#736 – Finding the Maximum Number of Touch Points at Run-time

You can write code that discovers at run-time the number of touch points supported by the hardware that you’re running on.  You do this by calling the GetSystemMetrics Win32 API call.

    class Program
    {
        [DllImport("user32.dll")]
        static extern int GetSystemMetrics(int nIndex);

        // Index passed in to GetSystemMetrics() indicates
        // what data we're asking for.
        private const int SM_DIGITIZER = 94;
        private const int SM_MAXIMUMTOUCHES = 95;

        // Masks used to check results from SM_DIGITIZER check
        private const int NID_READY = 0x80;
        private const int NID_MULTI_INPUT = 0x40;

        static void Main(string[] args)
        {
            string info;

            int digitizer = GetSystemMetrics(SM_DIGITIZER);

            if ((digitizer & (NID_READY + NID_MULTI_INPUT)) == NID_READY + NID_MULTI_INPUT)
            {
                int numTouchPoints = GetSystemMetrics(SM_MAXIMUMTOUCHES);
                info = string.Format("Multitouch ready, {0} inputs supported", numTouchPoints);
            }
            else
                info = "Multitouch not supported";

            Console.WriteLine(info);
            Console.ReadLine();
        }
    }