code: function computeIntersection(rootRect, targetRect) {
      const left      = Math.max(targetRect.left, rootRect.left);
      const right     = Math.min(targetRect.right, rootRect.right);
      const top       = Math.max(targetRect.top, rootRect.top);
      const bottom    = Math.min(targetRect.bottom, rootRect.bottom);
  
      const width = right - left;
      const height = bottom - top;
  
      return createRectangle(left, top, width, height);
  }
docs: Computes intersection rectangle between two rectangles.
  
  @param {ClientRect} rootRect - Rectangle of container element.
  @param {ClientRect} targetRect - Rectangle of target element.
  @returns {ClientRect} Intersection rectangle.