Struct StateManager 

pub struct StateManager { /* private fields */ }

StateManager is used to manage the mutable state associated with a particular component’s ID. Because components technically only exist while a layout tree is being calculated, this is where a component is expected to store all it’s durable state that must survive through the next layout pass. The StateManager also requires that all components implement StateMachineChild, even if they are stateless. A derive macro is provided for this case. Likewise, the internal state object must implement event::EventRouter, even if it doesn’t process any events, in which case it can simply set Input and Output to std::convert::Infallible

All components can access their own state by calling StateManager::get with their ID and the component::StateMachine wrapper type around their internal state object, which should have been created earlier by feather automatically calling StateMachineChild::init.

Examples

use feather_ui::{SourceID, StateManager, component::StateMachine, event::EventRouter};
use std::sync::Arc;
use std::convert::Infallible;

#[derive(Clone, PartialEq)]
struct FooBar {
  i: i32
}

impl EventRouter for FooBar {
   type Input = Infallible;
   type Output = Infallible;
}

fn layout(id: Arc<SourceID>, manager: &mut StateManager) {
    let outer = manager.get_mut::<StateMachine<FooBar, 0>>(&id).unwrap();
    outer.state.i = 3;
}

A component can even retrieve a different component’s internal state as long as it has the ID and knows the type of the inner state. This is how most feather components get the DPI for the current window.

use feather_ui::{SourceID, StateManager, component::StateMachine, event::EventRouter};
use std::sync::Arc;
use std::convert::Infallible;
use feather_ui::component::window::WindowStateMachine;

#[derive(Clone, PartialEq)]
struct FooBar {
  i: i32
}

impl EventRouter for FooBar {
   type Input = Infallible;
   type Output = Infallible;
}

fn layout(
    manager: &mut StateManager,
    window: &Arc<SourceID>,
) {
let dpi = manager
    .get::<WindowStateMachine>(window)
    .map(|x| x.state.dpi)
    .unwrap_or(feather_ui::BASE_DPI);
println!("{dpi:?}");
}

Implementations

impl StateManager

pub fn register_pointer<T>( &mut self, p: *const T, id: Arc<SourceID>, ) -> Option<Arc<SourceID>>

pub fn invalidate_pointer<T>(&mut self, p: *const T) -> Option<Arc<SourceID>>

pub fn mutate_pointer<T>(&mut self, p: *const T)

pub fn get<'a, State: 'static + StateMachineWrapper>( &'a self, id: &SourceID, ) -> Result<&'a State>

Gets a reference to a state for the given id. Returns an error if the state doesn’t exist or if the requested type doesn’t match.

pub fn get_mut<'a, State: 'static + StateMachineWrapper>( &'a mut self, id: &SourceID, ) -> Result<&'a mut State>

Gets a mutable reference to a state for the given id. Returns an error if the state doesn’t exist or if the requested type doesn’t match.

Trait Implementations

impl Default for StateManager

fn default() -> StateManager

Returns the “default value” for a type.