Scroll wheel zoom works on Win10 but not Win7

Bug description: Scroll wheel zoom not working in WinForms, enableScrollWheelZoom is set to true.

Steps to reproduce:

1. Drag and drop a formsPlot into the designer.
2. Enable the scroll with zoom using formsPlot1.Configure(enableScrollWheelZoom: true);
3. Start the program and try to zoom using the scroll wheel

Additional info: Everything else works as expected. You can zoom using right click. Using .Configure works on other settings properly. MouseWheel event is working properly. Everything works fine in the WPF version, this is a problem with the WinForms version. I’m using the 2017 version of Visual Studio with the latest version of ScottPlot on NuGet (4.0.29).

[swharden]

I couldn’t leave that stack overflow code block alone though 😅

Here’s a more straightforward version

/// <summary>
/// Return the version and name of the Windows operating system in use
/// </summary>
public static (decimal version, string name) GetOsInfo()
{
    // Derived from https://stackoverflow.com/questions/2819934/detect-windows-version-in-net
    int minorVersion = Environment.OSVersion.Version.Minor;
    int majorVersion = Environment.OSVersion.Version.Major;

    if (minorVersion == 0)
        return (0, "Windows 95");
    if (minorVersion == 10)
        return (2, "Windows 98");
    if (minorVersion == 90)
        return (3, "Windows ME");
    if (majorVersion == 3)
        return ((decimal)3.51, "Windows NT3");
    if (majorVersion == 4)
        return ((decimal)4.0, "Windows NT4");
    if (majorVersion == 5 && minorVersion == 0)
        return ((decimal)5.0, "Windows 2000");
    if (majorVersion == 5)
        return ((decimal)5.1, "Windows XP");
    if (majorVersion == 6 && minorVersion == 0)
        return (6, "Windows Vista");
    if (majorVersion == 6 && minorVersion == 1)
        return (7, "Windows 7");
    if (majorVersion == 6 && minorVersion == 2)
        return (8, "Windows 8");
    if (majorVersion == 6)
        return ((decimal)8.1, "Windows 8.1");
    if (majorVersion == 10)
        return (10, "Windows 10");

    throw new InvalidOperationException("Unknown Windows Version");
}

[swharden]

Thanks @vrdriver! I cleaned it up a bit and will leave it here for future people who may search for this similar question. I’m happy to hear you found a solution that works for you!

public void formsPlot2_MouseWheel(object sender, MouseEventArgs e)
{
    // Windows 7 and earlier need this to support scroll wheel zooming
    if (Environment.OSVersion.Version.Major <= 7)
    {
        formsPlot2.Focus();
        double xFrac = (e.Delta > 0) ? 1.15 : 0.85;
        double yFrac = (e.Delta > 0) ? 1.15 : 0.85;
        double zoomToX = formsPlot2.plt.CoordinateFromPixelX(e.Location.X);
        double zoomToY = formsPlot2.plt.CoordinateFromPixelY(e.Location.Y);
        formsPlot2.plt.AxisZoom(xFrac, yFrac, zoomToX, zoomToY);
        formsPlot2.Render();
        formsPlot2.Focus();
    }
}