/// <summary>
/// Create new touch event argument instance
/// </summary>
/// <param name="hWndWrapper">The target control</param>
/// <param name="touchInput">one of the inner touch input in the message</param>
internal InteropTouchEventArgs(IPointToClient HWndWrapper, float dpiX, float dpiY, ref TOUCHINPUT touchInput)
{
_HWndWrapper = HWndWrapper;
_dpiXFactor = 96F / dpiX;
_dpiYFactor = 96F / dpiY;
DecodeTouch(ref touchInput);
}
/// <summary>
/// Decode the message and create a collection of event arguments
/// </summary>
/// <remarks>
/// One Windows message can result a group of events
/// </remarks>
/// <returns>An enumerator of thr resuting events</returns>
/// <param name="hWnd">the WndProc hWnd</param>
/// <param name="msg">the WndProc msg</param>
/// <param name="wParam">the WndProc wParam</param>
/// <param name="lParam">the WndProc lParam</param>
public static IEnumerable <InteropTouchEventArgs> DecodeMessage(IPointToClient HWndWrapper, int msg, IntPtr wParam, IntPtr lParam, float dpiX, float dpiY)
{
// More than one touchinput may be associated with a touch message,
// so an array is needed to get all event information.
int inputCount = User32.LoWord((uint)wParam.ToInt32()); // Number of touch inputs, actual per-contact messages
TOUCHINPUT[] inputs; // Array of TOUCHINPUT structures
inputs = new TOUCHINPUT[inputCount]; // Allocate the storage for the parameters of the per-contact messages
try
{
// Unpack message parameters into the array of TOUCHINPUT structures, each
// representing a message for one single contact.
if (!User32.GetTouchInputInfo(lParam, inputCount, inputs, Marshal.SizeOf(inputs[0])))
{
// Get touch info failed.
throw new Exception("Error calling GetTouchInputInfo API");
}
// For each contact, dispatch the message to the appropriate message
// handler.
// Note that for WM_TOUCHDOWN you can get down & move notifications
// and for WM_TOUCHUP you can get up & move notifications
// WM_TOUCHMOVE will only contain move notifications
// and up & down notifications will never come in the same message
for (int i = 0; i < inputCount; i++)
{
InteropTouchEventArgs touchEventArgs = new InteropTouchEventArgs(HWndWrapper, dpiX, dpiY, ref inputs[i]);
yield return(touchEventArgs);
}
}
finally
{
User32.CloseTouchInputHandle(lParam);
}
}
