function calcXY(
  positionParams: PositionParams,
  top: number,
  left: number,
  w: number,
  h: number
): { x: number, y: number }
Translate x and y coordinates from pixels to grid units.
@param  {PositionParams} positionParams  Parameters of grid needed for coordinates calculations.
@param  {Number} top                     Top position (relative to parent) in pixels.
@param  {Number} left                    Left position (relative to parent) in pixels.
@param  {Number} w                       W coordinate in grid units.
@param  {Number} h                       H coordinate in grid units.
@return {Object}                         x and y in grid units.