Struct SnapshotStateObserver 

pub struct SnapshotStateObserver { /* private fields */ }

Observer that records state object reads performed inside a given scope and notifies the caller when any of the observed objects change.

This is a pragmatic Rust translation of Jetpack Compose’s SnapshotStateObserver. The implementation focuses on the core behaviour needed by the Cranpose runtime:

• Tracking state object reads per logical scope.
• Reacting to snapshot apply notifications.
• Scheduling invalidation callbacks via the supplied executor.

Advanced features from the Kotlin version (derived state tracking, change coalescing, queue minimisation) are deferred

Implementations

impl SnapshotStateObserver

pub fn new( on_changed_executor: impl Fn(Box<dyn FnOnce() + 'static>) + 'static, ) -> Self

Create a new observer that schedules callbacks using on_changed_executor.

pub fn observe_reads<T, R>( &self, scope: T, on_value_changed_for_scope: impl Fn(&T) + 'static, block: impl FnOnce() -> R, ) -> R

where T: Any + Clone + PartialEq + 'static,

Observe state object reads performed while executing block.

Subsequent calls to observe_reads replace any previously recorded observations for the provided scope. When one of the observed objects mutates, on_value_changed_for_scope will be invoked on the executor.

pub fn begin_frame(&self)

Notify the observer that a new composition frame is starting.

pub fn with_no_observations<R>(&self, block: impl FnOnce() -> R) -> R

Temporarily pause read observation while executing block.

pub fn clear<T>(&self, scope: &T)

where T: Any + PartialEq + 'static,

Remove any recorded reads for scope.

pub fn clear_if(&self, predicate: impl Fn(&dyn Any) -> bool)

Remove recorded reads for scopes that satisfy predicate.

pub fn clear_all(&self)

Remove all recorded observations.

pub fn start(&self)

Begin listening for snapshot apply notifications.

pub fn stop(&self)

Stop listening for snapshot apply notifications.

Trait Implementations

impl Clone for SnapshotStateObserver

fn clone(&self) -> SnapshotStateObserver

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.