calcThumb: function () {
            this.t = this.exp.el[this.wh] ? parseInt(this.exp.el[this.wh]) :
                this.exp.el['offset' + this.ucwh];
            this.tpos = this.exp.tpos[this.dim];
            this.tb = (this.exp.el['offset' + this.ucwh] - this.t) / 2;