Enable multitouch on WPF controls (v9)

The Eyeshot WPF control, in order to manage multitouch in an efficient way, disables the RealTimeStylus support from the application Window causing the multitouch gestures to no longer work on WPF controls other than the ViewportLayout (for instance a ScrollViewer).

To restore the multitouch functionality on the other WPF controls you need to add this code to your main window:

public const int WM_TOUCH = 0x0240;

public enum TouchWindowFlag : uint
{
    FineTouch = 0x1,
    WantPalm = 0x2
}


[DllImport("user32")]
public static extern bool RegisterTouchWindow(System.IntPtr hWnd, TouchWindowFlag flags);

protected override void OnSourceInitialized(EventArgs e)
{
    base.OnSourceInitialized(e);

    HwndSource source = PresentationSource.FromVisual(this) as HwndSource;
    source.AddHook(WndProc);


    var presentationSource = (HwndSource)PresentationSource.FromDependencyObject(this);
    if (presentationSource == null)
    {
        throw new Exception("Unable to find the parent element host.");
    }

    RegisterTouchWindow(presentationSource.Handle, TouchWindowFlag.WantPalm);
}

[DllImport("user32")]
public static extern bool GetTouchInputInfo(System.IntPtr hTouchInput, int cInputs, [In, Out] devDept.Eyeshot.Multitouch.Interop.TOUCHINPUT[] pInputs, int cbSize);

[DllImport("user32")]
public static extern void CloseTouchInputHandle(System.IntPtr lParam);

class TouchDeviceEmulator : TouchDevice
{
    public System.Windows.Point Position;
    public TouchDeviceEmulator(int deviceId) : base(deviceId)
    {
    }

    public override TouchPoint GetTouchPoint(IInputElement relativeTo)
    {
        System.Windows.Point pt = Position;
        if (relativeTo != null)
            pt = ActiveSource.RootVisual.TransformToDescendant((Visual)relativeTo).Transform(Position);

        var rect = new Rect(pt, new Size(1.0, 1.0));
        return new TouchPoint(this, pt, rect, TouchAction.Move);
    }

    public override TouchPointCollection GetIntermediateTouchPoints(IInputElement relativeTo)
    {
        throw new NotImplementedException();
    }

    public void SetActiveSource(PresentationSource activeSource)
    {
        base.SetActiveSource(activeSource);
    }

    public void Activate()
    {
        base.Activate();
    }

    public void ReportUp()
    {
        base.ReportUp();
    }

    public void ReportDown()
    {
        base.ReportDown();
    }

    public void ReportMove()
    {
        base.ReportMove();
    }

    public void Deactivate()
    {
        base.Deactivate();
    }
}

Dictionary<int, TouchDeviceEmulator> _devices = new Dictionary<int, TouchDeviceEmulator>();

// Touch event flags ((TOUCHINPUT.dwFlags) [winuser.h]
public const int TOUCHEVENTF_MOVE = 0x0001;
public const int TOUCHEVENTF_DOWN = 0x0002;
public const int TOUCHEVENTF_UP = 0x0004;
public const int TOUCHEVENTF_INRANGE = 0x0008;
public const int TOUCHEVENTF_PRIMARY = 0x0010;
public const int TOUCHEVENTF_NOCOALESCE = 0x0020;
public const int TOUCHEVENTF_PEN = 0x0040;
public const int TOUCHEVENTF_PALM = 0x0080;

private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
    // http://www.codeproject.com/Articles/692286/WPF-and-multi-touch
    // http://jayheu.lingohq.io/blog/archives/2015/07/25/multi-touch-and-wpf

    // Handle messages...
    if (msg == WM_TOUCH) //WM_TOUCH
    {
        handled = HandleTouch(wParam, lParam);
        return new IntPtr(1);
    }
    return IntPtr.Zero;
}

private bool HandleTouch(IntPtr wParam, IntPtr lParam)
{
    bool handled = false;
    var inputCount = wParam.ToInt32() & 0xffff;
    var inputs = new devDept.Eyeshot.Multitouch.Interop.TOUCHINPUT[inputCount];

    if (GetTouchInputInfo(lParam, inputCount, inputs, Marshal.SizeOf(inputs[0])))
    {
        for (int i = 0; i < inputCount; i++)
        {
            var input = inputs[i];
            var position = PointFromScreen(new System.Windows.Point((input.x * 0.01), (input.y * 0.01)));

            TouchDeviceEmulator device;
            if (!_devices.TryGetValue(input.dwID, out device))
            {
                device = new TouchDeviceEmulator(input.dwID);
                _devices.Add(input.dwID, device);
            }

            device.Position = position;

            if ((input.dwFlags & TOUCHEVENTF_DOWN) > 0)
            {
                device.SetActiveSource(PresentationSource.FromVisual(this));
                device.Activate();
                device.ReportDown();
            }
            else if (device.IsActive && (input.dwFlags & TOUCHEVENTF_UP) > 0)
            {
                device.ReportUp();
                device.Deactivate();
                _devices.Remove(input.dwID);
            }
            else if (device.IsActive && (input.dwFlags & TOUCHEVENTF_MOVE) > 0)
            {
                device.ReportMove();
            }
        }

        CloseTouchInputHandle(lParam);
        handled = true;
    }

    return handled;
}

In attachment the VB.NET code.