request destroy (destructor) {
}

event begin {
    serial: u32,
    time: u32,
    surface: id(wl_surface),
    fingers: u32,
}

event update {
    time: u32,
    dx: fixed,
    dy: fixed,
}

event end {
    serial: u32,
    time: u32,
    cancelled: i32,
}
