Hit-Testing Series

The Hit-Test API is set of virtual methods defined on BaseRenderableSeries, and overridden by some of the series types. This API is used by the RolloverModifier, SeriesSelectionModifier and TooltipModifier to transform mouse-clicks into data-points, and determine if a mouse-point is over a point or over a series.

To call the Hit-Test method, use the following code:

// Subscribed using this code:
// sciChartSurface.MouseLeftButtonUp += SciChartSurfaceMouseLeftButtonUp;
private void SciChartSurfaceMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    // Perform the hit test relative to the GridLinesPanel
    Point mousePoint = e.GetPosition(sciChartSurface.GridLinesPanel as UIElement);
    double datapointRadius = 8;
    bool useInterpolation = false;
    HitTestInfo result = sciChartSurface.RenderableSeries[0].HitTestProvider.HitTest(mousePoint,
                                      datapointRadius, useInterpolation);

    // Output results
    string formattedString =
        string.Format(
            "{6}:\tMouse Coord: {0:0}, {1:0}\t\tNearest Datapoint Coord: {2:0.0},
                                  {3:0.0}\tData Value: {4:0.0}, {5:0.0}",
            mousePoint.X, mousePoint.Y,
            result.HitTestPoint.X, result.HitTestPoint.Y,
            result.XValue, result.YValue,
            result.DataSeriesName);

    Console.WriteLine(formattedString);
}

The HitTestInfo Result

The HitTestInfo struct has many properties which are useful to determine what was under the mouse. For instance:

UseInterpolation Flag

The UseInterpolation flag increases the accuracy of HitTest at the expense of performance.

When used in a FastLineRenderableSeries, UseInterpolation=True will return IsHit=True if the input mouse-point is over the line, whereas if UseInterpolation=False, it will return IsHit=True only if the input mouse-point is over a data-point.

This is useful say if you wanted to show a tooltip only on datapoints (UseInterpolation=False), vs. a click event anywhere on the line (UseInterpolation=True).

For other series types, such as FastCandlestickRenderableSeries, FastColumnRenderableSeries, FastMountainRenderableSeries, setting UseInterpolation=True will result in an IsHit=True when the mouse is ‘over the series’ as opposed to ‘over the data-points’.