Hit-Test API for Line Segment Series

The IHitTestProvider.hitTest method on FastLineSegmentRenderableSeries📘 tests if the click was within the Line's bounds and returns a HitTestInfo📘 object with the following properties:

HitTest on 1 particular Line Segment Series:

The algorithm is as follows:

Find the nearest line in X direction.
Test if the click was within line bounds and update HitTestInfo.isHit📘 property.

First, you need to add at least 1 renderable series you plan to hit-test on:

// add a couple of line segments to the chart
const lineSegment1 = new FastLineSegmentRenderableSeries(wasmContext, {
    dataSeries: new XyDataSeries(wasmContext, {
        xValues: [0.5, 1, 2, 3, 5, 4, 6, 7, 8, 9],
        yValues: [4.5, 3.2, 5.1, 2.8, 4.0, 3.5, 4.8, 3.0, 2.3, 7.1],
        dataSeriesName: "Teal&Orange Segments"
    }),
    strokeThickness: 5,
    paletteProvider: new LineSegmentPaletteProvider(),
});
sciChartSurface.renderableSeries.add(lineSegment1);

And then, add an event-listener, likely on the mousedown event:

const SUCCESSFUL_HIT_SVG = `<svg width="8" height="8"><circle cx="50%" cy="50%" r="4" fill="#33AA33" stroke="#000000" stroke-width="0.7"/></svg>`;
const NO_HIT_SVG = `<svg width="4" height="4"><circle cx="50%" cy="50%" r="2" fill="#FF0000"/></svg>`;
const HIT_TEST_RADIUS = 10; // Radius for hit testing

// --- Minimal HitTest and SVG Annotation ---
const dotAnnotation = new CustomAnnotation({
    svgString: NO_HIT_SVG,
    isHidden: true, // initially hidden
    horizontalAnchorPoint: EHorizontalAnchorPoint.Center,
    verticalAnchorPoint: EVerticalAnchorPoint.Center,
    xCoordinateMode: ECoordinateMode.DataValue,
    yCoordinateMode: ECoordinateMode.DataValue
});
const textAnnotation = new NativeTextAnnotation({
    text: "",
    fontSize: 20,
    x1: 1,
    y1: 9,
    lineSpacing: 10,
    multiLineAlignment: EMultiLineAlignment.Left,
    xCoordinateMode: ECoordinateMode.DataValue,
    yCoordinateMode: ECoordinateMode.DataValue,
});
sciChartSurface.annotations.add(dotAnnotation, textAnnotation);

// Add an event listener for mouse down events
sciChartSurface.domCanvas2D.addEventListener("mousedown", (mouseEvent: MouseEvent) => {
    // Use our DpiHelper class to multiply coordinates, else screens with non-100% scaling will not work very well
    const x = mouseEvent.offsetX * DpiHelper.PIXEL_RATIO;
    const y = mouseEvent.offsetY * DpiHelper.PIXEL_RATIO;

    const rs = sciChartSurface.renderableSeries.get(0); // Get the renderable series

    if (rs.hitTestProvider && mouseEvent) {
        const hitTestInfo = rs.hitTestProvider.hitTest(x, y, HIT_TEST_RADIUS);

        dotAnnotation.x1 = hitTestInfo.hitTestPointValues.x;
        dotAnnotation.y1 = hitTestInfo.hitTestPointValues.y;
        dotAnnotation.isHidden = false;

        if (hitTestInfo.isHit) { 
            // Successful Hit
            dotAnnotation.svgString = SUCCESSFUL_HIT_SVG;
            textAnnotation.text = `Hit (x: ${hitTestInfo.hitTestPointValues.x.toFixed(2)}, y: ${hitTestInfo.hitTestPointValues.y.toFixed(2)})\n`
                + `- Series index: ${hitTestInfo.dataSeriesIndex}\n`
                + `- yValue: ${hitTestInfo.yValue}\n`
                + `- xValue: ${hitTestInfo.xValue}`;
        } else { 
            // No Hit
            dotAnnotation.svgString = NO_HIT_SVG;
            textAnnotation.text = `No hit detected\n`;
        }
    }
});

Which results in this following functionality:

HitTest on 1 particular Line Segment Series:​

HitTest on 1 particular Line Segment Series: