Trait Widget 

pub trait Widget: 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.

Widgets follow a measure-layout-paint cycle:

1. measure: Compute intrinsic size given constraints
2. layout: Position self and children within allocated bounds
3. paint: Generate draw commands

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.

Called during the measure phase to determine the widget’s preferred size.

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

Position children within allocated bounds.

Called during the layout phase after sizes are known.

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

Generate draw commands for rendering.

Called during the paint phase to produce GPU draw commands.

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

Handle input events.

Returns a message if the event triggered a state change.

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.

Returns the rectangle set during the last layout phase. Default returns zero-sized bounds at origin.

Implementors