function getPanAreaSize(options, viewportSize, itemData, index) {
  return {
    x: viewportSize.x - parsePaddingOption('left', options, viewportSize, itemData, index) - parsePaddingOption('right', options, viewportSize, itemData, index),
    y: viewportSize.y - parsePaddingOption('top', options, viewportSize, itemData, index) - parsePaddingOption('bottom', options, viewportSize, itemData, index)
  };
}
@param {PhotoSwipeOptions} options
@param {Point} viewportSize
@param {SlideData} itemData
@param {number} index
@returns {Point}