getPositionForResolution_(res) {
    const fn = this.getMap().getView().getValueForResolutionFunction();
    return clamp(1 - fn(res), 0, 1);
  }
Determines the relative position of the slider for the given resolution.  A
relative position of 0 corresponds to the minimum view resolution.  A
relative position of 1 corresponds to the maximum view resolution.

@param {number} res The resolution.
@return {number} The relative position value (between 0 and 1).
@private