Trait Component 

pub trait Component {
    type Props<'a>;

    // Required methods
    fn handle_event(
        &mut self,
        event: &EventKind,
        props: Self::Props<'_>,
    ) -> Vec<impl Action>;
    fn render(
        &mut self,
        frame: &mut Frame<'_>,
        area: Rect,
        props: Self::Props<'_>,
    );

    // Provided methods
    fn subscriptions(&self) -> Vec<EventType> { ... }
    fn area(&self) -> Option<Rect> { ... }
}

A pure UI component that renders based on props and emits actions

Components follow these rules:

1. Props contain ALL read-only data needed for rendering
2. handle_event returns actions, never mutates external state
3. render is a pure function of props (plus internal UI state like scroll position)

Internal UI state (scroll position, selection highlight) can be stored in &mut self, but data mutations must go through actions.

Focus and Context

Components receive EventKind (the raw event) rather than the full Event with context. Focus information and other context should be passed through Props. This keeps components decoupled from the specific ComponentId type used by the application.

Required Associated Types

type Props<'a>

Data required to render the component (read-only)

Required Methods

fn handle_event( &mut self, event: &EventKind, props: Self::Props<'_>, ) -> Vec<impl Action>

Handle an event and return actions to dispatch

Components receive the raw EventKind (key press, mouse event, etc.). Focus state and other context should be passed through Props.

fn render(&mut self, frame: &mut Frame<'_>, area: Rect, props: Self::Props<'_>)

Render the component to the frame

Provided Methods

fn subscriptions(&self) -> Vec<EventType>

Event types this component wants to receive

Return the event types this component should be subscribed to. Global events are always delivered regardless of this.

fn area(&self) -> Option<Rect>

Get the last rendered area (for hit-testing and focus management)

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors