Method _applyRootElementTransform

src/cdk/drag-drop/drag-ref.ts:1390–1407

* Applies a `transform` to the root element, taking into account any existing transforms on it. * @param x New transform value along the X axis. * @param y New transform value along the Y axis.

(x: number, y: number)

   * @param y New transform value along the Y axis.
   */
  private _applyRootElementTransform(x: number, y: number) {
    const scale = 1 / this.scale;
    const transform = getTransform(x * scale, y * scale);
    const styles = this._rootElement.style;

    // Cache the previous transform amount only after the first drag sequence, because
    // we don't want our own transforms to stack on top of each other.
    // Should be excluded none because none + translate3d(x, y, x) is invalid css
    if (this._initialTransform == null) {
      this._initialTransform =
        styles.transform && styles.transform != 'none' ? styles.transform : '';
    }

    // Preserve the previous `transform` value, if there was one. Note that we apply our own
    // transform before the user's, because things like rotation can affect which direction
    // the element will be translated towards.
    styles.transform = combineTransforms(transform, this._initialTransform);
  }

  /**
   * Applies a `transform` to the preview, taking into account any existing transforms on it.