Graphic Renderer of Indicators

Some indicators require a special drawing style, such as two lines for the BollingerBands indicator. Or points for the Fractals indicator. In these cases, you need to explicitly specify the graphic renderer of indicators in ChartIndicatorElement.

var chartIndicatorElement = new ChartIndicatorElement()
{
	IndicatorPainter = new BollingerBandsPainter(),
};

Let's consider how to create a custom IndicatorPainter using the Fractals indicator as an example.

All IndicatorPainters must inherit from the base class BaseChartIndicatorPainter<TIndicator> or implement the interface IChartIndicatorPainter:

/// <summary>
/// The chart element for <see cref="Fractals"/>.
/// </summary>
[Indicator(typeof(Fractals))]
public class FractalsPainter : BaseChartIndicatorPainter<Fractals>
{
	...
}

Let's define the chart elements ChartLineElement that will represent the upper and lower fractals:

/// <summary>
/// The chart element for <see cref="Fractals"/>.
/// </summary>
[Indicator(typeof(Fractals))]
public class FractalsPainter : BaseChartIndicatorPainter<Fractals>
{
	/// <summary>
	/// <see cref="Fractals.Up"/> dots color.
	/// </summary>
	[Display(
		ResourceType = typeof(LocalizedStrings),
		Name = LocalizedStrings.Str2035Key,
		Description = LocalizedStrings.Str2036Key)]
	public ChartLineElement Up { get; }

	/// <summary>
	/// <see cref="Fractals.Down"/> dots color.
	/// </summary>
	[Display(
		ResourceType = typeof(LocalizedStrings),
		Name = LocalizedStrings.Str2037Key,
		Description = LocalizedStrings.Str2038Key)]
	public ChartLineElement Down { get; }
	...
}

In the constructor of FractalsPainter, we set their values and main properties such as color, thickness, and drawing style. After that, we add them as child elements of the chart:

...

/// <summary>
/// Create instance.
/// </summary>
public FractalsPainter()
{
	Up = new ChartLineElement { Color = Colors.Green };
	Down = new ChartLineElement { Color = Colors.Red };
	Up.Style = Down.Style = DrawStyles.Dot;
	Up.StrokeThickness = Down.StrokeThickness = 4;
	AddChildElement(Up);
	AddChildElement(Down);
}

...

Override the OnDraw method, in which we draw the indicator using the DrawValues method:

...
/// <inheritdoc />
protected override bool OnDraw(Fractals ind, IDictionary<IIndicator, IList<ChartDrawData.IndicatorData>> data)
{
	var result = false;
	result |= DrawValues(data[ind.Down], Down);
	result |= DrawValues(data[ind.Up], Up);
	return result;
}
...

Complete code of FractalsPainter:

/// <summary>
/// The chart element for <see cref="Fractals"/>.
/// </summary>
[Indicator(typeof(Fractals))]
public class FractalsPainter : BaseChartIndicatorPainter<Fractals>
{
	/// <summary>
	/// <see cref="Fractals.Up"/> dots color.
	/// </summary>
	[Display(
		ResourceType = typeof(LocalizedStrings),
		Name = LocalizedStrings.Str2035Key,
		Description = LocalizedStrings.Str2036Key)]
	public ChartLineElement Up { get; }
	/// <summary>
	/// <see cref="Fractals.Down"/> dots color.
	/// </summary>
	[Display(
		ResourceType = typeof(LocalizedStrings),
		Name = LocalizedStrings.Str2037Key,
		Description = LocalizedStrings.Str2038Key)]
	public ChartLineElement Down { get; }
	/// <summary>
	/// Create instance.
	/// </summary>
	public FractalsPainter()
	{
		Up = new ChartLineElement { Color = Colors.Green };
		Down = new ChartLineElement { Color = Colors.Red };
		Up.Style = Down.Style = DrawStyles.Dot;
		Up.StrokeThickness = Down.StrokeThickness = 4;
		AddChildElement(Up);
		AddChildElement(Down);
	}
	/// <inheritdoc />
	protected override bool OnDraw(Fractals ind, IDictionary<IIndicator, IList<ChartDrawData.IndicatorData>> data)
	{
		var result = false;
		result |= DrawValues(data[ind.Down], Down);
		result |= DrawValues(data[ind.Up], Up);
		return result;
	}
	#region IPersistable
	/// <inheritdoc />
	public override void Load(SettingsStorage storage)
	{
		base.Load(storage);
		Up.Load(storage.GetValue<SettingsStorage>(nameof(Up)));
		Down.Load(storage.GetValue<SettingsStorage>(nameof(Down)));
	}
	/// <inheritdoc />
	public override void Save(SettingsStorage storage)
	{
		base.Save(storage);
		storage.SetValue(nameof(Up), Up.Save());
		storage.SetValue(nameof(Down), Down.Save());
	}
	#endregion
}