docs: function (controls, pixels) {
          var pxs = (arguments.length === 1) ? [] : pixels;
          for (var i=0, len=controls.length; i<len; i++) {
              var ctrl = controls[i];
              var px = (pxs[i]) ? pxs[i] : null;
              this.addControl( ctrl, px );
          }
      }