Method sort

src/cdk/drag-drop/sorting/mixed-sort-strategy.ts:83–133

* To be called when an item is being sorted. * @param item Item to be sorted. * @param pointerX Position of the item along the X axis. * @param pointerY Position of the item along the Y axis. * @param pointerDelta Direction in which the pointer is moving along each axis.

(
    item: DragRef,
    pointerX: number,
    pointerY: number,
    pointerDelta: {x: number; y: number},
  )

   * @param pointerDelta Direction in which the pointer is moving along each axis.
   */
  sort(
    item: DragRef,
    pointerX: number,
    pointerY: number,
    pointerDelta: {x: number; y: number},
  ): {previousIndex: number; currentIndex: number} | null {
    const newIndex = this._getItemIndexFromPointerPosition(item, pointerX, pointerY);
    const previousSwap = this._previousSwap;

    if (newIndex === -1 || this._activeItems[newIndex] === item) {
      return null;
    }

    const toSwapWith = this._activeItems[newIndex];

    // Prevent too many swaps over the same item.
    if (
      previousSwap.drag === toSwapWith &&
      previousSwap.overlaps &&
      previousSwap.deltaX === pointerDelta.x &&
      previousSwap.deltaY === pointerDelta.y
    ) {
      return null;
    }

    const previousIndex = this.getItemIndex(item);
    const current = item.getPlaceholderElement();
    const overlapElement = toSwapWith.getRootElement();

    if (newIndex > previousIndex) {
      overlapElement.after(current);
    } else {
      overlapElement.before(current);
    }

    moveItemInArray(this._activeItems, previousIndex, newIndex);

    const newOverlapElement = this._getRootNode().elementFromPoint(pointerX, pointerY);
    // Note: it's tempting to save the entire `pointerDelta` object here, however that'll
    // break this functionality, because the same object is passed for all `sort` calls.
    previousSwap.deltaX = pointerDelta.x;
    previousSwap.deltaY = pointerDelta.y;
    previousSwap.drag = toSwapWith;
    previousSwap.overlaps =
      overlapElement === newOverlapElement || overlapElement.contains(newOverlapElement);

    return {
      previousIndex,
      currentIndex: newIndex,
    };
  }

  /**
   * Called when an item is being moved into the container.