Interactive Data display in KeyboardNavigation

[07012220]

I read the source code KeyboardNavigation.cs in InteractiveDataDisplay.WPF . i just don't no why need

IsZoomEnable(rect)

to check before setting the zooming.

private void DoZoom(double factor) { if (masterPlot != null) { var rect = masterPlot.PlotRect;

        if (IsHorizontalNavigationEnabled)
            rect.X = rect.X.Zoom(factor);
        if (IsVerticalNavigationEnabled)
            rect.Y = rect.Y.Zoom(factor);


        if (IsZoomEnable(rect))// why need this check?
        {
            masterPlot.SetPlotRect(rect);
            masterPlot.IsAutoFitEnabled = false;
        }
    }
}

private bool IsZoomEnable(DataRect rect)
{
    bool res = true;
    if (IsHorizontalNavigationEnabled)
    {
        double e_max = Math.Log(Math.Max(Math.Abs(rect.XMax), Math.Abs(rect.XMin)), 2);
        double log = Math.Log(rect.Width, 2);
        res = log > e_max - 40;
    }
    if (IsVerticalNavigationEnabled)
    {
        double e_max = Math.Log(Math.Max(Math.Abs(rect.YMax), Math.Abs(rect.YMin)), 2);
        double log = Math.Log(rect.Height, 2);
        res = res && log > e_max - 40;
    }
    return res;
}