Line disappearing on zooming (using "Dynamic data display")

Question

In my WPF-project I'm using Dynamic data display for charting. I read somewhere that it's a common bug that lines disappear (are not drawn) if you zoom in very deeply.

Has anybody a solution for this bug?

Answer 1

While not an exact solution to your bug, you can prevent a user by zooming in too deep by using a zoom restriction. That way a user will never experience this bug by zooming in that deep. You can find at what zoom this bug is occuring, and restrict the zoom at that DataRect. I wrote my own class to restrict Zooming in D3 and will provide it for you.

Here:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;

namespace Microsoft.Research.DynamicDataDisplay.ViewportRestrictions {
/// <summary>
/// Represents a restriction, which limits the maximal size of <see cref="Viewport"/>'s Visible property.
/// </summary>
public class ZoomInRestriction : ViewportRestriction {
    /// <summary>
    /// Initializes a new instance of the <see cref="MaximalSizeRestriction"/> class.
    /// </summary>
    public ZoomInRestriction() { }

    /// <summary>
    /// Initializes a new instance of the <see cref="MaximalSizeRestriction"/> class with the given maximal size of Viewport's Visible.
    /// </summary>
    /// <param name="maxSize">Maximal size of Viewport's Visible.</param>
    public ZoomInRestriction(double height, double width) {
        Height = height;
        Width = width;
    }

    private double height;
    private double width;

    public double Height {
        get { return height; }
        set {
            if (height != value) {
                height = value;
                RaiseChanged();
            }
        }
    }

    public double Width {
        get { return width; }
        set {
            if (width != value) {
                width = value;
                RaiseChanged();
            }
        }
    }

    /// <summary>
    /// Applies the specified old data rect.
    /// </summary>
    /// <param name="oldDataRect">The old data rect.</param>
    /// <param name="newDataRect">The new data rect.</param>
    /// <param name="viewport">The viewport.</param>
    /// <returns></returns>
    public override DataRect Apply(DataRect oldDataRect, DataRect newDataRect, Viewport2D viewport) {
        if ((newDataRect.Width < width || newDataRect.Height < height)) {
            return oldDataRect;
        }
        return newDataRect;
    }
}
}

Now you can use this in your code to implement the restriction like this :

plotter.Viewport.Restrictions.Add(new ZoomInRestriction(height, width));

While not being the exact solution to the bug, you should at least be able to prevent a user from experiencing it.

Answer 2

See https://dynamicdatadisplay.codeplex.com/discussions/484160 for more details

In LineGraph.cs, method OnRenderCore. Replace the following line from

context.BeginFigure(FilteredPoints.StartPoint, false, false);

to

context.BeginFigure(FilteredPoints.StartPoint, true, false);