code: function(pos, pointer) {
      var mode = this.options.selection.mode,
          selection = this.selection.selection;
  
      if(mode.indexOf('x') == -1) {
        pos.x = (pos == selection.first) ? 0 : this.plotWidth;         
      }else{
        pos.x = boundX(pointer.relX, this);
      }
  
      if (mode.indexOf('y') == -1) {
        pos.y = (pos == selection.first) ? 0 : this.plotHeight - 1;
      }else{
        pos.y = boundY(pointer.relY, this);
      }
    }
docs: Calculates the position of the selection.
  @param {Object} pos - Position object.
  @param {Event} event - Event object.