nuit_core/state/
storage.rs

1use std::{collections::HashMap, any::Any, cell::{RefCell, Cell}};
2
3use crate::{Animation, StateKey, Update};
4
5/// A facility that manages view state internally.
6pub struct Storage {
7    state: RefCell<HashMap<StateKey, Box<dyn Any>>>,
8    changes: RefCell<HashMap<StateKey, Box<dyn Any>>>,
9    preapply: Cell<bool>,
10    update_callback: RefCell<Option<Box<dyn Fn(&Update)>>>,
11}
12
13impl Storage {
14    pub fn new() -> Self {
15        Self {
16            state: RefCell::new(HashMap::new()),
17            changes: RefCell::new(HashMap::new()),
18            preapply: Cell::new(false),
19            update_callback: RefCell::new(None),
20        }
21    }
22
23    pub(crate) fn initialize_if_needed<V>(&self, key: StateKey, value: impl FnOnce() -> V) where V: 'static {
24        if !self.state.borrow().contains_key(&key) {
25            self.state.borrow_mut().insert(key, Box::new(value()));
26        }
27    }
28
29    pub(crate) fn add_change<V>(&self, key: StateKey, value: V, animation: Option<Animation>) where V: 'static {
30        self.changes.borrow_mut().insert(key, Box::new(value));
31        self.fire_update_callback(&Update::new(animation));
32    }
33
34    pub(crate) fn get<T>(&self, key: &StateKey) -> T where T: Clone + 'static {
35        if self.preapply.get() && let Some(changed) = self.changes.borrow().get(key) {
36            changed.downcast_ref::<T>().cloned()
37        } else {
38            self.state.borrow()[key].downcast_ref::<T>().cloned()
39        }
40        .expect("State has invalid type")
41    }
42
43    pub(crate) fn with_preapplied_changes<T>(&self, action: impl FnOnce() -> T) -> T {
44        self.preapply.set(true);
45        let result = action();
46        self.preapply.set(false);
47        result
48    }
49
50    pub(crate) fn apply_changes(&self) {
51        let mut state = self.state.borrow_mut();
52        for (key, value) in self.changes.borrow_mut().drain() {
53            state.insert(key, value);
54        }
55    }
56
57    fn fire_update_callback(&self, update: &Update) {
58        if let Some(update_callback) = self.update_callback.borrow().as_ref() {
59            update_callback(&update);
60        }
61    }
62
63    pub fn set_update_callback(&self, update_callback: impl Fn(&Update) + 'static) {
64        *self.update_callback.borrow_mut() = Some(Box::new(update_callback));
65    }
66}
nuit_core/state/storage.rs

nuit_core/state/
storage.rs
