*
* @param[in] step The step of scroll distance(pixel) in X and Y axes.
*
* @note: If snap points are defined in the rulers, it will always
* scroll to the next snap point towards the scroll direction while
*
* @param[in] step The step of scroll distance(pixel) in X and Y axes.
*
* @note: If snap points are defined in the rulers, it will always
* scroll to the next snap point towards the scroll direction while