Method _updatePointerDirectionDelta

src/cdk/drag-drop/drag-ref.ts:1339–1363

Updates the current drag delta, based on the user's current pointer position on the page.

(pointerPositionOnPage: Point)

  /** Updates the current drag delta, based on the user's current pointer position on the page. */
  private _updatePointerDirectionDelta(pointerPositionOnPage: Point) {
    const {x, y} = pointerPositionOnPage;
    const delta = this._pointerDirectionDelta;
    const positionSinceLastChange = this._pointerPositionAtLastDirectionChange;

    // Amount of pixels the user has dragged since the last time the direction changed.
    const changeX = Math.abs(x - positionSinceLastChange.x);
    const changeY = Math.abs(y - positionSinceLastChange.y);

    // Because we handle pointer events on a per-pixel basis, we don't want the delta
    // to change for every pixel, otherwise anything that depends on it can look erratic.
    // To make the delta more consistent, we track how much the user has moved since the last
    // delta change and we only update it after it has reached a certain threshold.
    if (changeX > this._config.pointerDirectionChangeThreshold) {
      delta.x = x > positionSinceLastChange.x ? 1 : -1;
      positionSinceLastChange.x = x;
    }

    if (changeY > this._config.pointerDirectionChangeThreshold) {
      delta.y = y > positionSinceLastChange.y ? 1 : -1;
      positionSinceLastChange.y = y;
    }

    return delta;
  }

  /** Toggles the native drag interactions, based on how many handles are registered. */
  private _toggleNativeDragInteractions() {