Trait Widget 

pub trait Widget:
    Brick
    + Send
    + Sync {
    // Required methods
    fn type_id(&self) -> TypeId;
    fn measure(&self, constraints: Constraints) -> Size;
    fn layout(&mut self, bounds: Rect) -> LayoutResult;
    fn paint(&self, canvas: &mut dyn Canvas);
    fn event(&mut self, event: &Event) -> Option<Box<dyn Any + Send>>;
    fn children(&self) -> &[Box<dyn Widget>];
    fn children_mut(&mut self) -> &mut [Box<dyn Widget>];

    // Provided methods
    fn is_interactive(&self) -> bool { ... }
    fn is_focusable(&self) -> bool { ... }
    fn accessible_name(&self) -> Option<&str> { ... }
    fn accessible_role(&self) -> AccessibleRole { ... }
    fn test_id(&self) -> Option<&str> { ... }
    fn bounds(&self) -> Rect { ... }
}

Core widget trait that all UI elements implement.

Brick Architecture (PROBAR-SPEC-009)

Widget REQUIRES the Brick trait, enforcing the “tests define interface” philosophy:

• Every Widget has assertions that define its contract
• Every Widget has a performance budget
• Rendering is blocked if assertions fail (Popperian falsification)

Lifecycle

1. verify: Check Brick assertions (mandatory)
2. measure: Compute intrinsic size given constraints
3. layout: Position self and children within allocated bounds
4. paint: Generate draw commands (only if can_render() returns true)

Required Methods

fn type_id(&self) -> TypeId

Get the type identifier for this widget type.

fn measure(&self, constraints: Constraints) -> Size

Compute intrinsic size constraints.

fn layout(&mut self, bounds: Rect) -> LayoutResult

Position children within allocated bounds.

fn paint(&self, canvas: &mut dyn Canvas)

Generate draw commands for rendering.

Panics

Panics if called when can_render() returns false (Brick verification failed).

fn event(&mut self, event: &Event) -> Option<Box<dyn Any + Send>>

Handle input events.

fn children(&self) -> &[Box<dyn Widget>]

Get child widgets for tree traversal.

fn children_mut(&mut self) -> &mut [Box<dyn Widget>]

Get mutable child widgets.

Provided Methods

fn is_interactive(&self) -> bool

Check if this widget is interactive (can receive focus/events).

fn is_focusable(&self) -> bool

Check if this widget can receive keyboard focus.

fn accessible_name(&self) -> Option<&str>

Get the accessible name for screen readers.

fn accessible_role(&self) -> AccessibleRole

Get the accessible role.

fn test_id(&self) -> Option<&str>

Get the test ID for this widget (if any).

fn bounds(&self) -> Rect

Get the current bounds of this widget.

Implementors