page at which the user picked up the element. */
  private _pickupPositionOnPage!: Point;

  /**
   * Marker node used to save the place in the DOM where the element was
   * picked up so that it can be restored at the end of the drag sequence.
   */
  private _marker!: Comment;

  /**
   * Element indicating the position from which the item was picked up initially.
   */
  private _anchor: HTMLElement | null = null;

  /**
   * CSS `transform` applied to the element when it isn't being dragged. We need a
   * passive transform in order for the dragged element to retain its new position
   * after the user has stopped dragging and because we need to know the relative
   * position in case they start dragging again. This corresponds to `element.style.transform`.
   */
  private _passiveTransform: Point = {x: 0, y: 0};

  /** CSS `transform` that is applied to the element while it's being dragged. */
  private _activeTransform: Point = {x: 0, y: 0};

  /** Inline `transform` value that the element had before the first dragging sequence. */
  private _initialTransform?: string;

  /**
   * Whether the dragging sequence has been started. Doesn't
   * necessarily mean that the element has been moved.
   */
  private _hasStartedDragging = signal(false);

  /** Whether the element has moved since the user started dragging it. */
  private _hasMoved = false;

  /** Drop container in which the DragRef resided when dragging began. */
  private _initialContainer!: DropListRef;