Function pointer 

pub fn pointer(
    state: &mut AppState,
    kind: PointerKind,
    p: Point<f64, Logical>,
    under: Under,
) -> Verdict

The policy’s verdict on a pointer event at a logical layout point. A taken event makes the clients see the pointer leave, so a frame drag never scrolls or clicks what lies under the frame, and still moves the seat’s pointer, since a button is judged at the seat’s location: a menu whose motion the policy took would otherwise see every click at the spot it opened on. Under a client’s grab the seat’s pointer is not moved, so the first event the policy passes after taking some brings it to where the policy last took the pointer: the release that ends a frame drag reaches the client there, and the next relative delta adds to the drag’s end rather than its start.