37 type ObjectId = NonZeroU32;  typedef
226     event_devices: BTreeMap<ObjectId, EventDevice>,
548     next_id: ObjectId,
549     surfaces: BTreeMap<ObjectId, Surface>,
550     event_devices: BTreeMap<ObjectId, EventDevice>,
624                 next_id: ObjectId::new(1).unwrap(),  in open_display()
632         ObjectId::new(surface_id).and_then(move |id| self.surfaces.get(&id))  in surface_ref()
636         ObjectId::new(surface_id).and_then(move |id| self.surfaces.get_mut(&id))  in surface_mut()
640         ObjectId::new(event_device_id).and_then(move |id| self.event_devices.get(&id))  in event_device()
644         ObjectId::new(event_device_id).and_then(move |id| self.event_devices.get_mut(&id))  in event_device_mut()
736         self.next_id = ObjectId::new(self.next_id.get() + 1).unwrap();  in create_surface()
743             ObjectId::new(surface_id).and_then(|id| self.surfaces.remove(&id))  in release_surface()
814         self.next_id = ObjectId::new(self.next_id.get() + 1).unwrap();  in import_event_device()
820         ObjectId::new(event_device_id).and_then(|id| self.event_devices.remove(&id));  in release_event_device()
824         let event_device_id = match ObjectId::new(event_device_id) {  in attach_event_device()
828         let surface_id = match ObjectId::new(surface_id) {  in attach_event_device()