close method
Prevents new members from entering the arena.
Called after the framework has finished dispatching the pointer down event.
Implementation
void close(int pointer) {
final _GestureArena state = _arenas[pointer];
if (state == null)
return; // This arena either never existed or has been resolved.
state.isOpen = false;
assert(_debugLogDiagnostic(pointer, 'Closing', state));
_tryToResolveArena(pointer, state);
}