Can I get the visible data points from a chart after zoom in in Telerik ChartView?

Question

I have a telerik RadChartView that has some datas, my X axis is a DateTimeContinuousAxis and my Y axis is a LinearAxis. This RadChartView has a zoom button, that uses the LassoZoomController methods to make the zoom. I'm facing an issue to, after the zoom in or out, I want to get the visible points that the user can see in the zoom (ignoring the ones that are not visible in the zoom). Is there a way to get only the visible points in the chart after the zoom?

In the code bellow, I want to make a verification to add the dateTime on the list only if it's visible inside my radChartView

var categoricalDataPoints = radChartView.Series.Where(serie => serie.IsVisible).SelectMany(serie => serie.DataPoints)
    .OfType<CategoricalDataPoint>().ToList();

var visibleDateTimes = new List<DateTime>();

foreach (var categoricalDataPoint in categoricalDataPoints)
{
    if (categoricalDataPoint.Category is DateTime dateTime)
    {
        visibleDateTimes.Add(dateTime);
    }
}

I've tried to get the first axis and parse it to DateTimeContinuousAxis and use the ActualRange but this range is considering all the dateTimes of the chart, not only the visibles:

var categoricalDataPoints = radChartView.Series.Where(serie => serie.IsVisible).SelectMany(serie => serie.DataPoints)
    .OfType<CategoricalDataPoint>().ToList();

var visibleDateTimes = new List<DateTime>();

if (radChartView.Axes[0] is DateTimeContinuousAxis dateTimeContinuousAxis)
{
    foreach (var categoricalDataPoint in categoricalDataPoints)
    {
        if (categoricalDataPoint.Category is DateTime dateTime)
        {
            if (dateTime >= dateTimeContinuousAxis.ActualRange.Minimum && dateTime <= dateTimeContinuousAxis.ActualRange.Maximum)
            {
                visibleDateTimes.Add(dateTime);
            }
        }
    }
}

Answer 1

Gabriel, I have prepared a sample code snippet demonstrating how to get the visible data points after pan/zoom operations are executed. The below screenshots illustrate the achieved result:

    public partial class RadForm1 : Telerik.WinControls.UI.RadForm
{
    public RadForm1()
    {
        InitializeComponent();

        LineSeries lineSeries = new LineSeries();
        lineSeries.ShowLabels = true;
        lineSeries.PointSize = new SizeF(8, 8);
        for (int i = 0; i < 10; i++)
        {
            lineSeries.DataPoints.Add(new CategoricalDataPoint(6 + i * i, DateTime.Now.AddDays(i)));
        }
        DateTimeContinuousAxis continuousAxis = new DateTimeContinuousAxis();
        continuousAxis.PlotMode = AxisPlotMode.BetweenTicks;
        continuousAxis.LabelFormat = "{0:d}";
        //First assign the axis to the VerticalAxis property and then add the series to the chart
        lineSeries.HorizontalAxis = continuousAxis;
        radChartView1.Series.Add(lineSeries);

        this.radChartView1.ShowPanZoom = true;
        this.radChartView1.View.ZoomChanged += View_ZoomChanged;
        this.radChartView1.View.PanChanged += View_PanChanged;
    }

    private void View_ZoomChanged(object sender, EventArgs e)
    {
        GetVisiblePoints();
    }

    private void View_PanChanged(object sender, EventArgs e)
    {
        GetVisiblePoints();
    }

    public void GetVisiblePoints()
    {
        List<CategoricalDataPoint> visiblePoints = new List<CategoricalDataPoint>();
        IChartView view = ((IChartView)this.radChartView1.View);
        foreach (ChartSeries series in this.radChartView1.Series)
        {
            foreach (var dp in series.DataPoints)
            {
                CategoricalDataPoint cdp = (CategoricalDataPoint)dp;
                if (CheckIfDataPointIsVisible(view, cdp))
                { 
                    visiblePoints.Add(cdp); 
                }
            }
        }

        foreach (CategoricalDataPoint dp in visiblePoints)
        {
            Console.WriteLine(dp.Value +" >> "+dp.Category);
        }
    }

    private bool CheckIfDataPointIsVisible(IChartView view, CategoricalDataPoint cdp)
    {
        double width = ((ChartSeries)cdp.Presenter).Axes[1].Model.LayoutSlot.Width;
        RadRect viewport = new RadRect(-view.PlotOriginX + width, -view.PlotOriginY, view.ViewportWidth, view.ViewportHeight);
        return viewport.IntersectsWith(cdp.LayoutSlot);
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        GetVisiblePoints();
    }
}