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WPF DynamicDataDisplay - Slow plotting with Markers

由 浪尽此生 提交于 2019-12-04 13:50:23

I wrote my own class to hide markers when they are off screen. It's a virtualization technique that speeds up performance tenfold when you don't have tons of markers on screen. It looks like this :

using System;
using System.Windows;
using System.Windows.Media;
using Microsoft.Research.DynamicDataDisplay.DataSources;
using Microsoft.Research.DynamicDataDisplay.PointMarkers;
using Microsoft.Research.DynamicDataDisplay.Common;

namespace Microsoft.Research.DynamicDataDisplay.Charts {
public class FilteredMarkerPointsGraph : MarkerPointsGraph {
    public FilteredMarkerPointsGraph()
        : base() {
        ;
    }

    public FilteredMarkerPointsGraph(IPointDataSource dataSource)
        : base(dataSource) {
        ;
    }

    protected override void OnRenderCore(DrawingContext dc, RenderState state) {
        // base.OnRenderCore
        if (DataSource == null) return;
        if (Marker == null) return;

        var left = Viewport.Visible.Location.X;
        var right = Viewport.Visible.Location.X + Viewport.Visible.Size.Width;
        var top = Viewport.Visible.Location.Y;
        var bottom = Viewport.Visible.Location.Y + Viewport.Visible.Size.Height;

        var transform = Plotter2D.Viewport.Transform;

        DataRect bounds = DataRect.Empty;
        using (IPointEnumerator enumerator = DataSource.GetEnumerator(GetContext())) {
            Point point = new Point();
            while (enumerator.MoveNext()) {
                enumerator.GetCurrent(ref point);                                       

                if (point.X >= left && point.X <= right && point.Y >= top && point.Y <= bottom)
                {
                    enumerator.ApplyMappings(Marker);

                    Point screenPoint = point.DataToScreen(transform);

                    bounds = DataRect.Union(bounds, point);
                    Marker.Render(dc, screenPoint);
                }
            }
        }

        Viewport2D.SetContentBounds(this, bounds);
    }
}

Make sure you call FilteredMarkerPointsGraph in the XAML instead of MarkerPointsGraph!

EDIT

  1. I'm not sure what you need with the legend with markers, I've not actually used a legend in any of my graphs, but your solution seems to be fine.

  2. Redrawing the plot is quite easy actually.

The best way that I have found to do this, is to have a Property in your code behind that represents the DataSource and bind the chart's DataSource to that property. Have your code behind implement INotifyPropertyChanged and call OnPropertyChanged every time you update or re-assign your data source. This will force the plotter to observe the binding and redraw your graph.

Example:

EnumerableDataSource<Point> m_d3DataSource;
public EnumerableDataSource<Point> D3DataSource {
get {
    return m_d3DataSource;
}
set {                
    //you can set your mapping inside the set block as well             
    m_d3DataSource = value;
    OnPropertyChanged("D3DataSource");
}
}     

protected void OnPropertyChanged(PropertyChangedEventArgs e) {
    PropertyChangedEventHandler handler = PropertyChanged;
    if (handler != null) {
        handler(this, e);
    }
} 

protected void OnPropertyChanged(string propertyName) {
    OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}

And about your performance with your markers.. It's hard to pinpoint exactly what would be causing your performance issue, but my recommendation is to try using a different data source. I've been using EnumerableDataSource and it's always worked like a charm. Try bringing in your data in a singular object and setting the mapping in your set block like as shown above using:

value.SetYMapping(k => Convert.ToDouble(k.yData));
value.SetXMapping(k => Convert.ToDouble(k.xData));

The only thing you have to worry about is the mapping in Enumerable data source and D3 should handle the rest for you.

Well user can't probably see markers anyway when you are displaying the "Gazillion" of points: can't you switch the mode from line to markers when the zoom level is more reasonable ?

标签
c#
wpf
performance
marker
dynamic-data-display
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