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

All Known Implementing Classes:

PercentageCallback
```
public interface FormatterCallback
```
Callback interface of DataLabelsPlugin.ID plugin to set formatter property at runtime, using the plugin context.
Labels can be displayed on multiple lines by using the newline character \n between each line or by providing an array of strings where each item represents a new line.

Author:

Andrea "Stock" Stocchero

- Method Summary
  
  All Methods Instance Methods Abstract Methods
  Modifier and Type Method Description
  
  String invoke(DataLabelsContext context, DataItem dataItem)
  Returns the formatted label value.

- Method Detail
  - invoke
```
String invoke(DataLabelsContext context,
              DataItem dataItem)
```
    Returns the formatted label value.
    
    Parameters:
    
    context - DataLabelsPlugin.ID plugin context instance
    
    dataItem - value container to be formatted.
    Can be a simple double, String or a FloatingData.
    
    Returns:
    
    the label value to be showed