TimeTickCallback (Charba - J2CL and GWT charts library based on CHART.JS)

```
public interface TimeTickCallback
```
Interface to implement if wants to change the tick marks to include information about the data type, for cartesian time axes.

Author:

Andrea "Stock" Stocchero

See Also:

CartesianTimeAxis, CartesianTimeSeriesAxis

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`String`	`onCallback(Axis axis, Date value, String label, int index, List<ScaleTickItem> values)`	Changes the tick marks to include information about the data type.

- Method Detail
  - onCallback
```
String onCallback(Axis axis,
                  Date value,
                  String label,
                  int index,
                  List<ScaleTickItem> values)
```
    Changes the tick marks to include information about the data type.
    
    Parameters:
    
    axis - axis instance where this callback as been defined
    
    value - value of tick as date
    
    label - label of tick, passed by CHART.JS formatting the date by the selected TimeUnit and its display format.
    
    index - index of tick
    
    values - list of all tick values
    
    Returns:
    
    the tick to apply or if the callback returns null the associated grid line will be hidden.