User Action - LM

private bool _userAction = false;

void OnFrame(Frame frame)
{
    // if user has not taken an action (e.g., press a button), return
    if (!_userAction)
        return;

    // call functions to determine pinch, grab, etc.

    // you probably need a timeout. After 5 seconds, set the _userAction back to 'false'.
}

void OnButtonClick(e sender)
{
    // user has clicked in the button
    _userAction = true;
}