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Hit-Test API for Polar Column Series

The IHitTestProvider.hitTest method on PolarColumnRenderableSeriesšŸ“˜ tests if the click was within the Column's body and returns a HitTestInfošŸ“˜ object with the following properties:

HitTest on 1 particular Polar Column Series:ā€‹

Calling the hitTest method on one specific series is very easy and can be done this way:

const x = mouseEvent.offsetX * DpiHelper.PIXEL_RATIO;
const y = mouseEvent.offsetY * DpiHelper.PIXEL_RATIO;

const colHitTestInfo: HitTestInfo = colSeries1.hitTestProvider.hitTest(x, y);

The algorithm is as follows:

  1. Find the nearest column in X direction.
  2. Test if the click was within column body and update HitTestInfo.isHitšŸ“˜ property.

Here is how you would implement it on multiple Polar Column Series:ā€‹

First, you need to add the renderable series you plan to hit-test on:

// add a couple of polar columns to the chart
const polarColumn1 = new PolarColumnRenderableSeries(wasmContext, {
    dataSeries: new XyDataSeries(wasmContext, {
        xValues: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11],
        yValues: [2.5, 1.8, 3.0, 1.4, 2.0, 1.75, 2.4, 1.5, 3.0, 4.5, 2],
        dataSeriesName: "Red Columns"
    }),
    stroke: "white",
    fill: "#883333",
    dataPointWidth: 0.6
});

const polarColumn2 = new PolarColumnRenderableSeries(wasmContext, {
    dataSeries: new XyDataSeries(wasmContext, {
        xValues: [9, 10, 11, 12, 13, 14, 15, 16],
        yValues: [4.5, 3.2, 3.9, 2.8, 4.0, 3.5, 4.8, 3.0],
        dataSeriesName: "Blue Columns"
    }),
    stroke: "black",
    fill: "#3333AA99",
    dataPointWidth: 0.8
});

sciChartSurface.renderableSeries.add(polarColumn1, polarColumn2);

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

// 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;

    // optional - flag to stop checking for hit-test on other series once a hit is found
    let wasTheHitSuccessfulAtLeastOnce = false; 

    [...sciChartSurface.renderableSeries.asArray()] // copy the renderable series to an anonymous array to not modify the original collection
        .reverse() // The default layering of series is from bottom to top in the array, so we reverse it to check from top to bottom
        .forEach(rs => {
        console.log(`Trying hit test on: ${rs.getDataSeriesName()}`);
        
        if (rs.hitTestProvider && mouseEvent && !wasTheHitSuccessfulAtLeastOnce) {
            const hitTestInfo = rs.hitTestProvider.hitTestDataPoint(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: ${hitTestInfo.hitTestPointValues.y.toFixed(2)})\n`
                    + `- series: "${hitTestInfo.associatedSeries.getDataSeriesName()}"\n`
                    + `- column index: ${hitTestInfo.dataSeriesIndex}\n`
                    + `- yValue: ${hitTestInfo.yValue}`;
                wasTheHitSuccessfulAtLeastOnce = true;
            } else { 
                // No Hit
                dotAnnotation.svgString = NO_HIT_SVG;
                textAnnotation.text = `No hit detected\n`;
            }
        }
    });
});

Which results in this following functionality: