Find the Maximum/Minimum Values of Current Viewport

Question

Question: How do I find the maximum and minimum x-axis value of a RadCartesianChart's current viewport using DateTimeCategoricalAxis?

I can easily find the maximum/minimum values of the dataset and, if I were to use a DateTimeContinousAxis(unfortunately not an option), I could simply use ActualRange and ActualVisibleRange. However using DateTimeCategoricalAxis is a completely different story, since I cannot accurately find the datapoints within the current viewport. I even tried using the PlotAreaClip but to no avail. Not to mention, PlotAreaClip does not take into account the zoom size, which becomes a problem.

Any help would be great appreciated!

---

Here is a simplified version of my code:

XAML:

<UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
<Grid>
    <telerik:RadCartesianChart ZoomChanged="Zooming">

        <telerik:RadCartesianChart.Behaviors>
           <telerik:ChartPanAndZoomBehavior DragMode="Pan" 
                                             PanMode="Both" 
                                             ZoomMode="None" />
        </telerik:RadCartesianChart.Behaviors>

        <telerik:RadCartesianChart.Series>
            <telerik:OhlcSeries ItemsSource="{Binding Bars}" 
                                OpenBinding="Open"
                                HighBinding="High"
                                LowBinding="Low"
                                CloseBinding="Close"
                                CategoryBinding="Date">
            </telerik:OhlcSeries>
         </telerik:RadCartesianChart.Series>

        <telerik:RadCartesianChart.HorizontalAxis>
            <telerik:DateTimeCategoricalAxis DateTimeComponent="Ticks" 
                                             ShowLabels="False"
                                             PlotMode="OnTicks" 
                                             MajorTickInterval="100">
            </telerik:DateTimeCategoricalAxis>
        </telerik:RadCartesianChart.HorizontalAxis>

        <telerik:RadCartesianChart.VerticalAxis>
            <telerik:LinearAxis HorizontalLocation="Right" 
                                RangeExtendDirection="Both"
                                Minimum="{Binding PriceMinimum, Mode=OneWay}"
                                Maximum="{Binding PriceMaximum, Mode=OneWay}"
                                MajorStep="{Binding PriceMajorStep, Mode=OneWay}" />
         </telerik:RadCartesianChart.VerticalAxis>

        <telerik:RadCartesianChart.Grid>
            <telerik:CartesianChartGrid MajorXLinesRenderMode="All" 
                                        MajorLinesVisibility="XY" />
        </telerik:RadCartesianChart.Grid>

    </telerik:RadCartesianChart>
</Grid>
</UserControl>

CODE BEHIND:

public void Zooming(object sender, ChartZoomChangedEventArgs e)
    {
        RadCartesianChart chart = sender as RadCartesianChart;
        if (chart != null)
        {
            //PlotAreaClip.Location.X (PlotAreaClip.X also works) to get left side of clip
            //PlotAreaClip.Right to get right side of clip
            DataTuple dtMin = chart.ConvertPointToData(new Point(chart.PlotAreaClip.Location.X - Math.Abs(chart.PanOffset), chart.PlotAreaClip.Y), chart.HorizontalAxis, chart.VerticalAxis);
            DataTuple dtMax = chart.ConvertPointToData(new Point(chart.PlotAreaClip.Right - Math.Abs(chart.PanOffset), chart.PlotAreaClip.Y), chart.HorizontalAxis, chart.VerticalAxis);
            object xMin = dtMin.FirstValue;
            object xMax = dtMax.FirstValue;
            //these numbers are VERY inconsistent, especially when you zoom in!
        }
    }

The Telerik control being mentioned can be found here.

If anyone have any suggestions, I would greatly appreciate it! Thank you!

Answer 1

After doing some digging, I found this thread with the following solution:

private DataPoint[] FindFirstLastVisiblePoints(CategoricalSeries series)
{
    DataPoint firstPoint = null;
    DataPoint lastPoint = null;
    RadRect plotArea = this.radChart1.PlotAreaClip;

    foreach (DataPoint point in series.DataPoints)
    {
        if (point.LayoutSlot.IntersectsWith(plotArea))
        {
            if (firstPoint == null)
            {
                firstPoint = point;
            }
            lastPoint = point;
        }
    }

    return new DataPoint[] { firstPoint, lastPoint };
}

Basically, this method takes the current PlotAreaClip and returns the first and last datapoint within the current ViewPort. I really hope this helps others in the future!