rtl vertical

hi,
when we set direction to 'rtl' and it is vertial, it is not right to change offset ,
hin dragEvent function:
 if(this.dir === 'rtl') {
            offset = -offset;
        }

it should be :
        if (this.dir === 'rtl' && this.direction === 'horizontal') {
            offset = -offset;
        }