Add horzBehaviour getter on the Chart Api

src/api/chart-api.ts

@@ -337,6 +337,10 @@ export class ChartApi<HorzScaleItem> implements IChartApiBase<HorzScaleItem>, Da
 		this._chartWidget.model().clearCurrentPosition(true);
 	}
 
+	public horzBehaviour(): IHorzScaleBehavior<HorzScaleItem> {
+		return this._horzScaleBehavior;
+	}
+
 	private _addSeriesImpl<
 		TSeries extends SeriesType,
 		TData extends WhitespaceData<HorzScaleItem> = SeriesDataItemTypeMap<HorzScaleItem>[TSeries],

src/api/ichart-api.ts

@@ -4,6 +4,7 @@ import { ChartOptionsImpl } from '../model/chart-model';
 import { BarData, HistogramData, LineData, WhitespaceData } from '../model/data-consumer';
 import { Time } from '../model/horz-scale-behavior-time/types';
 import { CustomData, ICustomSeriesPaneView } from '../model/icustom-series';
+import { IHorzScaleBehavior } from '../model/ihorz-scale-behavior';
 import { Point } from '../model/point';
 import {
 	CustomSeriesOptions,
@@ -338,4 +339,9 @@ export interface IChartApiBase<HorzScaleItem = Time> {
 	 * @returns Dimensions of the chart pane
 	 */
 	paneSize(paneIndex?: number): PaneSize;
+
+	/**
+	 * Returns the horizontal scale behaviour.
+	 */
+	horzBehaviour(): IHorzScaleBehavior<HorzScaleItem>;
 }

src/api/yield-chart-api.ts

@@ -106,7 +106,7 @@ export class YieldChartApi extends ChartApi<number> implements IYieldCurveChartA
 	}
 
 	private _initWhitespaceSeries(): void {
-		const horzBehaviour = this._horzScaleBehavior as YieldCurveHorzScaleBehavior;
+		const horzBehaviour = this.horzBehaviour() as YieldCurveHorzScaleBehavior;
 		const whiteSpaceSeries = this.addSeries(lineSeries);
 
 		let currentWhitespaceHash: string;