ChartShaderMapper<T> typedef
Signature for the callback that returns the shader from the data source based on the index. Can get the data, index, color and rect values.
T - Data of the current data point
index - Index of the current data point
rect - Rect value of the current data point slice
color - Color of the current data point
Implementation
typedef ChartShaderMapper<T> = Shader Function(
T datum, int index, Color color, Rect rect);