StackedAreaSeries do not display properly if X-values are in descending order.

Fortunately, in making a demo of this problem I found that I can work around this problem by sorting my items so their x-axis values are in ascending order. However, should ascending order should be required? To see the problem first run the demo as is--the graph should display properly. Then uncomment the line "items = revItems;" and rerun to see the incorrect display.

Here is the XAML:

<Window x:Class="ChartTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:ms="http://namespaces.mindscape.co.nz/wpf"
    Title="MainWindow" Height="600" Width="800">

<ms:Chart x:Name="chart" LegendPosition="Bottom"/>

Here is the C#

    public partial class MainWindow : Window
{
    public class Item
    {
        public Item(double x, double y1, double y2, double y3, double y4, double y5)
        {
            X = x + 10;
            double yTotal = y1 + y2 + y3 + y4 + y5;
            Y1 = y1 / yTotal;
            Y2 = y2 / yTotal;
            Y3 = y3 / yTotal;
            Y4 = y4 / yTotal;
            Y5 = y5 / yTotal;
        }
        public double X { get; set; }
        public double Y1 { get; set; }
        public double Y2 { get; set; }
        public double Y3 { get; set; }
        public double Y4 { get; set; }
        public double Y5 { get; set; }
    }

    public MainWindow()
    {
        InitializeComponent();

        Item[] items = new Item[]
        {
            new Item(1, 1, 2, 3, 4, 5),
            new Item(2, 1, 3, 3, 4, 6),
            new Item(3, 2, 2, 3, 5, 5),
            new Item(4, 1, 3, 3, 4, 4),
            new Item(5, 1, 4, 4, 4, 5),
            new Item(6, 2, 1, 3, 4, 5),
            new Item(7, 2, 2, 2, 4, 6),
            new Item(8, 1, 3, 3, 4, 5),
            new Item(9, 3, 2, 4, 4, 7),
            new Item(10, 4, 2, 3, 4, 5),
        };

        Item[] revItems = new Item[items.Length];
        for (int i = 0; i < items.Length; ++i)
        {
            revItems[i] = items[revItems.Length - 1 - i];
        }

        //items = revItems;

        Brush[] brushes = new Brush[] { Brushes.Blue, Brushes.Green, Brushes.Red, Brushes.Purple, Brushes.Yellow };

        chart.XAxis.IsReversed = true;
        chart.YAxis.Maximum = 1.0;
        for (int i = 0; i < 5; ++i)
        {
            StackedAreaSeries series = new StackedAreaSeries();
            series.XBinding = new Binding("X");
            series.YBinding = new Binding("Y" + (i + 1));
            series.SeriesBrush = brushes[i];
            series.ItemsSource = items;
            chart.Series.Add(series);
        }
    }
}

Hello Peter

The chart assumes that all series are ordered by the independent values (apart from scatter/bubble series which of course can be all over the place). The correct order of values allows the Chart to perform binary searches to aid virtualization, and overall keep the performance high. Sure this could still work in reverse order, but unfortunately it would take quite a while to implement this - as there are several places that assume the data ordering, so I'm sorry to say we don't plan to implement this - at least not for a while. As you pointed out, the solution to this is to make sure the independent values are in ascending order.

-Jason Fauchelle