检查触摸设备最大支持点数

[DllImport("user32.dll")]
static extern int GetSystemMetrics(int nIndex);
private const int SM_DIGITIZER = 94;
private const int SM_MAXIMUMTOUCHES = 95;

private const int NID_READY = 0x80;
private const int NID_MULTI_INPUT = 0x40;

int digitizer = GetSystemMetrics(SM_DIGITIZER);

if ((digitizer & (NID_READY + NID_MULTI_INPUT)) == NID_READY + NID_MULTI_INPUT)
{
　　int numTouchPoints = GetSystemMetrics(SM_MAXIMUMTOUCHES);

 　　Console.WriteLine("Multitouch ready, {0} inputs supported", numTouchPoints);
}