code: function getValueAxisStart(baseAxis, valueAxis, stacked) {
      var extent = valueAxis.getGlobalExtent();
      var min;
      var max;
      if (extent[0] > extent[1]) {
          min = extent[1];
          max = extent[0];
      }
      else {
          min = extent[0];
          max = extent[1];
      }
  
      var valueStart = valueAxis.toGlobalCoord(valueAxis.dataToCoord(0));
      valueStart < min && (valueStart = min);
      valueStart > max && (valueStart = max);
  
      return valueStart;
  }
docs: See cases in `test/bar-start.html` and `#7412`, `#8747`.