Question: I am using this `std::bind` to bind function outside the class and gives a strange behavior.

It somewhat controls the value of private member variables.

```
//MClass.h
typedef std::function<void(void)> Action;

class MClass {

public:

  Action OnLeftClick;

//some other functions here

private:
  int totalContents;

  VScrollbar* _vscrollbar;

};

//MClass.cpp

```

in this kind of implementation it does not make any bug:

```
MClass::MClasss() {

  OnLefClick = std::bind(&VScrollbar::Scrolldown, this);

}

//but when I do this
//otherfile.h

MClass mclass;

void clickBar() {

  mclass.totalContents = 0;

}

void InitComponentns() {   

mclass.OnLeftClick = std::bind(clickBar, mclass);

}

```

and whenever I call the function assigned to `OnLeftClick()` that is `clickBar()`,
the value of `totalContents` does not change in value to 0 (totalContents value is incremented by other functions of MClass).

am I doing something wrong here?

Answer: 
In general plotBands doesn't have any tooltip or legend options, however it is possible to add some custom events to plotBand, for example mouseover. See: <http://api.highcharts.com/highcharts#xAxis.plotBands.events>

So you can create your own tooltip for this.
Since it's *(for instance)* not possible, you can place a `subtitle` below the chart (in my case, a gauge). For example:

```
subtitle: {
    text: '<span style="background-color: #55BF3B; border-radius: 2px; padding: 1px 2px;">' +
              '0-10' +
          '</span>' +
          '<span style="background-color: #DDDF0D; border-radius: 2px; padding: 1px 2px;">' +
              '10-20' +
          '</span>',
    useHTML: true,
    verticalAlign: 'bottom'
}

```