rosace_core/
context.rs

1use crate::types::ComponentId;
2use rosace_state::{hook_state, Atom};
3
4/// Per-component context passed to every [`Component::build`] call.
5///
6/// Carries the component's identity and provides access to persistent local
7/// state via [`Context::state`]. State is keyed by `(component_id, call_order)`
8/// — the hook model — so call order within `build()` must be stable across frames.
9pub struct Context {
10    pub(crate) component_id: ComponentId,
11    pub(crate) hook_index: usize,
12}
13
14impl Context {
15    pub fn new(id: ComponentId) -> Self {
16        Context {
17            component_id: id,
18            hook_index: 0,
19        }
20    }
21
22    pub fn component_id(&self) -> ComponentId {
23        self.component_id
24    }
25
26    /// Returns a persistent [`Atom<T>`] for local component state.
27    ///
28    /// On first call per slot the atom is seeded with `default`. On subsequent
29    /// frames the existing atom is returned, preserving the last value.
30    pub fn state<T: Clone + Send + Sync + 'static>(&mut self, default: T) -> Atom<T> {
31        let idx = self.hook_index;
32        self.hook_index += 1;
33        hook_state(self.component_id, idx, default)
34    }
35
36    /// D008's `permanent` tier, on the hook model (D114/D121): like
37    /// [`Context::state`], but the FIRST initialization reads `key` from
38    /// the installed persist backend (falling back to `default` if the
39    /// key is absent or its bytes are stale), and every later `set`
40    /// writes through — the value survives a full app restart.
41    ///
42    /// `key` is app-global: two components using the same key share the
43    /// same stored value (by design — it's a storage key, not a hook
44    /// slot). With no backend installed (headless tests, or before
45    /// `App::launch`) this behaves exactly like plain [`Context::state`].
46    ///
47    /// Uses the atom's single `on_change` slot for the write-through —
48    /// see `Atom::set_on_change`'s doc.
49    pub fn state_permanent<T>(&mut self, key: &str, default: T) -> Atom<T>
50    where
51        T: crate::persist::PersistValue + Clone + Send + Sync + 'static,
52    {
53        let wired = self.state(false);
54        let initial = if wired.get() {
55            default // atom already exists; hook_state ignores this value
56        } else {
57            match crate::persist::persist_backend().and_then(|b| b.get(key).ok().flatten()) {
58                Some(bytes) => T::from_persist_bytes(&bytes).unwrap_or(default),
59                None => default,
60            }
61        };
62        let atom = self.state(initial);
63        if !wired.get() {
64            wired.set(true);
65            if crate::persist::persist_backend().is_some() {
66                let key = key.to_string();
67                let value_atom = atom.clone();
68                atom.set_on_change(move |_, _| {
69                    if let Some(backend) = crate::persist::persist_backend() {
70                        let _ = backend.set(&key, &value_atom.get().to_persist_bytes());
71                    }
72                });
73            }
74        }
75        atom
76    }
77
78    /// Registers a cleanup function that runs when this component unmounts.
79    ///
80    /// Stored in the persistent [`rosace_state::cleanup_store`] keyed by
81    /// component ID. The reconciler fires these callbacks when the component
82    /// disappears from the element tree.
83    pub fn on_cleanup(&mut self, f: impl FnOnce() + Send + 'static) {
84        rosace_state::cleanup_store::register(self.component_id, Box::new(f));
85    }
86}
rosace_core/context.rs

rosace_core/
context.rs
